Endocrine Abstracts

Introduction: Mesenchymal stem cells (MSCs) are a type of multipotent cells readily found within the bone marrow, capable of undergoing self-renewal and giving rise to cells with different characteristics, such as, osteoblasts, adipocytes and chondrocytes. MSC differentiation requires optimal cell–matrix interaction and is also dependent on a number of growth factors.

Aim: To investigate the effect of GH, Rho-associated kinase (ROCK) and extracellular signal-regulated kinase (ERK) signaling on human MSC differentiation on nanoscale topography (NQ450) which represents a physiological in vitro model for cell–matrix interaction.

Methods: MSC were cultured on NQ450 and flat surfaces for variable durations and markers of adipogenesis, chondrogenesis and osteogenesis, were studied by immunofluorescence and qPCR. The model was then used to study the effect of GH, and JAK, ROCK and ERK inhibitor.

Results: An increase in bone formation markers, osteopontin (OPN) and osteocalcin (OCN) on NQ450 was observed in both 28- and 14-day cultures on immunofluorescence. qPCR showed significantly higher expression of BMPR2 and SOX9 genes on NQ450 than standard flat topography. The presence of GHR antibody did not affect BMPR2 expression on NQ450, but was associated with increased SOX9 levels, a marker of chondrogenesis. Although PPARG expression was not significantly higher on NQ450, an increase in PPARG expression was observed in the cells cultured on standard flat topography after GHR antibody exposure. The expression of OCN and OPN was stimulated with GH, reduced after inhibition of ROCK or ERK, and no cells were detected in the presence of JAK inhibitor.

Conclusion: ERK and ROCK signaling are important for topographically driven osteogenesis. Inhibition of GHR signaling shifted MSCs towards chondrogenic mode on NQ450 and adipogenic mode on standard topography. The interactive effect of GH and the ERK pathway on adhesion driven intracellular tension needs further study.