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

Summary

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.

Abstract

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.

Introduction

The extracellular matrix (ECM) provides not only structural support but is also important for biologic cell and tissue function¹. In the heart, the ECM participates in the regulation of pathophysiologic responses such as fibrosis, inflammation, angiogenesis, cardiomyocyte contractile function and viability, and resident progenitor cell fate. In addition to its primary components - fibrous glycoproteins, glycosaminoglycans, and proteoglycans - it contains a host of secreted growth factors, cytokines, and membranous vesicles containing nucleic acids and proteins^2,3.

Protocol

The study protocol conforms to the ethical principles outlined in the Declaration of Helsinki and was approved by the institutional review board and ethics committee of Charité Medical University. All patients provided written, informed consent for use of heart tissue for experimental studies.

1. Preparation of Human Myocardium for Sectioning

1. Obtain left ventricular myocardium (size varies depending on the type of surgery) directly from the operating room and transport in cold PBS in a sterile container.
2. Remove all fat tissue with a sterile scalpel with a no. 10 blade under sterile conditions.
3. Cut the my....

Results

The 3-step protocol for decellularization of human myocardium presented here results in near-complete removal of cellular material, while preserving the key ECM components and the fibrillar structure of ECM. After decellularization, the gross removal of cells from the tissue is evident by the change in color (Figure 1A). Histological analysis with H&E and Masson Trichrome stains revealed the complete absence of residual intact cells (.......

Discussion

When preparing human myocardial ECM, the goal is to achieve the following: removal of relevant immunogenic cellular material, preservation of ECM integrity and bioactivity, sterility, non-toxicity of the end-product, GMP-process compatibility, and suitability of the product for a given application in terms of handling. By combining our 3-step decellularization protocol with further processing into microparticles or self-assembling hydrogel, human cardiac ECM material is obtained that possesses specific biological activit.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Balance	DR Precisa, Dietikon, Switzerland	Precisa XR 205SM
Blades Nr.10 Skalpell Nr.3	InstrumenteNRW, Erftstadt, Germany	SK-10-004
Cell culture plates (6-well)	Greiner, Frickenhausen, Germany	657160
Cryostat CM	Leica, Wetzlar, Germany	3050S
EDTA	Carl Roth, Karlsruhe, Germany	8043.3
Eppendorf reaction tubes (1.5 or 2 ml)	Greiner, Frickenhausen, Germany	616201, 623201
Falcon 15ml, 50ml	Greiner, Frickenhausen, Germany	188271, 227270
Fetal Bovine Serum (FBS)	Biochrome, Berlin, Germany	S 0115
Freeze Dry System	Labconco, Kansas City, USA	7670520
Freezer (-80°C)	Thermo Scientific, Waltham, MA, USA	Forma 900 Series
HCl	Carl Roth, Karlsruhe, Germany	281.1
Microtome Blades Type 819	Leica, Wetzlar, Germany	14035838925
Minilys Homogeniser	PEQLAB Biotechnologie GmbH, Erlangen, Germany	91-PCSM
NaOH	Carl Roth, Karlsruhe, Germany	K021.1
Nystatin	PAN Biotech, Aidenbach, Germany	P06-07800
PBS	Thermo Scientific, Waltham, MA, USA	14190-094
Penicillin/streptomycin	Life Technologies, Darmstadt, Germany	15140122
Pepsin	Sigma-Aldrich, Taufkirchen, Germany	P6887-1G
Precellys Keramik-Kit 1.4 mm	Peqlab Biotechnolgie, Erlangen, Germany	91-PCS-CK14
Rotamax 120 Plate shaker	Heidolph, Schwabach, Germany	544-41200-00
SDS	Carl Roth, Karlsruhe, Germany	CN30.3
Stereo microscope	Leica, Wetzlar, Germany	M125
Steriflip-GP, 0,22 µm	Merck Millipore, Darmstadt, Germany	SCGP00525
Stuart analogue rocker & roller mixers	Sigma-Aldrich, Taufkirchen, Germany	Z675113-1EA
Tissue Tek O.C.T compound	Hartenstein, Wurzburg, Germany	TTEK
Transfusion set 200µm	Sarstedt, Nümbrecht, Germany	798.200.500
TRIS	Carl Roth, Karlsruhe, Germany	5429.3
vedena Skalpellgriff Fig. 3, Standard, 125 mm	Medical Highlights, Rohrdorf, Germany	CV102-003
Vortex-Genie2	Scientific Industry, New York, USA	SI-0256