Fig. 4

Sequential process of cartilage regeneration. Cartilage regeneration illustrated as a coordinated sequential process of chondrocyte proliferation and matrix turnover. The process may be initiated by sprifermin signaling to the chondrocytes to start proliferating. However, the chondrocytes are caged by the surrounding matrix, which preclude unlimited expansion. This may force the chondrocytes to initiate matrix degradation processes to expand the lacunae (get rid of their cage), and eventually we may see a larger population of chondrocytes that starts producing new matrix. Note that this figure illustrates a working hypothesis (and is hypothetical) as we do not know whether matrix degradation is required for regeneration of cartilage by pro-proliferative compounds like sprifermin