Calcium signalling in chondrogenesis: implications for cartilage repair.

Undifferentiated mesenchymal stem cells (MSCs) represent an important source for cell-based tissue regeneration techniques that require differentiation towards specific lineages, including chondrocytes. Chondrogenesis, the process by which committed mesenchymal cells differentiate into chondrocytes, is controlled by complex but not yet completely understood mechanisms that involve many components, including intracellular signalling pathways, as well as plasma membrane receptors and ion channels. Some of these signalling components are Ca2+ sensitive. Although the Ca2+-signalling toolkit of undifferentiated MSCs and mature chondrocytes are extensively studied, the adaptation of these components during differentiation and their role in chondrogenesis is not adequately established. In this review, various aspects of Ca2+ signalling are discussed in MSCs and in mature chondrocytes including spatial and temporal aspects, as well as Ca2+ entry and elimination processes, with implications for their involvement in chondrogenesis. A better understanding of these pathways is envisaged to provide a more efficient differentiation of MSCs towards chondrocytes that may lead to the development of better cartilage tissue engineering techniques.