Decellularized cartilage microcarriers as a novel platform for chondrogenic expansion

Abstract

Osteoarthritis is a degenerative disease associated with the degradation of cartilage. One of the few therapies aimed at regenerating cartilage, autologous chondrocyte implantation (ACI), involves ex vivo expansion and re-implantation of patient derived chondrocytes. Chondrocytes have relatively slow proliferation rates, however, and rapidly de-differentiate during the ex vivo culture performed with ACI. The objective of this study was to develop microcarriers (µCs) that provide a microenvironment that more closely mimics the complex extracellular matrix of native cartilage for chondrocyte expansion and retention of phenotype. Porcine cartilage was isolated, lyophilized, milled, and sifted overnight to obtain µCs approximately 450 µm and 600 µm in diameter. Multiple decellularization procedures were tested and ultimately a series of chemical and enzymatic washes resulted in removal of more than 98% of the original DNA content. Preliminary seeding experiments performed with chondrogenic ATDC5 cells resulted in chondrogenic proliferation and viability over 7 days of culture on decellularized cartilage microcarriers (DC µCs). Primary human chondrocytes were then cultured on the DC µCs, commercially available gelatin CultiSpher®-G (CG µCs), or tissue culture polystyrene over 14 days. Chondrocyte-laden DC µCs contained significantly more GAGs than the CG µCs or plated tissue culture polystyrene (TCPS) chondrocytes at all time points. Ongoing experiments are evaluating changes in chondrogenic phenotype on µCs through histological, immunohistochemical, and gene expression analysis. DC µCs support chondrocyte proliferation, and although the rate of expansion is slower than CG µCs or TCPS, these microcarriers have GAG/DNA ratios more similar to that of native cartilage. This makes DC µCs a promising platform for chondrogenic expansion and suitable for direct implantation.