Recombinant human midkine stimulates proliferation and decreases dedifferentiation of auricular chondrocytes in vitro.

Autologous chondrocyte implantation (ACI) is widely used for the repair of cartilage defects. However, due to the lack of chondrocyte growth factor and dedifferentiation of the cultured primary chondrocytes, cell source has limited the clinical potential of ACI. Auricular cartilage is an attractive potential source of cells for cartilage tissue engineering. Here we demonstrated that recombinant human midkine (rhMK) significantly promoted proliferation of rat primary auricular chondrocytes cultured and passaged in monolayer, which was mediated by the activation of mitogen-activated protein kinase and phosphoinositide 3-kinase pathways. Furthermore, rhMK attenuated the dedifferentiation of cultured chondrocytes by maintaining the expression of chondrocyte-specific matrix proteins during culture expansion and passage. Importantly, rhMK-expanded chondrocytes reserved their full chondrogenic potential and redifferentiated into elastic chondrocytes after being cultured in high density. The results suggest that rhMK may be used for the preparation of chondrocytes in cartilage tissue engineering.