Abstract
Cartilage tissue has been recalcitrant to tissue engineering approaches. In this study, human chondrocytes were formed into self-assembled cartilage sheets, cultured in physiologic (5%) and atmospheric (20%) oxygen conditions and underwent biochemical, histological and biomechanical analysis at 1- and 2-months. The results indicated that sheets formed at physiological oxygen tension were thicker, contained greater amounts of glycosaminoglycans (GAGs) and type II collagen, and had greater compressive and tensile properties than those cultured in atmospheric oxygen. In all cases, cartilage sheets stained throughout for extracellular matrix components. Type II-IX-XI collagen heteropolymer formed in the neo-cartilage and fibrils were stabilized by trivalent pyridinoline cross-links. Collagen cross-links were not significantly affected by oxygen tension but increased with time in culture. Physiological oxygen tension and longer culture periods both served to increase extracellular matrix components. The foremost correlation was found between compressive stiffness and the GAG to collagen ratio.
Highlights
Cartilage tissue has very poor intrinsic repair capacity
There was a significant increase in extracellular matrix content, both in terms of GAG/DNA (Figure 3B) and collagen/DNA (Figure 3C) in human tissue-engineered cartilage sheets when cultured in Physioxia vs Atm O2
To determine if cartilage-specific collagen type II-IX-XI heteropolymer formed in culture we used specific antibodies to qualitatively fingerprint cross-linked collagen chains as we previously established (Murdoch et al, 2016)
Summary
Cartilage tissue has very poor intrinsic repair capacity. While osteoarthritis is a complex, multifaceted disease, cartilage degradation is a core component. Autologs chondrocyte implantation and matrix assisted autologs chondrocyte implantation have provided relief to patients but commonly result in fibrocartilage repair (Shekkeris et al, 2012). Tissue engineering could potentially address this through in vitro culture methods to produce functional hyaline cartilage tissue, with several examples currently in clinical trials (Kwon et al, 2019). Others, have investigated media supplements and growth factors to improve the expansion and re-differentiation of the expanded chondrocytes (Vunjak-Novakovic et al, 1999; Enochson et al, 2012; Makris et al, 2013a; Dennis et al, 2020).
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