Histomorphometric assessment of the long-term effects of alendronate on bone quality and remodeling in patients with osteoporosis.

Treatment effects on bone quality and remodeling was assessed in postmenopausal women with osteoporosis treated with oral alendronate. One transiliac bone biopsy was obtained from 231 women at either 24 mo (n = 11) or 36 mo (n = 120) from the start of treatment with alendronate at doses of between 5 and 20 mg/d, or placebo. 64 biopsies at 24 mo (31 from the placebo group and 33 alendronate-treated patients) and 95 biopsies at 36 mo (40 from the placebo group and 55 alendronate-treated patients) provided adequate cancellous tissue, and were analyzed by histomorphometry. Mineral apposition rate was unaffected by treatment. At 24 and 36 mo, osteoid thickness, volume, and surface significantly decreased. At each of the doses studied, mineralizing surface and activation frequency significantly decreased at each time point (e.g., -92% and -87%, respectively, for the 10 mg daily dose after 2 yr). These diminutions were of the same magnitude for each dose at 24 mo, and for the two highest doses at 36 mo. A significant increase in wall thickness accompanied by a reduction in erosion depth was detected in biopsies obtained at 24 mo. These findings confirm that mineralization is normal, and trabecular bone turnover markedly decreased in patients receiving long-term dosing with alendronate. The findings also suggest that the observed increases in bone mineral density could result both from a reduction in the remodeling space due to a decreased activation frequency and a possible trend to a positive bone balance. In addition, further studies focused on a possible increase in the degree of mineralization of bone are required.

Contribution of the advanced glycation end product pentosidine and of maturation of type I collagen to compressive biomechanical properties of human lumbar vertebrae.

Collagen characteristics contribute to bone biomechanical properties. Yet, few studies have analyzed the independent contributions of bone mineral density (BMD) and post-translational modifications of type I collagen to whole bone strength. Thus, the aim of this study was to determine the relative contributions of BMD and both enzymatic and non-enzymatic collagen crosslink concentration to the biomechanical properties of human vertebrae. Nineteen L3 vertebrae were collected after necropsy (age 26-93; 10 males, 9 females). BMD of the vertebral body was measured by DXA, and the vertebrae were compressed to failure to assess the stiffness, failure load and work to fracture. After mechanical testing, the concentration of both enzymatic crosslinks pyridinoline (PYD), and deoxypyridinoline (DPD) as well as, and the non-enzymatic crosslinks pentosidine (PEN) were analyzed in trabecular and cortical bone by reversed-phase HPLC. The extent of aspartic acid isomerization of type I collagen C telopeptide (CTX) was evaluated by ELISA of native (alpha CTX) and isomerized (beta CTX) forms. BMD was significantly positively related with stiffness (R(2) = 0.74; P < 0.0001), failure load (R(2) = 0.69; P < 0.0001) and work to fracture (R(2) = 0.44; P = 0.002). Bivariate regression analysis showed no association between collagen traits and biomechanical properties. However, in a multiple regression model, BMD and trabecular PEN were both significantly associated with failure load and work to fracture (multiple R(2) = 0.83, P = 0.001 and R(2) = 0.67, P = 0.001, respectively). Similarly, BMD and trabecular alpha/beta CTX ratio were both associated with stiffness (multiple R(2) = 0.83, P = 0.015). These findings indicate that post-translational modifications of type I collagen have an impact on skeletal fragility.

Relationship between compressive properties of human os calcis cancellous bone and microarchitecture assessed from 2D and 3D synchrotron microtomography.

The aim of this study was to determine the contribution of 2D and 3D microarchitectural characteristics in the assessment of the mechanical strength of os calcis cancellous bone. A sample of cancellous bone was removed in a medio-lateral direction from the posterior body of calcaneus, taken at autopsy in 17 subjects aged 61-91 years. The sample was first used for the assessment of morphological parameters from 2D morphometry and 3D synchrotron microtomography (microCT) (spatial resolution=10 microm). The 2D morphometry was obtained from three slices extracted from the 3D microCT images. Very good concordance was shown between 3D microCT slices and the corresponding physical histologic slices. In 2D, the standard histomorphometric parameters, fractal dimension, mean intercept length, and connectivity were computed. In 3D, histomorphometric parameters were computed using both the 3D mean intercept length method and model-independent techniques. The 3D fractal dimension and the 3D connectivity, assessed by Euler density, were also evaluated. The cubic samples were subjected to elastic compressive tests in three orthogonal directions (X, Y, Z) close to the main natural trabecular network directions. A test was performed until collapse of trabecular network in the main direction (Z). The mechanical properties were significantly correlated to most morphological parameters resulting from 2D and 3D analysis. In 2D, the correlation between the mechanical strength and bone volume/tissue volume was not significantly improved by adding structural parameters or connectivity parameter (nodes number/tissue volume). In 3D, one architectural parameter (the trabecular thickness, Tb.Th) permitted to improve the estimation of the compressive strength from the bone volume/tissue volume alone. However, this improvement was minor since the correlation with the BV/TV alone was high (r=0.96). In conclusion, which is in agreement with the statistic's rules, we found, in this study, that the determination of the os calcis bone compressive strength using the 3D bone volume fraction cannot be improved by adding 3D architectural parameters.

Trabecular bone microarchitecture after alendronate treatment of osteoporotic women.

OBJECTIVE: To compare the microarchitecture of iliac crest trabecular bone from women treated for two to three years with alendronate versus that of women treated with placebo. RESEARCH DESIGN AND METHODS: Three-dimensional micro-computed tomography (micro-CT; resolution 20 microm) and two-dimensional histomorphometry (resolution 5-7 microm) were used to examine trabecular bone from single transilial biopsies obtained at the completion of clinical trials. MAIN OUTCOME MEASURES: Microarchitectural variables, including bone volume, trabecular number, trabecular thickness, and trabecular spacing in specimens from alendronate- and placebo-treated women were examined. Three-dimensional images of trabecular bone from both groups were constructed from CT images. Correlations among variables and between techniques were also calculated. RESULTS: Eighty-eight specimens were suitable for evaluation by both techniques. As measured by two-dimensional histomorphometry, bone volume fraction (as a proportion of total volume) and trabecular thickness were significantly greater in alendronate specimens, 17.1 +/- 5.5% vs. 13.4 +/- 5.5% (p = 0.0043) and 127 +/- 29 microm vs. 109 +/- 28 microm (p = 0.0090), respectively, and trabecular spacing was significantly smaller, 729 +/- 227 microm vs. 862 +/- 338 microm (p = 0.005). Micro-CT yielded similar findings: bone volume and trabecular number were significantly greater in alendronate specimens: 19.4 +/- 6.2% vs. 16.2 +/- 6.3% (p = 0.0412) and 1.46(+/-) 0.32 vs. 1.31(+/-) 0.33 per mm (p = 0.0346). Two-dimensional and micro-CT measured characteristics correlated strongly with one another, with Pearson product moment correlation coefficients ranging from 0.60 (for trabecular thickness) to 0.83 (for bone volume). CONCLUSIONS: Trabecular microarchitecture of the ilium, whether studied by two- or three-dimensional methods, is better (greater bone volume, greater trabecular thickness, decreased trabecular spacing) after alendronate treatment than after two to three years of treatment with placebo. Bone volume in a trabecular region is strongly correlated to its microarchitecture, suggesting that bone quantity predicts values for these microarchitectural endpoints.

Serum undercarboxylated osteocalcin correlates with hip bone mineral density in elderly women.

We previously showed that circulating undercarboxylated osteocalcin (ucOC) is elevated in elderly women and is a powerful marker of the subsequent risk of hip fracture in elderly institutionalized women (J Clin Invest 1993; 91:1769). To investigate the relationship between bone mass and ucOC, we measured bone mineral density (BMD) of the hip with dual-energy x-ray absorptiometry in 98 elderly institutionalized women, 81.4 +/- 6.0 years old. ucOC was negatively correlated with BMD at all sites (r = -0.26 to -0.38, p < 0.001 to p < 0.0001), even after exclusion of the effect of age by partial correlation (for the femoral neck, r = -0.26, p < 0.01) and after controlling for serum parathyroid hormone. BMD was significantly lower at all sites of measurement in women with elevated ucOC (> 1.65 ng/ml, upper limit of the normal range in young women) than in those with normal ucOC (for the neck, 0.58 +/- 0.13 versus 0.43 +/- 0.13 g/cm2, p < 0.001). Similar results were obtained for ucOC expressed as the fraction of total OC (ucOC%). Multiple regression showed that ucOC has the highest predictive value for BMD when including age and body weight in the equation. In summary, our data indicate that serum ucOC is an independent determinant of BMD of the hip in elderly women. The mechanism by which serum ucOC is related to bone mass is unclear and should be addressed in further studies. However, our data suggest that ucOC level may be an interesting marker in the investigation of bone status in the elderly.

Iliac trabecular bone formation predicts radial trabecular bone density changes in type 1 osteoporosis.

In 28 patients with idiopathic or postmenopausal type 1 (spinal crush fracture) osteoporosis, resorption indices and dynamic measurements of trabecular bone formation based on in vivo tetracycline labeling in 7.5 mm transiliac biopsies have been compared with trends in radial cortical and trabecular bone density measured with computed tomography. Positive correlations were observed between trabecular bone density trends in the radius and indices of bone formation in the ilium. These were improved when one of the two resorption indices was included with a formation index in bivariate regressions. Marked interindividual variations in radial bone density trends were also seen in cortical bone. These correlated poorly with trends in trabecular bone. Weak negative relationships between cortical bone trends and indices relating to bone formation and resorption were observed, but a positive association was seen with single-labeled surfaces on iliac trabeculae. If, as has been suggested, there are periodic variations in bone formation, the results suggest that axial and peripheral trabecular bone density trends are synchronized in osteoporosis, perhaps in response to systemic factors, such as circulating hormones.

Apparent pre- and postmenopausal bone loss evaluated by DXA at different skeletal sites in women: the OFELY cohort.

We measured the bone mineral density (BMD) at various skeletal sites (total body, hip, anteroposterior [AP] and lateral [lat] spine, and forearm) in a large population-based cohort of women aged 31-89 years (the OFELY cohort), and results were analyzed according to age and postmenopausal years. A significant apparent bone loss was found before the menopause in cancellous bone, i.e., at the lat spine and Ward's triangle (-10%; p < 0.05-0.001). Cross-sectional analysis indicated that, after the menopause, apparent bone loss was accelerated within the 10 years following menopause, continued thereafter at all sites except the AP spine, and was again accelerated in elderly menopausal for more than 25 years. Between 30 and 80 years, BMD decreased by 15 to 44% (T score -1.6 to -3.4) according to the site. The amount of apparent bone loss was highest at the Ward's triangle when expressed in percentage (44%) and at the mid- and distal radius when expressed in number of standard deviations from the peak bone mass (-3.4). As a result, the percentage of women classified as osteoporotic according to the World Heath Organization, i.e., with a T score < or = -2.5, varied substantially from site to site and was highest at the radius (37% and 46%) and lateral spine (25-31%), intermediate at the Ward's triangle, AP spine, and whole body BMD, and lowest at the whole body bone mineral content, femoral neck, and trochanter (10-12%). In conclusion, this cross-sectional but large study suggests that there is a moderate apparent premenopausal bone loss that occurs only at cancellous bone sites and that apparent bone loss is accelerated at most skeletal sites after the age of 75 years. Because of the highly variable coefficient of variation of the peak bone mass at various skeletal sites, the percentage of postmenopausal women identified as being osteoporotic varies widely according to the site of measurement.

Vitamin D receptor gene polymorphisms are not related to bone turnover, rate of bone loss, and bone mass in postmenopausal women: the OFELY Study.

Vitamin D receptor (VDR) gene polymorphisms have been reported to account for most of the well established genetic influence on bone mineral density (BMD). However, discordant studies have been published and it is still not clear whether VDR genotypes influence bone mass accretion and/or postmenopausal bone loss. In this study, we analyzed VDR gene polymorphisms, i.e., that of BsmI, ApaI, and TaqI restriction enzymes in 268 untreated postmenopausal women 1-26 years postmenopausal. There were 37 BBAA homozygote (absence of BsmI and ApaI restriction sites on both alleles), 55 bbaa homozygote (presence of restriction sites on both alleles), and 176 heterozygotes. At baseline, women between the three genotypes did not differ significantly in age, years since menopause, body mass index (BMI), nor dietary calcium intake. We found no relationship between VDR genotypes and bone turnover assessed by three serum markers of bone formation and three urinary bone resorption markers, nor with BMD measured at the spine, hip, forearm, and whole body by dual-energy X-ray absorptiometry (DXA). Rates of bone loss assessed by repeated DXA measurements over 2 years were highly significant (p = 0.02-0.0001) at all skeletal sites except for the lumbar spine but did not differ between genotypes at any sites either before or after adjustment for potential confounding factors such as years since menopause, BMI, calcium intake, serum 25 hydroxyvitamin D levels, and baseline BMD. When we restricted the analysis to early postmenopausal women, within 10 years of menopause (n = 128), lumbar spine bone loss became significant, but no significant difference between VDR genotypes in the rate of bone loss measured at any site was found. We conclude that VDR genotypes are not predictive of bone turnover, rate of postmenopausal bone loss, and bone mass in either early or late postmenopausal women. In a subgroup of women with a low calcium intake (below 600 mg/day), we also found no significant differences between genotypes in BMD and the rate of bone loss measured at any site, although the sample size (n = 64) may be too small to detect small differences. In conclusion, these data, along with the absence of relationships between VDR gene polymorphisms and peak bone mass that we recently reported, suggest that the determination of VDR genotypes is probably not a useful clinical test for the risk assessment of osteoporosis.

Evidence for a toxic effect of aluminum on osteoblasts: a histomorphometric study in hemodialysis patients with aplastic bone disease.

To evaluate the potential role of aluminum (Al) in a subset of dialysis patients with aplastic bone disease, we have studied tetracycline-labeled bone biopsies of 32 patients (22 males and 10 females, 45-73 years) on maintenance hemodialysis. Selection criteria included normal resorption surfaces (RS) and osteoid thickness. Eleven patients (Group I) had no stainable bone Al (Al-; 61.7 +/- 7.2 years) and 21 (Group II) had stainable bone Al (Al+; 57.7 +/- 6.8 years). Serum Al was normal to slightly elevated in Group I, but significantly higher in Group II (p less than 0.01). Al surfaces (AlS), undetectable in Group I, were 67.8 +/- 17.9% in Group II. Bone Al content (BAC) was much lower in Group I than in Group II (14.8 +/- 3.7 vs. 113.8 +/- 100.2 micrograms/g, p less than 0.01), but higher in Group I than in controls (p less than 0.05). Extensive thin osteoid seams were present in Group II. AlS was correlated with OS (r = 0.56, p less than 0.001) and OV (r = 0.48, p less than 0.01). Labeled surfaces were decreased in both groups. Labeled osteoid surfaces (TLS/OS) were below 2 SD of the mean control values in 96% of patients and calcification rate (CR) was depressed below 0.20 micros/day in 44% of patients. Bone formation rate (BFR) was strikingly depressed, values being below one SD of the mean control value in 92-100% of patients at both levels and below 2 SD of the mean in 82% of patients at BMU levels. Mineralization lag time (OMP) was markedly prolonged above 2 SD of controls in 89% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

The assessment of bone formation and bone resorption in osteoporosis: a comparison between tetracycline-based iliac histomorphometry and whole body 85Sr kinetics.

Bone formation and resorption have been measured in patients with idiopathic osteoporosis by histomorphometry of 7.5-mm trephine biopsies and in the whole body by 85Sr radiotracer methodology and calcium balances. The studies were synchronized and most were preceded by double in vivo tetracycline labeling. Correlations between histological and kinetic bone formation indices were better when better when based on the extent of double tetracycline labels than on measurements of osteoid by visible light microscopy. Correction of the kinetic data for long-term exchange, using 5 months' serial whole body counting of retained 85Sr, improved the fit of the kinetic to the histological data. A statistical analysis of the measurement uncertainties showed that the residual scatter in the best correlations (between exchange-corrected bone formation rates and double-labeled osteoid surface indices) could be attributed to measurement imprecision alone. The exchange-corrected resorption rate correlated fairly well with iliac trabecular resorption surfaces, and using a volume referent rather than a surface referent for the histological index improved the statistical fit when patients with therapeutically accelerated bone turnover were included. A much better correlation was obtained by including osteoid volume acting as an independent predictor of bone resorption in a bivariate regression with a resorption surface index. The residual errors could then be accounted for by known measurement uncertainties. Whereas osteoid taking a double label closely predicted the kinetic rate of bone formation, further analysis suggested that osteoid that took no label or a single label was more closely related to bone resorption, presumably as a secondary result of the coupling of bone formation to bone resorption. The idea that continued bone loss in some patients is associated with defective osteoblastic bone formation is supported by the low rates found in some patients by both techniques. Heuristically these studies validate both in vivo tetracycline labeling for dynamic histomorphometry and corrections for long-term exchange in kinetic studies of bone formation, providing a quantitative framework for the design and analysis of future studies of bone remodeling in the osteoporoses.

Comparative study of fluoride bioavailability following the administration of sodium fluoride alone and in combination with different calcium salts.

To assess whether an interval of a few hours would be advisable between an intake of sodium fluoride (NaF) and that of calcium salts when treating osteoporotic patients with vertebral collapse, we carried out three pharmacokinetic studies in 12 healthy fasting volunteer subjects to compare the fluoride bioavailability provided by NaF alone and NaF combined with two calcium salts. The results were as follows: (1) When NaF is accompanied by calcium, the fluoride peak level is lower and delayed. (2) Fluoride absorption varied greatly among individuals in both experiments, but none of the 6 subjects proved to be nonabsorbers. (3) The areas under the curves obtained with each of the three preparations were not significantly different, but 24-h urinary fluoride was significantly lower in volunteers receiving simultaneously NaF and calcium salts than in volunteers receiving only NaF.

Comparison of trabecular bone microarchitecture and remodeling in glucocorticoid-induced and postmenopausal osteoporosis.

Long-term treatment with glucocorticoids (GCs) leads to a rapid bone loss and to a greater risk of fractures. To evaluate the specific effects of this treatment on cancellous bone remodeling, structure, and microarchitecture, we compared 22 transiliac biopsy specimens taken in postmenopausal women (65 +/- 6 years) receiving GCs (> or = 7.5 mg/day, for at least 6 months) and 22 biopsy specimens taken in age-matched women with postmenopausal osteoporosis (PMOP), all untreated and having either at least one vertebral fracture or a T score < -2.5 SD. On these biopsy specimens, we measured static and dynamic parameters reflecting trabecular bone formation and resorption. Also, we performed the strut analysis and evaluated the trabecular bone pattern factor (TBPf), Euler number/tissue volume (E/TV), interconnectivity index (ICI), and marrow star volume (MaSV). Glucocorticoid-induced osteoporosis (GIOP), when compared with PMOP, was characterized by lower bone volume (BV/TV), trabecular thickness (Tb.Th), wall thickness (W.Th), osteoid thickness (O.Th), bone formation rate/bone surface (BFR/BS), adjusted mineral apposition rate/bone surface (Aj.AR/BS), and higher ICI and resorption parameters. After adjustment for BV/TV, the W.Th remained significantly lower in GIOP (p < 0.0001). The active formation period [FP(a+)] was not different. Patients with GIOP were divided into two groups: high cumulative dose GCs (HGCs; 23.7 +/- 9.7 g) and low cumulative dose GCs (LGCs; 2.7 +/- 1.2 g). HGC when compared with LGC was characterized by lower W.Th (p < 0.05), BV/TV (p < 0.001), Tb.Th (p < 0.05), trabecular number (Tb.N; p < 0.05), FP(a+)(p < 0.05), and nodes (p < 0.05), and higher E/TV (p < 0.05), ICI (p < 0.005), and TBPf (p < 0.05). When HGC was compared with PMOP, the results were similar except for the MaSV, which was significantly higher (p < 0.005). In summary, GIOP was characterized by lower formation and higher resorption than in PMOP, already present after LGC. With HGCs, these changes were associated with a more dramatic bone loss caused by a major loss of trabecular connectivity.

Effects of alendronate on bone quality and remodeling in glucocorticoid-induced osteoporosis: a histomorphometric analysis of transiliac biopsies.

Effects of alendronate (ALN) on bone quality and turnover were assessed in 88 patients (52 women and 36 men aged 22-75 years) who received long-term oral glucocorticoid exposure. Patients were randomized to receive oral placebo or alendronate 2.5, 5, or 10 mg/day for 1 year and stratified according to the duration of their prior glucocorticoid treatment. Transiliac bone biopsies were obtained for qualitative and quantitative analysis after tetracycline double-labeling at the end of 1 year of treatment. As previously reported in glucocorticoid-induced osteoporosis, low cancellous bone volume and wall thickness were noted in the placebo group as compared with normal values. Alendronate treatment was not associated with any qualitative abnormalities. Quantitative comparisons among the four treatment groups were performed after adjustment for age, gender, and steroid exposure. Alendronate did not impair mineralization at any dose as assessed by mineralization rate. Osteoid thickness (O.Th) and volume (OV/BV) were significantly lower in alendronate-treated patients, irrespective of the dose (P = 0.0003 and 0.01, respectively, for O.Th and OV/BV); however, mineral apposition rate was not altered. As anticipated, significant decreases of mineralizing surfaces (76% pooled alendronate group; P = 0.006), activation frequency (-72%; P = 0.004), and bone formation rate (-71%; P = 0.005) were also noted with alendronate treatment. No significant difference was noted between the changes observed with each dose. Absence of tetracycline label in trabecular bone was noted in approximately 4% of biopsies in placebo and alendronate-treated groups. Trabecular bone volume, parameters of microarchitecture, and resorption did not differ significantly between groups. In conclusion, alendronate treatment in patients on glucocorticoids decreased the rate of bone turnover, but did not completely suppress bone remodeling and maintained normal mineralization at all alendronate doses studied. Alendronate treatment did not influence the osteoblastic activity, which is already low in glucocorticoid-induced osteoporosis.

Active bone turnover of the cortico-endosteal envelope in postmenopausal osteoporosis.

We developed a computerized semiautomatic method allowing accurate measurement of bone remodeling activity of the cortico-endosteal envelope of iliac crest biopsies. Measurement of bone turnover of the cortico-endosteal and of the trabecular envelopes were performed in 33 untreated women with postmenopausal vertebral osteoporosis and in 8 age-matched normal women. In normal women, bone remodeling was not different in the trabecular and the cortico-endosteal envelopes. In contrast, osteoporotic women had a marked, significant increase of bone formation and resorption at the cortico-endosteal envelope when compared to trabecular bone. Despite this difference, bone turnover activities of both envelopes were related, as indicated by significant correlations for most parameters between both envelopes. Serum bone gla-protein, previously reported to reflect trabecular bone formation, was also highly correlated with static and dynamic assessment of bone formation of the cortico-endosteal envelope of osteoporotic women but did not reflect bone resorption. When trabecular and endosteal measurements were pooled, correlations between serum bone gla-protein and bone formation were similar or even improved. In conclusion, our data suggest that patients with postmenopausal osteoporosis have active bone turnover at the cortico-endosteal envelope which may contribute significantly to bone loss in this disease. Because the different bone envelopes react differently to various therapeutic regimens, bone turnover of the cortico-endosteal envelope should be considered when assessing the effect of new treatments.

Serum osteocalcin is increased in patients with osteomalacia: correlations with biochemical and histomorphometric findings.

The synthesis of osteocalcin or bone gla protein by osteoblasts is markedly stimulated by 1,25-(OH)2D, a key hormone in the regulation of bone mineralization. The circulating levels of osteocalcin have been shown to reflect both the osteoid matrix production and the formation rate of mineralized bone in several metabolic bone diseases (osteoporosis, thyrotoxicosis, primary hyperparathyroidism) in which both mechanisms are tightly coupled because of the absence of mineralization defect. In this study, we measured in 12 patients (7 women, 5 men, 56 +/- 15 yr old) with untreated osteomalacia serum osteocalcin and vitamin D metabolites (25OHD and 1,25-(OH)2D). The results were correlated with biochemical and histomorphometric assessment of bone remodeling. Osteomalacia was due to vitamin D deficiency (5 cases), to vitamin D malabsorption (6 cases), and to hypophosphataemia in 1 case. When compared to control values, serum osteocalcin was increased in patients with osteomalacia (7.4 +/- 4 vs. 3.7 +/- 1.3 ng/mL; P less than 0.001) and was positively correlated with serum alkaline phosphatase (r = 0.65; P = 0.03) and negatively with 25 OHD (r = -0.61; P = 0.04). Serum osteocalcin was not correlated with 1,25-(OH)2D [r = -0.45; not significant (NS)] even after exclusion of the patient with hypophosphataemia. Serum osteocalcin was positively correlated with the osteoid volume and osteoid perimeter (r = 0.71 and 0.69 respectively; P less than 0.01) but not with any of the tetracycline-based parameter of bone mineralization at the tissue level (r ranging from -0.41 to +0.42, NS). Serum 25 OHD, but not 1,25-(OH)2D, was positively correlated with the mineralization rate (r = 0.59; P less than 0.05 and r = 0.54; NS). We conclude that in patients with osteomalacia, a condition which is characterized by an increased osteoid accumulation due to a decreased mineralization rate, the increased level of serum osteocalcin reflects the increased osteoid synthesis but not the mineralization defect. In this disease, serum osteocalcin is inversely correlated to the severity of vitamin D deficiency reflected by serum 25 OHD, but not to the serum levels of 1,25-(OH)2D.

Serum bone Gla-protein in renal osteodystrophy: comparison with bone histomorphometry.

Serum bone Gla-protein (S-BGP) and other serum biochemical parameters, including alkaline phosphatase (S-AP) and immunoreactive PTH (S-iPTH), were measured in 42 patients undergoing chronic hemodialysis. Each patient also had a tetracycline-labeled transiliac bone biopsy, allowing correlations between the biochemical and trabecular bone histomorphometric parameters, S-BGP was markedly increased [64.0 +/- 74.8 (+/- SD) vs. 6.2 +/- 2.2 ng/ml in normal subjects] significantly correlated with S-AP (r = 0.53) and S-iPTH (r = 0.55) levels. S-BGP was significantly higher in the 14 patients with high turnover renal osteodystrophy (HT-ROD; S-BGP, 138.5 +/- 90.8 ng/ml) than in the 28 patients with low turnover (LT-ROD; S-BGP, 26.8 +/- 14.8 ng/ml). S-BGP was significantly correlated with the cellular parameters of bone resorption and formation (r = 0.57-0.69) and with the dynamic parameters of bone formation (r = 0.62-0.82). The extent of stainable bone aluminum was significantly negatively correlated with S-BGP (r = -0.51) and serum iPTH (r = -0.33), but not with S-AP. S-BGP measurement allowed better discrimination between LT-ROD and HT-ROD groups than did S-AP measurement. However, in the patients with LT-ROD, S-BGP did not discriminate between patients with or without osteomalacia. We conclude that S-BGP is a valuable marker for evaluating bone remodeling and, more specifically, the bone formation rate at the tissue level in hemodialyzed patients.

Skeletal blood flow, iliac histomorphometry, and strontium kinetics in osteoporosis: a relationship between blood flow and corrected apposition rate.

In 20 untreated patients with idiopathic or postmenopausal osteoporosis, kinetic studies of skeletal blood flow (using 18F) and bone turnover (using 85Sr) were combined with dynamic histomorphometry performed on transiliac biopsies taken within 6 weeks of each other. In 8 patients the combined studies were repeated after treatment. A further 5 patients were studied only while receiving treatment. As expected, skeletal blood flow measured by 18F correlated with an index of 85Sr uptake into the exchangeable pools of bone. Additionally and independently, skeletal blood flow correlated with an index of the work rate of the osteoblasts in each multicellular unit of bone (the corrected apposition rate of Parfitt). These correlations were statistically significant in both the untreated patients (P less than 0.05) and the whole group (P less than 0.001). Further indices related to bone turnover at the level of the skeleton as a whole were significantly associated with skeletal blood flow only in the combined group.

Heterogeneity of fracture syndromes in postmenopausal women.

Studies were performed on 32 women with vertebral crush fractures (mean age, 65.1 yr) and 27 patients with recent hip fractures (mean age, 83.6 yr). Histomorphometric analysis of undecalcified transiliac crest biopsies revealed significant differences between the two fracture groups. Trabecular bone volume (TBV) was significantly lower in vertebral fracture than in hip fracture patients (12.0 +/- 4.4% (+/- SD) vs. 14.8 +/- 3.6%; P = 0.014), while thickness of cortices was significantly lower for hip fracture than for vertebral fracture patients (436 +/- 231 vs. 823 +/- 465 microns; P less than 0.001). The TBV and radial bone mass (measured by absorptiometry on the shaft) for the vertebral fracture group were significantly lower than age-expected values. For the patients with hip fractures, the TBV was significantly above the expected value, and radial bone mass was not significantly different from the expected value. Other quantitative histological measurements did not generally differ between the two fracture groups and were compatible with normal or increased bone remodeling. The serum PTH in the hip fracture group was significantly increased above that expected in normal women of similar age. These data demonstrate the anatomical heterogeneity of osteoporotic fracture syndromes. Patients with vertebral fractures have an early deficit of trabecular bone for their age, while those with hip fractures have a deficit of both cortical and trabecular bone compared to women of age 50 yr, but the deficit is not excessive compared to others of similar age without fractures.

Intermethod variation in bone histomorphometry: comparison between manual and computerized methods applied to iliac bone biopsies.

The intermethod variation in the measurement of basic bone histomorphometric parameters was evaluated on 100 undecalcified transiliac bone biopsies. Two contiguous samples were taken from 50 patients (33 females; 17 males; mean age: 52 +/- 19 years) for diagnostic purposes. The diagnoses were osteoporosis (n = 38), renal osteodystrophy (n = 18), primary hyperparathyroidism (n = 16), osteomalacia (n = 12), metastatic bone disease (n = 2), thyrotoxic bone (n = 2), fluorosis (n = 2), and 10 biopsies were considered as "normal" bone. Trabecular bone volume (TBV) was measured with both a manual integrating eyepiece and an automatic (QUANTIMET 720-Cambridge Instruments, Cambridge, England) method. Trabecular resorption surfaces (TRS), trabecular osteoid surfaces (TOS), and volume (TOV) were measured with both a manual and a semiautomatic (VIDEOPLAN-Kontron, Munich, West Germany) method. The calcification rate (CR) was measured with both a manual and a semiautomatic method in eight cases after double labeling with tetracycline. Inter- and intraobserver variations were always lower with the automatic and semiautomatic methods than with the manual method, except for TOV. For all the parameters there was a highly significant correlation between manual and computerized methods (0.98 greater than r greater than 0.90). For TBV and CR no significant difference was noted, but for TBV the QUANTIMET appeared more sensitive, that is, better able to detect low values of the structure to be measured. For TRS, the manual method underestimated low values and appeared less sensitive than the semiautomatic method. For the 100 biopsies, the VIDEOPLAN underestimated the osteoid parameters by 13% for TOS and 26% for TOV.(ABSTRACT TRUNCATED AT 250 WORDS)

The anabolic effect of human PTH (1-34) on bone formation is blunted when bone resorption is inhibited by the bisphosphonate tiludronate--is activated resorption a prerequisite for the in vivo effect of PTH on formation in a remodeling system?

Parathyroid hormone (PTH) and its (1-34) fragment are stimulators of bone turnover that have an anabolic effect increasing trabecular bone mass when administered intermittently by daily subcutaneous injections. Its clinical use in osteoporosis, however, has been limited by the concomitant increased bone resorption and deleterious effect on cortical bone. To evaluate if a treatment combining PTH and a potent inhibitor of bone resorption would retain the anabolic effect of PTH without increasing bone resorption, we analyzed the effects of PTH (1-34) (500 IU/d) with or without the bisphosphonate tiludronate (1 mg/kg per day) for 3 months on biochemical and histological indices of bone turnover in old female sheep, an animal model which has a slow bone remodeling activity that resembles the one of elderly women. As expected, PTH (1-34) induced a significant increase of urinary pyridinoline and hydroxyproline (reflecting bone resorption), and of serum osteocalcin and alkaline phosphatase (reflecting bone formation), that were consistent with an increase of resorption and tetracycline-based formation of bone measured on iliac crest biopsy. In contrast, all biochemical and histological indices of bone turnover were decreased in sheep receiving tiludronate, a potent inhibitor of bone resorption. Surprisingly, in the combined therapy group, biochemical and histological indices of both resorption and formation did not differ from the control groups. Thus, the model of old sheep, which closely resembles the situation in old human, shows that the anabolic effect of PTH on bone is not maintained when PTH is coadministered with a bisphosphonate, in marked contrast to results noted in the growing rat.(ABSTRACT TRUNCATED AT 250 WORDS)