Fourier transform infrared microspectroscopic analysis of bones of osteocalcin-deficient mice provides insight into the function of osteocalcin
Fourier transform infrared microspectroscopic analysis of bones of osteocalcin-deficient mice provides insight into the function of osteocalcin
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DOI：
10.1016/s8756-3282(98)00092-1
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发表时间：
1998-09-01
期刊：
影响因子：
4.1
通讯作者：
Karsenty, G
中科院分区：
文献类型：
--
作者：
Boskey, AL;Gadaleta, S;Karsenty, G
骨钙素（Osteocalcin）是一种含有γ-羧基谷氨酸的蛋白质，在大多数物种中是骨和牙本质的主要非胶原蛋白，被认为在骨形成和骨重建中发挥作用。根据von Kossa染色和四环素标记骨中矿物质沉积率的测量，骨钙素敲除动物的骨矿化没有可检测的变化。为了验证这一假设，除了调节成骨细胞的活性，骨钙素参与调节矿物质的性质，一个更敏感的测定矿化，傅立叶变换红外显微光谱（FT-FTIR）被用来研究薄切片的股骨4周，6个月（完整和卵巢切除），和9个月大的野生型和骨钙素基因敲除小鼠。FT-FTIR光谱提供了相对矿物质和碳酸盐含量的空间分辨测量，以及指示磷灰石晶体大小和完整性的参数。在4周龄敲除小鼠和野生型小鼠的矿物质性质中没有检测到差异，表明矿化过程在该时间点没有改变，6个月大的野生型动物具有更高的矿物质含量。（矿物质：基质比）在皮质骨相比，小梁骨;敲除和野生型骨的矿物质含量仅仅没有不同，在每个年龄段的研究，碳酸盐：磷酸盐的比例往往是更大的野生型相比，敲除动物。对来自6个月大的野生型动物的光谱中的磷酸盐nu（1）、nu（3）振动的详细分析表明，与小梁骨相比，皮质骨中的晶体更大/更完美。相反，在6个月大的敲除动物的骨中，在碳酸盐含量或微晶尺寸和完美性方面，小梁骨和皮质骨之间没有差异。敲除动物的皮质骨和骨小梁的光谱参数与野生猿骨小梁相似，而与野生型皮质骨不同。在野生型皮质中，从骨膜到骨内膜，矿物质：基质比增加，而在敲除动物的骨中，矿物质：基质比是恒定的，卵巢切除敲除皮质具有较低的碳酸盐：磷酸盐比率高于野生型，微晶大小和完整性与野生型骨小梁相似，并且从骨膜到骨内膜没有增加。这些空间分辨数据提供了骨钙素是刺激骨矿物质成熟所必需的证据。(Bone 23：187-196; 1998）（C）Elsevier Science Inc. All rights reserved.
Osteocalcin, the gamma-carboxyglutamic acid-containing protein, which in most species is the predominant noncollagenous protein of bone and dentin, has been postulated to play roles in bone formation and remodeling, Recently, genetic studies showed that osteocalcin acts as an inhibitor of osteoblast function. Based on von Kossa staining and measurement of mineral apposition rates in tetracycline-labeled bones, osteocalcin knockout animals were reported to have no detectable alterations in bone mineralization. To test the hypothesis that, in addition to regulating osteoblastic activity, osteocalcin is involved in regulating mineral properties, a more sensitive assay of mineralization, Fourier transform infrared microspectroscopy (FT-IRM) was used to study thin sections of femora of 4-week-, 6-month- (intact and ovariectomized), and 9-month-old wild-type and osteocalcin-knockout mice. FT-IRM spectra provided spatially resolved measures of relative mineral and carbonate contents, and parameters indicative of apatite crystal size and perfection, No differences were detected in the mineral properties of the 4-week-old knockout and wild-type mice indicating that the mineralization process was not altered at this time point, Six-month-old wildtype animals had higher mineral contents (mineral:matrix ratios) in cortical as compared with trabecular bones; mineral contents in knockout and wild-type bones mere not different, At each age studied, carbonate:phosphate ratios tended to be greater in the wild-type as compared with knockout animals. Detailed analysis of the phosphate nu(1),nu(3) vibrations in the spectra from 6-month-old wild-type animals indicated that the crystals were larger/more perfect in the cortical as opposed to the trabecular bones, In contrast, in the knockout animals' bones at 6 months, there were no differences between trabecular and cortical bone in terms of carbonate content or crystallite size and perfection, Spectral parameters of the cortical and trabecular bone of the knockout animals resembled those in the wild-ape trabecular bone and differed from wild-type cortical bone, In ovariectomized 6-month-old animals, the mineral content (mineral:matrix ratio) in the wild-type cortices increased from periosteum to endosteum, whereas, in the knockout animals' bones, the mineral:matrix ratio was constant, Ovariectomized knockout cortices had lower carbonate:phosphate ratios than wildtype, and crystallite size and perfection resembled that in wild-type trabeculae, and did not increase from periosteum to endosteum, These spatially resolved data provide evidence that osteocalcin is required to stimulate bone mineral maturation. (Bone 23:187-196; 1998) (C) 1998 by Elsevier Science Inc. All rights reserved.