The applications and medical devices of Midkine in the field of biotechnology are described in this invention. This invention describes the applications of the protein as follow in (a) or (b) in preparing drugs for promoting cartilage growth or treating cartilage diseases, the protein as a growth factor for promoting chondrocyte proliferation, or medical devices containing this protein: (a) the protein whose amino acid sequence is shown as SEQ ID NO.1 (b) the proteins whose amino acid sequence have at least 60% homology comparing with amino acid sequence described in (a) and have activity for promoting proliferation of chondrocyte. The protein described in this invention promotes proliferation of three types of chondrocytes and is used for preparing drugs for treating cartilage disease. It may provide new therapy for treating cartilage diseases clinically, and new technology for expansion of chondrocytes in vitro for cartilage tissue engineering.
