Pufe T, Claassen H, Scholz-Ahrens K E, Varoga D, Drescher W, Franke A T M, Wruck C, Petersen W, Cellarius C, Schrezenmeir J, Glüer C-C
Department of Anatomy, Christian-Albrechts-University Kiel, Olshausenstrasse 40, 24098, Kiel, Germany.
Calcif Tissue Int. 2007 Mar;80(3):184-91. doi: 10.1007/s00223-006-0275-0. Epub 2007 Mar 3.
Ovariectomy (OVX) in animal models is an accepted method to simulate postmenopausal osteoprosis. Vascular endothelial growth factor (VEGF) has been recently shown to play an important role during endochondral bone formation, hypertrophic cartilage remodeling, ossification, and angiogenesis. We hypothesized that reduced VEGF expression in bone contributes to OVX-induced bone loss and tested it in a miniature pig model and in vitro using human osteoblasts. Seventeen primiparous sows (Göttingen miniature pigs) were allocated to two experimental groups when they were 30 months old: a control group (n = 9) and an OVX group (n = 8). After 15 months, VEGF levels in lumbar vertebrae were measured by enzyme-linked immunosorbent assay and verified by Western blot analysis. VEGF and its receptor (VEGFR) were localized by immunohistochemistry. Expression of VEGF mRNA was analyzed by real-time reverse-transcription polymerase chain reaction. Differently sulfated glycosaminoglycans were localized in subchondral bone histochemically. Osteoblasts were immunopositive for VEGF. VEGF concentration in the vertebra was 27% lower in OVX miniature pigs. VEGFR-2 could be immunostained on osteoblasts. VEGF mRNA and protein were detectable in the lumbar vertebrae of all animals. In subchondral trabecular bone of OVX animals, significantly more islands of mineralized cartilage containing chondroitin 4- and 6-sulfate or keratan sulfate occurred compared to the control group. The occurrence of remnants of mineralized cartilage in subchondral bone of the OVX group may be caused by a delayed bone turnover due to low VEGF levels. In vitro experiments revealed an increase of VEGF in the supernatant of osteoblasts after incubation with estradiol. In conclusion, estrogen seems to be a key factor for regulation of VEGF expression in bone. Loss of VEGF due to menopause may be a reason for reduction of bone density.
在动物模型中，卵巢切除术（OVX）是模拟绝经后骨质疏松症的一种公认方法。血管内皮生长因子（VEGF）最近已被证明在软骨内骨形成、肥大软骨重塑、骨化和血管生成过程中发挥重要作用。我们假设骨中VEGF表达降低会导致OVX诱导的骨质流失，并在小型猪模型中以及使用人成骨细胞进行体外实验对此进行了验证。17头初产母猪（哥廷根小型猪）在30月龄时被分为两个实验组：对照组（n = 9）和OVX组（n = 8）。15个月后，通过酶联免疫吸附测定法测量腰椎中的VEGF水平，并通过蛋白质印迹分析进行验证。通过免疫组织化学对VEGF及其受体（VEGFR）进行定位。通过实时逆转录聚合酶链反应分析VEGF mRNA的表达。通过组织化学方法在软骨下骨中定位不同硫酸化的糖胺聚糖。成骨细胞对VEGF呈免疫阳性。OVX小型猪椎骨中的VEGF浓度低27%。VEGFR-2可在成骨细胞上进行免疫染色。所有动物的腰椎中均可检测到VEGF mRNA和蛋白质。与对照组相比，OVX动物的软骨下小梁骨中含有硫酸软骨素4-和6-硫酸盐或硫酸角质素的矿化软骨岛明显更多。OVX组软骨下骨中矿化软骨残余物的出现可能是由于VEGF水平低导致骨转换延迟所致。体外实验显示，用雌二醇孵育后，成骨细胞上清液中的VEGF增加。总之，雌激素似乎是调节骨中VEGF表达的关键因素。绝经导致的VEGF缺失可能是骨密度降低的一个原因。
