Lips Katrin S, Yanko Özcan, Kneffel Mathias, Panzer Imke, Kauschke Vivien, Madzharova Maria, Henss Anja, Schmitz Peter, Rohnke Marcus, Bäuerle Tobias, Liu Yifei, Kampschulte Marian, Langheinrich Alexander C, Dürselen Lutz, Ignatius Anita, Heiss Christian, Schnettler Reinhard, Kilian Olaf
Laboratory for Experimental Trauma Surgery, Justus-Liebig University Giessen, Kerkraderstr. 9, 35394, Giessen, Germany.
Institute for Physical Chemistry, Justus-Liebig University Giessen, Heinrich-Buff-Ring 58, 35392, Giessen, Germany.
BMC Musculoskelet Disord. 2015 Jan 31;16(1):5. doi: 10.1186/s12891-015-0459-8.
Recently, analysis of bone from knockout mice identified muscarinic acetylcholine receptor subtype M3 (mAChR M3) and nicotinic acetylcholine receptor (nAChR) subunit α2 as positive regulator of bone mass accrual whereas of male mice deficient for α7-nAChR (α7KO) did not reveal impact in regulation of bone remodeling. Since female sex hormones are involved in fair coordination of osteoblast bone formation and osteoclast bone degradation we assigned the current study to analyze bone strength, composition and microarchitecture of female α7KO compared to their corresponding wild-type mice (α7WT).
Vertebrae and long bones of female 16-week-old α7KO (n = 10) and α7WT (n = 8) were extracted and analyzed by means of histological, radiological, biomechanical, cell- and molecular methods as well as time of flight secondary ion mass spectrometry (ToF-SIMS) and transmission electron microscopy (TEM).
Bone of female α7KO revealed a significant increase in bending stiffness (p < 0.05) and cortical thickness (p < 0.05) compared to α7WT, whereas gene expression of osteoclast marker cathepsin K was declined. ToF-SIMS analysis detected a decrease in trabecular calcium content and an increase in C4H6N(+) (p < 0.05) and C4H8N(+) (p < 0.001) collagen fragments whereas a loss of osteoid was found by means of TEM.
Our results on female α7KO bone identified differences in bone strength and composition. In addition, we could demonstrate that α7-nAChRs are involved in regulation of bone remodelling. In contrast to mAChR M3 and nAChR subunit α2 the α7-nAChR favours reduction of bone strength thereby showing similar effects as α7β2-nAChR in male mice. nAChR are able to form heteropentameric receptors containing α- and β-subunits as well as the subunits α7 can be arranged as homopentameric cation channel. The different effects of homopentameric and heteropentameric α7-nAChR on bone need to be analysed in future studies as well as gender effects of cholinergic receptors on bone homeostasis.
最近，对基因敲除小鼠骨骼的分析确定毒蕈碱型乙酰胆碱受体M3亚型（mAChR M3）和烟碱型乙酰胆碱受体（nAChR）α2亚基为骨量积累的正向调节因子，而α7 - nAChR缺陷的雄性小鼠（α7KO）在骨重塑调节方面未显示出影响。由于雌性激素参与成骨细胞骨形成和破骨细胞骨降解的适度协调，我们开展了本研究，以分析雌性α7KO小鼠与其相应野生型小鼠（α7WT）相比的骨强度、组成和微观结构。
提取16周龄雌性α7KO小鼠（n = 10）和α7WT小鼠（n = 8）的椎骨和长骨，通过组织学、放射学、生物力学、细胞和分子方法以及飞行时间二次离子质谱（ToF - SIMS）和透射电子显微镜（TEM）进行分析。
与α7WT相比，雌性α7KO小鼠的骨骼显示出弯曲刚度显著增加（p < 0.05）和皮质厚度增加（p < 0.05），而破骨细胞标志物组织蛋白酶K的基因表达下降。ToF - SIMS分析检测到小梁钙含量降低，C4H6N(+)（p < 0.05）和C4H8N(+)（p < 0.001）胶原片段增加，而通过TEM发现类骨质减少。
我们对雌性α7KO小鼠骨骼的研究结果确定了骨强度和组成的差异。此外，我们能够证明α7 - nAChRs参与骨重塑的调节。与mAChR M3和nAChR亚基α2不同，α7 - nAChR有利于降低骨强度，从而在雄性小鼠中显示出与α7β2 - nAChR相似的作用。nAChR能够形成包含α和β亚基的异五聚体受体，并且α7亚基可以排列成同五聚体阳离子通道。同五聚体和异五聚体α7 - nAChR对骨骼的不同作用以及胆碱能受体对骨稳态的性别影响需要在未来的研究中进行分析。
