Wang B, Sierad LN, Mercuri JJ, Simionescu A, Simionescu DT, et al.
Engineered regeneration •
Mitral valve (MV) tissue engineering is still in its early stage, and one major challenge in MV tissue engineering is to identify appropriate scaffold materials. With the potential of acellular MV scaffolds being demonstrated recently, it is important to have a full understanding of the biomechanics of the native MV components and their acellular scaffolds. In this study, we have successfully characterized the structural and mechanical properties of porcine MV components, including anterior leaflet (AL), posterior leaflet (PL), strut chordae, and basal chordae, before and after decellularization. Quantitative DNA assay showed more than 90% reduction in DNA content, and (GS) lectin immunohistochemistry confirmed the complete lack of porcine -Gal antigen in the acellular MV components. In the acellular AL and PL, the atrialis, spongiosa, and fibrosa trilayered structure, along with its ECM constitutes, i.e., collagen fibers, elastin fibers, and portion of GAGs, were preserved. Nevertheless, the ECM of both AL and PL experienced a certain degree of disruption, exhibiting a less dense, porous ECM morphology. The overall anatomical morphology of the strut and basal chordae were also maintained after decellularization, with longitudinal morphology experiencing minimum disruption, but the cross-sectional morphology exhibiting evenly-distributed porous structure. In the acellular AL and PL, the nonlinear anisotropic biaxial mechanical behavior was overall preserved; however, uniaxial tensile tests showed that the removal of cellular content and the disruption of structural ECM did result in small decreases in maximum tensile modulus, tissue extensibility, failure stress, and failure strain for both MV leaflets and chordae.
Wang B, Tedder ME, Perez CE, Wang G, de Jongh Curry AL, et al.
Journal of materials science. Materials in medicine •
Extracellular matrix (ECM) of myocardium plays an important role to maintain a multilayered helical architecture of cardiomyocytes. In this study, we have characterized the structural and biomechanical properties of porcine myocardial ECM. Fresh myocardium were decellularized in a rotating bioreactor using 0.1 % sodium dodecyl sulfate solution. Masson's trichrome staining and SEM demonstrated the removal of cells and preservation of the interconnected 3D cardiomyocyte lacunae. Movat's pentachrome staining showed the preservation of cardiac elastin ultrastructure and vascular elastin distribution/alignment. DNA assay result confirmed a 98.59 % reduction in DNA content; the acellular myocardial scaffolds were found completely lack of staining for the porcine α-Gal antigen; and the accelerating enzymatic degradation assessment showed a constant degradation rate. Tensile and shear properties of the acellular myocardial scaffolds were also evaluated. Our observations showed that the acellular myocardial ECM possessed important traits of biodegradable scaffolds, indicating the potentials in cardiac regeneration and whole heart tissue engineering.
Journal of biomedical materials research. Part A •
Numerous scaffold formulations have been investigated to support the regeneration of nucleus pulposus (NP) tissue for use as an early-stage therapy for intervertebral disc degeneration. Particular attention has focused on recreating the biochemical and mechanical properties of the native NP via the incorporation of exogenous extracellular matrix (ECM) components or synthetic surrogates. In the present study, we describe a novel approach to develop a tissue engineering (TE) scaffold comprised acellular porcine NP ECM. Complete decellularization of porcine NP was successfully achieved using a combination of chemical detergents, ultrasonication, and treatment with nucleases. Resulting NP scaffolds were devoid of host-cell remnants and the porcine antigen alpha-Gal. Native NP ECM components including aggrecan/chondroitin-6-sulfate and collagens types II, IX, and XI were found in physiologically relevant ratios within the NP scaffold. NP scaffold swelling capacity and unconfined mechanical properties were not significantly different from porcine NP tissue. Furthermore, NP scaffolds were conducive to repopulation with human adipose-derived stem cells as cell viability and proliferative capacity were maintained. These results demonstrate the successful decellularization of porcine NP and the resultant formation of a biomimetic scaffold exhibiting potential utility for TE the human NP.
Sierad LN, Simionescu A, Albers C, Chen J, Maivelett J, et al.
Cardiovascular engineering and technology •
Heart valve tissue engineering requires biocompatible and hemocompatible scaffolds that undergo remodeling and repopulation, but that also withstand harsh mechanical forces immediately following implantation. We hypothesized that reversibly stabilized acellular porcine valves, seeded with endothelial cells and conditioned in pulsatile bioreactors would pave the way for next generations of tissue engineered heart valves (TEHVs). A novel valve conditioning system was first designed, manufactured and tested to adequately assess TEHVs. The bioreactor created proper closing and opening of valves and allowed for multiple mounting methods in sterile conditions. Porcine aortic heart valve roots were decellularized by chemical extractions and treated with penta-galloyl glucose (PGG) for stabilization. Properties of the novel scaffolds were evaluated by testing resistance to collagenase and elastase, biaxial mechanical analysis, and thermal denaturation profiles. Porcine aortic endothelial cells were seeded onto the leaflets and whole aortic roots were mounted within the dynamic pulsatile heart valve bioreactor system under physiologic pulmonary valve pressures and analyzed after 17 days for cell viability, morphology, and metabolic activity. Our tissue preparation methods effectively removed cells, including the potent α-Gal antigen, while leaving a well preserved extra-cellular matrix scaffold with adequate mechanical properties. PGG enhanced stabilization of extracellular matrix components but also showed the ability to be reversible. Engineered valve scaffolds encouraged attachment and survival of endothelial cells for extended periods and showed signs of widespread cell coverage after conditioning. Our novel approach shows promise toward development of sturdy and durable TEHVs capable of remodeling and cellular repopulation.
