Yingling Vanessa R, Xiang Yongqing, Raphan Theodore, Schaffler Mitchell B, Koser Karen, Malique Rumena
Physical Education and Exercise Science, Brooklyn College (City University of New York), 2900 Bedford Avenue, Brooklyn, NY 11210, USA.
Bone. 2007 Feb;40(2):419-24. doi: 10.1016/j.bone.2006.07.019. Epub 2006 Sep 18.
Accrual of bone mass and strength during development is imperative in order to reduce the risk of fracture later in life. Although delayed pubertal onset is associated with an increased incidence of stress fracture, evidence supports the concept of "catch up" growth. It remains unclear if deficits in bone mass associated with delayed puberty have long-term effects on trabecular bone structure and strength. The purpose of this study was to use texture-based analysis and histomorphometry to investigate the effect of a delay in puberty on trabecular bone mass and structure immediately post-puberty and at maturity in female rats. Forty-eight female Sprague-Dawley rats (25 days) were randomly assigned to one of four groups; (1) short-term control (C-ST), (2) long-term control (C-LT), (3) short-term GnRH antagonist (G-ST) and (4) long-term GnRH antagonist (G-LT). Injections of either saline or gonadotropin-releasing hormone antagonist (GnRH-a) (100 microg/day) (Cetrotide, Serono, Inc.) were given intraperitoneally for 18 days (day 25-42) to both ST and LT. The ST groups were sacrificed after the last injection (day 43) and the LT groups at 6 months of age. Pubertal and gonadal development was retarded by the GnRA antagonist injections as indicated by a delay in vaginal opening, lower ovarian and uterine weights and suppressed estradiol levels in the short-term experimental animals (G-ST). Delayed puberty caused a transient reduction in trabecular bone area as assessed by histomorphometry. Specifically, the significant deficit in bone area resulted from a decreased trabecula number and an increase in trabecular separation. Texture analysis, a new method to assess bone density and structural anisotropy, correlated well with the standard histomorphometry and measured significant deficits in the density measure (M(Density)) in the G-ST group that remained at maturity (6 months). The texture energy deficit in the G-ST group was primarily in the 0 degrees orientation (-13.2%), which measures the longitudinal trabeculae in the proximal tibia. However, the deficit in the G-LT group was in the 45 degrees and 135 degrees orientations. These results suggest that any "catch-up" growth following the cessation of the GnRH-antagonist injection protocol may be directed in trabeculae oriented perpendicular to 0 degrees at the expense of trabeculae in other orientations.
在发育过程中积累骨量和骨强度对于降低日后生活中骨折风险至关重要。尽管青春期启动延迟与应力性骨折发病率增加有关，但有证据支持“追赶”生长的概念。目前尚不清楚与青春期延迟相关的骨量不足是否会对小梁骨结构和强度产生长期影响。本研究的目的是使用基于纹理的分析和组织形态计量学来研究青春期延迟对雌性大鼠青春期刚结束时和成年时小梁骨量和结构的影响。48只雌性斯普拉格-道利大鼠（25日龄）被随机分为四组之一：（1）短期对照组（C-ST），（2）长期对照组（C-LT），（3）短期促性腺激素释放激素拮抗剂组（G-ST）和（4）长期促性腺激素释放激素拮抗剂组（G-LT）。对ST组和LT组大鼠均于第25至42天腹腔注射生理盐水或促性腺激素释放激素拮抗剂（GnRH-a）（100微克/天）（西曲瑞克，雪兰诺公司），共注射18天。最后一次注射后（第43天）处死ST组，6月龄时处死LT组大鼠。如短期实验动物（G-ST）中阴道开口延迟、卵巢和子宫重量降低以及雌二醇水平受抑制所示，GnRA拮抗剂注射使青春期和性腺发育延迟。通过组织形态计量学评估，青春期延迟导致小梁骨面积短暂减少。具体而言，骨面积的显著不足是由于小梁数量减少和小梁间距增加所致。纹理分析是一种评估骨密度和结构各向异性的新方法，与标准组织形态计量学相关性良好，且测量出G-ST组在密度测量值（M（密度））方面存在显著不足，这种不足在成年期（6个月）时仍然存在。G-ST组的纹理能量不足主要在0度方向（-13.2%），该方向测量胫骨近端的纵向小梁。然而，G-LT组的不足在45度和135度方向。这些结果表明，GnRH拮抗剂注射方案停止后的任何“追赶”生长可能以垂直于0度方向的小梁为导向，而以其他方向的小梁为代价。
