Name: novel process for 3d printing decellularized matrices
Uploaded: 2019-01-07T14:00:00.000+00:00
Duration: 8 min 14 s
Description: Watch this Scientific Journal Video about Novel Process for 3D Printing Decellularized Matrices at JoVE.com

This project was partially funded by a grant from the Pediatric Orthopaedic Society of North America (POSNA) and the National Institutes of Health grant NIBIB R21EB025378-01 (Exploratory Bioengineering Research Grant).

1. Obtaining and Preprocessing Microspheres
<ol>
	<li>Produce microspheres with the desired matrix encapsulated (PLA-DM)2. 
	NOTE: It is imperative that the microspheres are of uniform size. For this reason, sieving the microspheres prior to use is essential. Although matrix decellularization and encapsulation have been detailed in previous publications2, a brief summary of the process follows.
	<ol>
		<li>First, harvest cartilage plugs from porcine hind limbs. Decellularize the cartilage in a series of washes with 0.05% trypsin/0.5 mm tetrasodium ethylenediaminetetraacetic acid (EDTA), Dulbecco&#39;s modified Eagle&#39;s medium (DMEM), and 1.5% peracetic acid and 2.0% Triton X-100 for 4 h each with distilled water washes before and after each step2.</li>
		<li>Drain the decellularized matrix, freeze it, lyophilize, grind, and dissolve into pepsin solution. Following dissolution, mix the pepsin solution with PLA which has been dissolved in dichloromethane.</li>
		<li>Add the mixture dropwise into a 3% polyvinyl alcohol in water solution. Centrifuge the resulting microspheres, rinse, drain, and lyophilize again. 
		NOTE: For full details on the process see the previously published protocol2.</li>
	</ol>
	</li>
	<li>Sieve the microspheres.
	<ol>
		<li>Ensure that all sieve plates have been thoroughly cleaned and are dry prior to use. If necessary, clean sieves using ultrasonic cleaner to ensure that all spheres are removed from the sieve.</li>
		<li>Assemble the sieve shaker with the 106 &#181;m sieve tray at the top, the 53 &#181;m tray after that, and the sieve pan at the bottom.</li>
		<li>Place dry microspheres in the topmost sieve tray and place the lid on the top tray. Turn on coarse sieving for 8 to 10 min. Repeat on fine for 8 to 10 min. 
		NOTE: The sieve times may need to be increased or decreased depending on the batch.</li>
		<li>Carefully remove the sieve plates one by one and place them upside down on a large weigh paper. Tap the sides gently to ensure that most of the spheres have fallen out of the sieve and onto the paper.</li>
		<li>Discard the oversized spheres (&#62;106 &#181;m) and undersized spheres (&#60;53 &#181;m). Add spheres that are in the 53 to 106 &#181;m size range to a labeled centrifuge tube with the type and batch number then place in a -20 &#176;C freezer until further use.</li>
	</ol>
	</li>
</ol>
2. Microsphere Quality Control Assessments
Note: See Figure 1.
<ol>
	<li>Perform macroscopic/visual assessment to check that the microspheres are uniform and spherical, with no aggregates present.</li>
	<li>Assess the microspheres using a scanning electron micrograph (SEM).
	<ol>
		<li>For this, place microspheres onto an SEM chuck and sputter coat with gold-palladium in argon atmosphere using a sputter coater to a thickness of 4 nm.</li>
		<li>Observe surface features, morphology, and diameters of the microspheres using a 10 kV accelerating voltage and a 10 mm working distance to ensure that production and sieving of the microspheres was successful.</li>
	</ol>
	</li>
</ol>
3. Filament Creation for 3D Printing
<ol>
	<li>Measure and record the mass of the microspheres obtained from steps 2 and 3; at least 25 g is needed.</li>
	<li>Add polycaprolactone (PCL) powder to the microspheres for a 1:4 weight ratio of microspheres to PCL.</li>
	<li>Mix the powder mixture on a miniature rolling mixer at 20 rpm for 5 min then flip the container and mix at 20 rpm for an additional 5 min (see Figure 2).</li>
	<li>Many commercially available extruders (see the Table of Materials) have insulating jackets because their intended working temperatures are for traditional fused deposition modeling (FDM) filaments. Modify the extruder (if necessary) by removing the insulating material and use it in combination with desktop fans (which blow ambient air onto the extruder and extruded filament) to use of the extruder at lower temperatures. 
	NOTE: Desktop fans which blow ambient air to cool the extruder and filament are useful for this procedure.</li>
	<li>Setup the equipment setup for extrusion. See Figure 3.
	<ol>
		<li>Setup the extruder so that its outlet is ~60 cm from the inlet to the spooler, with a direct path from the extrusion outlet to the spooler inlet. 
		NOTE: The spooler can optionally be raised 3-4 inches from the bench if it is found that the filament is drooping to the point of touching the benchtop.</li>
		<li>Place a desktop fan ~15 cm from the heating jacket and direct it towards the heating jacket to offer cooling with ambient air throughout filament production. Place a second cooling fan approximately halfway between the extruder and spooler and direct it towards the extrudate to assist in cooling the filament with ambient air.</li>
		<li>Adjust the positioning as needed throughout the process.</li>
	</ol>
	</li>
	<li>Set the modified extruder heating element to 52 &#176;C, turn on the desktop cooling fans, and allow the instrument to come to equilibrium for 20 to 30 min. Ensure that the proper nozzle is attached to the extruder.</li>
	<li>Just before beginning, fill the extruder hopper with the microsphere/PCL mixture from step 3.3. Turn on the spooler and the extruder auger to initiate extrusion of filament.</li>
	<li>When the initial filament is extruded, manually pull the extrudate from the extrusion outlet with forceps and feed it to the filament spooler.</li>
	<li>The desired filament will take some time to come out of the spooler. Using separate spools or tape, clearly mark when the filament composition visually appears uniform.</li>
	<li>Monitor the process closely and modify parameters as necessary. Adjust the extruder temperature, extrusion auger speed, and spooler speed to obtain a 1.75 mm diameter filament as measured by calipers. Adjust the fans as needed to cool the filament properly to avoid non-circular filament cross-sections. Mix and refill the hopper as necessary. 
	NOTE: Close attention is required during this process to obtain adequate filament for subsequent 3D printing. The above parameters will change depending on the ambient conditions, the fill level and uniformity of the mixture in the hopper, and the thermodynamics and flow dynamics of the specific batches of PCL and microspheres.</li>
	<li>Continue extruding until all of the powder has been used and the hopper is almost empty. Add PCL powder (without microspheres) to the hopper to flush out the microsphere mixture that is currently in the extruder. Continue adding PCL powder to the hopper until no more microspheres are visible in the extrudate.</li>
	<li>Be sure to label and separate the filament which contains the microspheres in the desired concentration, as after the filament is cooled it is harder to distinguish the uniform filament from non-uniform filament.</li>
	<li>Continue extruding until there is minimal powder left in the hopper, then turn off the spooler, extruder auger, extruder heating element, and fans.</li>
</ol>
4. Printing with the Filament
<ol>
	<li>Design a geometry of the desired shape and form using a computer aided design software. Then slice the model and dictate the toolpath using slicing software that is compatible with the 3D printing machine being used.</li>
	<li>Load the filament from step 3 onto any standard FDM printer, fitted with standard nozzles of the desired diameter (typically 0.4 mm). Begin the print (typically at 65-70 &#176;C and 300 mm/min linear speed) as the custom filament is deposited layer-by-layer by the machine.</li>
	<li>Make sure to pay special attention to the first layer and adjust settings as needed to get a good quality print. 
	NOTE: Adjustments may be made to the print speed, print temperature, platform temperature, extrusion multiplier, and other parameters. Refer to the printer and slicing manufacturer&#39;s troubleshooting guide for further assistance.</li>
</ol>
5. Quality Control Assessment
<ol>
	<li>Place the printed constructs on SEM chucks and sputter coat with gold-palladium in argon atmosphere using a sputter coater to a thickness of 4 nm.</li>
	<li>Observe under the microscope using a 10 kV accelerating voltage and a 10 mm working distance to check surface features and for the presence or absence of microspheres if applicable.</li>
</ol>
6. Functional Testing of the Printed Constructs
NOTE: Alkaline phosphatase (ALP) can be used as a surrogate for decellularized matrix to determine if encapsulated proteins are biologically active after the filament production process. ALP is used because it catalyzes a reaction from a substrate, p-nitrophenyl phosphate, to change from colorless to yellow byproducts, p-nitrophenol and inorganic phosphate, but only if ALP is in the functional conformation.
<ol>
	<li>Print a geometry (n = 3) that has an end mass of at least 400 mg with the ALP microsphere filament (PLA-ALP/PCL) using identical print parameters as the PLA-DM/PCL scaffolds. Also print PCL-only (PCL(-)) scaffolds of the same geometry as the PLA-ALP/PCL scaffolds. Submerge them in 1 mL Tris-HCl buffer and incubate for 24 h at 37 &#176;C and 110 rpm rotation to allow enzyme diffusion.</li>
	<li>Add 1 mL of 1 mg/mL p-nitrophenyl phosphate, disodium hexahydrate in Tris-HCl. Incubate at 37 &#176;C, 110 rpm for an additional 10 h. Read the supernatant absorbance at 415 nm.</li>
</ol>

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The authors have nothing to disclose.

Both decellularized matrices and 3D printed PCL scaffolds have independently been shown to allow adhesion and proliferation of cells, validating their use for osteochondral repair10,11,12. The use of decellularized matrix in engineering approaches to tissue repair has been a subject of much interest and success in the recent past2,3,14,15. We have previously noted the increased migration, adhesion, proliferation, and overall maintenance of resulting tissues when compared to traditional techniques2,15,16,17,18. Many have attributed these desirable results to the process of dynamic reciprocity through which the host cells receive cues from the decellularized matrix, dynamically respond, and replicate the cues for new cells by laying more extracellular matrix that typically resembles what is already present19,20,21,22. While this has been studied for many applications, many of the processes are not easy to replicate and cannot be adapted for different uses, unable to successfully create highly patient-specific constructs, unable to create complex morphologies, and unable to withstand in vivo forces2,3,4,13,14,15,16.
The innovative approach proposed herein avoids both transient and prolonged exposure to high temperatures that are typically required by 3D printing when using traditional mechanical extrusion-based FDM printers with a new carrier vehicle. Moreover, the carrier vehicle (PLA microspheres) helps protect the encapsulated biologic for the relatively short period of time it is exposed to heat and provides an all-in-one treatment option for fast turnover in the clinic2. The methods proposed herein demonstrate how to create biologically active filaments for 3D printing and scaffolds via 3D printing where a critical step is the extrusion of the filament and the printing of those filaments at low temperatures (65 &#176;C). The ability of the encapsulated proteins to remain functional was demonstrated by using ALP as a surrogate for DM throughout the process. ALP was used as the enzyme must be in a very specific functional conformation in order to catalyze the colorimetric reaction assessed in this protocol23. If the filament is not extruded with careful attention to diameter, temperature, and speed, the biologic activity and utility for 3D printing would be sacrificed.
In this protocol, microspheres containing decelluarized matrices (PLA-DM) were co-extruded with PCL to make 3D printable filaments and 3D printed scaffolds for osteochondral repair (PLA-DM/PCL). As mentioned in the protocol steps, continuous monitoring of the filament production process is essential for high quality of the filament. Adjustments must be made to extrusion speed, spooler speed, and extrusion temperature in order to maintain the desired filament diameter (typically 1.75 mm). The presence of the microspheres in the scaffolds is confirmed by SEM imaging and the maintenance of enzyme functionality is demonstrated by an alkaline phosphatase assay. Note that this protocol is limited by the large amount of microspheres required for production and the relatively lower resolution of fused deposition modeling to other 3D printing modalities. Nevertheless, the increased biologic activity is a major advancement. Although not the focus of this protocol, subsequent studies will concentrate on the impact of the microspheres on mechanical strength, cell migration and differentiation, and further characterizations of the scaffolds. Overall, the technique described herein allows decellularized matrix and other proteins to be printed at lower temperatures than previously allowed and in thermally protective barriers in order to maintain function and mechanical strength2,3.

Current tissue engineering techniques for clinical applications such as bone, cartilage, tendon, and ligament reconstruction use auto- and allografts to repair damaged tissue. Each of these techniques is performed routinely as a &#34;gold standard&#34; in clinical practice by first harvesting the donor tissue either from the patient or a cadaveric match, and then placing the donor tissue into the defect site2. However, these strategies are limited by donor site morbidity, donor site scarcity for large defects, risk of infection, and difficulty finding grafts that match the desired geometry. In addition, studies have shown that allografts used for reconstruction have reduced mechanical and biologic properties when compared with native tissue3. With these considerations in mind, tissue engineers have recently turned to three dimensional (3D) bioprinting to produce custom, complex geometries that are biologically active and designed to accommodate defect size and shape while providing sufficient mechanical properties until biologic remodeling is complete.
Ideally, a 3D-printed scaffold would consist of a polymeric backbone that can retain the required mechanical stability of native tissue while the incorporated biologics offer biochemical cues to surrounding cells, leading to their migration, proliferation, differentiation, and tissue production2,5. Unfortunately, most constructs that contain biologic components are made with gels or polymers that are too weak to withstand in vivo forces experienced by the targeted tissues for auto/allograft reconstruction. Other polymers such as polylactic acid (PLA) are bioresorbable, 3D printable and structurally sound, but are printed at temperatures at or above 210 &#176;C - making it impossible for biologics to be co-printed during fabrication. Polycaprolactone (PCL) is another FDA-cleared, bioresorbable polymer that can be 3D printed at a lower temperature (65 &#176;C), which has become increasingly popular in fabricating patient-specific implants with complex morphologies5,6,7,8,9. However, most bioprinters using pneumatic technology make it impossible to print PCL at lower temperatures where biological activities can remain unharmed. To date, the integration of these polymers with auto/allografts into a novel printable biomaterial has yet to be accomplished. In the absence of such a material, a true tissue engineered approach to tissue reconstruction is unlikely. Therefore, we have sought to combine PLA, PCL, and decellularized allograft matrices (DM) to utilize the advantages of each material in order to manufacture a viable construct capable of reconstructing complex tissues. This process would provide the initial mechanical strength necessary to resist in vivo forces and the thermal stability to accommodate additive manufacturing in a construct that induces formation of the desired tissue.
In a recent attempt to address the aforementioned hurdles, we showed that it is feasible to encapsulate decellularized cartilage extracellular matrix within a thermally protective PLA barrier that can be extruded within PCL filaments, maintaining the ability of DM to influence surrounding host cells2. This has inspired us to seek clinically effective approaches for tissue reconstruction. In the current study, we utilize the platform technology to build all-in-one scaffolds that include PLA, DM, and PCL (PLA-DM/PCL).
Our goal is to improve the efficacy and utility of allografts using the proposed novel biofabrication technique to more accurately recapitulate native tissue, to ultimately use them in various applications.

<table><tbody><tr><td>Sieve machine</td><td>Haver &amp;amp; Boecker Tyler</td><td>Ro-Tap RX 29-E Pure</td><td></td></tr><tr><td>Sieve 90 um</td><td>Fisherbrand</td><td>170328156</td><td>No. 170</td></tr><tr><td>Sieve 53 um</td><td>Fisherbrand</td><td>162513588</td><td>No. 270</td></tr><tr><td>Sieve 106 um</td><td>Fisherbrand</td><td>162018121</td><td>No. 140</td></tr><tr><td>Sputter coater</td><td>Leica</td><td>n/a</td><td></td></tr><tr><td>Scanning Electron Microscope</td><td>Hitachi, USA</td><td>n/a</td><td></td></tr><tr><td>Filabot EX2</td><td>Filabot.com</td><td>FB00061</td><td></td></tr><tr><td>Filabot Spooler</td><td>Filabot.com</td><td>FB00073</td><td></td></tr><tr><td>CAPA 6506</td><td>Perstorp</td><td>24980-41-4</td><td></td></tr><tr><td>Phosphate buffered saline, PBS</td><td>Gibco</td><td>10010023</td><td></td></tr><tr><td>6&quot; Fan</td><td>Comfort Zone, Amazon</td><td>n/a</td><td></td></tr><tr><td>Ultrasonic Water Bath</td><td>Cole Parmer</td><td>SK-08895-13</td><td></td></tr><tr><td>Dreamer</td><td>FlashForge</td><td>n/a</td><td></td></tr><tr><td>Drum Mixer</td><td>Custom made</td><td>n/a</td><td>Similar piece of equipment: https://www.coleparmer.com/i/argos-technologies-flexiroll-digital-tube-roller-shaker-120-vac/0439744?PubID=UX&amp;amp;persist=true&amp;amp;ip=&lt;br/&gt; no&amp;amp;gclid=CjwKCAjw-&lt;br/&gt; dXaBRAEEiwAbwCi5khGDMz0&lt;br/&gt; dTjsraEsBGfhMEH7ytx&lt;br/&gt; LQWGUPNgUJYQ1p3vj_yxkYoI_&lt;br/&gt; ixoC9GwQAvD_BwE</td></tr><tr><td>Micro Balance</td><td>Mettler Toledo, Fisher Scientific</td><td>01-913-851</td><td></td></tr><tr><td>Simplify3D</td><td>Simplify3D</td><td>n/a</td><td></td></tr><tr><td>SolidWorks</td><td>SolidWorks</td><td>n/a</td><td></td></tr><tr><td>Microspheres</td><td>Produced in-house, see concurrently submitted JoVE submission</td><td></td><td></td></tr><tr><td>p-nitrophenyl phosphate, disodium salt, hexahydrate</td><td>Millipore</td><td>4876-5GM</td><td></td></tr><tr><td>Phosphatase, alkaline</td><td>Roche Diagnostics GmbH</td><td>10 713 023 001</td><td></td></tr><tr><td>Absorbance Reader</td><td>Tecan</td><td>Sunrise</td><td></td></tr><tr><td>Tris-HCl Buffer</td><td>Sigma-Aldrich</td><td>T6455-100ML</td><td></td></tr><tr><td>Heated shaker</td><td>New Brunswick Scientific</td><td>Excella E24</td><td></td></tr></tbody></table>

novel process for 3d printing decellularized matrices

3D bioprinting aims to create custom scaffolds that are biologically active and accommodate the desired size and geometry. A thermoplastic backbone can provide mechanical stability similar to native tissue while biologic agents offer compositional cues to progenitor cells, leading to their migration, proliferation, and differentiation to reconstitute the original tissues/organs1,2. Unfortunately, many 3D printing compatible, bioresorbable polymers (such as polylactic acid, PLA) are printed at temperatures of 210 &#176;C or higher - temperatures that are detrimental to biologics. On the other hand, polycaprolactone (PCL), a different type of polyester, is a bioresorbable, 3D printable material that has a gentler printing temperature of 65 &#176;C. Therefore, it was hypothesized that decellularized extracellular matrix (DM) contained within a thermally protective PLA barrier could be printed within PCL filament and remain in its functional conformation. In this work, osteochondral repair was the application for which the hypothesis was tested. As such, porcine cartilage was decellularized and encapsulated in polylactic acid (PLA) microspheres which were then extruded with polycaprolactone (PCL) into filament to produce 3D constructs via fused deposition modeling. The constructs with or without the microspheres (PLA-DM/PCL and PCL(-), respectively) were evaluated for differences in surface features.

After sieving, microspheres should appear uniform and be free from aggregates. Under SEM, the sieved microspheres may have small pores on their surface, but will otherwise be spherical and smooth, as shown in Figure 1. All extruded filaments should be of uniform diameter and circular cross-section. A filament that contains microspheres (PLA-DM/PCL) will have a slightly more matte finish while a PCL-only (PCL(-)) filament would look more glossy. The PLA-DM/PCL filament would also feel coarser to the touch than the PCL(-) filament. Scaffolds should be printed in the desired geometry which was dictated by the software in step 4.1. The scaffold quality and shape should be repeatable and uniform from one print to another. After printing, scaffolds with and without microspheres will be difficult to distinguish macroscopically, but under SEM, microspheres should be visible on the surface and throughout the constructs. Under SEM, PCL(-) filament will appear smooth, with some striations as an artifact of the extrusion process (Figure 4B). Microspheres should be visible both protruding through and under the surface of the PLA-DM/PCL scaffolds (see Figure 4C). When using ALP as a surrogate for DM, the functionality of the enzyme within the scaffold should be maintained with significantly higher absorbance (t-test, p &#60; 0.05) at 415 nm than those of blank PCL(-) scaffolds, 0.297 &#177; 0.023 and 0.166 &#177; 0.012, respectively, Figure 5.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58720/58720fig1.jpg" /> 
Figure 1.&#160;Representative macroscopic (left) and SEM (right) images of microspheres after preparation and sieving2. Note that the microspheres are spherical and in the appropriate size range (53-106 &#181;m diameter). <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58720/58720fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58720/58720fig2.jpg" /> 
Figure 2. Custom made rolling mixer. The custom-made rolling mixer is used for combining the microspheres with PCL powder. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58720/58720fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58720/58720fig3.jpg" /> 
Figure 3. Filament production setup. The outlet of the extruder is set approximately 60 cm from the inlet of the spooler. Desktop fans are located near the heating element and approximately half way between the extruder and spooler. The spooler can optionally be elevated 3-4 inches above the benchtop. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58720/58720fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58720/58720fig4.jpg" /> 
Figure 4. Quality Assessments. (A) PCL(-) (left) and PLA-DM/PCL (right) scaffolds are difficult to distinguish macroscopically. (B) Under SEM, the PCL(-) scaffold appears mostly smooth, with a few striations as artifacts of the printing process. (C) Under SEM, microspheres are visible in the PLA-DM/PCL samples. Some of the microspheres are indicated using arrows. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58720/58720fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58720/58720fig5.jpg" /> 
Figure 5.&#160;Representative results of an ALP colorimetric assay. The absorbance of ALP-containing scaffolds (PLA-ALP/PCL) is significantly higher than that of the PCL-only (PCL(-)) scaffolds, indicating that the ALP enzyme catalyzed the reaction from colorless p-nitrophenyl phosphate to p-nitrophenol and inorganic phosphate. This demonstrates that the ability to print functional proteins with the process described in this manuscript. * significantly different (p &#60; 0.05) from all other groups. Error bars indicate standard deviation. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/58720/58720fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Novel Process for 3D Printing Decellularized Matrices at JoVE.com

Novel Process for 3D Printing Decellularized Matrices

This protocol describes the production of polycaprolactone (PCL) filament with embedded polylactic acid (PLA) microspheres which contain decellularized matrices (DM) for 3D printing of structural tissue engineering constructs.

3D bioprinting aims to create custom scaffolds that are biologically active and accommodate the desired size and geometry. A thermoplastic backbone can ...

novel-process-for-3d-printing-decellularized-matrices

Universidad San Sebastian

Research

JoVE Journal

Bioengineering

7.0K Views.  University of Cincinnati. This protocol describes the production of polycaprolactone (PCL) filament with embedded polylactic acid (PLA) microspheres which contain decellularized matrices (DM) for 3D printing of structural tissue engineering constructs.

Video: Novel Process for 3D Printing Decellularized Matrices

A Decellularization Methodology for the Production of a Natural Acellular Intestinal Matrix

Successful tissue engineering involves the combination of scaffolds with appropriate cells in vitro or in vivo. Scaffolds may be synthetic, naturally-derived or derived from tissues/organs. The latter are obtained using a technique called decellularization. Decellularization may involve a combination of physical, chemical, and enzymatic methods. The goal of this technique is to remove all cellular traces whilst maintaining the macro- and micro-architecture of the original tissue.
Intestinal tissue engineering has thus far used relatively simple scaffolds that do not replicate the complex architecture of the native organ. The focus of this paper is to describe an efficient decellularization technique for rat small intestine. The isolation of the small intestine so as to ensure the maintenance of a vascular connection is described. The combination of chemical and enzymatic solutions to remove the cells whilst preserving the villus-crypt axis in the luminal aspect of the scaffold is also set out. Finally, assessment of produced scaffolds for appropriate characteristics is discussed.

The article describes a methodology for the production of an acellular matrix from rat intestine. The derivation of intestinal scaffolds is important for future applications in tissue engineering, stem cell biology and drug testing.

Successful tissue engineering involves the  combination of scaffolds with appropriate cells in vitro or in vivo.  Scaffolds may be synthetic, ...

Processing of Human Cardiac Tissue Toward Extracellular Matrix Self-assembling Hydrogel for In Vitro and In Vivo Applications

Acellular extracellular matrix preparations are useful for studying cell-matrix interactions and facilitate regenerative cell therapy applications. Several commercial extracellular matrix products are available as hydrogels or membranes, but these do not possess tissue-specific biological activity. Because perfusion decellularization is usually not possible with human heart tissue, we developed a 3-step immersion decellularization process. Human myocardial slices procured during surgery are first treated with detergent-free hyperosmolar lysis buffer, followed by incubation with the ionic detergent, sodium dodecyl sulfate, and the process is completed by exploiting the intrinsic DNase activity of fetal bovine serum. This technique results in cell-free sheets of cardiac extracellular matrix with largely preserved fibrous tissue architecture and biopolymer composition, which were shown to provide specific environmental cues to cardiac cell populations and pluripotent stem cells. Cardiac extracellular matrix sheets can then be further processed into a microparticle powder without further chemical modification, or, via short-term pepsin digestion, into a self-assembling cardiac extracellular matrix hydrogel with preserved bioactivity.

Processing of Human Cardiac Tissue Toward Extracellular Matrix Self-assembling Hydrogel for In Vitro and In Vivo Applications

This protocol describes the complete decellularization of human myocardium while preserving its extracellular matrix components. Further processing of the extracellular matrix results in the production of microparticles and a cytoprotective self-assembling hydrogel.

Acellular extracellular matrix preparations are useful for studying cell-matrix interactions and facilitate regenerative cell therapy applications. ...

Developmental Biology

Fabrication of Extracellular Matrix-derived Foams and Microcarriers as Tissue-specific Cell Culture and Delivery Platforms

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus of this article is on the methods for fabricating ECM-derived porous foams and microcarriers for use as biologically-relevant substrates in advanced 3D in vitro cell culture models or as pro-regenerative scaffolds and cell delivery systems for tissue engineering and regenerative medicine. Using decellularized tissues or purified insoluble collagen as a starting material, the techniques can be applied to synthesize a broad array of tissue-specific bioscaffolds with customizable geometries. The approach involves mechanical processing and mild enzymatic digestion to yield an ECM suspension that is used to fabricate the three-dimensional foams or microcarriers through controlled freezing and lyophilization procedures. These pure ECM-derived scaffolds are highly porous, yet stable without the need for chemical crosslinking agents or other additives that may negatively impact cell function. The scaffold properties can be tuned to some extent by varying factors such as the ECM suspension concentration, mechanical processing methods, or synthesis conditions. In general, the scaffolds are robust and easy to handle, and can be processed as tissues for most standard biological assays, providing a versatile and user-friendly 3D cell culture platform that mimics the native ECM composition. Overall, these straightforward methods for fabricating customized ECM-derived foams and microcarriers may be of interest to both biologists and biomedical engineers as tissue-specific cell-instructive platforms for in vitro and in vivo applications.

The tissue-specific extracellular matrix (ECM) is a key mediator of cell function. This article describes methods for synthesizing pure ECM-derived foams and microcarriers that are stable in culture without the need for chemical crosslinking for applications in advanced 3D in vitro cell culture models or as pro-regenerative bioscaffolds.

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus ...

Comparable Decellularization of Fetal and Adult Cardiac Tissue Explants as 3D-like Platforms for In Vitro Studies

Current knowledge of extracellular matrix (ECM)-cell communication translates to large two-dimensional (2D) in vitro culture studies where ECM components are presented as a surface coating. These culture systems constitute a simplification of the complex nature of the tissue ECM that encompasses biochemical composition, structure, and mechanical properties. To better emulate the ECM-cell communication shaping the cardiac microenvironment, we developed a protocol that allows for the decellularization of the whole fetal heart and adult left ventricle tissue explants simultaneously for comparative studies. The protocol combines the use of a hypotonic buffer, a detergent of anionic surfactant properties, and DNase treatment without any requirement for specialized skills or equipment. The application of the same decellularization strategy across tissue samples from subjects of various age is an alternative approach to perform comparative studies. The present protocol allows the identification of unique structural differences across fetal and adult cardiac ECM mesh and biological cellular responses. Furthermore, the herein methodology demonstrates a broader application being successfully applied in other tissues and species with minor adjustments, such as in human intestine biopsies and mouse lung.

The cardiac extracellular matrix (ECM) is a complex network of molecules that orchestrate key processes in tissues and organs while enduring physiological remodeling throughout life. Standardized decellularization of fetal and adult hearts permits comparative experimental studies of both tissues in a 3D context by capturing native architecture and biomechanical properties.

Current knowledge of extracellular matrix (ECM)-cell communication translates to large two-dimensional (2D) in vitro culture studies where ECM components ...

Preparation of 3D Decellularized Matrices from Fetal Mouse Skeletal Muscle for Cell Culture

The extracellular matrix (ECM) plays a crucial role in providing structural support for cells and conveying signals that are important for various cellular processes. Two-dimensional (2D) cell culture models oversimplify the complex interactions between cells and the ECM, as the lack of a complete three-dimensional (3D) support can alter cell behavior, making them inadequate for understanding in vivo processes. Deficiencies in ECM composition and cell-ECM interactions are important contributors to a variety of different diseases. 
One example is LAMA2-congenital muscular dystrophy (LAMA2-CMD), where the absence or reduction of functional laminin 211 and 221 can lead to severe hypotony, detectable at or soon after birth. Previous work using a mouse model of the disease suggests that its onset occurs during fetal myogenesis. The present study aimed to develop a 3D in vitro model permitting the study of the interactions between muscle cells and the fetal muscle ECM, mimicking the native microenvironment. This protocol uses deep back muscles dissected from E18.5 mouse fetuses, treated with a hypotonic buffer, an anionic detergent, and DNase. The resultant decellularized matrices (dECMs) retained all ECM proteins tested (laminin &#945;2, total laminins, fibronectin, collagen I, and collagen IV) compared to the native tissue. 
When C2C12 myoblasts were seeded on top of these dECMs, they penetrated and colonized the dECMs, which supported their proliferation and differentiation. Furthermore, the C2C12 cells produced ECM proteins, contributing to the remodeling of their niche within the dECMs. The establishment of this in vitro platform provides a new promising approach to unravel the processes involved in the onset of LAMA2-CMD, and has the potential to be adapted to other skeletal muscle diseases where deficiencies in communication between the ECM and skeletal muscle cells contribute to disease progression.

In this work, a decellularization protocol was optimized to obtain decellularized matrices of fetal mouse skeletal muscle. C2C12 myoblasts can colonize these matrices, proliferate, and differentiate. This in vitro model can be used to study cell behavior in the context of skeletal muscle diseases such as muscular dystrophies.

The extracellular matrix (ECM) plays a crucial role in providing structural support for cells and conveying signals that are important for various ...

Fabrication of Decellularized Cartilage-derived Matrix Scaffolds

Osteochondral defects lack sufficient intrinsic repair capacity to regenerate functionally sound bone and cartilage tissue. To this extent, cartilage research has focused on the development of regenerative scaffolds. This article describes the development of scaffolds that are completely derived from natural cartilage extracellular matrix, coming from an equine donor. Potential applications of the scaffolds include producing allografts for cartilage repair, serving as a scaffold for osteochondral tissue engineering, and providing in vitro models to study tissue formation. By decellularizing the tissue, the donor cells are removed, but many of the natural bioactive cues are thought to be retained. The main advantage of using such a natural scaffold in comparison to a synthetically produced scaffold is that no further functionalization of polymers is required to drive osteochondral tissue regeneration. The cartilage-derived matrix scaffolds can be used for bone and cartilage tissue regeneration in both in vivo and in vitro settings.

Decellularized cartilage-derived scaffolds can be used as a scaffold to guide cartilage repair and as a means to regenerate osteochondral tissue. This paper describes the decellularization process in detail and provides suggestions to use these scaffolds in in vitro settings.

Osteochondral defects lack sufficient intrinsic repair capacity to regenerate functionally sound bone and cartilage tissue. To this extent, cartilage ...

Pancreatic Tissue-Derived Extracellular Matrix Bioink for Printing 3D Cell-Laden Pancreatic Tissue Constructs

The transplantation of pancreatic islets is a promising treatment for patients who suffer from type 1 diabetes accompanied by hypoglycemia and secondary complications. However, islet transplantation still has several limitations such as the low viability of transplanted islets due to poor islet engraftment and hostile environments. In addition, the insulin-producing cells differentiated from human pluripotent stem cells have limited ability to secrete sufficient hormones that can regulate the blood glucose level; therefore, improving the maturation by culturing cells with proper microenvironmental cues is strongly required. In this article, we elucidate protocols for preparing a pancreatic tissue-derived decellularized extracellular matrix (pdECM) bioink to provide a beneficial microenvironment that can increase glucose sensitivity of pancreatic islets, followed by describing the processes for generating 3D pancreatic tissue constructs using a microextrusion-based bioprinting technique.

Decellularized extracellular matrix (dECM) can provide suitable microenvironmental cues to recapitulate the inherent functions of target tissues in an engineered construct. This article elucidates the protocols for the decellularization of pancreatic tissue, evaluation of pancreatic tissue-derived dECM bioink, and generation of 3D pancreatic tissue constructs using a bioprinting technique.

The transplantation of pancreatic islets is a promising treatment for patients who suffer from type 1 diabetes accompanied by hypoglycemia and secondary ...

Fabrication of a Crystalline Nanocellulose Embedded Agarose Biomaterial Ink for Bone Marrow-Derived Mast Cell Culture

Three-dimensional (3D) bioprinting utilizes hydrogel-based composites (or biomaterial inks) that are deposited in a pattern, forming a substrate onto which cells are deposited. Because many biomaterial inks can be potentially cytotoxic to primary cells, it is necessary to determine the biocompatibility of these hydrogel composites prior to their utilization in costly 3D tissue engineering processes. Some 3D culture methods, including bioprinting, require that cells be embedded into a 3D matrix, making it difficult to extract and analyze the cells for changes in viability and biomarker expression without eliciting mechanical damage. This protocol describes as proof of concept, a method to assess the biocompatibility of a crystalline nanocellulose (CNC) embedded agarose composite, fabricated into a 24-well culture system, with mouse bone marrow-derived mast cells (BMMCs) using flow cytometric assays for cell viability and biomarker expression.
After 18 h of exposure to the CNC/agarose/D-mannitol matrix, BMMC viability was unaltered as measured by propidium iodide (PI) permeability. However, BMMCs cultured on the CNC/agarose/D-mannitol substrate appeared to slightly increase their expression of the high-affinity IgE receptor (Fc&#949;RI) and the stem cell factor receptor (Kit; CD117), although this does not appear to be dependent on the amount of CNC in the bioink composite. The viability of BMMCs was also assessed following a time course exposure to hydrogel scaffolds that were fabricated from a commercial biomaterial ink composed of fibrillar nanocellulose (FNC) and sodium alginate using a 3D extrusion bioprinter. Over a period of 6-48 h, the FNC/alginate substrates did not adversely affect the viability of the BMMCs as determined by flow cytometry and microtiter assays (XTT and lactate dehydrogenase). This protocol describes an efficient method to rapidly screen the biochemical compatibility of candidate biomaterial inks for their utility as 3D scaffolds for post-print seeding with mast cells.

This protocol highlights a method to rapidly assess the biocompatibility of a crystalline nanocellulose (CNC)/agarose composite hydrogel biomaterial ink with mouse bone marrow-derived mast cells in terms of cell viability and phenotypic expression of the cell surface receptors, Kit (CD117) and high-affinity IgE receptor (Fc&#949;RI).

Three-dimensional (3D) bioprinting utilizes hydrogel-based composites (or biomaterial inks) that are deposited in a pattern, forming a substrate onto ...

Decellularization for the Preparation of Highly Preserved Human Acellular Skin Matrix for Regenerative Medicine

Extracellular matrix (ECM) provides biophysical and biochemical stimuli to support self-renewal, proliferation, survival, and differentiation of surrounding cells due to its content of diverse bioactive molecules. Due to these characteristics, the ECM has been recently considered a promising candidate for the creation of biological scaffolds to boost tissue regeneration. Emerging studies have demonstrated that decellularized human tissues could resemble the native ECM in their structural and biochemical profiles, preserving the three-dimensional (3D) architecture and the content of fundamental biological molecules. Hence, decellularized ECM can be employed to promote tissue remodeling, repair, and functional reconstruction of many organs. Selecting the appropriate decellularization procedure is crucial to obtain acellular tissues that retain the characteristics of the ideal microenvironment for cells. 
The protocol described here provides a detailed step-by-step description of the decellularization method to obtain a reproducible and effective cell-free biological ECM. Skin fragments from patients undergoing plastic surgery were scaled down and decellularized using a combination of sodium dodecylsulfate (SDS), Triton X-100, and antibiotics. To promote the regular and homogeneous transport of the solution through the samples, they were enclosed in embedding cassettes to ensure protection from mechanical insults. After the decellularization procedure, the snow-white color of skin fragments indicated complete and successful decellularization. Additionally, decellularized samples showed an intact and well-preserved architecture. The results suggest that the proposed decellularization method was effective, fast, and reproducible and protected samples from architectural damages.

Decellularized human skin is suitable for tissue regeneration. A major issue of decellularization is the preservation of the native architecture, along with the appropriate content of structural proteins, glycosaminoglycans (GAGs), and growth factors. The method proposed allows fast and effective decellularization, producing decellularized skin with well-preserved native features.

Extracellular matrix (ECM) provides biophysical and biochemical stimuli to support self-renewal, proliferation, survival, and differentiation of ...

Comparative Study of Decellularization Techniques for Bovine Lung ECM Hydrogels

Development and Characterization of Decellularized Lung Extracellular Matrix Hydrogels

The use of extracellular matrix (ECM)-derived hydrogels in tissue engineering has become increasingly popular, as they can mimic cells&#39; natural environment in vitro. However, maintaining the native biochemical content of the ECM, achieving mechanical stability, and comprehending the impact of the decellularization process on the mechanical properties of the ECM hydrogels are challenging. Here, a pipeline for decellularization of bovine lung tissue using two different protocols, downstream characterization of the effectiveness of decellularization, fabrication of reconstituted decellularized lung ECM hydrogels and assessment of their mechanical and cytocompatibility properties were described. Decellularization of the bovine lung was pursued using a physical (freeze-thaw cycles) or chemical (detergent-based) method. Hematoxylin and Eosin staining was performed to validate the decellularization and retention of major ECM components. For the evaluation of residual collagen and sulfated glycosaminoglycan (sGAG) content within the decellularized samples, Sirius red and Alcian blue staining techniques were employed, respectively. Mechanical properties of the decellularized lung ECM hydrogels were characterized by oscillatory rheology. The results suggest that decellularized bovine lung hydrogels can provide a reliable organotypic<span style="font-size: 11pt; font-family: Calibri, sans-serif; color: black; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;">&#160;alternative to commercial ECM products by retaining most native ECM components. Furthermore, these findings reveal that the decellularization method of choice significantly affects gelation kinetics as well as the stiffness and viscoelastic properties of resulting hydrogels.

Author Spotlight: Optimizing Bovine Lung Decellularization for Organotypic Hydrogels

The protocol elucidates two distinct decellularization methodologies applied to native bovine pulmonary tissues, providing a comprehensive account of their respective characterizations.

The use of extracellular matrix (ECM)-derived hydrogels in tissue engineering has become increasingly popular, as they can mimic cells&#39; natural ...

Novel Process for 3D Printing Decellularized Matrices

Summary

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Chapters in this video

A Decellularization Methodology for the Production of a Natural Acellular Intestinal Matrix

Processing of Human Cardiac Tissue Toward Extracellular Matrix Self-assembling Hydrogel for In Vitro and In Vivo Applications

Fabrication of Extracellular Matrix-derived Foams and Microcarriers as Tissue-specific Cell Culture and Delivery Platforms

Comparable Decellularization of Fetal and Adult Cardiac Tissue Explants as 3D-like Platforms for In Vitro Studies

Preparation of 3D Decellularized Matrices from Fetal Mouse Skeletal Muscle for Cell Culture

Fabrication of Decellularized Cartilage-derived Matrix Scaffolds

Pancreatic Tissue-Derived Extracellular Matrix Bioink for Printing 3D Cell-Laden Pancreatic Tissue Constructs

Fabrication of a Crystalline Nanocellulose Embedded Agarose Biomaterial Ink for Bone Marrow-Derived Mast Cell Culture

Decellularization for the Preparation of Highly Preserved Human Acellular Skin Matrix for Regenerative Medicine

Development and Characterization of Decellularized Lung Extracellular Matrix Hydrogels