Cartilage and bone development have proven to be dependent upon perlecan expression. The protein becomes visible by immunostaining on day 15 during mouse development, independently from other basement membrane proteins, suggesting that it is simply a part of the ECM of developing chondrocytes, in addition to collagen II and other cartilage markers that are expressed starting on day 12. Taken with the data, that mice lacking the pln gene cannot maintain stable cartilage, it is apparent that perlecan is essential to the maturation and stability of cartilaginous structure. This is supported by a study showing that knockdown of perlecan production inhibits the final stages of chondrogenic differentiation in C3H10T1/2 fibroblasts in culture. Bone development, i.e. mineralization of cartilaginous tissue, correlates with loss of perlecan and heparan sulfate at the chondro-osseous junction (COJ). In an effort to understand how heparan sulfate and perlecan direct mesenchymal stem cells into the osteogenic pathway, human mesenchymal stem cells were treated with heparanase and chondroitinase in culture. This led to increased mineralization and expression of osteocyte markers, supporting the data showing that loss of heparan sulfate at the COJ is a key factor in osteogenesis. It is thought that the driving force behind heparanase and chondroitinase activation of osteogenesis is release of bone morphogenetic protein bound in the heparan sulfate chains.