Leptin expression by heterotopic ossification-isolated tissue in rats with Achilles' tenotomy

OBJECTIVE: To set up heterotopic ossification (HO) models according to McClure and determine whether leptin messenger ribonucleic acid (mRNA) and protein are expressed in HO-isolated tissue.

METHODS: This study was performed in the Department of Spine and Orthopedics, Southern Medical University, Guangzhou, China from November 2007 to June 2008. Thirty-six male rats were randomly divided into sham, partial achilles' tenotomy (PAT), and achilles' tenotomy (AT) groups, with 12 rats in each group. X-ray and histological examination were carried out to ensure the formation of HO at 5 and 10 weeks after operation. Specimens from achilles tendons and surrounding tissue were taken and processed. Meanwhile, the expression of leptin mRNA (5 and 10 weeks) and protein (10 weeks) in achilles tendons and the surrounding tissue were examined respectively using reverse transcription-polymerase chain reaction assay and immunohistochemical methods.

RESULTS: There were no leptin mRNA and protein expression in the sham and a weak expression in the PAT of Achilles tendons and surrounding tissue, whereas there was strong expression in the AT group.

CONCLUSION: Leptin is involved in the formation of HO, its mechanisms is related to induction of bone formation and maturation through a series of cellular events, including: proliferation/differentiation of many kinds of cells, collagen synthesis, mineralization, and vascularization of the extracellular matrix.