Division of Tissue Engineering and Biophotonics, Dental Institute, King's College London, Tower Wing, Guy's Hospital, London, SE1 9RT, UK.
Division of Tissue Engineering and Biophotonics, Dental Institute, King's College London, Tower Wing, Guy's Hospital, London, SE1 9RT, UK.
Mol Cell Endocrinol. 2018 Dec 5;477:140-147. doi: 10.1016/j.mce.2018.06.011. Epub 2018 Jun 19.
The osteoporosis-resistant nature of skull bones implies inherent differences exist between their cellular responses and those of other osteoporosis-susceptible skeletal sites. Phenotypic differences in calvarial and femoral osteoblastic responses to induction of osteogenesis, mechanical loading, estrogen, growth factor and cytokine stimulation were investigated. Primary rat calvarial and femoral adult male osteoblasts were cultured and osteoblastic mineralisation and maturation determined using Alizarin Red staining and expression of osteogenic marker genes assessed. Expression of known mechanically-responsive genes was compared between sites following loading of scaffold-seeded cells in a bioreactor. Cell proliferation and differentiation following growth factor and estrogen stimulation were also compared. Finally expression of estrogen receptors and associated genes during osteogenic differentiation were investigated. Calvarial osteoblasts exhibited delayed maturation (45d. vs 21d.) and produced less mineralised matrix than femoral osteoblasts when osteogenically induced. PDGF-BB and FGF2 both caused a selective increase in proliferation and decrease in osteoblastic differentiation of femoral osteoblasts. Mechanical stimulation resulted in the induction of the expression of Ccl2 and Anx2a selectively in femoral osteoblasts, but remained unchanged in calvarial cells. Estrogen receptor beta expression was selectively upregulated 2-fold in calvarial osteoblasts. Most interestingly, the estrogen responsive transcriptional repressor RERG was constitutively expressed at 1000-fold greater levels in calvarial compared with femoral osteoblasts. RERG expression in calvarial osteoblasts was down regulated during osteogenic induction whereas upregulation occurred in femoral osteoblasts. Bone cells of the skull are inherently different to those of the femur, and respond differentially to a range of stimuli. These site-specific differences may have important relevance in the development of strategies to tackle metabolic bone disorders.
颅骨的抗骨质疏松特性表明，其细胞反应与其他易发生骨质疏松的骨骼部位存在固有差异。研究了颅骨和股骨成骨诱导、机械加载、雌激素、生长因子和细胞因子刺激对成骨细胞反应的表型差异。原代大鼠颅骨和股骨成骨细胞培养后，用茜素红染色法测定成骨细胞矿化和成熟情况，并评估成骨标记基因的表达。在生物反应器中对支架接种细胞进行加载后，比较了两个部位已知的机械反应基因的表达。还比较了生长因子和雌激素刺激后细胞增殖和分化的情况。最后，研究了成骨分化过程中雌激素受体和相关基因的表达。成骨诱导时，颅骨成骨细胞成熟（45d. vs 21d.）延迟，产生的矿化基质少于股骨成骨细胞。PDGF-BB 和 FGF2 均导致股骨成骨细胞增殖选择性增加，成骨分化减少。机械刺激选择性诱导股骨成骨细胞表达 Ccl2 和 Anx2a，但在颅骨细胞中不变。雌激素受体β在颅骨成骨细胞中选择性上调 2 倍。最有趣的是，雌激素反应性转录抑制因子 RERG 在颅骨成骨细胞中的表达水平比股骨成骨细胞高 1000 倍，呈组成性表达。成骨诱导时，颅骨成骨细胞中 RERG 的表达下调，而在股骨成骨细胞中上调。颅骨骨细胞与股骨骨细胞不同，对各种刺激的反应也不同。这些部位特异性差异在制定治疗代谢性骨疾病的策略方面可能具有重要意义。
