Evaluation of Cartilage-Like Matrix Formation in a Nucleus Pulposus-Derived Cartilage Analog Scaffold

Abstract

The formation of fibrocartilage in microfracture (MFX) severely limits its long-term outlook. There is consensus in the scientific community that the placement of an appropriate scaffold in the MFX defect site can promote hyaline cartilage formation and improve therapeutic benefit. Accordingly, in this work, a novel natural biomaterial-the cartilage analog (CA)-which met criteria favorable for chondrogenesis, was evaluated in vitro to determine its candidacy as a potential MFX scaffold. Human bone marrow stem cells (hBMSCs) were seeded onto the CA and cultured for 28 days in chondrogenic differentiation media. Sulfated glycosaminoglycan (sGAG) and hydroxyproline (HYP) contents were significantly higher than their non-seeded counterparts on both Days 14 and 28 (average sGAG on Day 28: 73.26 vs. 23.82 μg/mg dry wt. of tissue; average HYP on Day 28: 56.19 vs. 38.80 ± 2.53 μg/mg dry wt. of tissue). Histological assessments showed cellular infiltration and abundant sGAG formation for seeded CAs at both time points with new cartilage-like matrix filling up its laser-drilled channels. Polarized light microscopy of picrosirius red stained samples showed collagen fibrils aligning along the path of the laser-drilled channels. However, the seeded scaffolds were also found to have contracted by 20% by the end of the study with their average aggregate moduli significantly lower than non-seeded controls (10.52 vs. 21.74 kPa). Nevertheless, the CA was ultimately found to support the formation of a cartilage-like matrix, and therefore, merits consideration as a scaffold of interest for improving MFX.

Keywords: bone marrow stem cells; bovine nucleus pulposus scaffold; collagen; glycosaminoglycans; hyaline cartilage; microfracture; moduli.