Stem Cells, Nitrogen-Rich Plasma-Polymerized Culture Surfaces, and Type X Collagen Suppression

Mesenchymal stem cells (MSCs) are multipotent cells that can differentiate into chondrocytes, osteoblasts, myocytes, adipocytes, and a variety of other cell types. Several studies have been directed toward using MSCs from patients with osteoarthritis (OA) for cartilage repair, not only because these are the ones that will require a source of autologous stem cells if biological repair of cartilage lesions is to be a therapeutic option, but also to further an understanding of stem cell differentiation. Previous studies have shown that a major drawback of current cartilage and intervertebral disc tissue repair is that human MSCs from OA patients express type X collagen (COL X). COL X, a marker of late-stage chondrocyte hypertrophy, is implicated in endochondral ossification. However, those studies also revealed that a novel plasma-polymerized thin film material, named nitrogen-rich plasma-polymerized ethylene (PPE:N), was able to inhibit COL X expression in committed MSCs. The specific aim of this present study was to determine if the suppression of COL X by PPE:N is maintained when MSCs are transferred to pellet cultures in serum-free media. Our results confirmed the potential of two different types of PPE:N surfaces (low-pressure-PPE:N [L-PPE:N] and high-pressure-PPE:N [H-PPE:N]) in suppressing COL X expression, more so on the latter. Interestingly, when MSCs were transferred to pellet cultures, the expression level of COL X was further decreased by preincubation on H-PPE:N, suggesting that these kinds of coatings show promise for tissue engineering of cartilage and disc tissues. Further studies are needed to assess the relative importance of surface-chemistry versus surface-morphology in the mechanism of COL X suppression.