Name: 3d bioprinting of murine cortical astrocytes for engineering neural-like tissue
Uploaded: 2021-07-16T13:30:00
Description: Watch this Scientific Journal Video about 3D Bioprinting of Murine Cortical Astrocytes for Engineering Neural-Like Tissue at JoVE.com

This work was supported by The S&#227;o Paulo Research Foundation (FAPESP), grant numbers 2018/23039-3 and 2018/12605-8; National Council for Scientific and Technological Development (CNPq), grant numbers 465656/2014-5 and 309679/2018-4; and Coordination for the Improvement of Higher Education Personnel (CAPES), financial code 001.

All the procedures involving animals followed international guidelines for animal use in research (http://www.iclas.org) and were approved by the Committee for Ethics in Research of Universidade Federal de S&#227;o Paulo (CEUA 2019/ 9292090519).
1. Mice brain dissection
<ol>
	<li>Transfer 10 mL of cold Hanks Buffered Salt Solution (HBSS) to a 100 mm culture dish and 1 mL to a 1.5 mL microtube. Prepare one microtube per animal. 
	NOTE: Both the culture dish and the microtube need to be k...

The 3D bioprinting technology has emerged as a biofabrication alternative that allows the engineering of refined constructs that structurally and physiologically resemble native tissues22, including the brain23. The biofabrication of neural-like tissues allows for in vitro native microenvironment modeling, being an important tool for understanding the cellular and molecular mechanisms associated with the development and treatment of many diseases that affect the CN...

Astrocytes are the most abundant cell type in the Central Nervous System (CNS) and play a key role in brain homeostasis. In addition to enduring neuronal support, astrocytes are responsible for modulating neurotransmitters uptake, maintaining the blood-brain barrier integrity, and regulating neuronal synaptogenesis1,2. Astrocytes also have an essential role in CNS inflammation, responding to injuries to the brain in a process that leads to astrocitary reactivity or reactive astrogliosis3,4, forming a glial scar that prevents healthy tissue exposition to degenerative agents5. This event results in changes in astrocytes&#39; gene expression, morphology, and function6,7. Therefore, studies involving astrocytes&#39; functionality are helpful for the development of therapies to treat neurologic disorders.
In vitro models are crucial for studying mechanisms related to neurological injuries, and although successful isolation and two-dimensional (2D) culture of cortical astrocytes have been established8, this model fails to provide a realistic environment that mimics native cell behavior and to reproduce the complexity of the brain9. In 2D condition, the poor mechanical and biochemical support, low cell-cell and cell-matrix interactions, and cell flattening leading to the absence of basal-apical polarity, affect cell signaling dynamics and experimental outcomes leading to altered cell morphology and gene expression, which compromise response to treatments10. Therefore, it is crucial to develop alternatives that provide a more realistic neural environment, aiming to translate the results to the clinic.
Three-dimensional (3D) cell culture represents a more advanced model that recapitulates with increased fidelity features of organs and tissues, including the CNS11. Regarding glial culture, 3D models contribute to the maintenance of astrocytes morphology, cell basal-apical polarity, and cell signaling12,13. The 3D bioprinting technology emerged as a powerful tool to biofabricate 3D living tissues in a controlled manner by using cells and biomaterials to recreate the structure and properties of native tissues. The use of this technology has led to a substantial improvement of results prediction and has contributed to regenerative medicine applied to the CNS14,15,16.
The protocol described here details the isolation and culture of cortical astrocytes. The protocol also details a reproducible method to bioprint astrocytes embedded in gelatin/gelatin methacryloyl (GelMA)/fibrinogen, supplemented with laminin. In this work, an extrusion-based bioprinter was used to print the biomaterial composition containing cortical astrocytes at a density of 1 x 106 cells/mL. Bioprinting shear stress was minimized by controlling the printing speed, and astrocytes showed high viability after the process. Bioprinted constructs were cultured for 1 week, and astrocytes were able to spread, attach, and survive within the hydrogel, maintaining the astrocytic morphology and expressing a specific marker glial fibrillary acidic protein (GFAP)4.
This procedure is compatible with piston-driven extrusion-based bioprinters and can be used to bioprint astrocytes derived from different sources. The 3D bioprinted model proposed here is suitable for a wide range of neural engineering applications, such as studies of the mechanisms involved in astrocytes functionality in healthy tissues and understanding the progression of neurological pathologies and treatment development.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>3D Bioprinter</td>
			<td>3D Biotechnology Solutions</td>
			<td></td>
			<td>Extrusion-based bioprinter</td>
		</tr>
		<tr>
			<td>Blunt-tip forceps</td>
			<td>Integra Miltex</td>
			<td>6--30</td>
			<td>Forceps for brain dissection previously sterilized</td>
		</tr>
		<tr>
			<td>Bovine serum albumin</td>
			<td>Sigma-Aldrich</td>
			<td>9048-46-8</td>
			<td>Protease free, fatty acid free, essentially globulin free</td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>Sigma-Aldrich</td>
			<td>10043-52-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture flask</td>
			<td>Fisher Scientific</td>
			<td>156340</td>
			<td>Culture flask T25</td>
		</tr>
		<tr>
			<td>Cell strainer</td>
			<td>Corning Incorporated</td>
			<td>352340</td>
			<td>Cell strainer 40 &#181;m</td>
		</tr>
		<tr>
			<td>Confocal microscope</td>
			<td>Leica</td>
			<td></td>
			<td>Confocal TCS SP8 microscopy coupled with an Olympus FluoView 300 confocal system</td>
		</tr>
		<tr>
			<td>Conical tubes</td>
			<td>Thermo Scientific</td>
			<td>339651, 339652</td>
			<td>Sterile tubes of 15 mL and 50 mL</td>
		</tr>
		<tr>
			<td>DAPI</td>
			<td>Abcam</td>
			<td>ab224589</td>
			<td>DAPI staining solution</td>
		</tr>
		<tr>
			<td>DMEM/F12</td>
			<td>Gibco; Life Technologies Corporation</td>
			<td>12500062</td>
			<td>DMEM/F-12 50/50, 1X (Dulbecco&#39;s Mod. Of Eagle&#39;s Medium/Ham&#39;s F12 50/50 Mix) with L-glutamine</td>
		</tr>
		<tr>
			<td>Dyalisis tubing</td>
			<td>Sigma-Aldrich</td>
			<td>D9527</td>
			<td>Molecular weight cut-off = 14 kDa</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Fisher Scientific</td>
			<td>64-15-5</td>
			<td>Reagent grade</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Gibco; Life Technologies Corporation</td>
			<td>12657011</td>
			<td>Research Grade</td>
		</tr>
		<tr>
			<td>Fibrinogen</td>
			<td>Sigma-Aldrich</td>
			<td>9001-32-5</td>
			<td>Fibrinogen cristalline powder from bovine plasma</td>
		</tr>
		<tr>
			<td>Gelatin</td>
			<td>Sigma-Aldrich</td>
			<td>9000-70-8</td>
			<td>Gelatin powder from porcine skin</td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Sigma-Aldrich</td>
			<td>56-40-6</td>
			<td>Glycine powder</td>
		</tr>
		<tr>
			<td>Hanks Buffered Salt Solution (HBSS)</td>
			<td>Gibco; Life Technologies Corporation</td>
			<td>14175095</td>
			<td>No calcium, no magnesium, no phenol red</td>
		</tr>
		<tr>
			<td>L-Glutamine</td>
			<td>Sigma-Aldrich</td>
			<td>56-85-9</td>
			<td>L-Glutamine crystalline powder</td>
		</tr>
		<tr>
			<td>Laminin</td>
			<td>Sigma-Aldrich</td>
			<td>114956-81-9</td>
			<td>Laminin 1-2 mg/mL L in 50 mM Tris-HCl</td>
		</tr>
		<tr>
			<td>Live dead kit cell imaging kit</td>
			<td>Thermo Scientific</td>
			<td>R37601</td>
			<td>Green fluorescence in live cells (ex/em 488 nm/515 nm). Red fluorescence in dead cells (ex/em 570 nm/602 nm)</td>
		</tr>
		<tr>
			<td>Methacrylic anhydride</td>
			<td>Sigma-Aldrich</td>
			<td>760-93-0</td>
			<td>For GelMA preparation</td>
		</tr>
		<tr>
			<td>Microtubes</td>
			<td>Corning Incorporated</td>
			<td>MCT-150-C</td>
			<td>Microtubes of 1,5 mL</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma-Aldrich</td>
			<td>7647-14-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Needle 22G</td>
			<td>Fisher Scientific</td>
			<td>NC1362045</td>
			<td>Sterile blunt needle</td>
		</tr>
		<tr>
			<td>Operating scissor</td>
			<td>Integra Miltex</td>
			<td>05--02</td>
			<td>Sharp scissor for brain dissection previously sterilized</td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>30525-89-4</td>
			<td>Paraformaldehyde powder</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>Gibco; Life Technologies Corporation</td>
			<td>15070063</td>
			<td>Pen Strep (5,000 Units/ mL Penicillin; 5,000 ug/mL Streptomycin)</td>
		</tr>
		<tr>
			<td>Petri dish</td>
			<td>Corning Incorporated</td>
			<td>430591, 430588</td>
			<td>Sterile petri dishes of 35 and 100 mm</td>
		</tr>
		<tr>
			<td>Phalloidin</td>
			<td>Abcam</td>
			<td>ab176753</td>
			<td>iFluor 488 reagent</td>
		</tr>
		<tr>
			<td>Photoinitiator</td>
			<td>Sigma-Aldrich</td>
			<td>106797-53-9</td>
			<td>2-Hydroxy-4&#8242;-(2-hydroxyethoxy)-2-methylpropiophenone</td>
		</tr>
		<tr>
			<td>Phosphate buffer saline (PBS)</td>
			<td>Gibco; Life Technologies Corporation</td>
			<td>10010023</td>
			<td>PBS 1 x, culture grade, no calcium, no magnesium</td>
		</tr>
		<tr>
			<td>Poly-L-lysine</td>
			<td>Sigma-Aldrich</td>
			<td>25988-63-0</td>
			<td>Poly-L-lysine hydrobromide mol wt 30,000-70,000</td>
		</tr>
		<tr>
			<td>Primary antobody</td>
			<td>Abcam</td>
			<td>ab4674</td>
			<td>Chicken polyclonal to GFAP</td>
		</tr>
		<tr>
			<td>Secondary antibody</td>
			<td>Abcam</td>
			<td>ab150176</td>
			<td>Alexa fluor 594 anti-chicken</td>
		</tr>
		<tr>
			<td>Spatula</td>
			<td>Miltex</td>
			<td>V973-70</td>
			<td>Number 24 cement spatula previously sterilized</td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Fisherbrand</td>
			<td>3000038</td>
			<td>Microscope for brain dissection</td>
		</tr>
		<tr>
			<td>Syringe 5 mL</td>
			<td>BD</td>
			<td>1222C84</td>
			<td>Sterile syringe</td>
		</tr>
		<tr>
			<td>Syringe filter 2 &#181;m</td>
			<td>Fisher Scientific</td>
			<td>09-740-105</td>
			<td>Polypropylene filter for sterilization</td>
		</tr>
		<tr>
			<td>Thrombin</td>
			<td>Sigma-Aldrich</td>
			<td>9002--04-4</td>
			<td>Thrombin cristalline powder from bovine plasma</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma-Aldrich</td>
			<td>9002-93-1</td>
			<td>Laboratory grade</td>
		</tr>
		<tr>
			<td>Trypsin-EDTA</td>
			<td>Gibco; Life Technologies Corporation</td>
			<td>15400054</td>
			<td>Trypsin no phenol red 1 x diluted in PBS</td>
		</tr>
		<tr>
			<td>Versene solution</td>
			<td>Gibco; Life Technologies Corporation</td>
			<td>15040066</td>
			<td>Versene Solution (0.48 mM) formulated as 0.2 g EDTA(Na4) per liter of PBS</td>
		</tr>
		<tr>
			<td>Well plate</td>
			<td>Thermo Scientific</td>
			<td>144530</td>
			<td>Sterile 24-well plate</td>
		</tr>
	</tbody>
</table>

3d bioprinting of murine cortical astrocytes for engineering neural-like tissue

Astrocytes are glial cells with an essential role in the central nervous system (CNS), including neuronal support and functionality. These cells also respond to neural injuries and act to protect the tissue from degenerative events. In vitro studies of astrocytes&#39; functionality are important to elucidate the mechanisms involved in such events and contribute to developing therapies to treat neurological disorders. This protocol describes a method to biofabricate a neural-like tissue structure rich in astrocytes by 3D bioprinting astrocytes-laden bioink. An extrusion-based 3D bioprinter was used in this work, and astrocytes were extracted from C57Bl/6 mice pups&#39; brain cortices. The bioink was prepared by mixing cortical astrocytes from up to passage 3 to a biomaterial solution composed of gelatin, gelatin-methacryloyl (GelMA), and fibrinogen, supplemented with laminin, which presented optimal bioprinting conditions. The 3D bioprinting conditions minimized cell stress, contributing to the high viability of the astrocytes during the process, in which 74.08% &#177; 1.33% of cells were viable right after bioprinting. After 1 week of incubation, the viability of astrocytes significantly increased to 83.54% &#177; 3.00%, indicating that the 3D construct represents a suitable microenvironment for cell growth. The biomaterial composition allowed cell attachment and stimulated astrocytic behavior, with cells expressing the specific astrocytes marker glial fibrillary acidic protein (GFAP) and possessing typical astrocytic morphology. This&#160;reproducible protocol provides a valuable method to biofabricate 3D neural-like tissue rich in astrocytes that resembles cells&#39; native microenvironment, useful to researchers that aim to understand astrocytes&#39; functionality and their relation to the mechanisms involved in neurological diseases.

This work aimed to develop a neural-like tissue using the 3D bioprinting technology to deposit layer-by-layer primary astrocytes-laden gelatin/GelMA/fibrinogen bioink. Astrocytes were extracted and isolated from the cerebral cortex of mice pups (Figure 1), added to a biomaterial composition, allowing the biofabrication of a living 3D construct.
The computer-aided-design (CAD) was developed using the G-code&#160;(Supplemental file) as an interconne...

Watch this Scientific Journal Video about 3D Bioprinting of Murine Cortical Astrocytes for Engineering Neural-Like Tissue at JoVE.com

3D Bioprinting of Murine Cortical Astrocytes for Engineering Neural-Like Tissue

Here we report a method of 3D bioprinting murine cortical astrocytes for biofabricating neural-like tissues to study the functionality of astrocytes in the central nervous system and the mechanisms involving glial cells in neurological diseases and treatments.

Astrocytes are glial cells with an essential role in the central nervous system (CNS), including neuronal support and functionality. These cells also ...

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