Perlecan: an important component of the cartilage pericellular matrix.

Perlecan (Pln) is a large proteoglycan that can bear HS (heparan sulfate) and chondroitin sulfate glycosaminoglycans. Previous studies have demonstrated that Pln can interact with growth factors and cell surfaces either via its constituent glycosaminoglycan chains or core protein. Herein, we summarize studies demonstrating spatially and temporally regulated expression of Pln mRNA and protein in developing and mature cartilage. Mutations either in the Pln gene or in genes involved in glycosaminoglycan assembly result in severe cartilage phenotypes seen in both human syndromes and mouse model systems. In vitro studies demonstrate that Pln can trigger chondrogenic differentiation of multipotential mouse CH310T1/2 stem cells as well as maintain the phenotype of adult human chondrocytes. Structural mapping indicates that these activities lie entirely within domain I, a region unique to Pln, and that they require glycosaminoglycans. We also discuss data indicating that Pln cooperates with the key chondrogenic growth factor, BMP-2, to promote expression of hypertrophic chondrocyte markers. Collectively, these studies indicate that Pln is an important component of human cartilage and may have useful applications in tissue engineering and cartilage-directed therapeutics.