Stimulated Type I Collagen Turnover in Patients With Giant Cell Tumor of Bone

The aim of this study was to determine type I collagen turnover in giant cell tumor of bone (GCT) by biochemical markers of type I procollagen aminoterminal propeptide (PINP) and type I collagen carboxyterminal telopeptide (ICTP) as synthesis and degradation markers, respectively. The serum concentrations of PINP and ICTP were measured in 11 patients with GCT using radioimmunoassay, and analyzed by the correlation to the grades of GCT progression described by Campanacci. Serum of the 11 healthy subjects was available for comparison. The serum concentration of PINP was significantly higher in patients with GCT (82.4 ± 46.2 ng/ml) than in controls (40.8 ± 12.1 ng/ml) (P < 0.01), and that of ICTP was also significantly higher in GCT (5.3 ± 2.0 ng/ml) than in controls (3.2 ± 0.8 ng/ml) (P < 0.01). In GCT, the PINP concentration of grade 3 (127.6 ± 38.8 ng/ml) was higher than that in grade 1 patients (46.9 ± 4.8 ng/ml) (P < 0.01). ICTP concentration of both grades 2 (7.1 ± 1.4 ng/ml) and 3 (5.8 ± 1.8 ng/ml) patients was significantly higher than that of grade 1 (3.5 ± 0.6 ng/ml) patients (P < 0.01, P < 0.05, respectively). Two cases of serum concentration of PINP and ICTP after resection of GCT demonstrated that these biomarkers decreased to the control levels in the absence of GCT. Our results indicated that type I collagen turnover evaluated by ICTP and PINP was stimulated in the presence of GCT. Moreover, this enhanced metabolic turnover reflects the grade of GCT.     

A New Monoclonal Antibody ELISA for Detection and Characterization of C-telopeptide Fragments of Type I Collagen in Urine

Clinical studies have shown that measurements of urine concentration of degradation products of C-terminal telopeptides of type I collagen provide a selective marker to assess bone resorption. Assays for C-telopeptide fragments have been described using antibodies generated against an eight amino acid synthetic peptide EKAHDGGR. In this study, we describe development of a rat monoclonal antibody against a synthetic linear peptide, DFSFLPQPPQEKAHDGGR, which we isolated and characterized from Paget's urine by chromatographic methods. An ELISA procedure was developed to evaluate the efficacy of this monoclonal to measure bone resorption and characterize urinary degradation products of C-terminal type I collagen. The measuring range of ELISA was 10-1,000 ng/ml with a detection limit of 10 ng/ml. Averaged intraassay and interassay CVs were <7% (n = 8) and <11% (n = 3), respectively. Mean spike and dilution recoveries range between 90 and 116%. In assessing the clinical performance, we observed approximately 48% higher values for postmenopausal patients (n = 20) compared with premenopausal women (n= 19), Z score = 2.7 (P = 0.0091). The discriminatory power to assess subtle changes in bone turnover between pre- and postmenopausal women compares well with the commercially available markers of bone resorption. Comparison of C-telopeptide concentration in a population including normal and osteoporotic patients (n = 74) shows a strong correlation with DPYR r = 0.95 (P < 0.001). In addition, in postmenopausal osteoporotic patients, a 44% (P < 0.05) decrease in C-telopeptide concentration was observed after 3 months of treatment with Alendronate, as compared with basal values. The antibody developed in this study displays a slightly different epitope than that reported previously using eight amino acid residues EKAHDGGR. In addition, isolation and characterization of circulating forms of C-telopeptide from healthy children by immunoaffinity purification revealed the presence of two novel urinary fragments corresponding to amino acid sequence EKAHDGGR and EKAHDG, in addition to the previously known two fragments composed of two alpha-1 chains linked together by a pyridinium crosslinks. The origin of the fragment EKAHDG could not be explained by the known mechanisms involved in collagen degradation, indicating that it could be a product of renal handling of C-telopeptide fragments generated from bone. The preliminary clinical data suggest that the new assay may be useful for further investigation of the clinical importance of measurement of these type I collagen degradation products.     

Posttranslational Modifications of Bone Collagen Type I are Related to the Function of Rat Femoral Regions

This study analyzes the relationship between the function of femoral regions in the rat and the extent of collagen type I posttranslational modifications, to assess whether the different functional roles, i.e., mechanical or metabolic, of the bone tissues are related to the molecular structure of the matrix. For this purpose, 18 female, 100-day-old Sprague-Dawley rats were sacrificed, under anesthesia, and their femurs were removed and dissected free of adhering tissue. The spongy bone of the proximal metaphysis and the diaphysis were then selected as regions exerting prevalently a mechanical function, and the spongy bone of the distal metaphysis was selected as mainly related to metabolic function. Bone prepared from these regions was used to extract and purify the major component of the matrix, type I collagen. The content of hydroxyproline, hydroxylysine, glycosylated hydroxylysine, and pyridinium crosslinks was evaluated and the amount of each compound was expressed as a molar ratio to hydroxyproline. The amount of glycosylated hydroxylysine and pyridinium crosslinks in the distal metaphysis are significantly different from the amounts measured both in the diaphysis and the proximal metaphysis. On the contrary, the amounts of the same compounds in the diaphysis and the proximal metaphysis are statistically the same. The amount of free hydroxylysine, however, appears to be different in the proximal metaphysis and in the diaphysis. The conclusion is that matrix composition differs among different skeletal regions according to the main function they exert. Received: 5 February 1999 / Accepted: 13 August 1999     

Type III Collagen Regulates Osteoblastogenesis and the Quantity of Trabecular Bone

Type III collagen (Col3), a fibril-forming collagen, is a major extracellular matrix component in a variety of internal organs and skin. It is also expressed at high levels during embryonic skeletal development and is expressed by osteoblasts in mature bone. Loss of function mutations in the gene encoding Col3 (Col3a1) are associated with vascular Ehlers–Danlos syndrome (EDS). Although the most significant clinical consequences of this syndrome are associated with catastrophic failure and impaired healing of soft tissues, several studies have documented skeletal abnormalities in vascular EDS patients. However, there are no reports of the role of Col3 deficiency on the murine skeleton. We compared craniofacial and skeletal phenotypes in young (6–8 weeks) and middle-aged (>1 year) control (Col3^+/+) and haploinsufficient (Col3^+/?) mice, as well as young null (Col3^?/?) mice by microcomputed tomography (μCT). Although Col3^+/? mice did not have significant craniofacial abnormalities based upon cranial morphometrics, μCT analysis of distal femur trabecular bone demonstrated significant reductions in bone volume (BV), bone volume fraction (BV/TV), connectivity density, structure model index and trabecular thickness in young adult female Col3^+/? mice relative to wild-type littermates. The reduction in BV/TV persisted in female mice at 1 year of age. Next, we evaluated the role of Col3 in vitro. Osteogenesis assays revealed that cultures of mesenchymal progenitors collected from Col3^?/? embryos display decreased alkaline phosphatase activity and reduced capacity to undergo mineralization. Consistent with this data, a reduction in expression of osteogenic markers (type I collagen, osteocalcin and bone sialoprotein) correlates with reduced bone Col3 expression in Col3^+/? mice and with age in vivo. A small but significant reduction in osteoclast numbers was found in Col3^+/? compared to Col3^+/+ bones. Taken together, these findings indicate that Col3 plays a role in development of trabecular bone through its effects on osteoblast differentiation.     

Lymphocyte Proliferation to Collagen Type I in Dogs

The objective of this study was to investigate if cellular reactivity to collagen type I exists in dogs with unilateral cranial cruciate ligament (CrCL) rupture and if it relates to disease progression. The patient group consisted of 10 dogs with unilateral CrCL rupture. The control dogs consisted of three healthy control dogs, and two healthy dogs with unilateral sham operations of the stifle joint. All dogs were assayed repeatedly every 6 months for 12–24 months. Peripheral blood mononuclear cells were isolated from whole blood and were cultured with human collagen type I at concentrations of 5, 20 and 40 μg/ml for 6 and 7 days. Lymphocyte reactivity to collagen type I occurred not only in dogs with CrCL rupture, but also in sham‐operated dogs and healthy dogs. Five of the eight assays (63%) performed at the time of operation or at the time of diagnosis of CrCL rupture had a stimulation index (SI) ≥3.0. This was not significantly different compared to healthy control dogs, not to the sham‐operated control dogs. The CrCL rupture was assessed intraoperatively in six cases. Three cases had partial rupture and three had complete rupture. Only one dog with partial rupture, and two dogs with complete rupture had a positive SI. An increase in proliferation to collagen type I was seen in dogs with CrCL rupture, whereas it either remained stable or decreased in the control dogs. No distinct pattern in lymphocyte reactivity to collagen type I could be established from the dogs that sustained a CrCL rupture in the contralateral stifle joint, although most dogs that did not sustain a CrCL rupture in the contralateral stifle joint remained negative during this study with exception of one dog. Further research is required to determine whether cellular reactivity to collagen type I may play an initiating role in cruciate degradation.     

Assessment of Bone Health in Patients With Type 1 Gaucher Disease Using Impact Microindentation

Gaucher disease (GD), one of the most common lysosomal disorders (a global population incidence of 1:50,000), is characterized by beta‐glucocerebrosidase deficiency. Some studies have demonstrated bone infiltration in up to 80% of patients, even if asymptomatic. Bone disorder remains the main cause of morbidity in these patients, along with osteoporosis, avascular necrosis, and bone infarcts. Enzyme replacement therapy (ERT) has been shown to improve these symptoms. This cross‐sectional study included patients with type 1 Gaucher disease (GD1) selected from the Catalan Study Group on GD. Clinical data were collected and a general laboratory workup was performed. Bone mineral density (BMD) was measured at the lumbar spine and hip using dual‐energy X‐ray absorptiometry (DXA). Patients with bone infarcts or any other focal lesion in the area of indentation visible on imaging were excluded. Bone Material Strength index (BMSi) was measured by bone impact microindentation using an Osteoprobe instrument. Analysis of covariance (ANCOVA) models were fitted to adjust for age, sex, weight, and height. Sixteen patients with GD1 and 29 age‐ and sex‐matched controls were included. GD1 was associated with significantly lower BMSi (adjusted beta –9.30; 95% CI, –15.18 to –3.42; p = 0.004) and reduced lumbar BMD (adjusted beta –0.14; 95% CI, –0.22 to –0.06; p = 0.002) and total hip BMD (adjusted beta –0.09; 95% CI, –0.15 to –0.03; p = 0.006), compared to GD1‐free controls. Chitotriosidase levels were negatively correlated with BMSi (linear R² = 51.6%, p = 0.004). Bone tissue mechanical characteristics were deteriorated in patients with GD1. BMSi was correlated with chitotriosidase, the marker of GD activity. Bone disorder requires special consideration in this group of patients, and microindentation could be an appropriate tool for assessing and managing their bone health. © 2017 American Society for Bone and Mineral Research.     

胶原膜与复合自体骨髓的自体骨引导骨再生的实验研究

目的　观察胶原膜引导骨再生的效果 ,探讨胶原膜的理化特性、自体骨髓、膜下空间的维持在引导性骨再生中的作用。方法　建立兔双侧桡骨缺损模型 ,实验组移植胶原膜与复合自体骨髓的自体骨 ,对照组仅移植复合自体骨髓的自体骨 ,并行大体标本、组织学、生物力学检查。结果　实验组新骨生长及成熟骨替代过程较对照组快 ,且有增生的小血管及神经纤维。结论胶原膜是一种理想的骨移植材料 ,它能有效地发挥阻隔及引导的作用     

Bone Sialoprotein (BSP) is a Crucial Factor for the Expression of Osteoblastic Phenotypes of Bone Marrow Cells Cultured on Type I Collagen Matrix

In this study, we demonstrated that type I collagen matrix induced the expression of osteoblastic phenotypes of bone marrow cells, and that antibone sialoprotein (BSP) monoclonal antibody suppressed the expression of these phenotypes. On the other hand, BSP accelerated the expression of osteoblastic phenotypes of bone marrow cells. The adherent bone marrow cells were harvested from rat femur and cultured on type I collagen matrix gels in medium containing 15% fetal calf serum, neither β-glycerophosphate nor glucocorticoid. Cells showed osteoblastic phenotypes (high alkaline phosphatase activity, osteocalcin synthesis, and responsiveness against parathyroid hormone) on collagen matrix gels at week 3 after the inoculation, and simultaneously, BSP was detected in the conditioned medium by Western blotting using an anti-BSP monoclonal antibody. However, cells in the conventional culture dishes did not show osteoblastic phenotypes during the experimental period. To investigate the physiological function of BSP in osteoblastic differentiation, bone marrow cells were cultured on collagen matrix with an anti-BSP monoclonal antibody for 3 weeks. This treatment suppressed the expression of the osteoblastic phenotypes, and the effect of the antibody was abolished by the addition of bovine bone BSP. Furthermore, bovine bone BSP stimulated the expression of osteoblastic phenotypes of bone marrow cells. Our results indicate that BSP plays a crucial role in the expression of osteoblastic phenotypes of bone marrow cells. Received: 17 February 1999 / Accepted: 14 December 1999     

骨胶原的制备及作为骨形成蛋白载体修复骨缺损的研究

在提取BMP的过程中,从废去的中间产物骨基质胶中同时提取胶原作为BMP的载体用于修复兔颅骨缺损.40只大白兔随机分为A、B两组,在兔颅顶骨两侧对称各制造直径为1cm的圆形骨缺损,A组兔颅顶骨缺损左侧植入骨胶原/BMP,右侧植入单纯骨胶原,B组兔左侧植入BMP,右侧空白对照,组织学检查显示:植入后7夭,骨胶原/BMP组即有软骨细胞岛出现,旦在各期的成骨面积均大于单纯BMP组和胶原组.另外,移植材料内的灰量测定结果及X线摄片结果也表明,骨胶原/BMP的成骨量明显大于单纯骨胶原组和BMP组(P<0.01),认为骨胶原作为BMP的载体有更多的优越性.     

Using Mendelian Randomization to Decipher Mechanisms of Bone Disease

Purpose of Review

This review summarizes the basic principles of Mendelian randomization (MR) and provides evidence for the causal effect of multiple modifiable factors on bone outcomes.

Recent Findings

Several studies using MR approach have provided support for the causal effect of obesity on bone mineral density (BMD). Strikingly, studies have failed to prove a causal association between elevated 25(OH) D concentrations and higher BMD in community-dwelling individuals.

Summary

The MR approach has been successfully used to evaluate multiple factors related to bone mineral density variation and/or fracture risk. The MR approach avoids some of the classical observational study limitations and provides more robust causal evidence, ensuring bigger success of the clinical trials. The selection of interventions based on genetic evidence could have a substantial impact on clinical practice.

     

The Effect of Carboxyl-Terminal Propeptide of Type I Collagen (c-Propeptide) on Collagen Synthesis of Preosteoblasts and Osteoblasts

Recently we found that the carboxyl-terminal propeptide of type I collagen (c-propeptide) is a major secretory protein of osteoblasts. Mature osteoblasts secreted 64 nM c-propeptide, and it was reported that 40 nM c-propeptide inhibited collagen synthesis at 80% of the control level. In this study, we investigated the effect of c-propeptide on collagen synthesis of preosteoblasts and osteoblasts, and found that preosteoblasts downregulated collagen synthesis by 40 nM c-propeptide, but osteoblasts were not affected by the same condition. When the binding activities of c-propeptide for preosteoblasts and osteoblasts were compared, osteoblasts showed weak affinity to c-propeptide compared with preosteoblasts, and the number of receptors for c-propeptide decreased in osteoblasts. These results imply that a decrease of receptors in osteoblasts might reduce the sensitivity of osteoblasts to c-propeptide. Received: 6 August 1999 / Accepted: 9 May 2000 / Online publication: 22 September 2000     

Disturbed Synthesis of Type II Collagen Interferes with Rate of Bone Formation and Growth and Increases Bone Resorption in Transgenic Mice

Transgenic mice carrying an internally deleted human type II collagen gene (COL2A1) were used to study bone growth and development. This mutation has previously been shown to disturb the development of collagen fibrils in articular cartilage, causing chondrodysplasia and osteoarthritis. Type II collagen expression in bones was investigated with immunohistochemistry. The development and mineralization of the skeleton and anthropometric measurements on bones were evaluated using X-rays and dynamic histomorphometry. Type II collagen was expressed in the cartilage of developing bones. The bones of transgenic mice were smaller compared with the controls. The bone mass remained almost unchanged in transgenic mice after 1 month of age, leading to differences of 47% in trabecular bone volume (P = 0.012) and 40% in trabecular thickness (P < 0.01) at the age of 3 months compared with controls. At the age of 3 months the eroded surface per bone volume was 31% greater in transgenic mice compared with controls (P < 0.05). Trabecular thickness correlated positively with body weight (R = 0.71, P < 0.001). Interestingly, body weight correlated with bone volume in control mice (R = 0.27, P < 0.01), but no correlation was observed in transgenic mice. The disturbed synthesis of cartilage-specific type II collagen in growing transgenic mice retarded bone development, increased bone resorption, and altered tissue properties. This led to a negative net bone balance and small bone size. The results support the idea that an altered synthesis of cartilage-specific molecule(s) can disturb postnatal bone development and growth.     

Studies of Bone Density, Quantitative Ultrasound, and Vertebral Fractures in Relation to Collagen Type I Alpha 1 Alleles in Elderly Women

Previous studies have demonstrated that an Sp1 binding site polymorphism in the collagen type I gene (COLIA1) is related to reduced bone mineral density (BMD) and osteoporotic fractures in certain populations, particularly in the elderly. We have examined the relationship among these COLIA1 Sp1 alleles, BMD, quantitative ultrasound properties of bone, and fractures in a population-based cohort of elderly women from the UK. The study group comprised 314 women aged 75 years and over who agreed to participate in a clinical study of bisphosphonate therapy in preventing bone loss at the hip. Women were enrolled regardless of the presence or absence of osteoporosis, but those with other diseases that might affect skeletal metabolism were excluded. The genotype distribution for the Sp1 polymorphism was in Hardy-Weinberg equilibrium (SS - 78%; Ss - 20%; ss - 2%) but the proportion of individuals who carried the "s" allele (22%) was significantly lower than previously observed in another study of the UK population (37.1%) (P < 0.001). There were no significant associations between COLIA1 genotypes and metacarpal cortical index, BMD of the forearm, tibial SOS, calcaneal SOS, or calcaneal BUA. While there was a trend towards lower BMD values at the hip in patients with Ss and ss genotypes, this was not statistically significant (SS = 0.721 +/- 0.14; Ss = 0.704 +/- 0.13; ss = 0.683 +/- 0.20 P = 0.6). Prevalent vertebral fractures occurred in 22% of subjects and prior fractures of the wrist, ankle, and hip were reported by 20%, but there was no significant difference in COLIA1 genotype distribution between fracture patients and controls. We conclude that COLIA1 Sp1 alleles are not significantly associated with BMD, ultrasound properties of bone, or fractures in this population-based sample of elderly women.     

Diabetes,Collagen, and Bone Quality

Diabetes increases risk of fracture, although type 2 diabetes is characterized by normal or high bone mineral density (BMD) compared with the patients without diabetes. The fracture risk of type 1 diabetes as well as type 2 diabetes increases beyond an explained by a decrease of BMD. Thus, diabetes may reduce bone strength without change in BMD. Whole bone strength is determined by bone density, structure, and quality, which encompass the micro-structural and tissue material properties. Recent literature showed that diabetes reduces bone material properties rather than BMD. Collagen intermolecular cross-linking plays an important role in the expression of bone strength. Collagen cross-links can be divided into beneficial enzymatic immature divalent and mature trivalent cross-links and disadvantageous nonenzymatic cross-links (Advanced glycation end products: AGEs) induced by glycation and oxidation. The formation pathway and biological function are quite different. Not only hyperglycemia, but also oxidative stress induces the reduction in enzymatic cross-links and the formation of AGEs. In this review, we describe the mechanism of low bone quality in diabetes and the usefulness of the measurement of plasma or urinary level of AGEs for estimation of fracture risk.     

Impact of Bone Marrow Transplantation on Type I Diabetes

Type I diabetes is a systemic autoimmune disease. Evidence is accumulating that autoimmune diseases such as type I diabetes are linked to the bone marrow hematopoietic stem cell (HSC) itself rather than its derivatives. HSC chimerism achieved through bone marrow transplantation (BMT) may affect type I diabetes in two ways: first, to induce tolerance to pancreas and islet cell transplants; and second, to reverse the autoimmune process prior to the development of terminal complications. Transplantation of bone marrow from normal donors into patients with hematologic malignancy and coexistent type I diabetes has reversed the systemic diabetic autoimmune process. Donor HSCs can also be utilized for the induction of donor-specific tolerance to islet cell transplants. Islet or whole pancreas transplantation is the most physiologic approach to treating type I diabetes. Currently, this is limited by the requirement for high-dose chronic nonspecific immunosuppression to prevent rejection. Despite these agents, chronic rejection remains the primary cause for late graft loss. Donor-specific tolerance eliminates the requirement for immunosuppression and prevents the development of chronic rejection. Bone marrow transplantation does have limitations. In particular these limitations include the morbidity associated with lethal conditioning, graft-versus-host disease, and failure of engraftment. Currently the morbidity and mortality associated with lethal conditioning could not be justified for tolerance induction or interruption of the autoimmune state in type I diabetes. The goal of current research is to identify those factors in both recipient and donor that optimize engraftment to reverse the risk/benefit ratio associated with BMT. This article reviews the state of the art for HSC chimerism affecting diabetes.