Expression and significance of related genes in the early stage of post-traumatic heterotopic ossification in a rat model of Achilles tenotomy

Objective: This study aims to determine expression profiles of relevant genes in the early stages of post-traumatic heterotopicossification (HO) in a rat model of Achilles tenotomy.Methods: A total of 80 male Sprague-Dawley rats were randomly assigned to two groups: the HO group and the control group.Tenotomy was performed in the Achilles tendon of the rats in the HO group, and no intervention was conducted in the controlgroup. On the 3rd, 5th, 8th, and 14th days after the operation, 8 rats were taken from each group at each time point, and the Achillestendon and surrounding tissue specimens were collected. Gene expressions of TGF-β, BMP, GDF, IL, and MMP families as wellas TNF-α, HIF-1α chordin, gremlin, noggin, and NODAL were analyzed by qRT-PCR. The relevant genes that were highly expressed at different time points were screened, and immunohistochemical staining was then used to verify their expression. Atthe 10th week, HO formation was explored by radiographic and histological examination in the remaining 8 rats of each group.Results: Both the radiographic and histological analyses indicated that all the rats developed HO in the HO group (100%),whereas no HO occurred in the control group. Surrounding tissues obtained from the HO group showed significantly highergene expressions of TGF-β1, BMP-1, IL1β, HIF-1α, and MMP-2 but lower expressions of BMP-4, GDF-8, and TNF-α comparedwith the control group. In addition, immunohistochemical staining confirmed the higher protein expression levels of relevantgenes in the HO group.Conclusion: TGF-β1, BMP-1, IL-1β, HIF-1α, MMP-2, BMP4, GDF-8, and TNF-α may be associated with the formation of traumatic HO; and BMP4, GDF-8, and TNF-α may play a protective role in the early stage of HO. In this study, we investigated theexpression levels of the related cytokines in the early stages of traumatic HO in the Achilles tendon tenotomy rat model to betterunderstand the pathogenesis of HO.

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