Relationship of Bone Mineralization Density Distribution (BMDD) in Cortical and Cancellous Bone Within the Iliac Crest of Healthy Premenopausal Women

Bone mineralization density distribution (BMDD) is an important determinant of bone mechanical properties. The most available skeletal site for access to the BMDD is the iliac crest. Compared to cancellous bone much less information on BMDD is available for cortical bone. Hence, we analyzed complete transiliac crest bone biopsy samples from premenopausal women (n = 73) aged 25–48 years, clinically classified as healthy, by quantitative backscattered electron imaging for cortical (Ct.) and cancellous (Cn.) BMDD. The Ct.BMDD was characterized by the arithmetic mean of the BMDD of the cortical plates. We found correlations between Ct. and Cn. BMDD variables with correlation coefficients r between 0.42 and 0.73 (all p < 0.001). Additionally to this synchronous behavior of cortical and cancellous compartments, we found that the heterogeneity of mineralization densities (Ct.Ca_Width), as well as the cortical porosity (Ct.Po) was larger for a lower average degree of mineralization (Ct.Ca_Mean). Moreover, Ct.Po correlated negatively with the percentage of highly mineralized bone areas (Ct.Ca_High) and positively with the percentage of lowly mineralized bone areas (Ct.Ca_Low). In conclusion, the correlation of cortical with cancellous BMDD in the iliac crest of the study cohort suggests coordinated regulation of bone turnover between both bone compartments. Only in a few cases, there was a difference in the degree of mineralization of >1wt % between both cortices suggesting a possible modeling situation. This normative dataset of healthy premenopausal women will provide a reference standard by which disease- and treatment-specific effects can be assessed at the level of cortical bone BMDD.     

Annual intravenous zoledronic acid for three years increased cancellous bone matrix mineralization beyond normal values in the HORIZON biopsy cohort

The efficacy of 3 years of annual intravenous administration of zoledronic acid (ZOL) in reducing vertebral and nonvertebral fractures in postmenopausal osteoporosis has been shown by the HORIZON pivotal fracture trial. Histomorphometric analysis of transiliac bone biopsies from the HORIZON participants revealed significantly improved trabecular architecture and reduced bone remodeling for the ZOL‐treated versus placebo‐treated patients. The aim of our study was to evaluate the cancellous and cortical bone mineralization density distribution (BMDD) in these biopsies by quantitative backscattered electron imaging (qBEI). The study cohort comprised 82 patients on active treatment (ZOL, yearly doses of 5 mg) and 70 treated with placebo, and all received adequate Ca and VitD supplementation. Comparison of ZOL‐treated versus placebo‐treated cancellous (Cn.) and cortical (Ct.) BMDD‐derived variables resulted in significantly higher average (Cn.CaMean + 3.2%, Ct.CaMean + 2.7%) and mode calcium concentrations (Cn.CaPeak + 2.1%, Ct.CaPeak + 1.5%), increased percentages of highly mineralized bone areas (Cn.CaHigh + 64%, Ct.CaHigh + 31%), lower heterogeneity of mineralization (Cn.CaWidth ?14%, Ct.CaWidth ?13%), and decreased percentages of low mineralized bone areas (Cn.CaLow ?22%, Ct.CaLow ?26%) versus placebo (all p < 0.001). Cn. BMDD from the patients on active treatment also revealed a statistically significant shift to higher Ca concentrations when compared to a historical normal reference BMDD. These differences in BMDD from ZOL patients compared to the other groups were in line with the correlation of BMDD variables with previously determined cancellous mineralizing surface per bone surface (Cn. MS/BS, a primary histomorphometric index for bone turnover), showing that those with lower Cn. MS/BS had a higher degree of bone matrix mineralization. However, the differences in BMDD variables between the study groups remained when adjusted for Cn. MS/BS, suggesting that other factors in addition to reduced bone turnover might contribute to the higher bone matrix mineralization after ZOL treatment. © 2013 American Society for Bone and Mineral Research.     

Increased Heterogeneity of Bone Matrix Mineralization in Pediatric Patients Prone to Fractures: A Biopsy Study

Idiopathic osteoporosis (IOP) in children is characterized by fragility fractures and/or low bone mineral density in otherwise healthy individuals. The aim of the present work was to measure bone mineralization density distribution (BMDD) based on quantitative backscattered electron imaging (qBEI) in children with suspected IOP. Entire cross‐sectional areas of transiliac bone biopsy samples from children (n = 24, 17 boys; aged 6.7–16.6 years) with a history of fractures (n = 14 with at least one vertebral fracture) were analyzed for cancellous (Cn) and cortical (Ct) BMDD. Outcomes were compared with normal reference BMDD data and correlated with the patients' clinical characteristics and bone histomorphometry findings. The subjects had similar average degree but significantly higher heterogeneity of mineralization in both Cn and Ct bone (Cn.CaWidth +23%, Ct.CaWidth +15%, p < 0.001 and p = 0.002, respectively), together with higher percentages of low mineralized cancellous (Cn.CaLow +35%, p < 0.001) and highly mineralized cortical bone areas (Ct.CaHigh +82%, p = 0.032). Ct.CaWidth and Ct.CaLow were positively correlated with mineralizing surface per bone surface (MS/BS; a primary histomorphometric determinant of bone formation) and with serum bone turnover markers (all p < 0.05). The correlations of the mineralization heterogeneity with histomorphometric and serum bone turnover indices suggest that an enhanced variation in bone turnover/formation contributes to the increased heterogeneity of mineralization. However, it remains unclear whether the latter is cause for, or the response to the increased bone fragility in these children with suspected IOP. © 2014 American Society for Bone and Mineral Research.     

Intravenous Treatment With Ibandronate Normalizes Bone Matrix Mineralization and Reduces Cortical Porosity After Two Years in Male Osteoporosis: A Paired Biopsy Study

The spectrum of therapeutic options and the amount of clinical trials for male osteoporosis (mOP) is lower than those for postmenopausal osteoporosis. Therefore, we examined the effects of 24 months of ibandronate (IBN) treatment (3 mg/3 mL intravenously every 3 months) on bone material quality in 19 subjects with mOP within an open‐label, single‐center, prospective phase III study (Eudract number 2006‐006692‐20). Patients (median age [25th, 75th percentiles] 53.0 [44.5; 57.0] years) were included if they had low bone mineral density (BMD) and/or at least one low trauma fracture and no secondary cause of osteoporosis. The primary endpoint was to evaluate IBN effects on cancellous (Cn.) and cortical (Ct.) bone mineralization density distribution (BMDD) based on quantitative backscattered electron imaging (qBEI) of paired transiliacal bone biopsies (baseline, 24 months). Secondary endpoints included changes in areal bone mineral density (BMD by dual‐energy X‐ray absorptiometry [DXA]) and serum markers of bone turnover including type I collagen peptides CrossLaps (CTX), procollagen type 1 amino‐terminal propeptide (P1NP), and osteocalcin (OC). At baseline, cancellous bone matrix mineralization from mOP was lower than published reference data (mean degree of mineralization Cn.CaMean ?1.8%, p < 0.01). IBN treatment increased calcium concentrations versus baseline (Cn.CaMean +2.4%, Ct.CaMean, +3.0% both p < 0.01), and reduced heterogeneity of mineralization (Cn.CaWidth ?14%, p = 0.044; Ct.CaWidth, ?16%, p = 0.001), leading to cancellous BMDD within normal range. IBN treatment was associated with a decrease in porosity of mineralized cortical tissue (?25%, p = 0.01); increases in BMD at the lumbar spine, the femoral neck, and the total hip (+3.3%, +1.9%, and +5.6%, respectively, p ≤ 0.01); and reductions in CTX (?37.5%), P1NP (?44.4%), and OC (?36.3%, all p < 0.01). Our BMDD findings are in line with the reduction of bone turnover markers and the increase in BMD by IBN in our patients and suggest that the latter mainly reflects the increase in matrix mineralization and the reduction of cortical porosity in this cohort with mOP. © 2014 American Society for Bone and Mineral Research.     

Bone material properties in premenopausal women with idiopathic osteoporosis

Idiopathic osteoporosis (IOP) in premenopausal women is characterized by fragility fractures at low or normal bone mineral density (BMD) in otherwise healthy women with normal gonadal function. Histomorphometric analysis of transiliac bone biopsy samples has revealed microarchitectural deterioration of cancellous bone and thinner cortices. To examine bone material quality, we measured the bone mineralization density distribution (BMDD) in biopsy samples by quantitative backscattered electron imaging (qBEI), and mineral/matrix ratio, mineral crystallinity/maturity, relative proteoglycan content, and collagen cross‐link ratio at actively bone forming trabecular surfaces by Raman microspectroscopy and Fourier transform infrared microspectroscopy (FTIRM) techniques. The study groups included: premenopausal women with idiopathic fractures (IOP, n = 45), or idiopathic low BMD (Z‐score ≤ ?2.0 at spine and/or hip) but no fractures (ILBMD, n = 19), and healthy controls (CONTROL, n = 38). BMDD of cancellous bone showed slightly lower mineral content in IOP (both the average degree of mineralization of cancellous bone [Cn.Ca_Mean] and mode calcium concentration [Cn.Ca_Peak] are 1.4% lower) and in ILBMD (both are 1.6% lower, p < 0.05) versus CONTROL, but no difference between IOP and ILBMD. Similar differences were found when affected groups were combined versus CONTROL. The differences remained significant after adjustment for cancellous mineralizing surface (MS/BS), suggesting that the reduced mineralization of bone matrix cannot be completely accounted for by differences in bone turnover. Raman microspectroscopy and FTIRM analysis at forming bone surfaces showed no differences between combined IOP/ILBMD groups versus CONTROL, with the exceptions of increased proteoglycan content per mineral content and increased collagen cross‐link ratio. When the two affected subgroups were considered individually, mineral/matrix ratio and collagen cross‐link ratio were higher in IOP than ILBMD. In conclusion, our findings suggest that bone material properties differ between premenopausal women with IOP/ILBMD and normal controls. In particular, the altered collagen properties at sites of active bone formation support the hypothesis that affected women have osteoblast dysfunction that may play a role in bone fragility. © 2012 American Society for Bone and Mineral Research.     

Histomorphometry and Bone Matrix Mineralization Before and After Bisphosphonate Treatment in Boys With Duchenne Muscular Dystrophy: A Paired Transiliac Biopsy Study

Duchenne muscular dystrophy (DMD) is a genetic disorder causing progressive muscle weakness. To prolong independent ambulation, DMD patients are treated with glucocorticoids, which, in turn, can increase bone fragility. In a cohort with vertebral fractures, intravenous bisphosphonate (iv BP) therapy stabilized vertebrae and reduced back pain. To characterize the effects of glucocorticoid therapy and bisphosphonate treatment on bone tissue and material properties, paired transiliac biopsy samples (before and after on average 2.4 years of iv BP) from 9 boys with DMD were studied for histomorphometry and bone mineralization density distribution (BMDD) and compared to reference values. Before iv BP, the boys had low cancellous bone volume (BV/TV) and cortical thickness (Ct.Wi) (both on average 56% of the healthy average, p < 0.001 versus reference), and mineralizing surface (MS/BS) in the lower normal range (on average 74% of the healthy average). The average degree of mineralization of cancellous (Cn.CaMean) and cortical compartments (Ct.CaMean) was 21.48 (20.70, 21.90) wt% and 20.42 (19.32, 21.64) wt%, respectively (median [25th, 75th percentiles]), which was not different from reference. After iv BP, BV/TV and Ct.Wi were, on average, unchanged. However, at the individual patient level, BV/TV Z‐scores increased in 2, remained unchanged in 4, and declined in 3 patients. Additionally, on average, MS/BS decreased (–85%, p < 0.001), Cn.CaMean (+2.7%) increased, whereas the heterogeneity of cancellous (Cn.CaWidth –19%) and cortical bone mineralization (Ct.CaWidth –8%, all p < 0.05) decreased versus baseline. The changes in bone mineralization are consistent with the antiresorptive action of iv BP. At the same time, our observations point to the need for novel therapies with less or absent bone turnover suppression, including the fact that bone turnover was low even before bisphosphonate therapy, that bone turnover declined further (as expected) with treatment, and that declines in trabecular bone volume were observed in some boys despite bisphosphonate therapy. © 2015 American Society for Bone and Mineral Research     

Subtle changes in bone mineralization density distribution in most severely affected patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is associated with low aBMD as measured by DXA and altered microstructure as assessed by bone histomorphometry and microcomputed tomography. Knowledge of bone matrix mineralization is lacking in COPD. Using quantitative backscatter electron imaging (qBEI), we assessed cancellous (Cn.) and cortical (Ct.) bone mineralization density distribution (BMDD) in 19 postmenopausal women (62.1 ± 7.3 years of age) with COPD. Eight had sustained fragility fractures, and 13 had received treatment with inhaled glucocorticoids. The BMDD outcomes from the patients were compared with healthy reference data and were correlated with previous clinical and histomorphometric findings.In general, the BMDD outcomes for the patients were not significantly different from the reference data. Neither the subgroups of with or without fragility fractures or of who did or did not receive inhaled glucocorticoid treatment, showed differences in BMDD. However, subgroup comparison according to severity revealed 10% decreased cancellous mineralization heterogeneity (Cn.CaWidth) for the most severely affected compared with less affected patients (p = 0.042) and compared with healthy premenopausal controls (p = 0.021). BMDD parameters were highly correlated with histomorphometric cancellous bone volume (BV/TV) and formation indices: mean degree of mineralization (Cn.CaMean) versus BV/TV (r = 0.58, p = 0.009), and Cn.CaMean and Ct.CaMean versus bone formation rate (BFR/BS) (r = -0.71, p < 0.001). In particular, those with lower BV/TV (< 50th percentile) had significantly lower Cn.CaMean (p = 0.037) and higher Cn.CaLow (p = 0.020) compared with those with higher (> 50th percentile) BV/TV.The normality in most of the BMDD parameters and bone formation rates as well as the significant correlations between them suggests unaffected mineralization processes in COPD. Our findings also indicate no significant negative effect of treatment with inhaled glucocorticoids on the bone mineralization pattern. However, the observed concomitant occurrence of relatively lower bone volumes with lower bone matrix mineralization will both contribute to the reduced aBMD in some patients with COPD.     

Abnormally High and Heterogeneous Bone Matrix Mineralization After Childhood Solid Organ Transplantation: A Complex Pathology of Low Bone Turnover and Local Defects in Mineralization

Chronic renal, liver, and heart failure in children associates with multiple skeletal complications. Increased fracture incidence often persists after transplantation and could be related to alterations in bone material properties. In the present cohort study we evaluated bone mineralization density distribution (BMDD) by quantitative backscattered electron imaging (qBEI) in 23 pediatric solid organ allograft recipients with suspected osteoporosis. We measured BMDD in the entire cross‐sectional area of transiliac bone biopsies obtained from kidney (n = 9), liver (n = 9), and heart (n = 5) transplant recipients (aged 7.6 to 19.7 years; 6.0 ± 5.6 years posttransplantation, patients with a history of clinical fractures: n = 14). The BMDD findings were compared with age‐appropriate references and with a previously presented cohort of children with chronic kidney disease on dialysis (CKD5D, n = 18). Furthermore, we related the BMDD parameters with patients’ clinical and bone histomorphometric outcomes. Compared to healthy children, qBEI results for cancellous and cortical bone in transplant recipients revealed an increase in the most frequently occurring calcium concentration (+2.9%, p = 0.001; +3.5%, p = 0.014), in the portion of fully mineralized bone (fivefold; 10‐fold, both p < 0.0001) and in heterogeneity of mineralization (+26,5% and +27.8%, both p < 0.0001), respectively. Moreover, the BMDD parameters were nonsignificantly distinct from CKD5D cohort except that the heterogeneity in mineralization was higher posttransplantation. There was a strong inverse correlation between the average calcium content of the bone matrix and patients’ biochemical ALP levels, histomorphometric indices of bone formation and resorption. The abnormally high bone matrix mineralization in transplant recipients, consistent with serum and histomorphometric outcomes, suggests a history of low bone turnover with accumulation of fully mineralized bone packets. Additionally, the increased heterogeneity of mineralization suggests local alterations in mineralization kinetics, which may be linked to dysfunctional osteocytes that were recently shown to accumulate within the bone matrix during organ failure and concomitant glucocorticoid and immunosuppressive medication. © 2017 American Society for Bone and Mineral Research.     

Evidence of Reduced Bone Turnover and Disturbed Mineralization Process in a Boy with Stickler Syndrome

We describe a tall-statured 14-year-old boy who illustrated the full phenotypic and radiographic features of Stickler syndrome type I. A bone biopsy showed evidence of reduced bone mass and bone turnover, such as reduced BV/TV (–43%), TbTh (–29%), and OS/BS (–48%), Ob.S/BS (–27%), and Oc/BS (–47%) compared to “age-matched” controls. Moreover, there was evidence that the mineralization process was severely disturbed. Quantitative backscattered electron imaging revealed that the bone mineralization density distribution (BMDD) of cancellous (Cn) as well as cortical (Ct) bone was shifted toward lower mineralization compared to a young control reference cohort. BMDD parameters of mean degree of mineralization, Cn Ca (–9.8%) and Ct Ca (–18.0%), were dramatically decreased. To the best of our knowledge this is the first clinical report describing bone biopsy findings in a boy with Stickler syndrome. Such a severe undermineralization of bone matrix might essentially contribute to the compromised mechanical competence of the skeleton found in this patient.     

Bone matrix mineralization is preserved during early perimenopausal stage in healthy women: a paired biopsy study

Summary

Bone matrix mineralization based on quantitative backscatter electron imaging remained unchanged during the first year of menopause in paired transiliac biopsy samples from healthy women. This suggests that the reported early perimenopausal reductions in bone mineral density are caused by factors other than decreases in the degree of mineralization.

Introduction

It is unknown whether perimenopausal loss of bone mass is associated with a drop in bone matrix mineralization.

Methods

For this purpose, we measured the bone mineralization density distribution (BMDD) by quantitative backscatter electron imaging (qBEI) in n?=?17 paired transiliac bone biopsy samples at premenopausal baseline and 12 months after last menses (obtained at average ages of 49?±?2 and 55?±?2 years, respectively) in healthy women. For interpretation of BMDD outcomes, previously measured bone mineral density (BMD) and biochemical and histomorphometric markers of bone turnover were revisited for the present biopsy cohort.

Results

Menopause significantly decreased BMD at the lumbar spine (?4.5 %) and femoral neck (?3.8 %), increased the fasting urinary hydroxyproline/creatinine ratio (+60 %, all p?<?0.01) and histomorphometric bone formation rate (+25 %, p?<?0.05), but affected neither cancellous nor cortical BMDD variables (paired comparison p?>?0.05). Mean calcium concentrations of cancellous (Cn.CaMean) and cortical bone (Ct.CaMean) were within normal range (p?>?0.05 compared to established reference data). Ct.CaMean was significantly correlated with Cn.CaMean before (R?=?0.81, p?<?0.001) and after menopause (R?=?0.80, p?<?0.001) and to cortical porosity of mineralized tissue (Ct.Po.) after menopause (R?=??0.57, p?=?0.02).

Conclusions

Surprisingly, the BMDD was found not affected by the changes in bone turnover rates in this cohort. This suggests that the substantial increase in bone formation rates took place shortly before the second biopsy, and the bone mineralization changes lag behind. We conclude that during the first year after the last menses, the degree of bone matrix mineralization is preserved and does not contribute to the observed reductions in BMD.

     

PTH(1–84) administration reverses abnormal bone‐remodeling dynamics and structure in hypoparathyroidism

Hypoparathyroidism is associated with abnormal structural and dynamic skeletal properties. We hypothesized that parathyroid hormone(1–84) [PTH(1–84)] treatment would restore skeletal properties toward normal in hypoparathyroidism. Sixty‐four subjects with hypoparathyroidism were treated with PTH(1–84) for 2 years. All subjects underwent histomorphometric assessment with percutaneous iliac crest bone biopsies. Biopsies were performed at baseline and at 1 or 2 years. Another group of subjects had a single biopsy at 3 months, having received tetracycline before beginning PTH(1–84) and prior to the biopsy (quadruple‐label protocol). Measurement of biochemical bone turnover markers was performed. Structural changes after PTH(1–84) included reduced trabecular width (144 ± 34 µm to 128 ± 34 µm, p = 0.03) and increases in trabecular number (1.74 ± 0.34/mm to 2.07 ± 0.50/mm, p = 0.02) at 2 years. Cortical porosity increased at 2 years (7.4% ± 3.2% to 9.2% ± 2.4%, p = 0.03). Histomorphometrically measured dynamic parameters, including mineralizing surface, increased significantly at 3 months, peaking at 1 year (0.7% ± 0.6% to 7.1% ± 6.0%, p = 0.001) and persisting at 2 years. Biochemical measurements of bone turnover increased significantly, peaking at 5 to 9 months of therapy and persisting for 24 months. It is concluded that PTH(1–84) treatment of hypoparathyroidism is associated with increases in histomorphometric and biochemical indices of skeletal dynamics. Structural changes are consistent with an increased remodeling rate in both trabecular and cortical compartments with tunneling resorption in the former. These changes suggest that PTH(1–84) improves abnormal skeletal properties in hypoparathyroidism and restores bone metabolism toward normal euparathyroid levels. © 2011 American Society for Bone and Mineral Research     

Daily parathyroid hormone 1-34 replacement therapy for hypoparathyroidism induces marked changes in bone turnover and structure

Parathyroid hormone (PTH) has variable actions on bone. Chronically increased PTH is catabolic and leads to osteoporosis; yet intermittent administration is anabolic and increases bone mass. PTH deficiency is associated with decreased bone remodeling and increased bone mass. However, the effects of PTH replacement therapy on bone in hypoparathyroidism are not well known. We discontinued calcitriol therapy and treated 5 hypoparathyroid subjects (2 adults and 3 adolescents) with synthetic human PTH 1‐34 (hPTH 1‐34), injected two to three times daily for 18 months, with doses individualized to maintain serum calcium at 1.9 to 2.25 mmol/L. Biochemical markers and bone mineral density (BMD) were assessed every 6 months; iliac‐crest biopsies were performed before and after 1 year of treatment. hPTH 1‐34 therapy significantly increased bone markers to supranormal levels. Histomorphometry revealed that treatment dramatically increased cancellous bone volume and trabecular number and decreased trabecular separation. Changes in trabecular width were variable, suggesting that the increase in trabecular number was due to the observed intratrabecular tunneling. Cortical width remained unchanged; however, hPTH 1‐34 treatment increased cortical porosity. Cancellous bone remodeling was also stimulated, inducing significant changes in osteoid, mineralizing surface, and bone formation rate. Similar changes were seen in endocortical and intracortical remodeling. BMD Z‐scores were unchanged at the spine and femoral neck. Total hip Z‐scores increased; however, total body BMD Z‐scores decreased during the first 6 months of treatment and then stabilized, remaining significantly decreased compared to baseline. Radial Z‐scores also decreased with treatment; this was most pronounced in the growing adolescent. Daily hPTH 1‐34 therapy for hypoparathyroidism stimulated bone turnover, increased bone volume, and altered bone structure in the iliac crest. These findings suggest that treatment with hPTH 1‐34 in hypoparathyroid adults and adolescents has varying effects in the different skeletal compartments, leading to an increase in trabecular bone and an apparent trabecularization of cortical bone. Published 2012 American Society for Bone and Mineral Research. This article is a US Government work and, as such, is in the public domain in the United States of America.     

Hypermineralization and High Osteocyte Lacunar Density in Osteogenesis Imperfecta Type V Bone Indicate Exuberant Primary Bone Formation

In contrast to “classical” forms of osteogenesis imperfecta (OI) types I to IV, caused by a mutation in COL1A1/A2, OI type V is due to a gain‐of‐function mutation in the IFITM5 gene, encoding the interferon‐induced transmembrane protein 5, or bone‐restricted interferon‐inducible transmembrane (IFITM)‐like protein (BRIL). Its phenotype distinctly differs from OI types I to IV by absence of blue sclerae and dentinogenesis imperfecta, by the occurrence of ossification disorders such as hyperplastic callus and forearm interosseous membrane ossification. Little is known about the impact of the mutation on bone tissue/material level in untreated and bisphosphonate‐treated patients. Therefore, investigations of transiliac bone biopsy samples from a cohort of OI type V children (n = 15, 8.7 ± 4 years old) untreated at baseline and a subset (n = 8) after pamidronate treatment (2.6 years in average) were performed. Quantitative backscattered electron imaging (qBEI) was used to determine bone mineralization density distribution (BMDD) as well as osteocyte lacunar density. The BMDD of type V OI bone was distinctly shifted toward a higher degree of mineralization. The most frequently occurring calcium concentration (CaPeak) in cortical (Ct) and cancellous (Cn) bone was markedly increased (+11.5%, +10.4%, respectively, p < 0.0001) compared to healthy reference values. Treatment with pamidronate resulted in only a slight enhancement of mineralization. The osteocyte lacunar density derived from sectioned bone area was elevated in OI type V Ct and Cn bone (+171%, p < 0.0001; +183.3%, p < 0.01; respectively) versus controls. The high osteocyte density was associated with an overall immature primary bone structure (“mesh‐like”) as visualized by polarized light microscopy. In summary, the bone material from OI type V patients is hypermineralized, similar to other forms of OI. The elevated osteocyte lacunar density in connection with lack of regular bone lamellation points to an exuberant primary bone formation and an alteration of the bone remodeling process in OI type V. © 2017 American Society for Bone and Mineral Research.     

Effects of Parathyroid Hormone Administration on Bone Strength in Hypoparathyroidism

The microstructural skeletal phenotype of hypoparathyroidism (HypoPT), a disorder of inadequate parathyroid hormone secretion, is altered trabecular microarchitecture with increased trabecular bone volume and thickness. Using 2‐D histomorphometric analysis, we previously found that 2 years of PTH(1‐84) in HypoPT is associated with reduced trabecular thickness (Tb.Th) and an increase in trabecular number (Tb.N). We have now utilized direct 3‐D microstructural analysis to determine the extent to which these changes may be related to bone strength. Iliac crest bone biopsies from HypoPT subjects (n = 58) were analyzed by microcomputed tomography (μCT) and by microfinite element (μFE) analysis. Biopsies were performed at baseline and at 1 or 2 years of recombinant human PTH(1‐84) [rhPTH(1‐84)]. In a subset of subjects (n = 13) at 3 months, we demonstrated a reduction in trabecular separation (Tb.Sp, 0.64 ± 0.1 to 0.56 ± 0.1 mm; p = 0.005) and in the variance of trabecular separation (Tb.SD, 0.19 ± 0.1 to 0.17 ± 0.1 mm; p = 0.01), along with an increase in bone volume/total volume (BV/TV, 26.76 ± 10.1 to 32.83 ± 13.5%; p = 0.02), bone surface/total volume (BS/TV, 3.85 ± 0.7 to 4.49 ± 1.0 mm²/mm³; p = 0.005), Tb.N (1.84 ± 0.5 versus 2.36 ± 1.3 mm^?1; p = 0.02) and Young's modulus (649.38 ± 460.7 to 1044.81 ± 1090.5 N/mm²; p = 0.049). After 1 year of rhPTH(1‐84), Force increased (144.08 ± 102.4 to 241.13 ± 189.1 N; p = 0.04) and Young's modulus tended to increase (662.15 ± 478.2 to 1050.80 ± 824.1 N/m²; p = 0.06). The 1‐year change in cancellous mineralizing surface (MS/BS) predicted 1‐year changes in μCT variables. The biopsies obtained after 2 years of rhPTH(1‐84) showed no change from baseline. These data suggest that administration of rhPTH(1‐84) in HypoPT is associated with transient changes in key parameters associated with bone strength. The results indicate that rhPTH(1‐84) improves skeletal quality in HypoPT early in treatment. © 2016 American Society for Bone and Mineral Research.     

Effects of cerivastatin and parathyroid hormone on the lumbar vertebra of aging male Sprague-Dawley rats

Both men and women lose bone at a late age (aging bone loss). The aim of this study was to determine whether cerivastatin and parathyroid hormone (PTH) can prevent aging bone loss in men. Bone loss in aged male Sprague-Dawley (SD) rats was used as a model for age-related bone loss in men. Nine-month-old male SD rats were divided into six groups: (1) baseline controls (killed at the beginning of the study); (2) age-matched controls; (3) parathyroid hormone (PTH; 80 microg/kg body weight per day for 5 days/week) treated; (4) low-dose cerivastatin (0.2 mg/kg body weight per day) treated; and (5) medium-dose cerivastatin (0.4 mg/kg body weight per day) treated; and (6) high-dose cerivastatin (0.8 mg/kg body weight per day) treated. Groups 2-6 were treated for 23 weeks between the ages of 9 and 15 months and killed at the end of 23 weeks. The fourth lumbar vertebra was analyzed using peripheral quantitative computed tomography (pQCT). It is shown that age-matched controls had decreased cancellous bone mineral content (Cn. BMC) by 19% (p < 0.05) and cancellous bone mineral density Cn. BMD) by 22% (p < 0.01) when compared with baseline controls. All three doses of cerivastatin resulted in lower Cn. BMC and Cn. BMD when compared with age-matched controls, but this decrease was not statistically significant. In the PTH-treated group, Cn. BMC increased by 5% (p < 0.0001) and Cn. BMD increased by 37% (p < 0.0001) when compared with age-matched controls. In age-matched controls, cortical bone mineral content (Ct. BMC) and cortical bone mineral density (Ct. BMD) decreased slightly, but not significantly, when compared with baseline controls. Ct. BMD did not change significantly at any of the three doses in the cerivastatin-treated groups. In the PTH-treated group, Ct. BMC increased by 23% (p < 0.0001) when compared with age-matched controls. We confirmed that male SD rats lose bone with aging in the lumbar vertebra, and it is concluded that cerivastatin, at all doses administered, did not prevent this age-related bone loss. In contrast, PTH prevented age-related bone loss in the vertebra of male SD rats.     

Mineralization density distribution of postmenopausal osteoporotic bone is restored to normal after long‐term alendronate treatment: qBEI and sSAXS data from the fracture intervention trial long‐term extension (FLEX)

Long‐term treatment studies showed that the therapeutic effects of alendronate (ALN) were sustained over a 10‐year treatment period. However, data on the effects on intrinsic bone material properties by long‐term reduction of bone turnover are still sparse. We analyzed transiliacal bone biopsies of a subgroup of 30 Fracture Intervention Trial Long‐Term Extension (FLEX) participants (n = 6 were treated for 10 years with ALN at dose of 10 mg/day, n = 10 were treated for 10 years with ALN at dose of 5 mg/day, and n = 14 were treated for 5 years with ALN plus a further 5 years with placebo) by quantitative backscattered electron imaging (qBEI) and scanning small‐angle X‐ray scattering (sSAXS) to determine the bone mineralization density distribution (BMDD) and the mineral particle thickness parameter T. BMDD data from these FLEX participants were compared with those from a previously published healthy population (n = 52). Compared with 5 years of ALN plus 5 years of placebo 10 years of ALN treatment (independent of the dose given) did not produce any difference in any of the BMDD parameters: The weighted mean (Ca_mean), the typical calcium concentration (Ca_peak), the heterogeneity of mineralization (Ca_width), the percentage of low‐mineralized bone areas (Ca_low), and the portion of highly mineralized areas (Ca_high) were not different for the patients who continued ALN from those who stopped ALN after 5 years. Moreover, no significant differences for any of the BMDD parameters between the FLEX participants and the healthy population could be observed. In none of the investigated cases were abnormally high mineralization or changes in mineral particle thickness observed (Ca_high and T were both in the normal range). The findings of this study support the recommendation that antiresorptive treatment with ALN should be maintained for 5 years. Even with longer treatment durations of up to 10 years, though, no negative effects on bone matrix mineralization were observed. Copyright © 2010 American Society for Bone and Mineral Research     

The effect of adding PTH(1–84) to conventional treatment of hypoparathyroidism: A randomized,placebo‐controlled study

In hypoparathyroidism, plasma parathyroid hormone (PTH) levels are inadequate to maintain plasma calcium concentration within the reference range. On conventional treatment with calcium supplements and active vitamin D analogues, bone turnover is abnormally low, and BMD is markedly increased. We aimed to study the effects of PTH‐replacement therapy (PTH‐RT) on calcium‐phosphate homeostasis and BMD. In a double‐blind design, we randomized 62 patients with hypoparathyroidism to daily treatment with PTH(1–84) 100 µg or similar placebo for 24 weeks as add‐on therapy to conventional treatment. Compared with placebo, patients on PTH(1–84) reduced their daily dose of calcium and active vitamin D significantly by 75% and 73%, respectively, without developing hypocalcemia. However, hypercalcemia occurred frequently during the downtitration of calcium and active vitamin D. Plasma phosphate and renal calcium and phosphate excretion did not change. Compared with placebo, PTH(1–84) treatment significantly increased plasma levels of bone‐specific alkaline phosphatase (+226% ± 36%), osteocalcin (+807% ± 186%), N‐terminal propeptide of procollagen 1 (P1NP; +1315% ± 330%), cross‐linked C‐telopeptide of type 1 collagen (CTX; +1209% ± 459%), and urinary cross‐linked N‐telopeptide of type 1 collagen (NTX; (+830% ± 165%), whereas BMD decreased at the hip (?1.59% ± 0.57%), lumbar spine (?1.76% ± 1.03%), and whole body (?1.26% ± 0.49%) but not at the forearm. In conclusion, the need for calcium and active vitamin D is reduced significantly during PTH‐RT, whereas plasma calcium and phosphate levels are maintained within the physiologic range. In contrast to the effect of PTH(1–84) treatment in patients with osteoporosis, PTH‐RT in hypoparathyroidism causes a decrease in BMD. This is most likely due to the marked increased bone turnover. Accordingly, PTH‐RT counteracts the state of overmineralized bone and, during long‐term treatment, may cause a more physiologic bone metabolism. © 2011 American Society for Bone and Mineral Research     

Changes in Skeletal Microstructure Through Four Continuous Years of rhPTH(1–84) Therapy in Hypoparathyroidism

Bone remodeling is reduced in hypoparathyroidism, resulting in increased areal bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) and abnormal skeletal indices by transiliac bone biopsy. We have now studied skeletal microstructure by high-resolution peripheral quantitative computed tomography (HR-pQCT) through 4 years of treatment with recombinant human PTH(1–84) (rhPTH[1–84]) in 33 patients with hypoparathyroidism (19 with postsurgical disease, 14 idiopathic). We calculated Z-scores for our cohort compared with previously published normative values. We report results at baseline and 1, 2, and 4 years of continuous therapy with rhPTH(1–84). The majority of patients (62%) took rhPTH(1–84) 100 μg every other day for the majority of the 4 years. At 48 months, areal bone density increased at the lumbar spine (+4.9% ± 0.9%) and femoral neck (+2.4% ± 0.9%), with declines at the total hip (−2.3% ± 0.8%) and ultradistal radius (−2.1% ± 0.7%) (p < .05 for all). By HR-pQCT, at the radius site, very similar to the ultradistal DXA site, total volumetric BMD declined from baseline but remained above normative values at 48 months (Z-score + 0.56). Cortical volumetric BMD was lower than normative controls at baseline at the radius and tibia (Z-scores −1.28 and − 1.69, respectively) and further declined at 48 months (−2.13 and − 2.56, respectively). Cortical porosity was higher than normative controls at baseline at the tibia (Z-score + 0.72) and increased through 48 months of therapy at both sites (Z-scores +1.80 and + 1.40, respectively). Failure load declined from baseline at both the radius and tibia, although remained higher than normative controls at 48 months (Z-scores +1.71 and + 1.17, respectively). This is the first report of noninvasive high-resolution imaging in a cohort of hypoparathyroid patients treated with any PTH therapy for this length of time. The results give insights into the effects of long-term rhPTH(1–84) in hypoparathyroidism. © 2020 American Society for Bone and Mineral Research.     

Bone Matrix Quality After Sclerostin Antibody Treatment

Sclerostin antibody (Scl‐Ab) is a novel bone‐forming agent that is currently undergoing preclinical and clinical testing. Scl‐Ab treatment is known to dramatically increase bone mass, but little is known about the quality of the bone formed during treatment. In the current study, global mineralization of bone matrix in rats and nonhuman primates treated with vehicle or Scl‐Ab was assayed by backscattered scanning electron microscopy (bSEM) to quantify the bone mineral density distribution (BMDD). Additionally, fluorochrome labeling allowed tissue age–specific measurements to be made in the primate model with Fourier‐transform infrared microspectroscopy to determine the kinetics of mineralization, carbonate substitution, crystallinity, and collagen cross‐linking. Despite up to 54% increases in the bone volume after Scl‐Ab treatment, the mean global mineralization of trabecular and cortical bone was unaffected in both animal models investigated. However, there were two subtle changes in the BMDD after Scl‐Ab treatment in the primate trabecular bone, including an increase in the number of pixels with a low mineralization value (Z₅) and a decrease in the standard deviation of the distribution. Tissue age–specific measurements in the primate model showed that Scl‐Ab treatment did not affect the mineral‐to‐matrix ratio, crystallinity, or collagen cross‐linking in the endocortical, intracortical, or trabecular compartments. Scl‐Ab treatment was associated with a nonsignificant trend toward accelerated mineralization intracortically and a nearly 10% increase in carbonate substitution for tissue older than 2 weeks in the trabecular compartment (p < 0.001). These findings suggest that Scl‐Ab treatment does not negatively impact bone matrix quality. © 2014 American Society for Bone and Mineral Research.     

Longitudinal HR‐pQCT and Image Registration Detects Endocortical Bone Loss in Kidney Transplantation Patients

Patients with chronic kidney disease (CKD) who undergo kidney transplantation experience bone loss and increased risk of fracture. However, the mechanisms of this bone loss are unclear. Our objective was to use image registration to define the cortex to assess changes in cortical porosity (Ct.Po) in patients undergoing first‐time kidney transplantation. We obtained serial measurements of parathyroid hormone (PTH) and bone turnover markers and used high‐resolution peripheral quantitative computed tomography (HR‐pQCT) to scan the distal radius and tibia in 31 patients (21 men, 10 women; aged 51.9 ± 13.4 years) at transplant and after 1 year. Baseline and 1‐year images were aligned using a fully automated, intensity‐based image registration framework. We compared three methods to define the cortical region of interest (ROI) and quantify the changes: 1) cortical bone was independently defined in baseline and follow‐up scans; 2) cortical bone was defined as the common cortical ROI; and 3) the cortical ROI at baseline was carried forward to 1‐year follow‐up (baseline‐indexed). By the independently defined ROI, Ct.Po increased 11.7% at the radius and 9.1% at the tibia, whereas by the common ROI, Ct.Po increased 14.6% at the radius and 9.1% at the tibia. By the baseline‐indexed ROI, which provides insight into changes at the endocortical region, Ct.Po increased 63.4% at the radius and 17.6% at the tibia. We found significant relationships between changes in Ct.Po and bone formation and resorption markers at the radius. The strongest associations were found between markers and Ct.Po using the baseline‐index method. We conclude that Ct.Po increases throughout the cortex after kidney transplant, and this increase is particularly marked at the endocortical surface. These methods may prove useful for all HR‐pQCT longitudinal studies, particularly when changes are expected at the endocortical region. © 2014 American Society for Bone and Mineral Research.