Name: 3d microtissues for injectable regenerative therapy and high-throughput drug screening
Uploaded: 2017-10-04T11:45:00
Description: Watch this Scientific Journal Video about 3D Microtissues for Injectable Regenerative Therapy and High-throughput Drug Screening at JoVE.com

This work was financially supported by the National Natural Science Foundation of China (Grants: 81522022, 51461165302). The authors would like to acknowledge all Du lab members for general assistance.

Animal experiments followed strict protocol approved by the Animal Ethics Committee on the Center of Biomedical Analysis, Tsinghua University. Under approval of Ethics Committee, human adipose tissue was obtained from Department of Plastic Surgery of Peking Union Hospital with informed consent from the patients.
1. Fabrication of 3D Microcryogels
<ol>
	<li>Design and fabrication of microstencil array chips
	<ol>
		<li>Use a commercial software to design arrays of specific ge...

Regenerative medicine and in vitro models for drug screening are two important applications for tissue engineering5,6,7,8,9. While these two applications have vastly different needs, a common ground between them lies in the need for a more biomimetic culturing condition to enhance cell functions19. Only with improved cell funct...

Traditional cell culture on flattened two-dimensional (2D) surfaces, such as a culture dish or multi-well plates, can hardly elicit cell behaviors close to their native states. Accurate recapitulation of native cellular microenvironments, which comprise of various cell types, extracellular matrices and bioactive soluble factors in three-dimensional (3D) architectures1,2,3,4, is essential to construct biomimicking tissues in vitro for applications in tissue engineering, regenerative medicine, fundamental biology research and drug discovery5,6,7,8,9.
In lieu of 2D cell culture, 3D cell culture is widely used to advance biomimetic micro-architectural and functional features of cells cultured in vitro. A popular 3D cell culture method is to aggregate cells into spheroids7,8,9,10. Cellular spheroids could be injected to injured tissues with enhanced cellular retention and survival in comparison to injection of dispersed cells. However, non-uniform spheroid sizes and inevitable mechanical injury imposed on cells by fluid shear force during injection lead to poor cell therapeutic effects11,12,13. Similarly, the inherent non-uniformity during aggregation of spheroids has made their translation to 3D cell-based high-throughput drug screening challenging10.
Another method for 3D cell culture is achieved with the assistance of biomaterials, which typically encapsulates cells in aqueous hydrogels or porous scaffolds. It allows for greater flexibilities in constructing 3D architectures. For therapy, cells encapsulated in bulk scaffolds are usually delivered to animal body via surgical implantation, which is invasive and traumatic, hence restricting its wide translation to bedside. On the other hand, aqueous hydrogels enable minimally invasive therapy by injecting cells suspended in hydrogel precursor solution into animal bodies, allowing in situ gelation via thermo-, chemical or enzymatic crosslinking11. However, as cells are delivered whilst the hydrogel precursors are still in an aqueous state, they are also exposed to mechanical shear during injection. Not only so, chemical or enzymatic crosslinking during in situ gelation of hydrogel could also impose damage to cells within. For drug screening, biomaterial-assisted cell cultures face problems with uniformity, controllability and throughput. Using hydrogels, cells are typically involved during gelation, by which the process may affect cell viability and function. Gelation during cell seeding also hampers usage by most high-throughput equipment, since the hydrogel may need to be kept on ice to prevent gelation before cell seeding, and the hydrogel might jam dispensing tips, which are usually very thin to ensure accuracy for high-throughput screening. Pre-formed scaffolds could potentially separate biomaterial fabrication procedures from cell culture, however most scaffold-based products are available as bulk materials with relatively lower throughput14.
To overcome some of the shortcomings of current 3D culture methods, we have developed a microfabrication-cryogelation integrated technology to fabricate an off-the-shelf and user-friendly microcryogel array chip15. In this protocol, gelatin is selected to exemplify the microcryogel fabrication technique as it is biocompatible, degradable, cost-effective, and no further modification is required for cell attachment. Other polymers of natural or synthetic sources could also be used for fabrication, depending on the application. Via this technology, we can fabricate miniaturized and highly elastic microcryogels with controllable size, shape and layout. When loaded with a variety of cell types, 3D microtissues could be formed for various applications. These unique features enable desired injectability, cell protection and site-directed retention after injection in vivo for enhanced therapeutic effects. Not only so, the microcryogels could be further processed to form 3D microtissue arrays that are compatible with common laboratory equipment and instruments to realize high-throughput cell culture for versatile drug screening and other cellular assays. Herein, we shall detail the fabrication process of microcryogels and its post-treatment as individual 3D microtissues or 3D microtissue arrays for two important applications, cell therapy and drug screening, respectively10,15.

<table border="0" cellpadding="0" cellspacing="0" width="803">
	<tbody>
		<tr height="53">
			<td height="53" style="height:53px;width:199px;">Gelatin</td>
			<td style="width:211px;">sigma</td>
			<td style="width:111px;">G7041</td>
			<td style="width:283px;">All other reagents were purchased from Sigma-Aldrich (St. Louis, MO) unless otherwise indicated.</td>
		</tr>
		<tr height="53">
			<td height="53" style="height:53px;width:199px;">Glutaraldehyde&#160;</td>
			<td style="width:211px;">J&#38;K</td>
			<td style="width:111px;">902042</td>
			<td style="width:283px;">Used as crosslinker in preparation of material.</td>
		</tr>
		<tr height="53">
			<td height="53" style="height:53px;width:199px;">Glass cover slip (24X50mm)</td>
			<td style="width:211px;">CITOGLASS, China</td>
			<td style="width:111px;">10212450C</td>
			<td style="width:283px;">To scrape prcursor solution onto microstencils array chips.</td>
		</tr>
		<tr height="53">
			<td height="53" style="height:53px;width:199px;">Sodium&#160;borohydride, NaBH4</td>
			<td style="width:211px;">Beijing Chemical Works</td>
			<td style="width:111px;">116-8</td>
			<td style="width:283px;">To wash remaining glutaraldehyde away after gelation.</td>
		</tr>
		<tr height="53">
			<td height="53" style="height:53px;width:199px;">Vacuum jar</td>
			<td style="width:211px;">asperts, China</td>
			<td style="width:111px;">VC8130</td>
			<td style="width:283px;">To preserve microgels under vacuum.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:199px;">Polymethylmethacrylate (PMMA) sheets&#160;</td>
			<td style="width:211px;">Sunjin Electronics Co., Ltd, China</td>
			<td style="width:111px;"></td>
			<td style="width:283px;">Ordinary PMMA sheets.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Rayjet laser system</td>
			<td style="width:211px;">Rayjet, Australia</td>
			<td style="width:111px;">Rayjet 50 C30</td>
			<td style="width:283px;">To engrave PMMA sheets to form wells.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Plasma Cleaner</td>
			<td style="width:211px;">Mycro Technologies, USA</td>
			<td style="width:111px;">PDC-32G</td>
			<td style="width:283px;">To make PMMA hyphophilic.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Lyophilizer</td>
			<td style="width:211px;">Boyikang, China</td>
			<td style="width:111px;">SC21CL</td>
			<td style="width:283px;">To lyophilize materials.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Trypan Blue solution (0.4%)</td>
			<td style="width:211px;">Zhongkekeao, China</td>
			<td style="width:111px;">DA0065</td>
			<td style="width:283px;">To dye microgels.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Doxorubicin hydrochloride</td>
			<td style="width:211px;">ENERGY CHEMICAL, China</td>
			<td style="width:111px;">A01E0801360010</td>
			<td style="width:283px;">To test drug resistance of cells in 2D or 3D microgel.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:199px;">Live/dead assay</td>
			<td style="width:211px;">Dojindo Molecular Technologies (Kumamoto, Japan)</td>
			<td style="width:111px;">CS01-10</td>
			<td style="width:283px;">To distinguish alive and dead cells.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Cell Titer-Blue</td>
			<td style="width:211px;">Promega (Wisconsin, USA).</td>
			<td style="width:111px;">G8080</td>
			<td style="width:283px;">To test cell viability.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Cell strainer</td>
			<td style="width:211px;">BD Biosciences, USA</td>
			<td style="width:111px;">352360</td>
			<td style="width:283px;">To collect microgels.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">D-Luciferin</td>
			<td style="width:211px;">SYNCHEM (Germany)</td>
			<td style="width:111px;">s039</td>
			<td style="width:283px;">To tack cells.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Scanning electron microscope</td>
			<td style="width:211px;">FEI, USA</td>
			<td style="width:111px;">Quanta 200</td>
			<td style="width:283px;">To characterize microgel morphology.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">&#160;Mechanical testing machine</td>
			<td style="width:211px;">Bose, USA</td>
			<td style="width:111px;">3230</td>
			<td style="width:283px;">To measure mechanical features.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Programmable syringe pump&#160;</td>
			<td style="width:211px;">World Precision Instruments, USA</td>
			<td style="width:111px;">ALADINI 1000</td>
			<td style="width:283px;">To test injactabiliy.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:199px;">Digital force gauge</td>
			<td style="width:211px;">HBO, Yueqing Haibao Instrument Co., Ltd., China</td>
			<td style="width:111px;">H-50&#160;</td>
			<td style="width:283px;">To test injactabiliy.</td>
		</tr>
		<tr height="48">
			<td height="48" style="height:48px;width:199px;">Ethylene oxide sterilization system</td>
			<td style="width:211px;">Anprolene, Anderson Sterilization, Inc., Haw River, NC</td>
			<td style="width:111px;">AN74i</td>
			<td style="width:283px;">To sterilize microgels with ethylene oxide gas.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Microplate reader</td>
			<td style="width:211px;">Molecular Devices,USA</td>
			<td style="width:111px;">M5</td>
			<td style="width:283px;">To measure fluorescence intensity in micro-array.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Confocal microscope</td>
			<td style="width:211px;">Nikon, Japan</td>
			<td style="width:111px;">A1Rsi</td>
			<td style="width:283px;">To observe cell distribution in 3D.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Xenogen&#160; Lumina II imaging system</td>
			<td style="width:211px;">Caliper Life Sciences, USA</td>
			<td style="width:111px;">IVIS</td>
			<td style="width:283px;">To track cell in animals.</td>
		</tr>
		<tr height="26">
			<td height="26" style="height:27px;width:199px;">Liquid work stataion</td>
			<td style="width:211px;">Apricot design,USA</td>
			<td style="width:111px;">S-pipette</td>
			<td style="width:283px;">To load medium or cell suspension high-throuputly.</td>
		</tr>
	</tbody>
</table>

3d microtissues for injectable regenerative therapy and high-throughput drug screening

To upgrade traditional 2D cell culture to 3D cell culture, we have integrated microfabrication with cryogelation technology to produce macroporous microscale cryogels (microcryogels), which can be loaded with a variety of cell types to form 3D microtissues. Herein, we present the protocol to fabricate versatile 3D microtissues and their applications in regenerative therapy and drug screening. Size and shape-controllable microcryogels can be fabricated on an array chip, which can be harvested off-chip as individual cell-loaded carriers for injectable regenerative therapy or be further assembled on-chip into 3D microtissue arrays for high-throughput drug screening. Due to the high elastic nature of these microscale cryogels, the 3D microtissues exhibit great injectability for minimally invasive cell therapy by protecting cells from mechanical shear force during injection. This ensures enhanced cell survival and therapeutic effect in the mouse limb ischemia model. Meanwhile, assembly of 3D microtissue arrays in a standard 384-multi-well format facilitates the use of common laboratory facilities and equipment, enabling high-throughput drug screening on this versatile 3D cell culture platform.

Fabrication and characterization of microcryogels for 3D microtissue formation.
According to this protocol, microcryogels were fabricated to form the 3D microtissues and individual microcryogels or microcryogel arrays, and were applied to regenerative therapy and drug screening, respectively (Figure 1). Microstencil array chips fabricated from PMMA were applied as micromolds for mic...

Watch this Scientific Journal Video about 3D Microtissues for Injectable Regenerative Therapy and High-throughput Drug Screening at JoVE.com

3D Microtissues for Injectable Regenerative Therapy and High-throughput Drug Screening

This protocol describes the fabrication of elastic 3D macroporous microcryogels by integrating microfabrication with cryogelation technology. Upon loading with cells, 3D microtissues are generated, which can be readily injected in vivo to facilitate regenerative therapy or assembled into arrays for in vitro high-throughput drug screening.

To upgrade traditional 2D cell culture to 3D cell culture, we have integrated microfabrication with cryogelation technology to produce macroporous ...

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