Department of Orthopaedics and Trauma, Medical University Graz, 8036 Graz, Austria.
Department of Neurosurgery, Research Unit for Experimental Neurotraumatology, Medical University of Graz, 8036 Graz, Austria; Bio-Tech-Med Graz, 8010 Graz, Austria.
Cells Dev. 2024 Sep;179:203927. doi: 10.1016/j.cdev.2024.203927. Epub 2024 May 11.
Postnatal bone growth primarily relies on chondrocyte proliferation and osteogenic differentiation within the growth plate (GP) via endochondral ossification. Despite its importance, the GP is vulnerable to injuries, affecting 15-30 % of bone fractures. These injuries may lead to growth discrepancies, influence bone length and shape, and negatively affecting the patient's quality of life. This study aimed to investigate the molecular and cellular physiological and pathophysiological regeneration following sustained growth plate injury (GPI) in an ex vivo rat femur organotypic culture (OTC) model. Specifically, focusing on postnatal endochondral ossification process. 300 μm thick ex vivo bone cultures with a 2 mm long horizontal GPI was utilized. After 15 days of cultivation, gene expression analysis, histological and immunohistochemistry staining's were conducted to analyze key markers of endochondral ossification. In our OTCs we observed a significant increase in Sox9 expression due to GPI at day 15. The Ihh-PTHrP feedback loop was affected, favoring chondrocyte proliferation and maturation. Ihh levels increased significantly on day 7 and day 15, while PTHrP was downregulated on day 7. GPI had no impact on osteoclast number and activity, but gene expression analysis indicated OTCs' efforts to inhibit osteoclast differentiation and activation, thereby reducing bone resorption. In conclusion, our study provides novel insights into the molecular and cellular mechanisms underlying postnatal bone growth and regeneration following growth plate injury (GPI). We demonstrate that chondrocyte proliferation and differentiation play pivotal roles in the regeneration process, with the Ihh-PTHrP feedback loop modulating these processes. Importantly, our ex vivo rat femur organotypic culture model allows for the detailed investigation of these processes, providing a valuable tool for future research in the field of skeletal biology and regenerative medicine.
出生后骨骼的生长主要依赖于生长板（GP）内软骨细胞的增殖和成骨分化，通过软骨内成骨实现。尽管生长板很重要，但它很容易受到损伤，约 15-30%的骨折发生在生长板。这些损伤可能导致生长差异，影响骨骼的长度和形状，并对患者的生活质量产生负面影响。本研究旨在探讨在体外大鼠股骨器官培养（OTC）模型中持续生长板损伤（GPI）后的分子和细胞生理及病理生理再生。具体来说，我们关注的是出生后的软骨内成骨过程。使用厚度为 300μm、长 2mm 的水平生长板损伤的体外骨培养物。培养 15 天后，进行基因表达分析、组织学和免疫组织化学染色，以分析软骨内成骨的关键标志物。在我们的 OTC 中，我们观察到 GPI 导致 Sox9 表达在第 15 天显著增加。Ihh-PTHrP 反馈环受到影响，有利于软骨细胞增殖和成熟。Ihh 水平在第 7 天和第 15 天显著增加，而 PTHrP 在第 7 天下调。GPI 对破骨细胞数量和活性没有影响，但基因表达分析表明 OTC 努力抑制破骨细胞分化和激活，从而减少骨吸收。总之，本研究为生长板损伤后出生后骨骼生长和再生的分子和细胞机制提供了新的见解。我们证明了软骨细胞增殖和分化在再生过程中起着关键作用，Ihh-PTHrP 反馈环调节这些过程。重要的是，我们的体外大鼠股骨器官培养模型允许对这些过程进行详细研究，为骨骼生物学和再生医学领域的未来研究提供了有价值的工具。
