Molligan Jeremy, Mitchell Reed, Schon Lew, Achilefu Samuel, Zahoor Talal, Cho Young, Loube Jeffery, Zhang Zijun
Orthobiologic Laboratory, MedStar Union Memorial Hospital, Baltimore, Maryland, USA.
Department of Radiology, School of Medicine, Washington University in St. Louis, St. Louis, Missouri, USA.
Stem Cells Transl Med. 2016 Jun;5(6):745-53. doi: 10.5966/sctm.2015-0082. Epub 2016 Apr 25.
: By using surgical mouse models, this study investigated how the tissue environment influences the osteogenic potential of muscle progenitors (m-progenitors) and potentially contributes to heterotopic ossification (HO). Injury was induced by clamping the gluteus maximus and medius (group M) or osteotomy of greater trochanter (group O) on the right hip, as well as combined muscle injury and osteotomy of greater trochanter (group M+O). The gluteus maximus and medius of the operated hips were harvested at days 1, 3, 5, and 10 for isolation of m-progenitors. The cells were cultured in an osteogenic medium for 3 weeks, and osteogenesis was evaluated by matrix mineralization and the expression of osteogenesis-related genes. The expression of type I collagen, RUNX2 (runt-related transcription factor 2), and osteocalcin by the m-progenitors of group M+O was significantly increased, compared with groups M and O. Osteogenic m-progenitors in group O increased the expression of bone morphogenetic protein 2 and also bone morphogenetic protein antagonist differential screening-selected gene aberrative in neuroblastoma. On histology, there was calcium deposition mostly in the muscles of group M+O harvested at day 10. CD56, representing myogenic progenitors, was highly expressed in the m-progenitors isolated from group M (day 10), but m-progenitors of group M+O (day 10) exhibited the highest expression of platelet-derived growth factor receptor α (PDGFR-α), a marker of muscle-derived mesenchymal stem cells (M-MSCs). The expressions of PDGFR-α and RUNX2 were colocalized in osteogenic m-progenitors. The data indicate that the tissue environment simulated in the M+O model is a favorable condition for HO formation. Most likely, M-MSCs, rather than myogenic progenitors, in the m-progenitors participate in HO formation.
The prevalence of traumatic heterotopic ossification (HO) is high in war injury. The pathogenesis of HO is still unknown. This study clarified the contribution of a tissue environment created by bone or muscle injury to the formation of HO. The study also found that muscle-derived mesenchymal stem cells, but not myogenic progenitors, are involved in the formation of HO. The findings of this study could be used to strategize the prevention and treatment of HO.
本研究通过使用手术小鼠模型，探究了组织环境如何影响肌肉祖细胞（m祖细胞）的成骨潜能以及如何潜在地导致异位骨化（HO）。通过夹闭右侧臀部的臀大肌和臀中肌（M组）或大转子截骨术（O组），以及联合肌肉损伤和大转子截骨术（M+O组）诱导损伤。在术后第1、3、5和10天采集手术侧臀部的臀大肌和臀中肌以分离m祖细胞。将细胞在成骨培养基中培养3周，并通过基质矿化和成骨相关基因的表达来评估成骨情况。与M组和O组相比，M+O组m祖细胞中I型胶原蛋白、RUNX2（ runt相关转录因子2）和骨钙素的表达显著增加。O组的成骨m祖细胞增加了骨形态发生蛋白2以及神经母细胞瘤中差异筛选的骨形态发生蛋白拮抗剂异常基因的表达。组织学检查显示，在第10天采集的M+O组肌肉中大多有钙沉积。代表肌源性祖细胞的CD56在从M组（第10天）分离的m祖细胞中高表达，但M+O组（第10天）的m祖细胞表现出肌肉来源间充质干细胞（M-MSCs）标志物血小板衍生生长因子受体α（PDGFR-α）的最高表达。PDGFR-α和RUNX2的表达在成骨m祖细胞中共定位。数据表明，M+O模型模拟的组织环境是HO形成的有利条件。很可能，m祖细胞中的M-MSCs而非肌源性祖细胞参与了HO的形成。
创伤性异位骨化（HO）在战伤中的发生率很高。HO的发病机制仍然未知。本研究阐明了由骨或肌肉损伤产生的组织环境对HO形成的作用。该研究还发现，参与HO形成的是肌肉来源的间充质干细胞而非肌源性祖细胞。本研究的结果可用于制定HO的预防和治疗策略。
