Expression of cartilage oligomeric matrix protein (COMP) by embryonic and adult osteoblasts.

Cartilage oligomeric matrix protein has been implicated as an important component of endochondral ossification because of its direct effects on chondrocytes. The importance of this protein for skeletal development and growth has been recently illustrated by the identification of mutations in cartilage oligomeric protein genes in two types of inherited chondrodysplasias and osteoarthritic phenotypes: multiple epiphyseal dysplasia and pseudoachondroplasia. In the present study, we report the presence of cartilage oligomeric protein in embryonic and adult osteoblasts. A foot from a 21-week-old human fetus, subchondral bone obtained from knee replacement surgery in an adult patient, and a limb from a 19-day-postcoital mouse embryo were analyzed with immunostaining and in situ hybridization. In the human fetal foot, cartilage oligomeric protein was localized to osteoblasts of the bone collar and at the newly formed bone at the growth plate and bone diaphyses. Immunostaining was performed on the adult subchondral bone and showed positive intracellular staining for cartilage oligomeric protein of the osteoblasts lining the trabecular bone. There was no staining of the osteocytes. Immunostaining of the mouse limb showed the most intense staining for cartilage oligomeric protein in the hypertrophic chondrocytes and in the surrounding osteoblast cells of the developing bone. Cartilage oligomeric protein mRNA and protein were detected in an osteoblast cell line (MG-63), and cartilage oligomeric protein mRNA was detected from human cancellous bone RNA. These results suggest that the altered structure of cartilage oligomeric protein by the mutations seen in pseudoachondroplasia and multiple epiphyseal dysplasia may have direct effects on osteoblasts, contributing to the pathogenesis of these genetic disorders.     

Human adult chondrocytes express hepatocyte growth factor (HGF) isoforms but not HgF: potential implication of osteoblasts on the presence of HGF in cartilage.

HGF is increased in human OA cartilage, possibly from Ob's. RT-PCR shows HGF isoforms are differently regulated between chondrocytes and Ob. A paracrine cross-talk between subchondral bone and cartilage may occur during OA. Recently, hepatocyte growth factor (HGF) has been identified by immunohistochemistry in cartilage and more particularly in the deep zone of human osteoarthritic (OA) cartilage. By investigating HGF expression in cartilage, we found that chondrocytes did not express HGF; however, they expressed the two truncated isoforms, namely HGF/NK1 and HGF/NK2. Because the only other cells localized near the deep zone are osteoblasts from the subchondral bone plate, we hypothesized that they were expressing HGF. Indeed, we found that HGF was synthesized by osteoblasts from the subchondral bone plate. Moreover, OA osteoblasts produced five times more HGF than normal osteoblasts and almost no HGF/NK1, unlike normal osteoblasts. Because prostaglandin E2 (PGE2) and pro-inflammatory cytokines such as interleukin (IL)-1 and IL-6 are involved in OA progression, we investigated whether these factors impact HGF produced by normal osteoblasts. PGE2 was the only factor tested that was able to stimulate HGF synthesis. However, the addition of NS398, a selective inhibitor of cyclo-oxygenase-2 (COX-2) had no effect on HGF produced by OA osteoblasts. HGF/NK2 had a moderate stimulating effect on HGF production by normal osteoblasts, whereas osteocalcin was not modulated by either HGF or HGF/NK2. When investigating signaling routes that might be implicated in OA osteoblast-produced HGF, we found that protein kinase A was at least partially involved. In summary, this study raises the hypothesis that the HGF found in articular cartilage is produced by osteoblasts, diffuses into the cartilage, and may be implicated in the OA process.     

雄激素对大鼠胎颅盖骨成骨细胞雌激素受体基因表达的影响

目的 通过研究雄激素（十一酸睾酮）对成骨细胞雌激素受体基因表达的影响，探讨雄激素对成骨细胞增殖和分化的调控机制。方法 通过对体外培养的胎鼠颅盖骨成骨细胞实施含10^-10mol／L、10^-9mol／L、10^-8mol／L三种浓度雄激素的培养液干预，采用RT-PCR的方法半定量观察成骨细胞中雌激素受体基因mRNA表达的变化，用以分析雄激素对成骨细胞中雌激素受体的影响，并进而探讨雄激素对成骨细胞的影响。结果 实验选用的各浓度组均未出现细胞毒性反应，雄激素干预使成骨细胞中雌激素受体alpha基因表达上调，而雌激素受体beta基因表达轻微下调。结论 雄激素可以特异性地在转录水平调节成骨细胞中雌激素受体基因的表达。     

Peripheral blood lymphocytes P-glycoprotein (P-gp, gp-170) expression in allogenic kidney transplant patients

AIM AND METHODS: P-glycoprotein (gp-170, P-gp) is a transmembrane transporter involved in drug, for example cyclosporine A, efflux from the cells thus limiting their intracellular concentration. Expression of the transporter on the surface of immune competent cells may be associated with poor prognosis in kidney transplant patients. The aim of the present study was to evaluate P-gp expression on the surface of CD4(+), CD8(+), CD19(+) and CD56(+) cells in kidney transplant patients treated with cyclosporine A as a main immunosuppressant, using flow cytometry. RESULTS: It was found that P-gp expression in kidney transplant patients with acute rejection did not differ significantly from transplanted patients without rejection studied in the same period after transplantation, as well as from the healthy controls. Administration of 3-day course of 1,000 mg/24 h methylprednisolone did not affect the expression of P-gp in the studied cells, except for significant elevation in CD56(+) cells, which disappeared at 2 weeks after cessation of steroid administration. CONCLUSION: Based on the results from the present study it can be concluded that P-gp expression is not a prognostic factor of acute kidney graft rejection.     

Prevention of glucocorticoid induced-apoptosis of osteoblasts and osteocytes by protecting against endoplasmic reticulum (ER) stress in vitro and in vivo in female mice

Endoplasmic reticulum (ER) stress is associated with increased reactive oxygen species (ROS), results from accumulation of misfolded/unfolded proteins, and can trigger apoptosis. ER stress is alleviated by phosphorylation of eukaryotic translation initiation factor 2α (eIF2α), which inhibits protein translation allowing the ER to recover, thus promoting cell viability. We investigated whether osteoblastic cell apoptosis induced by glucocorticoids (GCs) is due to induction of ROS/ER stress and whether inhibition of eIF2α dephosphorylation promotes survival opposing the deleterious effects of GC in vitro and in vivo. Apoptosis of osteocytic MLO-Y4 and osteoblastic OB-6 cells induced by dexamethasone was abolished by ROS inhibitors. Like GC, the ER stress inducing agents brefeldin A and tunicamycin induced osteoblastic cell apoptosis. Salubrinal or guanabenz, specific inhibitors of eIF2α dephosphorylation, blocked apoptosis induced by either GC or ER stress inducers. Moreover, GC markedly decreased mineralization in OB-6 cells or primary osteoblasts; and salubrinal or guanabenz increased mineralization and prevented the inhibitory effect of GC. Furthermore, salubrinal (1 mg/kg/day) abolished osteoblast and osteocyte apoptosis in cancellous and cortical bone and partially prevented the loss of BMD at all sites and the decreased vertebral cancellous bone formation induced by treatment with prednisolone for 28 days (1.4 mg/kg/day). We conclude that part of the pro-apoptotic actions of GC on osteoblastic cells is mediated through ER stress, and that inhibition of eIF2α dephosphorylation protects from GC-induced apoptosis of osteoblasts and osteocytes in vitro and in vivo and from the deleterious effects of GC on the skeleton.     

酒精诱导体外培养成骨细胞凋亡及Bcl-2、Bax mRNA表达的实验研究

目的 观察酒精对体外培养成骨细胞凋亡的影响及凋亡相关基因Bcl-2、Bax mRNA表达变化.方法 体外分离培养成骨细胞,随机分组进行不同浓度酒精干预,利用AO/EB染色观察细胞凋亡形态学改变、DNA Ladder检测凋亡细胞DNA片段形成等定性方法证实凋亡发生.流式细胞技术定量测定细胞凋亡率.RT-PCR检测细胞凋亡相关基因Bcl-2、Bax mRNA表达.结果 不同浓度酒精干预后,成骨细胞发生皱缩,AO/EB染色出现凋亡细胞,随酒精浓度增加形成规则的DNA Ladder梯状条带,100mM浓度时最明显.流式细胞仪分析,与对照组(3.42%±1.07%)相比,100 mM酒精干预48h后细胞凋亡率增加,为11.94%±1.14%,差异有统计学意义(P<0.05).与对照组比较,成骨细胞经100 mM酒精干预培养24 h后,Bcl-2 mRNA表达强度降低66%,Bax mRNA表达强度增高11%,Bcl-2/Bax比值下降69%,差异均有统计学意义(P<0.05).结论 酒精引起体外培养成骨细胞凋亡,是酒精性骨损害的发生机制之一.凋亡相关基因Bcl-2 mRNA表达下调和Bax mRNA表达上调与酒精引起成骨细胞凋亡有关.     

含胎牛血清胶原酶消化法培养兔成骨细胞

目的:用含胎牛血清的胶原酶消化胎兔颅盖骨骨组织,进行体外成骨细胞培养.方法:妊娠28d的孕兔,无菌条件下剖腹取出胎兔,然后取胎兔的颅盖骨,剔净、漂洗、剪碎.用含胎牛血清的胶原酶消化,培养成骨细胞.台盼蓝染色测定细胞的存活率,细胞内碱性磷酸酶(ALP)染色鉴定和测定成骨细胞的纯度.结果:用含胎牛血清的胶原酶消化并培养出成骨细胞,台盼蓝染色拒染率高达98%,ALP染色阳性区域不少于95%.结论:用含胎牛血清胶原酶消化胎兔颅盖骨骨组织,培养出的成骨细胞具有典型的成骨细胞特征,且成分单一,存活率高.     

Differential modulation of growth and phenotypic expression of chondrocytes in sparse and confluent cultures by growth factors in cartilage

The growth-promoting actions of cartilage extracts (CE) on rabbit cultured chondrocytes were studied to assess the role of local acting growth factors in the generation and expansion of highly differentiated cells. In the present study, DNA synthesis and proteoglycan synthesis in the cultured chondrocytes were monitored by flow cytofluorometry and double-isotope autoradiography by using [3H]thymidine and [35S]sulfate. We report here that actions of the same set of growth factors extracted from cartilage evokes differential cellular responses depending upon cell density. Growth factors in the optimal dose of CE (2 micrograms/ml) or epidermal growth factor (EGF, 40 ng/ml) did not reveal such a cell density-dependent effect on cellular proliferation. However, growth factors in CE induced proteoglycan synthesis selectively in nonproliferating and expressing cells in confluent culture.     

Enhanced expression of insulin-like growth factor-binding proteins in human osteoarthritic cartilage detected by immunohistochemistry and in situ hybridization

OBJECTIVE: To determine the roles of insulin-like growth factor (IGF) and IGF-binding protein (IGFBP) in the pathogenesis of osteoarthritis (OA). DESIGN: Cartilage tissues were obtained from the femoral heads of patients with OA, and those from patients with femoral neck fractures were used as a control. The expression of IGFBP-3, -4, and -5 was examined using immunohistochemistry and in situ hybridization, and IGF-I and IGF-I receptors were also immunohistochemically detected. The percentages of positive chondrocytes were determined by counting the total number of chondrocytes over the area of the surface, middle, and deep zones of the cartilage. RESULTS: There was a marked increase in the percentage of positive chondrocytes in all IGFBPs on protein and messenger RNA levels for OA compared to that of the control cartilage. Furthermore, enhanced expression of IGFBPs and the IGF-I/IGF-I receptor was positively correlated with the histologic score for cartilage lesions. CONCLUSION: Up-regulation of IGFBPs as well as IGF-I and its receptor was observed for OA cartilage tissue, suggesting the involvement of IGFBPs in the pathogenesis of OA.     

Expression of bone morphogenetic proteins, receptors, and tissue inhibitors in human fetal, adult, and osteoarthritic articular cartilage.

Coordinate expression of BMPs and their receptors and inhibitors is likely necessary for physiologic BMP regulation and activity. To characterize the expression of such factors in fetal, normal adult, and end-stage osteoarthritic articular cartilage, samples from these sources were analyzed. PCR-amplified sequences (BMPs 1-11), receptors (IA, IB, II), TGF-beta1, TGF-beta2, inhibitors noggin and follistatin, CDMP-1, COMP, and GAPDH from cDNAs generated from extracted total RNA were resolved by gel electrophoresis. Protein levels of BMPs 3, 7, and 8 were also analyzed by SDS-PAGE and Western blotting. RT-PCR revealed that BMPs 1, 2, 4-6, and 11, BMPR-IA and II, noggin, follistatin, CDMP-1, COMP, and GAPDH mRNAs were expressed in similar fashion in both fetal and adult (normal or osteoarthritic) cartilage. BMPs 9 and 10 mRNAs were not expressed in either group. BMPs 7, 8, and BMPR-IB mRNAs were consistently expressed in fetal but not in adult cartilage. BMP-3 mRNA was expressed in fetal and normal adult, but not in osteoarthritic samples. TGF-beta1 was expressed in both adult normal and osteoarthritic, but not fetal, samples. Similarly, Western blotting demonstrated BMPs 7 and 8 to be present in fetal but not in adult samples. BMP-3 protein was present in fetal and adult normal samples, to a lesser extent, but absent in osteoarthritic cartilage.     

Oxidative stress induces expression of osteoarthritis markers procollagen IIA and 3B3(-) in adult bovine articular cartilage

OBJECTIVE: Oxidative stress occurs when the metabolic balance of a cell is disrupted through exposure to excess pro-oxidant. Whilst it is known that unregulated production or exposure to exogenous sources of pro-oxidants induces chondrocyte cell death and degrades matrix components in vitro, relatively little is known of the effects of pro-oxidants on articular cartilage in situ. The objective of this study was to determine if a single exposure to the pro-oxidant hydrogen peroxide (H(2)O(2)) induces a degenerative phenotype. METHODS: Articular cartilage explants were obtained from skeletally mature bovine steers and exposed to a single dose of hydrogen peroxide (0.1-1.0 mM) and cultured for up to 21 days. Cell death, and sulfated glycosaminoglycan loss into the medium and gene expression were quantitatively determined. Adoption of an abnormal chondrocyte phenotype was analyzed through the expression of 3B3(-), nitrotyrosine and procollagen type IIA epitopes in cartilage explants. RESULTS: Cell death occurred primarily at the surface zone of cartilage in a dose-dependent manner in H(2)O(2) treated explants, and supplementation of standard serum-free medium with insulin-selenium-transferrin significantly reduced cell death (>fourfold). Nitric oxide synthase-2 gene expression and proteoglycan loss increased in oxidant treated explants in a concentration-dependent manner. Antibody labeling to 3B3(-), procollagen type IIA and nitrotyrosine was present in all treated explants but absent in untreated explants. CONCLUSIONS: This study demonstrates that a single exposure to high levels of pro-oxidant causes the expression of genes and antibody epitopes that are associated with early degenerative changes observed in experimental osteoarthritis.     

Localization of parathyroid hormone-related protein mRNA expression in breast cancer and metastatic lesions by in situ hybridization.

Parathyroid hormone-related protein (PTHrP) has been identified immunohistochemically in 60% of breast carcinoma and in 92% of breast cancer metastases in bone. To establish whether the localization of the PTHrP antigen reflects protein synthesis and also to investigate the role of PTHrP in metastatic disease, as part of an ongoing study, we used in situ hybridization to study the localization of PTHrP mRNA in a retrospective series of primary breast tumors and their metastatic lesions. Paraffin sections of 17 primary and 26 metastatic lesions, 11 of which were in bone, were available for the study: 10 of the 17 (59%) primary lesions, 8 of 11 (73%) breast cancer metastases to bone, and 3 of 15 (20%) metastases to non-bone sites showed specific localization of PTHrP mRNA. These findings establish that PTHrP is commonly synthesized by primary breast cancers and support previous immunohistochemical studies reporting a higher incidence of PTHrP-positive tumor cells in skeletal metastases than in nonskeletal metastases.     

Documentation of EWS gene rearrangements by fluorescence in-situ hybridization (FISH) in frozen sections of Ewing's sarcoma-peripheral primitive neuroectodermal tumor

Prompt and accurate diagnosis of small round cell tumors warrants ancillary studies. Recently, two-color fluorescence in-situ hybridization (FISH) using probes for specific gene rearrangements has gained wide acceptance. EWS gene rearrangements, present in essentially 100% of Ewing's Sarcoma/peripheral primitive neuroectodermal tumor, were evaluated by FISH on frozen sections (FS) of tumor biopsies from 10 patients, plus a negative control, and in seven other malignant neoplasms of childhood. 4mu FS were hybridized overnight, using a single EWS gene-specific probe spanning the EWS breakpoint. We identified EWS rearrangements in 8 of 10 cases (80%) of Ewing's Sarcoma/pPNET. There are no known false positives in diploid or near-diploid tumors, or in any of the non-EWS tumors tested; the uncommon false negative can be confirmed by RT-PCR. Hyperdiploid cases with multiple copies of chromosome 22 may be better evaluated by two-color FISH. This is the first use on FS biopsy material of a single probe for EWS, capable of detecting all known EWS rearrangements, in ES and other tumors. Utilization of this ancillary technique on FS for ES/pPNET and other tumors with distinctive chromosomal translocation is highly specific, reliable, expeditious (24-36 hours) and cost-effective.