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Midkine is expressed during repair of bone fracture and promotes chondrogenesis
1Department of Biochemistry, Nagoya University School of Medicine, Nagoya, Japan.
Abstract:
Midkine (MK) is a heparin-binding growth/differentiation factor implicated in the control of development and repair of various tissues. Upon fracture of the murine tibia, MK was found to be transiently expressed during bone repair. MK was immunohistochemically detected in spindle-shaped mesenchymal cells at the fracture site on day 4 after fracture and in chondrocytes in the area of endochondral ossification on day 7. MK expression was decreased on day 14 and scarcely seen on day 28 when bone repair was completed. This mode of MK expression is reminiscent of MK expression during development. MK was expressed in hypertrophic chondrocytes of the prebone cartilage rudiments on embryonic day 14 in mouse embryos. MK was also strongly expressed in the epiphyseal growth plate. MK was localized intracellularly during both bone repair and development, and this localization was confirmed by immunoelectron microscopy for embryonic chondrocytes. When MK cDNA was transfected into ATDC5 chondrogenic cells and overexpressed, the majority of transfected cells with strong MK expression showed enhanced chondrogenesis as revealed by increased synthesis of sulfated glycosaminoglycans, aggrecan, and type II collagen. These results suggest that MK plays important roles in chondrogenesis and contributes to bone formation and repair.
Insights
Midkine (MK) is crucial for bone repair and development. This study shows MK enhances chondrogenesis, promoting bone formation and healing in mice.
Area of Science:
- Cell Biology
- Developmental Biology
- Orthopedics
Background:
- Midkine (MK) is a heparin-binding growth factor involved in tissue development and repair.
- MK expression is transiently observed during murine tibia fracture healing.
Purpose of the Study:
- To investigate the role of Midkine (MK) in bone repair and chondrogenesis.
- To elucidate the expression patterns and functional significance of MK during skeletal development and fracture healing.
Main Methods:
- Immunohistochemistry and immunoelectron microscopy were used to detect MK expression in murine tibia fractures and embryonic cartilage.
- MK cDNA was transfected into ATDC5 chondrogenic cells to assess its effect on chondrogenesis.
Main Results:
- MK was transiently expressed in mesenchymal cells and chondrocytes during bone repair, mirroring developmental expression patterns.
- MK was localized intracellularly in chondrocytes during both development and repair.
- Overexpression of MK in ATDC5 cells significantly enhanced chondrogenesis, indicated by increased synthesis of sulfated glycosaminoglycans, aggrecan, and type II collagen.
Conclusions:
- Midkine (MK) plays a significant role in chondrogenesis.
- MK contributes to bone formation and fracture repair processes.