INSULIN-LIKE GROWTH-FACTOR GENE-EXPRESSION IN HUMAN FRACTURE CALLUS

The effects of insulinlike growth factors on bone and cartilage-derive d cells in culture have been extensively investigated, but there is li ttle information on their role in vivo in bone, especially in fracture healing. This study investigated insulinlike growth factor (IGF) I an d II mRNA expression in normally healing human fractures by in situ hy bridization. Endothelial and mesenchymal cells at the granulation tiss ue stage expressed IGF-II mRNA. At the stage of bone and cartilage for mation, osteoblasts and non-hypertrophic chondrocytes expressed mRNA f or both IGF-I and II. Some osteoclasts were positive for IGF-II mRNA a t the stage of bone remodeling. The greater time span of IGF-II expres sion relative to IGF-I reflects the predominance of IGF-II in human bo ne matrix. Taken together with the known effects of IGFs on bone and c artilage cells in vitro, these findings support a role for IGFs in loc al cellular regulation in human fracture healing.