Osteoid Perimeter Research Articles

Relationship between biochemical parameters of mineral bone disease and static bone histomorphometry in chronic kidney disease patients on hemodialysis: An Indian cross-section study

AimWe estimated the relationship between routine biochemical laboratory parameters with static bone histomorphometric parameters and their high and low bone turnover capacity predictability in hemodialysis patients. MethodIt was a single-center cross-sectional study, included 28 hemodialysis patients. The routine biochemical parameters measured including calcium, phosphorous, alkaline phosphatase, intact PTH, and 25-hydroxycholecalciferol. The histomorphometric parameters assessed were osteoblasts perimeter, osteoclast perimeter, eroded perimeter, osteoid perimeter, bone fibrosis and bone volume. ResultTotal 28 hemodialysis patients underwent bone biopsy. Seventy percent were male, with a mean age was 33.07±10.42 yrs; serum alkaline phosphatase was 219.10±311.3IU/ml; vitamin D was 18.18±9.56ng/ml, and intact PTH was 650.7±466.0pg/ml. Intact PTH had a significant positive association with osteoblast, osteoclast, eroded surface, and osteoid perimeter. Serum alkaline phosphatase had a significant relationship with bone fibrosis (r=0.525, p-value=0.004). Intact PTH was significantly higher in females than males (1078.75±533.04 vs. 479.6±309.83; p-value=0.004). The osteoid surface was significantly high in females compared to males (p=0.038). Age had a significant impact on osteoblast and eroded surface (p=0.008 and p=0.031, respectively). Intact PTH is a reliable biomarkers for bone turnover compare to ALP (p<0.001 and p=0.554, respectively). ConclusionIntact PTH strongly associated with bone formation, bone resorption parameters. Gender and age had significant impact on static histomorphometric parameters in our study.

Relationship between biochemical parameters of mineral bone disease and static bone histomorphometry in chronic kidney disease patients on hemodialysis: An Indian cross-section study

AimWe estimated the relationship between routine biochemical laboratory parameters with static bone histomorphometric parameters and their high and low bone turnover capacity predictability in hemodialysis patients. MethodIt was a single-center cross-sectional study, included 28 hemodialysis patients. The routine biochemical parameters measured including calcium, phosphorous, alkaline phosphatase, intact PTH, and 25-hydroxycholecalciferol. The histomorphometric parameters assessed were osteoblasts perimeter, osteoclast perimeter, eroded perimeter, osteoid perimeter, bone fibrosis and bone volume. ResultTotal 28 hemodialysis patients underwent bone biopsy. Seventy percent were male, with a mean age was 33.07±10.42 yrs; serum alkaline phosphatase was 219.10±311.3IU/ml; vitamin D was 18.18±9.56ng/ml, and intact PTH was 650.7±466.0pg/ml. Intact PTH had a significant positive association with osteoblast, osteoclast, eroded surface, and osteoid perimeter. Serum alkaline phosphatase had a significant relationship with bone fibrosis (r=0.525, p-value=0.004). Intact PTH was significantly higher in females than males (1078.75±533.04 vs. 479.6±309.83; p-value=0.004). The osteoid surface was significantly high in females compared to males (p=0.038). Age had a significant impact on osteoblast and eroded surface (p=0.008 and p=0.031, respectively). Intact PTH is a reliable biomarkers for bone turnover compare to ALP (p<0.001 and p=0.554, respectively). ConclusionIntact PTH strongly associated with bone formation, bone resorption parameters. Gender and age had significant impact on static histomorphometric parameters in our study.

Novel non-resorbable polymeric-nanostructured scaffolds for guided bone regeneration.

The aim of this study was to evaluate the bone-regeneration efficiency of novel polymeric nanostructured membranes and the effect of zinc, calcium, titanium, and bone morpho-protein loading on membranes, through an in vivo rabbit model. Nanostructured membranes of methylmethacrylate were loaded with zinc, calcium, TiO2 nanoparticles, and bone-morphogenetic protein (BMP). These membranes covered the bone defects prepared on the skulls of six rabbits. Animals were sacrificed 6weeks after surgery. Micro computed tomography was used to evaluate bone architecture through BoneJ pluging and ImageJ script. Three histological processing of samples, including von Kossa silver nitrate, toluidine blue, and fluorescence by the deposition of calcein were utilized. Zn-membranes (Zn-Ms) promoted the highest amount of new bone and higher bone perimeter than both unloaded and Ti-membranes (Ti-Ms). Ca-membranes (Ca-Ms) attained higher osteoid perimeter and bone perimeter than Zn-Ms. The skeleton analysis showed that Zn-Ms produced more branches and junctions at the trabecular bone than BMP-loaded membranes (BMP-Ms). Samples treated with Ti-Ms showed less bone formation and bony bridging processes. Both Zn-Ms and Ca-Ms achieved higher number of osteoblasts than the control group. BMP-Ms and Ca-Ms originated higher number of blood vessels than Ti-Ms and control group. Zn incorporation in novel nanostructured membranes provided the highest regenerative efficiency for bone healing at the rabbit calvarial defects. Zn-Ms promoted osteogenesis and enhanced biological activity, as mineralized and osteoid new bone with multiple interconnected ossified trabeculae appeared in close contact with the membrane.

Can Intestinal Phosphate Binding or Inhibition of Hydroxyapatite Growth in the Vascular Wall Halt the Progression of Established Aortic Calcification in Chronic Kidney Disease?

Vascular calcification significantly contributes to mortality in chronic kidney disease (CKD) patients. Sevelamer and pyrophosphate (PPi) have proven to be effective in preventing vascular calcification, the former by controlling intestinal phosphate absorption, the latter by directly interfering with the hydroxyapatite crystal formation. Since most patients present with established vascular calcification, it is important to evaluate whether these compounds may also halt or reverse the progression of preexisting vascular calcification. CKD and vascular calcification were induced in male Wistar rats by a 0.75% adenine low protein diet for 4weeks. Treatment with PPi (30 or 120µmol/kg/day), sevelamer carbonate (1500mg/kg/day) or vehicle was started at the time point at which vascular calcification was present and continued for 3weeks. Hyperphosphatemia and vascular calcification developed prior to treatment. A significant progression of aortic calcification in vehicle-treated rats with CKD was observed over the final 3-week period. Sevelamer treatment significantly reduced further progression of aortic calcification as compared to the vehicle control. No such an effect was seen for either PPi dose. Sevelamer but not PPi treatment resulted in an increase in both osteoblast and osteoid perimeter. Our study shows that sevelamer was able to reduce the progression of moderate to severe preexisting aortic calcification in a CKD rat model. Higher doses of PPi may be required to induce a similar reduction of severe established arterial calcification in this CKD model.

Thoroughbred horses in race training have lower levels of subchondral bone remodelling in highly loaded regions of the distal metacarpus compared to horses resting from training

Bone is repaired by remodelling, a process influenced by its loading environment. The aim of this study was to investigate the effect of a change in loading environment on bone remodelling by quantifying bone resorption and formation activity in the metacarpal subchondral bone in Thoroughbred racehorses. Sections of the palmar metacarpal condyles of horses in race training (n = 24) or resting from training (n = 24) were examined with light microscopy and back scattered scanning electron microscopy (BSEM). Bone area fraction, osteoid perimeter and eroded bone surface were measured within two regions of interest: (1) the lateral parasagittal groove (PS); (2) the lateral condylar subchondral bone (LC). BSEM variables were analysed for the effect of group, region and interaction with time since change in work status. The means ± SE are reported.For both regions of interest in the training compared to the resting group, eroded bone surface was lower (PS: 0.39 ± 0.06 vs. 0.65 ± 0.07 per mm, P = 0.010; LC: 0.24 ± 0.04 vs. 0.85 ± 0.10 per mm, P < 0.001) and in the parasagittal groove osteoid perimeter was higher (0.23 ± 0.04% vs. 0.12 ± 0.02%). Lower porosity was observed in the subchondral bone, reflected by a higher bone area fraction in the LC of the training group (90.8 ± 0.6%) compared to the resting group (85.3 ± 1.4%, P = 0.0010).Race training was associated with less bone resorption and more bone formation in the subchondral bone of highly loaded areas of the distal metacarpus limiting the replacement of fatigued bone. Periods of reduced intensity loading are important for facilitating subchondral bone repair in Thoroughbred racehorses.

Preservation of bone mass and biomechanical properties during winter sleep—the raccoon dog (Nyctereutes procyonoides) as a novel model species

It has been established that almost 40% of postmenopausal women in the United States have osteopenia and models to study its prevention are thus urgently needed. Bears (Ursus spp.) displaying winter sleep were previously introduced as promising models to study the treatment of disuse-induced bone loss. The present study examined the potential of another analogous model species, the raccoon dog (Nyctereutes procyonoides), in bone research. Similar to bears, raccoon dogs display prolonged passivity and catabolism in winter, but they are of a moderate body mass, easy to handle and reared on farms. Wild specimens (n=51) were hunted in winter 2007–2008. The bone mineral density of femoral diaphysis and neck was examined with peripheral quantitative computed tomography, after which their mechanical properties were tested with the three-point bending and femoral neck loading tests. A subsample of the specimens was analyzed histologically. While the body mass of the raccoon dogs decreased from 7.0±0.3 to 4.5±0.2kg (−36%) during winter, the bone mass and biomechanical properties remained unchanged despite of heavy wintertime catabolism similar to bears. Thus, the cortical mineral density remained at approximately 1400mg/cm3, the trabecular mineral density at 450mg/cm3 and the maximum load of the femoral neck at 700N. However, in histological samples, the proportion of osteoid perimeter vs. mineralized bone perimeter decreased during wintering. A possible mechanism of bone mass preservation is the endocrine status of overwintering raccoon dogs, which could participate in preventing bone loss.

Bone Remodeling Rate and Remodeling Balance Are Not Co-Regulated in Adulthood: Implications for the Use of Activation Frequency as an Index of Remodeling Rate

Use of activation frequency as a measure of remodeling rate assumes co-regulation of remodeling rate and remodeling balance. In iliac crest biopsy specimens from 57 healthy subjects 19-80 yr of age, no correlations were shown between these variables, an observation that challenges the use of activation frequency as an estimate of remodeling rate. The histomorphometric derivation of activation frequency assumes that the remodeling rate is dependent on the duration of the remodeling cycle and the amount of bone formed in individual remodeling units. This implies that remodeling balance and remodeling rate are co-regulated. We tested this assumption in normal human adult cancellous bone. Relationships between indices of bone formation at the basic multicellular unit (BMU) level (wall width and mineral apposition rate) and indices of remodeling rate (mineralizing perimeter and osteoid perimeter) were examined in iliac crest biopsies obtained from 57 healthy adults (24 men) 19-80 yr of age. Univariate analysis revealed a negative correlation between wall width and osteoid perimeter (r = -0.38; p = 0.0004), but there was no correlation between wall width and mineralizing perimeter or between mineral apposition rate and either mineralizing or osteoid perimeter. After adjustment for age and sex, the association between wall width and osteoid perimeter was no longer observed. Both wall width and mineral apposition rate correlated negatively with age (r = -0.75, p < 0.0001 and r = -0.27, p = 0.05, respectively). Our results indicate that remodeling balance and remodeling rate are not co-regulated in adult human bone. Activation frequency, as currently derived from histomorphometric variables, may therefore be unreliable as an indicator of remodeling rate.

Variant of Adynamic Bone Disease in Hemodialysis Patients: Fact or Fiction?

Adynamic bone disease is a type of renal osteodystrophy characterized by low bone turnover and paucity of bone cells. It was proposed that a new type of this disease featuring high osteoclastic resorption without parathyroid hormone stimulus and designated adynamic bone disease variant occurs in hemodialysis patients. The present study is designed to evaluate the frequency and characteristics of both diseases in a large series of bone biopsy specimens. We reviewed 1,160 bone biopsy specimens from hemodialysis patients. Specimens in which adynamic bone disease was diagnosed were selected and categorized as classic or variant based on osteoclastic surface. In 218 bone biopsy specimens (18.8%), adynamic bone disease was identified, whereas the variant form was identified in 35 specimens (38.8%). Biopsy specimens categorized as the variant form were from patients who were younger and had greater phosphorus and parathyroid hormone levels. Histologically, the variant form presented greater osteoid volume, fibrosis volume, osteoid surface, osteoblast surface, and eroded surface. Similarly, values for all dynamic parameters were greater in the variant group. Osteoclastic surface correlated with phosphorus level, parathyroid hormone level, and osteoblast surface. Age and osteoblast surface were identified as independent determinants of the variant form. Adynamic bone disease variant seems to occur in younger hemodialysis patients with greater levels of parathyroid hormone, which acts on cell-covered bone surfaces. It probably is a transitional phase from low- to high-turnover status, rather than a true entity within the spectrum of renal osteodystrophy.

Time-evolution and reversibility of strontium-induced osteomalacia in chronic renal failure rats

Patients with impaired renal function can accumulate strontium in the bone, which has been associated with the development of osteomalacia. A causal role for strontium in the development of the disease was presented in chronic renal failure (CRF) rats. Strontium-ranelate has been put forward as a therapeutic agent in the treatment of osteoporosis. Since the target population for strontium treatment consists mainly in postmenopausal osteoporotic women, who may have a reduced renal function, the risk for osteomalacia should be considered. To determine the time evolution and reversibility of the strontium-induced mineralization defect, CRF rats were loaded with strontium (2 g/L) (+/- 200 mg/kg/day) during 2, 6, and 12 weeks, followed by a washout period of 0, 2, 4, or 8 weeks. Histologic examination of the bone of the animals treated with strontium revealed signs of osteomalacia already after 2 weeks. Animals that received strontium during 6 and 12 weeks had a significantly higher osteoid perimeter, area and thickness as compared to CRF controls. After 12 weeks, the mineralization was significantly affected, as evidenced by a lower double-labeled surface, mineral apposition and bone formation rate in combination with an increased osteoid maturation time and mineralization lag time. The osteoblast perimeter was significantly lower in the strontium-treated animals. After the washout periods, these effects were reversed and the bone lesions evolved to the values of CRF controls. This went along with an 18% reduction of the bone strontium content. A significant rise in serum alkaline phosphatase (ALP) activity was apparent in the strontium-treated animals as compared to CRF controls. This was not only due to higher levels of the bone ALP but also to those of the liver and the intestinal isoenzymes. Serum parathyroid hormone (PTH) levels decreased during strontium treatment. After cessation of the treatment, the serum ALP activity and PTH concentration reversed to control levels. In this study evidence is provided for the rapid development of a mineralization defect in strontium-loaded CRF rats, accompanied by a reduced osteoblast number, reduced PTH synthesis or secretion, and increased serum ALP levels. These effects can be rapidly reversed after withdrawal of the compound.

Loss of vertebral bone and mechanical strength in estrogen-deficient rats is prevented by long-term administration of zoledronic acid

This study investigated the protective effect of long-term treatment with the bisphosphonate zoledronic acid on bone mass, structure, and strength in adult, estrogen-deficient rats. Rats were ovariectomized (OVX) at the age of 4 months and divided into four groups of 20 rats: one group of saline-treated OVX controls, and three groups of OVX rats treated with 0.3, 1.5, or 7.5 microg/kg/week s.c. zoledronic acid (ZOL). An additional group of sham-operated, saline-treated rats served as normal controls. Biochemical assays were performed after 16 and 51 weeks, respectively, and bone mineral density (BMD) determinations after 17 and 52 weeks, respectively. Before the end of the experiment animals were injected with tetracyclines for the determination of dynamic bone indexes. Finally, animals were sacrificed after 52 weeks, and vertebral bones (LV5) were subjected to mechanical compression testing. LV4 were used for histology and LV2 for microcomputed tomography. ZOL treatment abolished the rise of osteocalcin and reduced urinary deoxypyridinoline excretion. BMD was reduced in the OVX group in comparison to sham controls, and the decline was dose-dependently prevented by ZOL treatment. Tetracycline labeling showed a significant increase in bone formation rate (BFR) in OVX rats which was abolished by ZOL treatment. The same was observed for osteoid perimeter (Os.Pm) suggesting that ZOL diminished the high bone turnover associated with estrogen deficiency. Architectural parameters (BV/TV, Tb.Th*, Tb.N*, Tb.Sp*, SMI, CD) underwent the expected changes toward structural deterioration which was completely prevented by ZOL administration at doses of 1.5 and 7.5 microg/kg/week s.c. Similar results were obtained in compression testing: maximum stress fell significantly after OVX, and this effect was effectively prevented by ZOL treatment. Regression analysis suggests that in this rat model, SMI and Tb.Th* significantly contribute to compressive strength, albeit to a smaller degree than total cross-sectional area. The data further suggest that in the aged OVX rat, SMI and TB.Th* change in an interdependent way. ZOL prevents this process by inhibiting plate thinning and the transition into rod-shaped trabeculae.

Subchondral bone thickness, hardness and remodelling are influenced by short-term exercise in a site-specific manner

It was hypothesised that subchondral bone thickness, hardness and remodelling are influenced by exercise intensity, and by location within a joint. Dorsal carpal osteochondral injury is a major cause of lameness in horses undergoing high intensity training. This project aimed to determine the subchondral bone thickness, formation, resorption and hardness at sites with high and low incidence of pathology in 2 year-old horses undergoing 19 weeks high intensity treadmill training or low intensity exercise, and to compare these factors between exercise groups. Dorsal and palmar test sites were identified on radial, intermediate and third carpal articular surfaces after euthanasia. Adjacent osteochondral samples from each test site underwent histomorphometric analysis (for subchondral bone thickness, osteoid perimeter, osteoid seam width, eroded cavity area and eroded cement line surface length) and microhardness testing. Bone from horses undergoing high intensity training was thicker with a greater osteoid perimeter, and at individual sites had a smaller osteoid seam width and eroded cavity. Exercise-related differences were most marked at dorsal locations. Maximal differences in bone formation indices were observed at dorsal radial and medial third carpal locations. Overall subchondral bone from dorsal sites was thicker with a greater osteoid perimeter. Subchondral bone from dorsal sites was approximately 35% harder than bone from palmar sites. These results show topographical variations in subchondral bone structure, formation, resorption and material properties and a site-specific response to exercise. The maximal response to exercise was at high load sites with a clinical predisposition to injury. These findings indicate that the combined effect of exercise and local load variations within a joint may lead to maximal adaptive responses or overload of these responses at sites predisposed to injury.

Systemic administration of adrenomedullin(27-52) increases bone volume and strength in male mice.

Adrenomedullin is a 52-amino acid peptide first described in a human phaeochromocytoma but since been found to be present in many tissues, including the vascular system and bone. Because of its structural similarity to amylin and calcitonin gene-related peptide, both of which have actions on bone cells, we have previously assessed the effects of adrenomedullin on the skeleton, and found that it increases osteoblast proliferation in vitro and bone formation following local injection in vivo. The present study carries this work forward by assessing the effects on bone of the systemic administration of a fragment of this peptide lacking the structural requirements for vasodilator activity. Two groups of 20 adult male mice received 20 injections of human adrenomedullin(27-52) 8.1 microg or vehicle over a 4-week period and bone histomorphometry and strength were assessed. In the tibia, adrenomedullin(27-52) produced increases in the indices of osteoblast activity, osteoid perimeter and osteoblast perimeter (P<0.05 for both using Student's t-test). Osteoclast perimeter was not affected. There was a 21% increase in cortical width and a 45% increase in trabecular bone volume in animals treated with adrenomedullin(27-52) (P<0.002 for both). Assessment of bone strength by three-point bending of the humerus showed both the maximal force and the displacement to the point of failure were increased in the animals treated with adrenomedullin(27-52) (P<0.03 for both). There was also a significant increase in the thickness of the epiphyseal growth plate. No adverse effects of the treatment were noted. It is concluded that adrenomedullin(27-52) acts as an anabolic agent on bone. These findings may be relevant to the normal regulation of bone mass and to the design of agents for the treatment of osteoporosis.

Transforming growth factor-β administration modifies cyclosporine A-induced bone loss

Cyclosporine A (CsA), a potent immunosuppressant used in transplantation, induces increased formation with excess resorption in the rat with resultant osteopenia. These findings are confirmed in the human model. Transforming growth factor-β (TGF-β) is reported to be involved in the coupling of bone formation with resorption and in vivo and in vitro stimulates osteoblasts, and in vitro inhibits osteoclasts. CsA stimulates secretion of TGF-β1 in humans, which, while improving immunosuppression, may also contribute to renal toxicity. This study was performed determine whether exogenously administered TGF-β would modify the bone effects of CsA. Male Sprague-Dawley rats, 6 months of age, were randomized to receive: TGF-β and CsA vehicle (group A); TGF-β 5 μg/kg three times per week and CsA vehicle (group B); TGF-β vehicle and CsA 10 mg/kg (group C); or TGF-β 5 μg/kg three times per week and CsA 10 mg/kg (group D). These were compared with control over 28 days. CsA, but not TGF-β, increased serum 1,25(OH) 2D levels throughout the study. CsA increased osteocalcin (BGP), but TGF-β negated this effect. Histomorphometry confirmed the known effects of CsA, whereas TGF-β alone had no effect. However, in combination, TGF-β blocked CsA’s effect and increased osteoblast recruitment and activity, as reflected by increased percent mineralizing surface, percent osteoid perimeter, bone formation rate (bone volume referent), and activation frequency. Thus, it appears as if TGF-β administration may have potential in modulating the deleterious bone effects of CsA.

Antagonism of the osteoclast vitronectin receptor with an orally active nonpeptide inhibitor prevents cancellous bone loss in the ovariectomized rat.

An orally active, nonpeptide Arg-Gly-Asp (RGD) mimetic alpha(v)beta3 antagonist, (S)-3-Oxo-8-[2-[6-(methylamino)-pyridin-2-yl]-1-ethoxy]-2-(2,2,2-trifluoroethyl)-2,3,4,5-tetrahydro-1H-2-benzazepine-4-acetic acid (compound 1), has been generated, which prevented net bone loss and inhibited cancellous bone turnover in vivo. The compound binds alpha(v)beta3 and the closely related integrin alpha(v)beta5 with low nanomolar affinity but binds only weakly to the related integrins alpha(IIb)beta3, and alpha5beta1. Compound 1 inhibited alpha(v)beta3-mediated cell adhesion with an IC50 = 3 nM. More importantly, the compound inhibited human osteoclast-mediated bone resorption in vitro with an IC50 = 11 nM. In vivo, compound 1 inhibited bone resorption in a dose-dependent fashion, in the acute thyroparathyroidectomized (TPTX) rat model of bone resorption with a circulating EC50 approximately 20 microM. When dosed orally at 30 mg/kg twice a day (b.i.d.) in the chronic ovariectomy (OVX)-induced rat model of osteopenia, compound 1 also prevented bone loss. At doses ranging from 3 to 30 mg/kg b.i.d., compound 1 partially prevented the OVX-induced increase in urinary deoxypyridinoline. In addition, the compound prevented the OVX-induced reduction in cancellous bone volume (BV), trabecular number (Tb.N), and trabecular thickness (Tb.Th), as assessed by quantitative microcomputerized tomography (microCT) and static histomorphometry. Furthermore, both the 10-mg/kg and 30-mg/kg doses of compound prevented the OVX-induced increase in bone turnover, as measured by percent osteoid perimeter (%O.Pm). Together, these data indicate that the alpha(v)beta3 antagonist compound 1 inhibits OVX-induced bone loss. Mechanistically, compound 1 prevents bone loss in vivo by inhibiting osteoclast-mediated bone resorption, ultimately preventing cancellous bone turnover.

Pamidronate prevents bone loss associated with carrageenan arthritis by reducing resorptive activity but not recruitment of osteoclasts.

Carrageenan arthritis is associated with high-turnover bone loss. We sought to determine whether the bisphosphonate pamidronate can modify this effect of inflammatory arthritis. Sixty mature, New Zealand White rabbits were randomly assigned to five groups: normal; normal with a therapeutic dose of pamidronate (300 microg/kg/day, administered subcutaneously); arthritis (induced in the right tibiofemoral joint with 10 intraarticular carrageenan injections); arthritis with a therapeutic dose of pamidronate (300 microg/kg/day, subcutaneous); and arthritis with a low dose of pamidronate (7.5 microg/kg/day, subcutaneous). All animals received the fluorochrome calcein green (0.5 g/l/day) in drinking water ad libitum from days 21 to 49. Undecalcified, transverse sections of the distal femur were photographed or imaged to determine bone volume; new bone volume; resting, eroded, osteoid, and osteoblast perimeters; and osteoclast number. Results were evaluated with analysis of variance and pairwise Bonferroni's tests. In trabecular bone adjacent to the joint affected by carrageenan arthritis, resting perimeter was substantially reduced compared with normal joints, and primary indices of osteoblast and osteoclast activity were abnormally high (p < 0.001). Daily treatment with a therapeutic dose of pamidronate (300 microg/kg/day, subcutaneous) during the induction of arthritis significantly decreased new bone volume, osteoid perimeter, and osteoblast perimeter compared with the untreated arthritis group (p < 0.001). Osteoclast number and eroded perimeter remained abnormally high despite treatment with pamidronate. The concomitant increase of bone volume and these osteoclast indices show that pamidronate prevents bone loss in this model of experimental inflammatory arthritis by inhibiting the resorptive activity, but not the formation or recruitment, of osteoclasts. These findings are relevant to the use of bisphosphonates in the treatment of rheumatoid arthritis.

High insulin and low IGF-I plasma levels following pancreas transplantation in rats. Implications for bone and mineral metabolism

Primary disturbances in mineral metabolism and deficiencies in insulin and insulin-like growth factor-I (IGF-I) have been implicated in the pathogenesis of diabetic osteopenia. This prompted us to investigate whether normal bone minerals and bone morphology are preserved after pancreas transplantation. To this end, 8 inbred rats (transplants) were compared with 9 sham-operated rats (controls) 20 months after orthotopic pancreas transplantation. While basal levels of insulin remained unaffected by transplantation, an oral glucose load elicited hyperinsulinemia (integrated incremental response: mean +/- SEM, 62+/-8 nmol l(-1) 60 min in transplants vs. 32+/-6 nmol l(-1) 60 min in controls; p<0.01) in the presence of normal glucose levels. Fecal and urinary excretion and fractional intestinal absorption of calcium, magnesium and phosphorus, net calcium absorption and the respective serum mineral levels were unchanged after transplantation, as were those of the calciotropic hormones. Serum osteocalcin and bone alkaline phosphatase remained unaffected, and urinary excretion of pyridinium and deoxypyridinium were unchanged. Fasting plasma IGF-I concentration was significantly decreased in transplants (930+/-42 ng ml(-1)) vs. control rats (1074+/-49 ng ml(-1); p < 0.05). Despite similar physical and chemical properties of bone in both groups, histomorphometry revealed slight osteopenia in transplant rats, as reflected by a 38% reduction in the cancellous bone area of the proximal tibial metaphysis. Plasma IGF-I levels were significantly correlated with bone mineral apposition rate (r=0.70, p<0.02), osteoblast perimeter (r=0.60, p<0.05) and osteoid perimeter (r=0.60, p<0.05). In conclusion, pancreas transplantation preserves physical and chemical properties of bone, but bone metabolism is not completely normal after transplantation, as evidenced by decreased cancellous bone. This might have resulted from the insulin resistance associated with the lowering of the plasma IGF-I level, which was correlated with the mineral apposition rate.

Histomorphometric Evaluation of Titanium Implants in Osteoporotic Rabbits

In this study, the osteointegration of two kinds of titanium implants were analyzed (cylindrical and screw-type) inserted in the tibiae of control (n = 8) and osteoporotic (n = 12) female rabbits. Osteoporosis was induced by the surgical removal of the ovaries (oophorectomy). Bone mass density of all animals was evaluated by densitometry of the tibiae and vertebrae. Densitometry was carried out at the beginning of the study and 4 months after oophorectomy. Mass loss in the tibia was not observed, however, in the vertebrae there was an 11% loss compared with the initial value. The implants remained for 8 weeks, after which the animals were then sacrificed and bone segments were analyzed by histomorphometry. The trabecular volume and mineral apposition rate was significantly greater in control animals than in osteoporotic animals, independent of which type of implant was used. In the osteoporotic animals, the area and osteoid perimeter were greater than in the control animals. By measuring the thickness of the compact layer in the tibia, it was observed that in the control animals, it was 28% thicker than in the osteoporotic animals. This study leads to the conclusion that bone formation was greater in the control animals than in the osteoporotic animals. The screw-type implants yielded the greatest formation of bone both in the control and in the osteoporotic animals.

Skeletal Effects of Zinc Deficiency in Growing Rats

There is ample evidence that zinc plays an important role in bone metabolism and zinc deficiency has been implicated as a risk factor in the development of osteoporosis. It was the aim of the present study to investigate the skeletal effects of alimentary zinc deficiency in growing rats using quantitative bone histomorphometry. Twenty-four male Sprague Dawley rats with a mean initial body weight of 101 +/- 2 g were allocated in two groups of 12 rats each and had free access to a semi-synthetic, casein-based, zinc-deficient diet (0.76 mg zinc/kg) or to the same diet supplemented with 60 mg zinc per kg. All rats were sacrificed 42 days after the start of the experiment and the right distal femur was removed for bone histomorphometry. Relative to controls (+Zn), the zinc-deficient rats (-Zn) had a significantly lower body weight and about an 80% reduction in plasma and femur zinc concentration. The histomorphometric evaluation of the distal femoral metaphysis showed that zinc deficiency led to a 45% reduction (p < 0.01) in cancellous bone mass and to a deterioration of trabecular bone architecture, with fewer and thinner trabeculae. The osteopenia in -Zn rats was accompanied by significant reductions in osteoid perimeter (-31%, p < 0.05), osteoblast perimeter (-30%, p < 0.05), and osteoclast number (-38%, p < 0.01) relative to +Zn controls. We conclude that zinc deficiency induced low turnover osteopenia in femoral cancellous bone of growing rats. These results support the hypothesis that zinc deficiency during growth may impair the accumulation of maximal bone mass in humans; additionally, they suggest that zinc deficiency may play a role as a risk factor in the pathogenesis of osteoporosis.

Viability of the acetabular bone bed at revision surgery following cemented primary arthroplasty

Loosening of total hip replacements is often associated with severe loss of periprosthetic bone. The notion exists that the remaining bone is sclerotic, avascular, and displays little osteogenic activity, and that it therefore potentially compromises the revitalization of bone grafts used to restore bony defects. To verify this opinion we studied the bone characteristics in acetabular bone biopsies taken at primary total hip arthroplasty (PTH) and revision total hip arthroplasty (RTH) for a cemented PTH. In 6 PTH patients and in 10 RTH patients, acetabular bone biopsies were taken from the roof, the center, and the lower rim of each acetabulum. Specimens were evaluated by light microscopy and histomorphometrically measured for specimen size, bone area, perimeter, active osteoid perimeter, number of vessels, and osteoclasts. The vascularity and vitality appeared to be comparable in the RTH and PTH bone biopsies. However, the trabecular organization of the RTH bone differed from that of the PTH biopsies. In the PTH biopsies, the trabeculae were running perpendicular to the subchondral bone layer, whereas in the RTH biopsies the layers of bone were oriented parallel to the implant surface. There was abundant remodeling activity in the RTH bone, with large quantities of active osteoid and osteoclasts. These histologic parameters differed, but not statistically significant, from the PTH biopsies. In conclusion, we found that at revision, the acetabular bone was viable with sufficient vascularity and remodeling activity to provide an acceptable recipient host bone bed for revision surgery combined with bone grafting.

Bone disease in children and adolescents undergoing successful renal transplantation

Little is known about the extent and severity of bone disease in children undergoing successful renal transplantation. To address this issue, 47 patients with stable renal function 3.2 +/- 1.7 years after transplantation (Tx) underwent iliac crest bone biopsy. The mean age of patients was 12 +/- 2.0 years; 36 had received cadaveric renal grafts, whereas 11 had undergone living-related Tx. Immunosuppressive drugs included cyclosporine 0.17 +/- 0.4 mg/kg/day, prednisone 7.5 +/- 2.1 mg/kg/day, and either azathioprine 1.6 +/- 0.9 mg/kg/day or mycophenolate mofetil 30 +/- 3 mg/kg/day. In addition to quantitative bone histomorphometry, the bone mineral content (BMC) of the lumbar spine was measured by dual energy X-ray absorptiometry (DXA) in 24/47 patients. Thirty-one transplant recipients had normal bone formation (N-Bfr), 11 had mild hyperparathyroidism (HPT) and 5 had adynamic skeletal lesions (AD). The interval since Tx, duration of dialysis before Tx and cumulative prednisone dose did not differ among groups. Trabecular bone area was highest in subjects with HPT. Unexpectedly, eroded bone perimeter exceeded normal reference values both in patients with AD and in those with N-Bfr; the osteoid area and osteoid perimeter were also elevated in these two groups. Hyperparathyroidism improved or resolved after Tx in all 14 subjects with this skeletal lesion prior to Tx, but one patient developed AD after Tx. Bone histology did not change after Tx in those with N-Bfr during regular dialysis, but bone formation increased after Tx in two of three patients with AD during regular dialysis. Z-scores for height in pre-pubertal patients after Tx were below age-appropriate values in each histologic subgroup, but values did not differ among groups. Z-scores for bone mineral content at the lumbar spine were also less than age-predicted values, -0.67 +/- 1.2. After adjusting for the degree of growth retardation, height-adjusted z-scores for lumbar spine BMC after Tx were above normal in all three histologic groups (0.68 +/- 1.0). The results suggest that reductions in bone mass and post-transplant osteoporosis are not prominent findings in pediatric renal transplant recipients when the influence of growth retardation on bone mass measurements by DXA is carefully considered.