骨细胞密度对骨生物力学性能的影响

目的 探讨骨细胞密度是否为衡量骨生物力学性能的指标. 方法 40只7月龄雌性SD大鼠随机分为去卵巢组(OVX)、OVX+金雀异黄酮(GEN,5 mg·kg-1·d-1)和OVX+1713雌二醇(EST,10 μg·kg-1·d-1)组及假手术组(SHAM),每组lO只.手术后15周第5腰椎(L5)椎体进行压缩试验,L6椎体先行显微CT扫描测量三维骨密度和骨微结构参数,然后进行疲劳损伤试验,最后行大块组织品红染色、塑料包埋和磨片.磨片标本用于微损伤、骨细胞密度检测. 结果 去卵巢后15周时,OVX组骨细胞密度为(1268.1±191.2)个/mm2,较SHAM组(1760.8±376.6)个/mm2及EST组(1550.9±202.2)个/mm2降低(F=3.531,P<0.05);OVX组最大应力为(84.4±16.9)N,较SHAM(110.3±25.6)N、EST(103.9±15.8)N及GEN组(110.1±4.9)N降低(F=9.561,P<0.05);OVX组骨小梁连接密度为(47.4±7.4)mm-3,较SHAM(71.8±16.0)mm-3及EST组(74.0±12.7)mm-3降低(F=7.635,P<0.05);OVX组骨矿含量为(6.5±2.2)g,较SHAM组(7.9±1.2)g降低(F=2.489,P<0.05);OVX组微破裂平均长度(58.1±6.8)μm,较SHAM(24.2±8.1)/Lm、EST(36.5±9.7)μm及GEN组(28.5±7.5)μm增加(F=3.179,P<0.05);OVX组骨小梁间隔(315.0±32.7)μm,较SHAM(222.5±21.7)μm及EST组(273.3±50.O)μm增加(F=7.007,P<0.05).骨细胞密度与最大应力(R2=0.7874,P<0.05)、骨小梁连接密度(R2=0.1153,P<0.05)、骨矿含量(R2=0.1309,P<0.05)呈正相关,与微破裂平均长度(R2=0.5738,P<0.05)、骨小梁分离度(R2=0.3964,P<0.05)负相关. 结论 骨细胞在维持骨力学性能中起重要作用,骨细胞密度可能是潜在的评价骨力学性能的重要指标.

Osteocyte density may be an important influencing factor for the bone biomechanical property

Objective To investigate osteocyte density as a potential index of bone biomechanical property. Methods Forty 7-month-old female Sprague-Dawley rats were randomly group (EST) and sham operation group (SHAM). At 15 weeks postoperation, the compression test was performed on L5 vertebral body and micro-computed tomography (μ-CT) was used to estimate the three-dimensional bone mineral density (BMD) and three-dimensional microstructure parameters of L6 vertebral body. After fatigue damage testing, the L6 vertebral body was bulk-stained in 1% basic fuchsin and embedded in methylmethacrylate. Mounted bone slices were used to measure microcrack parameters and osteocyte density. Results At 15 weeks postoperation, osteocyte density (Ot. N/T. area) was significantly decreased in OVX group compared with SHAM group and EST group (1268. 1 ±191.2)/mm2 vs. (1760. 8 ± 376.6)/mm2 and (1550. 9± 202.2)/mm2, F = 3.513,P<0. 05]. Maximum load (ML) was significantly decreased and the length of microcrack (Cr. Le) was significantly increased in OVX group compared with SHAM group, EST group and GEN group (84. 4±16.9)N vs. (110.3±25.6),(103. 9±15. 8)and(110.1±4. 9)N; (58. 1±6.8) μm vs. (24.2±8. 1), (36. 5±9. 7)and(28.5±7. 5)μm, F=9. 561,3. 179, all P<0. 05]. Compared with SHAM group and EST group, bone trabecula connection density (Conn. D) was significantly decreased and trabecular separation (Tb. Sp) was significantly increased in OVX group (47.4±7.4) m-3 vs. (71.8±16.0)and (74.0±12.7)m-3;(315.0±32.7)μm vs. (222. 5±21.7)and (273.3± 50.0)μm, F=7. 635,7. 007, all P<0. 05]. Bone mineral content (BMC) was lower in OVX group than that in SHAM group(6.5±2. 2)g vs. (7. 9±1.2)g, P<0. 05]. When data in four groups were overall analyzed, Ot. N/T. Ar was positively correlated with ML, Conn. D and BMC (R2 = 0. 7874, 0. 1153, 0. 1309, all P<0. 05), but was negatively correlated with Cr. Le and Tb. Sp (R2 =0. 5738, 0. 3964, both P < 0.05). Conclusions Osteocyte plays a crucial role in maintaining bone biomechanical property and osteocyte density may be considered as a useful indicator for assessing bone biomechanical property.