Inhibition of sphingosine 1-phosphate protects mice against chondrocyte catabolism and osteoarthritis.

OBJECTIVE: Cartilage loss observed in osteoarthritis (OA) is prevented when osteoclasts in the subchondral bone are inhibited in mice. Here, we investigated the role of the osteoclast secretome and of the lipid mediator sphingosine 1-phosphate (S1P) in chondrocyte metabolism and OA. MATERIALS AND METHODS: We used SphK1LysMCre and wild type mice to assess the effect of murine osteoclast secretome in chondrocyte metabolism. Gene and protein expressions of matrix metalloproteinase (Mmp) were quantified in chondrocytes and explants by RT-qPCR and Western blots. SphK1LysMCre mice or wild type mice treated with S1P2 receptor inhibitor JTE013 or anti-S1P neutralizing antibody sphingomab are analyzed by OA score and immunohistochemistry. RESULTS: The osteoclast secretome increased the expression of Mmp3 and Mmp13 in murine chondrocytes and cartilage explants and activated the JNK signaling pathway, which led to matrix degradation. JTE013 reversed the osteoclast-mediated chondrocyte catabolism and protected mice against OA, suggesting that osteoclastic S1P contributes to cartilage damage in OA via S1P/S1P2 signaling. The activity of sphingosine kinase 1 (SphK1) increased with osteoclast differentiation, and its expression was enhanced in subchondral bone of mice with OA. The expression of Mmp3 and Mmp13 in chondrocytes was low upon stimulation with the secretome of Sphk1-lacking osteoclasts. Cartilage damage was significantly reduced in SphK1LysMCre mice, but not the synovial inflammation. Finally, intra-articular administration of sphingomab inhibited the cartilage damage and synovial inflammation. CONCLUSIONS: Lack of S1P in myeloid cells and local S1P neutralization alleviates from osteoarthritis in mice. These data identify S1P as a therapeutic target in OA.

The Matrilin-3 T298M mutation predisposes for post-traumatic osteoarthritis in a knock-in mouse model.

OBJECTIVE: The human matrilin-3 T303M (in mouse T298M) mutation has been proposed to predispose for osteoarthritis, but due to the lack of an appropriate animal model this hypothesis could not be tested. This study was carried out to identify pathogenic mechanisms in a transgenic mouse line by which the mutation might contribute to disease development. METHODS: A mouse line carrying the T298M point mutation in the Matn3 locus was generated and features of skeletal development in ageing animals were characterized by immunohistology, micro computed tomography, transmission electron microscopy and atomic force microscopy. The effect of transgenic matrilin-3 was also studied after surgically induced osteoarthritis. RESULTS: The matrilin-3 T298M mutation influences endochondral ossification and leads to larger cartilage collagen fibril diameters. This in turn leads to an increased compressive stiffness of the articular cartilage, which, upon challenge, aggravates osteoarthritis development. CONCLUSIONS: The mouse matrilin-3 T298M mutation causes a predisposition for post-traumatic osteoarthritis and the corresponding knock-in mouse line therefore represents a valid model for investigating the pathogenic mechanisms involved in osteoarthritis development.

Identification of TGFß signatures in six murine models mimicking different osteoarthritis clinical phenotypes.

OBJECTIVE: TGFß is a key player in cartilage homeostasis and OA pathology. However, few data are available on the role of TGFß signalling in the different OA phenotypes. Here, we analysed the TGFß pathway by transcriptomic analysis in six mouse models of OA. METHOD: We have brought together seven expert laboratories in OA pathophysiology and, used inter-laboratories standard operating procedures and quality controls to increase experimental reproducibility and decrease bias. As none of the available OA models covers the complexity and heterogeneity of the human disease, we used six different murine models of knee OA: from post-traumatic/mechanical models (meniscectomy (MNX), MNX and hypergravity (HG-MNX), MNX and high fat diet (HF-MNX), MNX and seipin knock-out (SP-MNX)) to aging-related OA and inflammatory OA (collagenase-induced OA (CIOA)). Four controls (MNX-sham, young, SP-sham, CIOA-sham) were added. OsteoArthritis Research Society International (OARSI)-based scoring of femoral condyles and ribonucleic acid (RNA) extraction from tibial plateau samples were done by single operators as well as the transcriptomic analysis of the TGFß family pathway by Custom TaqMan® Array Microfluidic Cards. RESULTS: The transcriptomic analysis revealed specific gene signatures in each of the six models; however, no gene was deregulated in all six OA models. Of interest, we found that the combinatorial Gdf5-Cd36-Ltbp4 signature might discriminate distinct subgroups of OA: Cd36 upregulation is a hallmark of MNX-related OA while Gdf5 and Ltbp4 upregulation is related to MNX-induced OA and CIOA. CONCLUSION: These findings stress the OA animal model heterogeneity and the need of caution when extrapolating results from one model to another.

Secular trends of hip fractures in France: impact of changing characteristics of the background population.

INTRODUCTION: Hip fractures are a societal burden because of their high morbidity and mortality and the cost they generate. With the aging of the population, worries grow about an increase of the incidence and incidence rate of hip fracture in the future. Controversial data have been provided in relation to the referencepopulation used. The aim of this study was to assess the impact of the choice of the reference population in the incidence rate of hip fracture. METHODS: Data were extracted from the French National Hospital Database related to the hospitalizations for hip fracture in France between 2002 and 2013 in patients over 59 years and were classified by gender and age (59-74, 75-84, over 84 years, over 59 years). The crude incidence rates of hip fracture were calculated by dividing the number of hospitalizations for hip fracture by the corresponding populations. To assess the impact of the choice of the reference population, we then calculated the adjusted incidence rates using direct standardization on age for the 2013 reference population. RESULTS: From 2002 to 2013, the incidence of hip fracture rose by 4.8% in women (from 49,287 to 51,661) and 21.8% in men (from 12,716 to 15,482) aged over 59 years. Meanwhile, French population over 59 years increased more with a rise of 21.3% in women and 28.7% in men, resulting in a decrease in the crude incidence rates of 13.6% in women and 5.4% in men. However, this decrease was larger after direct standardization on the 2013 population of reference as 25.6% in women and 19.2% in men as a result of a difference in age-structure of the population. CONCLUSIONS: The incidence of hip fractures continues to grow despite a reduced incidence rate throughout a 12-year-period.

Iron overload in a murine model of hereditary hemochromatosis is associated with accelerated progression of osteoarthritis under mechanical stress.

OBJECTIVE: Hereditary hemochromatosis (HH) is a disease caused by mutations in the Hfe gene characterised by systemic iron overload and associated with an increased prevalence of osteoarthritis (OA) but the role of iron overload in the development of OA is still undefined. To further understand the molecular mechanisms involved we have used a murine model of HH and studied the progression of experimental OA under mechanical stress. DESIGN: OA was surgically induced in the knee joints of 10-week-old C57BL6 (wild-type) mice and Hfe-KO mice. OA progression was assessed using histology, micro CT, gene expression and immunohistochemistry at 8 weeks after surgery. RESULTS: Hfe-KO mice showed a systemic iron overload and an increased iron accumulation in the knee synovial membrane following surgery. The histological OA score was significantly higher in the Hfe-KO mice at 8 weeks after surgery. Micro CT study of the proximal tibia revealed increased subchondral bone volume and increased trabecular thickness. Gene expression and immunohistochemical analysis showed a significant increase in the expression of matrix metallopeptidase 3 (MMP-3) in the joints of Hfe-KO mice compared with control mice at 8 weeks after surgery. CONCLUSIONS: HH was associated with an accelerated development of OA in mice. Our findings suggest that synovial iron overload has a definite role in the progression of HH-related OA.

Dementia is a major risk factor for hip fractures in patients with chronic kidney disease.

UNLABELLED: Chronic kidney disease increases the risk of hip fractures which can be promoted by dementia. We here showed that dementia increased the risk of hip fractures in dialysis patients, but in a similar manner than without dialysis. Attention should be paid to dementia to prevent hip fractures. INTRODUCTION: Hip fractures (HF) are associated with significant morbidity and is further increased in patients with chronic kidney disease (CKD). Dementia, frequent in CKD, might be a risk factor for HF. We here aimed to assess if dementia increased the risk of hip fracture in CKD. METHODS: The study was derived from the French National Database of Hospitalization. Data were obtained over the period 2011-2013. Three populations of subjects >60 years were extracted. Hip fractures, dialysis, and dementia were the main studied factors. The three populations were crossed to estimate the fracture risk based on dementia or dialysis, adjusted for age and gender. The fracture risk was calculated using a multiple logistic regression model. RESULTS: Over this period, 213,180 patients experienced a HF, 660,434 patients were diagnosed for dementia, and 47,430 patients were on dialysis. There was an effect of age and gender on the incidence of HF and dementia. In CKD patients, the risk of HF was significantly higher in demented patients compared to those without dementia: OR 2.0 [95 % CI 1.7-2.4], this being the same for men (OR 2.4 [1.8-3.1]) and women (OR 2.6 [2.0-3.3]) and at any age. However, the adjusted risk for HF in demented patients on dialysis therapy is not different than in demented patients without CKD (OR 1.3 [1.0-1.6]). CONCLUSIONS: Dementia significantly increases the risk of HF in patients on dialysis, but this risk in demented patients is equally high whether receiving dialysis therapy or not. These results highlight dementia as a major risk factor for HF in dialysis and indicate that reduction of fracture risk should include dementia as a risk factor.

Incidence and risk factors for hip fractures in dialysis patients.

UNLABELLED: This study described the incidence of hip fractures, associated diseases, and related costs generated in dialysis versus non-dialysis patients. INTRODUCTION: Skeletal fractures are a great concern in chronic kidney disease patients and, in particular, hip fractures that enhance the mortality. We aimed to accurately determine the incidence of hip fractures and associated diseases and to calculate the costs generated in dialysis patients. METHODS: We obtained data from the 2010 French National Hospital Database. We first extracted the hospital stays related to hip fractures as a primary diagnosis according to the ICD-10 codes and then the hospitalizations for dialysis. We compared the frequency of comorbidities in both populations. RESULTS: Among the 88,962 patients who suffered from hip fractures, 362 were on dialysis. The incidence was significantly higher in dialysis patients (x4) compared to non-dialysis patients. Women on dialysis experienced hip fractures at an earlier age than non-dialysis women. Dementia was identified as a major risk factor in the dialysis patients (72 vs. 26%, p < 0.0001). Moreover, diabetes and cardiovascular diseases were comorbidities strongly associated with hip fractures in both gender, but hypertension and malnutrition were observed exclusively in men on dialysis. Mortality rate and length of hospital stay were increased (5 days) in both genders. CONCLUSION: The incidence of hip fractures is increased in dialysis patients, affecting a larger percentage of men and women on dialysis than in the non-dialysis population and enhancing the financial burden and mortality. Dementia is a major risk factor for hip fractures in dialysis patients in addition to diabetes and cardiovascular diseases.

Animal models in OA: a means to explore bone.

Cartilage damage which characterizes osteoarthritis is accompanied with bone lesions. Joint integrity results from the balance in the physiological interactions between bone and cartilage. Several local factors regulate physiological remodeling of cartilage, the disequilibrium of these leading to a higher cartilage catabolism. Several cytokines secreted by bone cells can induce chondrocyte differentiation which suggests their role in the dialogue between both cells. Several animal models of osteoarthritis have been developed in order to assess the mechanism of cartilage loss and chondrocyte functions that encompassed surgical, chemical, or genetic approaches. Indeed, the animal models are helpful to investigate the cartilage changes in relation to changes in bone remodeling. Accumulative in vivo evidence show that increased bone resorption occurs at early stage of the development of osteoarthritis. Inhibition of bone resorbing molecules prevents cartilage damage, confirming the role of bone factors in the cross talk between both tissues. Among these numerous molecules, some participate to the imbalance in cartilage homeostasis and in the pathophysiology of osteoarthritis. These local factors are potential candidates for new drug targets.

Microcracks in subchondral bone plate is linked to less cartilage damage.

OBJECTIVES: Osteoarthritis (OA) is a disease of the whole joint characterized by cartilage loss and subchondral bone remodeling. The role of microcracks in cartilage integrity and subchondral bone homeostasis is not fully understood. The main goal of this work was to evaluate microcrack density in both calcified cartilage and subchondral bone plate in relation to cartilage damage in humans and to better define the association of microcracks and osteocyte density in subchondral bone. METHODS: We investigated 18 bone cores from cadaveric human knees that were stained with En-Bloc Basic Fuchsin. We quantified microcrack density, osteocyte density, cartilage surfaces and cartilage damage. The presence of microcracks was confirmed for each bone core by scanning electron microscopy. Finally, trabecular subchondral bone parameters were measured by micro-CT. RESULTS: Microcracks were detected in both calcified cartilage and subchondral bone plate. The density of microcracks in both calcified cartilage (CC) and subchondral bone plate (SBP) was negatively correlated with cartilage damage (r = -0.45, p < 0.05). The presence of microcracks in SBP was associated with a lower histological OA score. Osteocytes formed a dendrite network that abruptly stopped at the border of calcified cartilage. Osteocyte density in subchondral bone plate was increased in the presence of microcracks in calcified cartilage. CONCLUSIONS: Subchondral bone plate microcracks might be required for maintaining cartilage homeostasis. Microcracks in calcified cartilage may trigger osteocyte density in subchondral bone plate with subsequent regulation of subchondral bone remodeling to prevent cartilage damage.

Annexin 5 overexpression increased articular chondrocyte apoptosis induced by basic calcium phosphate crystals.

OBJECTIVES: Basic calcium phosphate (BCP) crystals (octacalcium phosphate (OCP), carbapatite (CA) and hydroxyapatite (HA)) are associated with severe forms of osteoarthritis. In advanced osteoarthritis, cartilage shows chondrocyte apoptosis, overexpression of annexin 5 (A5) and BCP crystal deposition within matrix vesicles. We assessed in vitro whether BCP crystals and overexpression of A5 increased chondrocyte apoptosis. METHODS: Apoptosis was induced by BCP crystals, tumour necrosis factor (TNF)-alpha (20 ng/ml) and Fas ligand (20 ng/ml) in normal articular chondrocytes (control) and in A5 overexpressed chondrocytes, performed by adenovirus infection. Apoptosis was assessed by caspase 3 (Cas3) activity, and DNA fragmentation. RESULTS: All BCP crystals, TNF-alpha and Fas ligand induced chondrocyte apoptosis as demonstrated by decreased cell viability and increased Cas3 activity and DNA fragmentation. TUNEL (terminal deoxyribonucleotide transferase-mediated dUTP nick end-labelling)-positive staining chondrocytes were increased by OCP (12.4 (5.2)%), CA (9.6 (2.6)%) and HA (9.2 (3.0)%) crystals and TNF-alpha (9.6 (2.4)%) stimulation compared with control (3.1 (1.9)%). BCP crystals increased Cas3 activity in a dose-dependent fashion. BCP-crystal-induced chondrocyte apoptosis was independent from TNF-alpha and interleukin-1beta pathways but required cell-crystal contact and intralysosomal crystal dissolution. Indeed, preincubation with ammonium chloride, a lysosomal inhibitor of BCP crystal dissolution, significantly decreased BCP-crystal-induced Cas3 activity. Finally, overexpression of A5 enhanced BCP crystal- and TNF-alpha-induced chondrocyte apoptosis. CONCLUSIONS: Overexpression of A5 and the presence of BCP crystals observed in advanced osteoarthritis contributed to chondrocyte apoptosis. Our results suggest a new pathophysiological mechanism for calcium-containing crystal arthropathies.

[Recommendations for the management of bone demineralization in cystic fibrosis]. / Recommandations pour la prise en charge de la déminéralisation osseuse dans la mucoviscidose.

A high prevalence of low bone mineralization is documented in adult patients with cystic fibrosis (CF). Osteopenia is present in as much as 85% of adult patients and osteoporosis in 13 to 57% of them. In children, studies are discordant probably because of different control database. Denutrition, inflammation, vitamin D and vitamin K deficiency, altered sex hormone production, glucocorticoid therapy, and physical inactivity are well known risk factors for poor bone health. Puberty is a critical period and requires a careful follow-up for an optimal bone peak mass. This review is a consensus statement established by the national working group of the French Federation of CF Centers to develop practice guidelines for optimizing bone health in patients with CF. Recommendations for screening and for calcium, vitamin D and K supplementation are given. Further work is needed to define indications for treatment with biphosphonates and anabolic agents.

Functional and physicochemical studies of hemoglobin St. Louis beta 28 (B10) Leu replaced by Gln: a variant with ferric beta heme iron.

Studies have been performed on a 20-yr-old man exhibiting methemoglobinemia and a severe hemolytic anemia involving formation of Heinz bodies. This condition was due to an abnormal Hb present in the red cells of the proband: Hb St. Louis, beta 28 (B10) replaced by Gln, whose structural characteristics have been previously reported. This unstable Hb represented 30% of the total and was isolated by starch block electrophoresis at pH 8.6. Electrophoretic and spectral studies showed Hb St. Louis to be a valency hybird, alpha 2 beta 2+. The presence of hemichrome in this Hb was detected by electron paramagnetic resonance studies. During this study, an electrophoretic technique was developed that allows study of the mobility of hemichrome. Oxygen equilibria performed on purified Hb St. Louis revealed a high oxygen affinity and a markedly reduced cooperativity. The Bohr effect was normal, but the interaction of this hemoglobin with 2,3-diphosphoglycerate was decreased. The oxidation rate of Hb St. Louis was normal. Hb St. Louis was completely reduced by dithionite and ferrous citrate, and the functional properties of this reduced form were normal. In contrast, Hb St. Louis was only partially reduced by diaphorase. The mechanism of the oxidation of Hb St. Louis therefore appears to differ markedly from that postulated for other Hbs M.

Etelcalcetide: injectable calcimimetic for the treatment of secondary hyperparathyroidism in hemodialysis-dependent patients.

Chronic kidney disease is associated with mineral and bone disorders that are now considered as a syndrome. One of the major complications of this syndrome is secondary hyperparathyroidism (SHPT). SHPT increases bone turnover and the risk of fracture. SHPT is also associated with cardiovascular calcification and high mortality risk. The classical medical therapies of SHPT lack long-term efficacy and have undesirable effects on serum calcium and phosphate levels. Surgical parathyroidectomy is a radical therapeutic solution potentially exposing patients to a permanent state of hypoparathyroidism among other complications. Oral cinacalcet revolutionized the treatment of SHPT because of its great efficacy; however, more than one-third of patients do not respond appropriately to cinacalcet, mostly because of intolerance and lack of compliance. Intravenous etelcalcetide improves medical adherence and reduces pill burden. It is 10-15% superior than cinacalcet in controlling parathyroid hormone, but also leads to more frequent episodes of hypocalcemia.

Estradiol inhibits adhesion and promotes apoptosis in murine osteoclasts in vitro.

Osteoporosis caused by estrogen deficiency is characterized by enhanced bone resorption mediated by osteoclasts. Adhesion to bone matrix and survival of differentiated osteoclasts is necessary to resorb bone. The aim of our study was to investigate the in vitro effects of estradiol on murine osteoclasts. RAW 264.7 cells treated with 30 ng/ml RANK-L were used as a model for osteoclastogenesis. Estradiol (10(-8)M) for 5 days induced an inhibition of osteoclast differentiation and beta3 expression. Estradiol inhibited significantly the adhesion of mature osteoclasts by 30%. Furthermore estradiol-induced apoptosis shown by with nuclear condensation and Bax/Bcl2 ratio. In addition, estradiol enhanced caspase-3, -8 and -9 activities. This effect completely disappeared using specific caspase-8 inhibitor. However, increased caspase-3 activity by estradiol was observed in the presence of caspase-9 inhibitor, indicating the preferential involvement of caspase-8 pathway. Fas and FasL mRNA expression was not regulated by estradiol. However, estradiol enhanced caspase-3 activity in Fas-induced apoptosis on mature osteoclasts, suggesting that this might interact with the Fas-signaling pathway. These data suggest that estradiol decreases bone resorption by several mechanisms including adhesion and apoptosis of osteoclasts.

Multiscale and multimodality computed tomography for cortical bone analysis.

In clinical studies, high resolution peripheral quantitative computed tomography (HR-pQCT) is used to separately evaluate cortical bone and trabecular bone with an isotropic voxel of 82 µm3, and typical cortical parameters are cortical density (D.comp), thickness (Ct.Th), and porosity (Ct.Po). In vitro, micro-computed tomography (micro-CT) is used to explore the internal cortical bone micro-structure with isotropic voxels and high resolution synchrotron radiation (SR); micro-CT is considered the 'gold standard'. In 16 tibias and 8 femurs, HR-pQCT measurements were compared to conventional micro-CT measurements. To test modality effects, conventional micro-CT measurements were compared to SR micro-CT measurements at 7.5 µm3; SR micro-CT measurements were also tested at different voxel sizes for the femurs, specifically, 7.5 µm3 versus 2.8 µm3. D.comp (r = -0.88, p < 10-3) was the parameter best correlated with porosity (Po.V/TV). The correlation was not affected by the removal of pores under 130 µm. Ct.Th was also significantly highly correlated (r = -0.89 p < 10-3), while Ct.Po was correlated with its counterpart Po.V/TV (r = 0.74, p < 10-3). From SR micro-CT and conventional micro-CT at 7.5 µm3 in matching areas, Po.V/TV and pore diameter were underestimated in conventional micro-CT with mean ± standard deviation (SD) biases of -2.5 ± 1.9% and -0.08 ± 0.08 mm, respectively. In contrast, pore number (Po.N) and pore separation (Po.Sp) were overestimated with mean ± SD biases of +0.03 ± 0.04 mm-1 and +0.02 ± 0.04 mm, respectively. The results from the tibia and femur were similar when the results of SR micro-CT at 7.5 µm3 and 2.8 µm3 were compared. Po.V/TV, specific surface of pores (Po.S/Po.V), and Po.N were underestimated with mean biases of -1.7 ± 0.9%, -4.6 ± 4.4 mm-1, and -0.26 ± 0.15 mm-1, respectively. In contrast, pore spacing was overestimated at 7.5 µm3 compared to 2.8 µm3 with mean biases of 0.05 ± 0.03 mm. Cortical bone measurements from HR-pQCT images provided consistent results compared to those obtained using conventional micro-CT at the distal tibia. D.comp was highly correlated to Po.V/TV because it considers both the micro-porosity (Haversian systems) and macro-porosity (resorption lacunae) of cortical bone. The complexity of canal organization, (including shape, connectivity, and surface) are not fully considered in conventional micro-CT in relation to beam hardening and cone beam reconstruction artifacts. With the exception of Po.V/TV measurements, morphological and topological measurements depend on the characteristics of the x-ray beam, and to a lesser extent, on image resolution.

Hemoglobin Pitie-Salpetriere beta 34 (B16) Val replaced by Phe. A new high oxygen affinity variant associated with familial erythrocytosis.

Hemoglobin Pitie-Salpetriere was detected by routine isoelectric focusing. It moved up on isoelectric focusing between hemoglobin A and hemoglobin F, near Hb F. On cellulose acetate strips at pH 8.6, it moved as hemoglobin A. This new variant exhibits a high oxygen affinity associated with familial erythrocytosis. The valine residue in position beta 34 has been replaced by a phenylalanine residue. This residue is involved in the alpha 1 beta 1 contact.

LRP5 gene polymorphisms and idiopathic osteoporosis in men.

Mutations in the low-density lipoprotein receptor-related protein 5 gene (LRP5) have demonstrated the role of LRP5 in bone mass acquisition. LRP5 variants were recently reported to contribute to the population-based variance in vertebral bone mass and size in males. To investigate whether LRP5 variants are implicated in idiopathic male osteoporosis, we studied 78 men with low BMD (<2.5 T score or < -2 Z score) aged less than 70 years (mean +/- SD: 50 +/- 16 years) in whom secondary causes of osteoporosis had been excluded and 86 controls (51 +/- 10 years). Genotypes and haplotypes were based on LRP5 missense substitutions in exons 9 (c.2047G > A, p.V667M) and 18 (c.4037C > T, p.A1330V), and their association with osteoporosis evaluated after adjustment for multiple clinical and environmental variables using logistic regression. The presence of osteoporosis was significantly associated with LRP5 haplotypes (P = 0.0036) independent of age (P = 0.006), weight (P = 0.004), calcium intake (P = 0.002), alcohol (P = 0.005) and tobacco (P = 0.004) consumption. Accordingly, the odds ratio for osteoporosis was 3.78 (95% CI 1.27-11.26, P < 0.001) in male carriers of haplotype 3 (c.2047A-4037T, n = 20 cases and 12 controls) versus homozygous carriers of haplotype 1 (c.2047G-4037C, n = 42 cases and 61 controls). In conclusion, these data indicate beyond a significant role for environmental factors, an association between LRP5 variants and idiopathic osteoporosis in males, pointing to a role of LRP5 in this disease.

Relationship between the number of resorbing cells and the amount resorbed in metabolic bone disorders.

The relationship between bone-resorbing cells, assessed by the presence of tartrate-resistant acid phosphatases (TRAP) and morphologic indices of bone resorption, was determined in 29 osteoporotic patients (14 postmenopausal females and 15 males) and 15 dialyzed patients. The number of TRAP-positive cells per unit of cancellous bone area (N.Oc/B.Ar) was higher in dialyzed patients than in those with osteoporosis (16.8 +/- 15.3 versus 4.95 +/- 2.86, p less than 0.05). The amount of bone resorbed at the basic multicellular unit level was estimated by calculating eroded area containing TRAP cells per bone area (E.Ar+/BA). This novel parameter was similar in dialyzed and in osteoporotic patients (41,700 +/- 28,400 versus 32,300 +/- 24,600). In contrast, trabecular spacing (Tb.Sp) was identical in both metabolic bone diseases. Trabecular width (169 +/- 38 versus 127 +/- 32 microns, p less than 0.05) and bone area were higher in dialyzed than in osteoporotic patients. N.Oc/B.Ar was significantly related to E.Ar+/BA in dialyzed (r = 0.76, p less than 0.05) but not in osteoporotic patients. Tb.Sp was significantly correlated to N.Oc/B.Ar and to the number of TRAP-positive cell nuclei per B.Ar (r = 0.44, p less than 0.05) in osteoporotic but not in dialyzed patients. This last result shows that in overt osteoporosis with thin trabeculae, trabecular spacing is related to the number of resorbing cells. In contrast, the spacing of thick trabeculae in dialysis osteodystrophy is not dependent on the number of osteoclasts.

A new method for measuring cancellous bone erosion depth: application to the cellular mechanisms of bone loss in postmenopausal osteoporosis.

We have devised a new method for measurement of final depth of erosion in cancellous bone with an intra-individual precision of 4.3% and applied it to determine the mechanism of continuing reduction in trabecular thickness after menopause. Mean erosion depth (SD) was 40.8 (2.0) microns in 10 healthy postmenopausal women and 41.4 (2.1) microns in 10 age-matched patients with postmenopausal osteoporosis; the difference was not statistically significant. In contrast, wall thickness, using a method based on density differences between new and old bone, was 39.5 (2.0) microns in the normal subjects and 35.3 (2.0) microns in the patients with osteoporosis (p less than 0.0001). The balance per remodeling cycle (delta BMU) was -1.34 (2.49) microns in the normal subjects and -6.11 (1.95) microns in the patients with osteoporosis. This difference was also highly significant (p less than 0.001). Indirect estimations of erosion depth and delta BMU, based on the fall in trabecular thickness from an assumed premenopausal value of 147 microns and the number of remodeling cycles accumulated since menopause, agreed closely with the measured values. Erosion depth measured by the Eriksen method also showed no significant difference between the two groups, but because the values were substantially higher delta BMU was improbably high in both groups, did not differ significantly between groups, and was inconsistent with the observed difference in trabecular thickness.(ABSTRACT TRUNCATED AT 250 WORDS)

Short-term local injections of transforming growth factor-beta 1 decrease ovariectomy-stimulated osteoclastic resorption in vivo in rats.

Estrogen deficiency in rats is responsible for increased osteoclastic resorption and a subsequent rapid bone loss. TGF-beta, which is known to have acute effects on bone resorption in several in vitro models, has been shown to be secreted by osteoblastic cells in vitro in response to 17 beta-estradiol, but little is known about its in vivo effects on bone resorption. We therefore decided to investigate the short-term effect of TGF-beta 1 on bone resorption in ovariectomized rats. TGF-beta 1 (0.04-20 ng/injection), or vehicle, was injected daily directly into the bone marrow space, through a thin catheter implanted in the distal end of the right femur, during 4 consecutive days, starting 14 days after the ovariectomy. Bone histomorphometry was performed in the secondary spongiosa of the metaphysis of injected femurs and compared with vehicle-injected femurs of sham ovariectomized rats. Ovariectomy was associated with a marked increase in the resorption surface, a 2-fold increase in the number of osteoclasts, and no change in the number of TRAP-positive marrow cells distant from bone surfaces. Bone resorption was significantly lower in the TGF-beta 1-injected bones of ovariectomized rats, as compared with vehicle injected bones: the osteoclast surface and the number of osteoclasts were, respectively, 11.0 +/- 5.1% versus 20.8 +/- 1.3% and 287 +/- 41 versus 505 +/- 53, in bones injected with 0.2 ng of TGF-beta 1 as compared with vehicle-injected bones (mean +/- SE, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)