大剂量1,25二羟维生素D_3对发育期小鼠骨稳态的影响

Effects of bone homeostasis induced by high-dose 1,25( OH)_2D_3 in pubertal mice

目的观察大剂量1,25二羟维生素D3[1,25(OH)2D3]对小鼠发育期骨稳态的影响。方法怀孕13.5 d的C3h小鼠分成3组,每日分别经腹腔注射1%的乙醇溶液(对照组),0.5 ng/g的1,25(OH)2D3(低剂量组)和5 ng/g的1,25(OH)2D3(大剂量组),持续至孕鼠分娩。新生小鼠从第3天开始隔天注射相同剂量的1,25(OH)2D3,连续1个月。观察小鼠出生以及身长、体质量等生长变化情况;1月龄的小鼠分别行X线检查、Micro-CT扫描,胫骨组织石蜡包埋、切片后经HE、藏红固绿染色,行组织学、骨形态计量分析,观察不同分组发育期小鼠骨骼结构及骨代谢的变化情况。结果从E13.5 d开始注射不同剂量的1,25(OH)2D3对孕鼠怀孕过程和小鼠出生没有明显的影响,出生后第7天开始,大剂量组小鼠身长、体质量明显低于对照组(P<0.05),1月龄时,差异增大,大剂量组身长、体质量显著低于对照组和小剂量组(P<0.01);X线检测显示1月龄大剂量组小鼠发生病理性骨折(n=10),其余2组未发现;Micro-CT结果提示大剂量组小鼠骨量较对照组显著降低(P<0.01),低剂量组小鼠仅骨皮质厚度有所增加(P<0.05);胫骨组织切片形态计量分析显示大剂量组小鼠破骨细胞数量较其余2组显著增加(P<0.01),而低剂量组破骨细胞数量的增加差异无统计学意义;低剂量组成骨细胞数量较其余2组有明显增加(P<0.05)。结论大剂量1,25(OH)2D3显著降低C3h小鼠骨量,同时使骨皮质菲薄,骨骼质量变差,从而易骨折。这种作用主要是通过促进破骨细胞的形成实现的。

Objective To investigate the effects of high-dose 1,25-dihydroxy-vitamin D3 [ 1,25 （OH）2D3] on the bone homeostasis of mice in puberty. Methods Pregnant C3h mice were allocated in 3 groups with intraperitoneal （ i. p. ） injection of 1% ethanol （ control group）, 0.5 ng/g 1,25 （OH） 2 D3 （ lowdose group） and 5 ng/g 1,25 （OH）2 D3 （high-dose group）, respectively, from El3.5 until delivery. The newboms of each group were injected with the same dose of 1,25 （OH）2D3 as their mothers did from day 3 after birth, every 2 days, to 1 month. The body weight and length of the newborns were recorded per week. All mice were subjected to X-ray filming and Micro-CT scanning at 1 month and then sacrificed. The tibiae were dissected and decalcified for histological and histomorphometry analysis. Results The injection of 1,25 （OH）2D3 from El3.5 had no significant effect on pregnancy and birth. Compared with the control group, the mice in the high-dose group had significantly shortened body length and lightened body weight from day 7 after birth （P 〈 0. 05）. At 1 month after birth, the significant differences were enlarged （ P 〈 0. 001 ）. X-ray filming showed spontaneous bone fracture of mice with high-dose 1,25 （OH）2D3 injection, which did not exist in other groups. Micro-CT scanning demonstrated a significant decrease in bone volume of mice in the high-dose group （P 〈 0. 001 ）, while in the low-dose group only the thickness of cortical bone had increased （P 〈 0.05 ）. Histological analysis revealed significantly increased number of osteoclasts in the high-dose group compared with other groups （P 〈0. 001 ）, while only a slight increase which had no statistic significance in the number of osteoclasts from the low-dose group was detected. Only mice from the low-dose group had significantly increased osteoblasts （P 〈0. 05）. Conclusion High dose of 1,25 （OH）2D3 results in decreased bone volume and compromised bone integrity, leading to higher risk of bone fracture. These negative effects may predominantly result from an increase in the population of osteoclasts.