Clay microparticles for the enhancement of bone regeneration: in vitro studies

Humans develop osteoporosis as they age, a disease characterized by the slow and consistent reduction in bone mass and the subsequent risk of fractures. Due to aging, the mesenchymal stem cells within the bone marrow niche, show a shift in differentiation from osteogenesis to adipogenesis. The challenge of osteoporosis treatment is being met with advances in nanotechnology and tissue engineering. In this study , we evaluated the potential of palygorskite clay mineral microparticles for the promotion of the osteogenic differentiation in human mesenchymal stem cells (hMSCs) in vitro. Alkaline phosphatase (ALP) activity and Alizarin red staining showed that osteogenic differentiation of hMSCs is enhanced in the presence of palygorskite clay. Although, gene expression analysis did not reveal upregulation of several osteogenic markers in the presence of the clay microparticles, another interaction mechanism resulted in the enhanced osteogenic differentiation of hMSCs. The charged surfaces of the palygorskite clay particles interact with the stem cells using their high adhesion characteristics, leading to complete bridging, adherence, and enveloping of the stem cells' cadherins and integrins with their environment. This restoration of the adhesion among the stem cells and their environment most probably promotes/restores the osteogenic differentiation of hMSCs. Therefore, palygorskite clay microparticles are a promising candidate for further in vivo studies on bone regeneration.