Background: Although Semaphorin 3A (Sema3A)/ Neuropilin-1(NRP1)/Plexin A1 is one of the important targets in bone metabolism, few studies are performed on this target in the glucocorticoids- induced osteoporosis. Luteolin is a chemical component of Honeysuckle and it has various bioactivities. The effect of Luteolin on the glucocorticoids-induced osteoporosis (primary osteoblasts model) remain unknown.

Objective: The aim of this study was to investigate the action of Sema3A/ NRP1/Plexin A1 in Luteolin- induced osteoprotection against high-dose Dexamethasone.

Methods: The effect of Luteolin on the proliferation, late differentiation, and apoptosis of primary osteoblasts model of glucocorticoids-induced osteoporosis in vitro as well as the expression of Sema3A/ NRP1/Plexin A1 are investigated by using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-Htetrazolium bromide, Cell Counting Kit-8, reverse transcription-quantitative real-time polymerase chain reaction, western bolting and so on.

Results: Suckling SD rats’ calvarial osteoblasts were isolated and identified. The glucocorticoidsinduced primary osteoporosis cell model was established by 100 μM Dexamethasone in 48 h (P<0.01). Luteolin promotes osteoblasts either in physiological condition (without Dexamethasone) or pathological condition (with Dexamethasone) at 1 μM concentration for 48h (P<0.01). Luteolin partly reverses down-regulated expression of proliferation markers such as proliferating cell nuclear and CyclinD1. (P<0.01) Similarly, Luteolin partly reverses up-regulated expression of apoptosis markers such as Bax/B-cell lymphoma-2. (P<0.01) The expression of mRNA and protein of Sema3A/ NRP1/Plexin A1 decreased in model one which significantly increased in Luteolin protecting one. (P<0.05) Interestingly, the late differentiation marker such as osteocalcin and collagenase Ⅰ sharply decreased in Luteolin protecting group compared with model one. (P<0.01).

Conclusion: The thesis concludes that Luteolin promoted the proliferation of osteoblast and inhibited its apoptosis and late differentiation in this glucocorticoids-induced primary osteoporosis cell model. This function may be related to the expression of up-regulated Sema3A/NRP1/Plexin A1. Therefore, Luteolin may be a potential medicine for the glucocorticoids-induced osteoporosis.

背景：虽然Semaphorin 3A (Sema3A)/ Neuropilin-1(NRP1)/Plexin A1 是骨代谢的重要靶点之一，但在糖皮质激素诱导的骨质疏松症中对该靶点进行的研究很少。木犀草素是金银花的化学成分，具有多种生物活性。木犀草素对糖皮质激素诱导的骨质疏松症（原发性成骨细胞模型）的影响仍然未知。

目的：本研究的目的是研究 Sema3A/NRP1/Plexin A1 在木犀草素诱导的针对高剂量地塞米松的骨保护中的作用。

方法: 用 3-(4,5-二甲基氨基丁酸-2-thiazolyl)-2,5-diphenyl-2-Htetrazolium bromide、Cell Counting Kit-8、逆转录-定量实时聚合酶链反应、Westernbolting等。

结果：分离鉴定出哺乳SD大鼠的颅骨成骨细胞。100 μM地塞米松48 h建立糖皮质激素诱导的原发性骨质疏松细胞模型（P<0.01）。木犀草素在生理条件（无地塞米松）或病理条件（有地塞米松）下以 1 μM 浓度促进成骨细胞 48 小时（P < 0.01）。木犀草素部分逆转增殖标志物（如增殖细胞核和 CyclinD1）的下调表达。(P<0.01) 同样，木犀草素可部分逆转细胞凋亡标志物（如 Bax/B 细胞淋巴瘤-2）的上调表达。(P<0.01)Sema3A/NRP1/Plexin A1 mRNA和蛋白在模型一中降低，而在木犀草素保护模型中显着升高。(P<0.05) 有趣的是，与模型1相比，木犀草素保护组的骨钙素和胶原酶Ⅰ等晚期分化标志物急剧下降。(P<0.01)。

结论：本论文得出结论，木犀草素在糖皮质激素诱导的原发性骨质疏松细胞模型中具有促进成骨细胞增殖并抑制其凋亡和晚期分化的作用。该功能可能与上调 Sema3A/NRP1/Plexin A1 的表达有关。因此，木犀草素可能是治疗糖皮质激素诱发的骨质疏松症的潜在药物。