Bone Histomorphometry Research Articles

Histomorphometric Analysis of Osseointegrated Intraosseous Dental Implants Using Undecalcified Specimens: A Scoping Review

Bone histology and histomorphometry are reliable diagnostic tools for the assessment of the bone–implant interface, material safety and biocompatibility, and tissue response. They allow for the qualitative and quantitative analysis of undecalcified bone specimens. This scoping review aims to identify the most common staining techniques, study models for in vivo experiments, and histomorphometric parameters used for quantitative bone evaluation of osseointegrated dental implants in the last decade. The Web of Science, PubMed, and Scopus databases were searched on 1 July 2024 for relevant articles in English, published in the last ten years, and the data were exported to an MS Excel spreadsheet. A total of 115 studies met the eligibility criteria and were included in the present review. The results indicate that the most common study models are dogs, rabbits, and pigs. Some of the most frequently used methods for the assessment of the bone–implant interface are the Toluidine blue, Stevenel’s blue with Van Gieson, and Levai–Laczko stainings. The results from this study demonstrate that the most commonly used histomorphometric parameters in implant dentistry are the bone-to-implant contact (BIC), bone area fraction occupancy (BAFO), bone area (BA), and bone density (BD). This review presents the recent trends in histomorphometric analysis of dental implants and identifies some research gaps that necessitate further research.

Teriparatide administration is osteoanabolic but does not impact atherosclerotic plaque calcification and progression in a mouse model of menopause

Menopause exacerbates osteoporosis and increases the risk of atherosclerotic plaque rupture, leading to cardiovascular mortality. Osteoporotic women are increasingly treated with teriparatide (TPTD, 1–34 parathyroid hormone), one of the few treatments that stimulate bone formation. Despite the fact that atherosclerotic plaque calcification is a hallmark of plaque development, the impact of TPTD administration on plaque calcification remain unclear. In this context, we sought to determine the effects of TPTD administration on atherosclerosis in ovariectomized (OVX) apolipoprotein E deficient mice (ApoE−/−), as a model of postmenopausal osteoporosis. OVX ApoE−/− mice, fed a high fat, high cholesterol diet to induce atherosclerosis, received either vehicle or TPTD daily injections (40 μg/kg/d) for 4 or 10 weeks, at which points plaques are respectively weakly and heavily calcified. After sacrifice, bone remodeling was evaluated by serum markers and bone histomorphometry. Bone architectural parameters were measured by μCT. Aortic plaques were analyzed histologically, and their calcification with von Kossa staining and the calcium tracer Osteosense. Plaque inflammation and calcification markers were measured by RT-qPCR. Intermittent TPTD increased bone volume in OVX mice, due to a higher stimulation of bone formation relatively to bone resorption. These effects were not accompanied by changes in serum levels of cholesterol, triglycerides, glucose or insulin. TPTD neither significantly affected aortic plaque size, inflammation, and calcification, even if it slightly increased vascular smooth muscle cell transdifferentiation into calcifying cells. In conclusion, TPTD exhibits osteoanabolic effects in OVX ApoE−/− mice, without significantly influencing atherosclerotic plaque progression or calcification in the short term.

Osteoclast indices in osteogenesis imperfecta: systematic review and meta-analysis.

Osteogenesis imperfecta (OI) is a rare bone fragility disorder caused by mutations in genes encoding collagen type I or that affect its processing. Alterations in osteoclasts were suggested to contribute to OI pathophysiology. We aimed to systematically identify studies reporting measures of osteoclast formation and function in patients and mouse models of OI, to quantify OI-induced changes. The systematic search of Medline, Ovid, and Web of Science identified 798 unique studies. After screening, we included 23 studies for meta-analysis, reporting osteoclast parameters in 310 patients with OI of 9 different types and 16 studies reporting osteoclast parameters in 406 animals of 11 different OI mouse models. The standardized mean difference with 95% confidence interval (CI) was used as the effect size, and random-effects meta-analysis was performed. In patients with OI, collagen degradation markers were significantly higher compared with age-matched controls, with an effect size of 1.23 (CI: 0.36, 2.10]. Collagen degradation markers were the most elevated in the 3- to 7-year-old age group and in patients with more severe forms of OI. Bone histomorphometry demonstrated the trends for higher osteoclast numbers (1.16; CI: -0.22, 2.55) and osteoclast surface (0.43; CI: -0.63, 1.49), and significantly higher eroded surface (3.24; CI: 0.51, 5.96) compared with age-matched controls. In OI mice, meta-analysis demonstrated significant increases in collagen degradation markers (1.59; CI: 1.07, 2.11), in osteoclast numbers (0.94; CI: 0.50, 1.39), osteoclast surface (0.73; CI: 0.22, 1.23), and eroded surface (1.31; CI: 0.54, 2.08). The largest differences were in OI mice with the mutations in Col1a1 and Col1a2 genes. There were no differences between males and females in clinical or animal studies. Quantitative estimates of changes in osteoclast indices and their variance for patients with OI are important for planning future studies. We confirmed that similar changes are observed in mice with OI, supporting their translational utility.

Bone Histomorphometry in Patients with CKD Stage 2-5ND with or without Bone Loss Defined by Bone Densitometry

Bone Histomorphometry in Patients with CKD Stage 2-5ND with or without Bone Loss Defined by Bone Densitometry

Impact of Phosphate Binders on Bone Histomorphometry in Rats Submitted to Diets with Different Concentrations of Phosphorus

Impact of Phosphate Binders on Bone Histomorphometry in Rats Submitted to Diets with Different Concentrations of Phosphorus

Effects of GBT1118, a voxelotor analog, on bone disease in sickle cell disease mice

We assessed the effect of GBT1118, a sickle hemoglobin polymerization inhibitor on bone loss in humanized sickle cell disease (SCD) mice. Healthy control (Ctrl) 4-months-old female and male mice were fed Vehicle-chow for 2-months, while SCD mice were fed Vehicle-chow or GBT1118-chow. By micro-CT, GBT1118 significantly increased femur metaphyseal trabecular thickness (Tb.Th) and tissue mineral density (TMD), and significantly decreased trabecular spacing in female SCD mice. In SCD male mice, there was significant reduction in epiphyseal trabecular bone volume fraction (BV/TV), Tb.Th and TMD and GBT1118 significantly increased BV/TV and TMD but not Tb.Th. A significant decrease in cortical area fraction in SCD female mice was rescued by GBT1118 but not SCD males. Markedly decreased mineralized femur trabeculae in SCD females and males was partially rescued by GBT1118. Bone histomorphometry of femurs demonstrated significantly decreased bone formation parameters and increased bone resorption parameters in SCD mice of both sex that were rescued by GBT1118. Significant alteration in bone and hypoxia related genes of SCD mice of both sexes were differentially modulated by GBT1118. We conclude that "a sickle hemoglobin polymerization inhibitor" might be efficacious in improving some parameters of SCD bone loss.

Does arelation between bone histomorphometry and fractures exist? The case ofthe equine radius and tibia.

Fractures oflong bones inlimbs are rare traumatic events inhorses. This study investigates whether theincidence and types offractures can berelated tothe histomorphometric features ofthe radius and tibia, which experience different biomechanical stresses and exhibit varying incidences and types offractures. Clinical observations suggest that, inadults, slightly transverse and comminuted fractures are present inthe radius, while thetibia shows ahigher frequency oflongitudinal and spiral fractures. Microscopic observations reveal noapparent distinctive characteristics between the radius and tibia, whereas the histomorphometric data highlight differences inthe osteon density, eccentricity, and diameters ofthe osteons and Haversian canals. Tosum up, tibial osteons are more numerous and smaller than those inthe radius, resulting ina15% higher total extension ofthe cement line inthe tibia compared tothe radius. These histomorphometric differences are anevolutionary adaptation tothe different biomechanical stresses that involve the thoracic and pelvic limbs. Our results could help better understand numerous clinical realities detectable through retrospective analyses and aid inevaluating aspecific bone's predisposition towards traumatic events inall mammals, including humans.

Zoledronate alleviates subchondral bone collapse and articular cartilage degeneration in a rat model of rotator cuff tear arthropathy

To evaluate the humeral head bone volume of patients with cuff tear arthropathy (CTA) and examine the therapeutic effect of zoledronate in a rat modified model of CTA (mCTA). The bone mass in patients with CTA was measured using Hounsfield units from CT images. The mCTA was induced by transecting the rotator cuff, biceps brachii tendon, and superior half of the joint capsule in adult rat shoulders. A single subcutaneous injection of zoledronate was followed by bone histomorphometry and immunohistochemistry of the humeral head, as well as the Murine Shoulder Arthritis Score (MSAS) assessment. The humeral head bone volume was decreased in patients with CTA. In the mCTA model, M1 macrophages were increased in the synovium and were decreased by zoledronate treatment. The increased expressions of TNF-α, IL-1β and IL-6 in mCTA synovium and articular cartilage were suppressed in the zoledronate-treated mCTA group. The expression of catabolic enzymes in the articular cartilage and MSAS showed similar results. The zoledronate-treated mCTA group showed a decreased subchondral bone collapse with a decreased RANKL/OPG expression ratio and a suppressed number of osteoclasts compared with the control mCTA group. The enhanced expressions of HMGB1 and S100A9 in the mCTA shoulders were eliminated in the zoledronate-treated mCTA group. The humeral head subchondral bone was decreased in patients with CTA. In the mCTA model, the collapse and osteoarthritic changes were prevented by zoledronate administration. Zoledronate seemed to suppress the number of M1 macrophages in the synovium and osteoclasts in the subchondral bone.

Evaluation of bone mineral density (BMD) and trabecular bone score (TBS) in pheochromocytoma and paraganglioma; a multi-centric case-control study from India.

Pheochromocytoma and paraganglioma (PPGL) have been associated with low bone mineral density (BMD) and increased fracture risks. Sympathetic nervous system stimulation has been shown to increase bone resorption and decrease bone formation via β2 receptors. Chronic inflammation and increased cytokine production add to more bone loss. TBS (trabecular bone score) is an established surrogate marker for bone histomorphometry. BMD and TBS data in pheochromocytoma and PPGL are scarce. The aim was to assess the BMD and TBS in pheochromocytoma and PPGL and look for clinical and biochemical predictors. This case-control study had sample size of 58 (29 cases and controls each). BMI-, age-, and sex-matched controls were taken for comparison. Both cases and controls had undergone DXA scan and BMD {Z-scores and bone mineral concentration (BMC) in g/cm2} and TBS were analyzed. Detailed clinical histories and relevant biochemistry values were noted. The mean age of our case population was 29.5 ± 9.4years with a mean age of HTN onset at 26.86 ± 6.6years. Lumbar spine BMC (0.86 ± 0.14 vs 0.96 ± 0.15; p = 0.036), femoral neck Z-score (- 1.23 ± 1.07 vs - 0.75 ± 0.97; p = 0.003), and whole body BMC (0.91 ± 0.14 vs 1.07 ± 0.11; p = 0.000) were significantly low in cases compared to controls. Similarly, TBS was significantly lower in cases compared to controls (1.306 ± 0.113 vs 1.376 ± 0.083; p = 0.001). This study establishes both low bone mass and poor bone quality in an Indian pheochromocytoma and PPGL patient's cohort. Plasma-free nor-metanephrine and duration of hypertension were found to be most consistent predictive factors in multivariate regression analysis.

Histomorphometry specific to anthropological studies concerning the human condition.

Bone histomorphometry refers to the study of the structure and microscopic features of bone tissue. It involves the measurement and assessment of bone microanatomy, and it provides valuable information on bone properties. Through the application of histomorphometry, researchers can acquire information on bone metabolism and on remodeling dynamics, which is useful to the study of bone health. During the last 50 years, biological anthropologists have adopted the use of histomorphometry while examining issues specific to human health and evolutionary trends from prehistoric remains. Scientists coming from the medical field have applied histomorphometry in their research as it allows the study of bone changes, useful to describe pathological conditions among these ancient human remains. This paper reflects on some of the research that involves histomorphometric analysis specific to diet and health, forensic anthropology, taphonomic assessment of bone, non-human primate research and biomechanics. The purpose of the paper is to consider past and future applications of bone histomorphometry to enable a discussion which might direct research towards under-explored areas of bone biology. For example, looking at renewed interest in clavicular histology and stimulating investigations that focus on osteocyte density. Additionally, a discussion is offered concerning OPD values used to correlate chronological age to biological age estimations.

Bone matrix properties in adults with osteogenesis imperfecta are not adversely affected by setrusumab-a sclerostin neutralizing antibody.

Osteogenesis imperfecta (OI) is a skeletal dysplasia characterized by low bone mass and frequent fractures. Children with OI are commonly treated with bisphosphonates to reduce fracture rate, but treatment options for adults are limited. In the Phase 2b ASTEROID trial, setrusumab (a sclerostin neutralizing antibody, SclAb) improved bone density and strength in adults with type I, III, and IV OI. Here, we investigate bone matrix material properties in tetracycline-labeled trans iliac biopsies from 3 groups: (1) control: individuals with no metabolic bone disease, (2) OI: individuals with OI, (3) SclAb-OI: individuals with OI after 6 mo of setrusumab treatment (as part of the ASTEROID trial). In addition to bone histomorphometry, bone mineral and matrix properties were evaluated with nanoindentation, Raman spectroscopy, second harmonic generation imaging, quantitative backscatter electron imaging, and small-angle X-ray scattering. Spatial locations of fluorochrome labels were identified to differentiate inter-label bone of the same tissue age and intra-cortical bone. No difference in collagen orientation was found between the groups. The bone mineral density distribution and analysis of Raman spectra indicate that OI groups have greater mean mineralization, greater relative mineral content, and lower crystallinity than the control group, which was not altered by SclAb treatment. Finally, a lower modulus and hardness were measured in the inter-label bone of the OI-SclAb group compared to the OI group. Previous studies suggest that even though bone from OI has a higher mineral content, the extracellular matrix (ECM) has comparable mechanical properties. Therefore, fragility in OI may stem from contributions from other yet unexplored aspects of bone organization at higher length scales. We conclude that SclAb treatment leads to increased bone mass while not adversely affecting bone matrix properties in individuals with OI.

Prevention of bone dehiscence associated with orthodontic tooth movement by prophylactic injection of bone anabolic agents in mice

Although bone dehiscence may occur during orthodontic tooth movement into the narrow alveolar ridge, a non-invasive prevention method is yet to be fully established. We show for the first time prevention of bone dehiscence associated with orthodontic tooth movement by prophylactic injection of bone anabolic agents in mice. In this study, we established a bone dehiscence mouse model by applying force application and used the granular type of scaffold materials encapsulated with bone morphogenetic protein (BMP)-2 and OP3-4, the receptor activator of NF-κB ligand (RANKL)-binding peptide, for the prophylactic injection to the alveolar bone. In vivo micro-computed tomography revealed bone dehiscence with decreased buccal alveolar bone thickness and height after force application, whereas no bone dehiscence was observed with the prophylactic injection after force application, and alveolar bone thickness and height were kept at similar levels as those in the control group. Bone histomorphometry analyses revealed that both bone formation and resorption parameters were significantly higher in the injection with force application group than in the force application without the prophylactic injection group. These findings suggest that the prophylactic local delivery of bone anabolic reagents can prevent bone dehiscence with increased bone remodelling activity.

Retrospective Characterization of Bone Histomorphometric Findings in Clinical Patient Specimens.

Bone histomorphometry provides comprehensive information on bone metabolism and microstructure. In this retrospective study, we aimed to obtain an overview of the typical indications, referring hospitals, and histomorphometric quantification-based diagnoses of the bone tissue in our histomorphometry laboratory, the only laboratory in Finland carrying out histomorphometric examination of clinical bone biopsies. Between January 1, 2005 and December 31, 2020, 553 clinical bone biopsies were sent to our histomorphometry laboratory for histomorphometric examination. The median age of the patients was 55 years (range, 0.2-89.9 years), 51% of them were males, and 18% comprised pediatric patients. We received bone biopsy specimens from 23 hospitals or healthcare units. The majority of the samples we sent by nephrologists. The most common bone biopsy indications were suspicion of renal osteodystrophy (ROD), unknown bone turnover status in osteoporosis, and several or untypical fractures. The most common quantitative bone histomorphometry-based diagnosis was ROD. This study provides information on the clinical application of bone histomorphometry in Finland. Precise and quantitative ROD evaluation is the most common indication for bone histomorphometry, being crucial in clinical decision-making and targeted treatment of this patient group.

Insight into the potential of bone turnover biomarkers: integration in the management of osteoporosis and chronic kidney disease-associated osteoporosis.

Disturbances in mineral and bone metabolism occurring in osteoporosis and chronic kidney disease-associated osteoporosis place patients at high risk of fracture making these conditions a major public health concern. Due to the limited use of bone histomorphometry in clinical practice, the gold standard for assessing bone turnover, extensive efforts have been made to identify bone turnover markers (BTMs) as noninvasive surrogates. Since the identification of certain commonly used markers several decades ago, considerable experience has been acquired regarding their clinical utility in such bone disorders. Mounting evidence suggested that BTMs represent a simple, low-risk, rapid and convenient way to obtain data on the skeletal health and that they may be useful in guiding therapeutic choices and monitoring the response to treatment. BTMs could provide clinicians with useful information, independent from, and often complementary to bone mineral density (BMD) measurements. They have proven valuable for monitoring the effectiveness of osteoporosis therapy, as well as promising for discriminating low and high turnover states. Improved performance is observed when BTMs are combined, which may be useful for selecting treatments for chronic kidney disease-bone mineral disorders (CKD-MBD).

#2223 Glycosylated hemoglobin levels and bone phenotype in patients with end-stage kidney disease

Abstract Background and Aims Diabetes mellitus is common as both cause and comorbidity of patients with chronic kidney disease (CKD). Both diabetes and CKD are states of increased fracture risk compared to healthy controls, with multiple potential contributing mechanisms. In type 2 diabetes, hyperglycemia contributes to the accumulation of advanced glycation end-products and osteocyte dysfunction, and it may play a pathogenic role in bone fragility. In this study, we wanted to examine the association between glycemic status and bone phenotype in patients with end-stage kidney disease (ESKD). Method This is a cross-sectional cohort study of 626 patients with CKD G5-5D referred for kidney transplantation between April 2006 and December 2013. Patients with type 1 diabetes were excluded. Patients were divided into quartiles based on HbA1c. Laboratory parameters of bone mineral metabolism (including biointact parathyroid hormone (PTH), fibroblast growth factor-23 (FGF23), and sclerostin), and bone turnover markers (bone alkaline phosphatase (BALP), trimeric pro-collagen type 1 N-terminal pro-peptide (intact P1NP), and tartrate-resistant acid phosphatase 5b (TRAP5b)) were measured. Bone mineral density (BMD) assessed by dual-energy X-ray absorptiometry (DEXA) (n = 537), bone histomorphometry (n = 180), and bone trabecular score (TBS) (n = 192) were available for subsets of patients. Results The median HbA1c were 4.8% in Q1, 5.1% in Q2, 5.4% in Q3, and 5.9% in Q4. Age and BMI differed across quartiles, with the highest age and BMI in Q4. Differences in bone turnover markers were found, with decreasing bone formation (BALP and intact P1NP) and decreasing bone resorption (TRAP5b) with ascending quartiles (Fig. 1). No differences across quartiles were found for FGF23, or circulating levels of sclerostin; however a weak, positive correlation between HbA1c and sclerostin was noted (rho = 0.08, p = 0.047). Overall, BMD at lumbar spine, femoral neck, and total hip increased across quartiles, the highest values in Q4 (Table 1). There were no differen in bone histomorphometry or TBS based on glycemic status. Conclusion Chronic hyperglycemia associates with suppressed bone turnover and higher BMD in patients with ESKD, even in non-diabetics. Potential mechanisms linking glucose metabolism to bone quantity and quality requires further investigation.

#911 A mice model of SHPT with bone abnormalities in CKD and potential functional role of sphingolipid in renal osteodystrophy

Abstract Background and Aims Renal osteodystrophy (ROD) is the skeletal disease of chronic kidney disease associated mineral and bone disorder (CKD-MBD). ROD is characterized by abnormal bone mineralization and impaired bone remodeling, leading to increased risk of fractures and mortality in patients with CKD. To date, the pathology of ROD remains poorly understood due to the lack of a suitable animal model. Hence, we successfully established a stable mouse model of ROD using an optimized adenine diet and explored the possible signaling based on RNA-seq expression analyses. Method Blood biochemical analysis, micro-computed tomography (micro-CT) and bone histomorphometry were performed to analyze the skeletal characteristics. RNA sequencing (RNA-seq) was used to investigate the mechanisms involved in ROD. The functions of differentially expressed genes (DEGs) were evaluated by Gene Ontology (GO) analyses, Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses and Gene Set Enrichment Analyses (GSEA). DEGs were validated by quantitative real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). Results The mice with ROD induced by optimized adenine diet showed severe abnormalities in serum creatinine (Scr) and blood urea nitrogen (BUN) along with marked hyperparathyroidism and hyperphosphatemia. The bone mineral density (BMD) of femurs was significantly lower in the ROD mice than that in the control (CTL) mice. The trabecular and cortical bone parameters of femurs significantly showed bone loss and severe cortical porosity. ROD mice showed high bone turnover with increased osteoid, eroded, osteoblast, and osteoclast perimeters as well as increased bone formation rate and mineral apposition rate. Transcriptomic profiling identified 1286 genes were upregulated in the femurs of ROD mice compared to the CTL mice and 333 genes that were downregulated. GO, KEGG and GSEA pathway analyses indicated that these genes were highly enriched in functions related to lipid metabolism pathway, sphingolipid signaling pathway, among others. The differential expression of alkaline ceramidase 1(Acer1), ceramide synthase 4 (Cers4) sphingomyelin phosphodiesterase 3 (Smpd3), sphingosine-1-phosphate phosphatase 2 (Sgpp2) in skeletal tissue and serum of CKD patients were validated by qRT-PCR. Since sphingolipid pathways have been recently implicated in bone metabolism, these genes are potential target genes in the settings of ROD. Conclusion In conclusion, our findings demonstrated that the CKD mice with bone abnormalities induced by optimized adenine diet may serve as a useful model for skeletal analysis in ROD. Based on the RNA-seq, we identified that sphingolipid might play a crucial role in the pathogenesis of ROD and provided new therapeutic targets for future study.

#2215 Early molecular and cellular features of aortic remodeling in a mild CKD-MBD model with low bone turnover

Abstract Background and Aims Vascular calcification associated with a maladaptive bone response is common in CKD and is a major cause of mortality (up to 60% depending on CKD stage). Alterations in several intracellular signaling pathways have been reported during the cellular phenotype transition and vascular calcification, however the initial phases of vascular remodeling in early CKD-MBD remain poorly understood. The aim of this study was to investigate the early molecular and cellular features of aortic remodeling prior to calcification in a model of mild CKD-MBD with low bone turnover. Method We induced CKD-MBD by 3/4 nephrectomy (Nx, n = 8) in adult male spontaneously hypertensive rats (SHR) with normal phosphate (Pi) intake (0.6%). Controls were sham-operated Wistar rats (n = 8) and SHR (n = 8). Chronic kidney injury and Pi exchange parameters, serum levels of calciprotein particles (CPPs), intact PTH, intact FGF23, dickkopf-1 and sclerostin, static bone histomorphometry, aortic morphology (H&E, Masson's trichrome, calcein, von Kossa stain), CD31, aSMA, nestin, Col1a1, PDGFR-beta, PiT1, LGR4 and intracellular signaling molecules—phospho-ERK1/2, active (non-phospho) beta-catenin, Hes1, Gli1 were analyzed by IHC with quantitative morphometry and IF after 4 months. Confocal microscopy was performed at the Centre for Collective Use of the Pavlov Institute of Physiology, Russian Academy of Sciences (Zeiss LSM 710). Results The study found that Nx rats with chronic kidney injury comparable to human CKD S2 exhibited lower bone turnover (Fig. 1). The Nx group had higher serum levels of Pi and CPPs vs. control group, but there were no differences in Pi-regulatory factors (Figs 1, 2b). Additionally, the Nx group showed aorta remodeling, which was characterized by an increase in intima thickness, cellularity, and collagen accumulation in the medial layer (Figs 1, 2a). The histological parameters of intimal remodeling and perivascular fibrosis were found to be directly correlated with serum levels of Pi and CPPs. In Nx, there was a decrease in medial αSMA expression accompanied by an increase in phospho-ERK1/2, PiT1, nestin, Gli1, beta-catenin, dickkopf-1, and an decrease in Hes1 immunomorphological staining (Figs 1, 2a, c). αSMA-negative cells demonstrated the expression of osteogenesis-related molecules, such as phospho-ERK1/2 (Fig. 2a, c), and occasionally, RunX2 (Fig. 2a). Phospho-ERK1/2 and PiT1 were found to co-localize in Nx (Fig. 2c). Intimal remodeling was observed, characterized by increased beta-catenin and nestin expression (Fig. 2c). Conclusion In mild CKD-MBD with low bone turnover, early intimal and medial aortic remodeling was associated with higher serum Pi and CPPs levels, and upregulation of PiT1, ERK1/2. In addition, other signals likely related to osteogenesis (RunX2, LGR4) and regulation of vascular progenitor cells (Nestin, Wnt, Notch, Hedgehog) may be implicated.

#1496 High levels of sclerostin promote bone resorption and changes and mineral metabolism

Abstract Background and Aims The physiological function of sclerostin (SOST) remains unknown. It is known that SOST is produced in osteocytes and functions as an inhibitor of the Wnt/β-catenin pathway. Similarly, it is well-established that low levels of SOST lead to bone alterations affecting cortical bone, resulting in osteopetrosis and reduced calciuria. High levels of SOST are associated with osteoporosis. In this study, we aimed to investigate the impact of three elevated doses of SOST on cortical, trabecular, and subchondral bone, as well as its relationship with other parameters of mineral metabolism. Method Bone histomorphometry, mCT, immunohistochemistry, and analysis of mineral metabolism parameters revealed that high doses of SOST over a 14-day period led to a reduction in trabecular bone volume due to a significant increase in bone resorption through the direct activation of osteoclastogenesis. Results Bone resorption, as measured by TRAP activity, was higher in trabecular, cortical, and subchondral bone. Similarly, high doses of SOST increased the number of hypertrophic chondrocytes, consequently expanding the growth plate area. Cortically, positive TRAP staining was observed, suggesting osteocytic osteolysis and trabecularization of cortical bone. The increased bone resorption resulted in a substantial rise in urinary excretion of phosphorus and calcium, accompanied by elevated levels of FGF23 and a significant decrease in PTH. Conclusion The findings suggest that elevated levels of SOST promote bone resorption through the activation of osteoclasts and the generation of osteocytic osteolysis. The increase in calcium and phosphorus levels led to changes in mineral metabolism, indicating a close relationship between SOST and other mineral metabolism parameters.

#1725 Co-relation of bone mineral density (BMD) with static bone histomorphometric parameters in haemodialysis patients

Abstract Background and Aims A mineral bone disorder of CKD (CKD MBD) is a complication with abnormal bone turnover, mineralization, volume, vascular calcification, and a spectrum of biochemical abnormalities. This clinical study was designed to determine the correlation between BMD (DEXA parameter) and static bone histomorphometry in hemodialysis patients. Method This was a cross-sectional study in patients undergoing maintenance hemodialysis aged 18-60 years. Bone biopsy was done from the iliac crest, fixed in alcohol, processed, and stained by RGB trichrome stain. Histomorphometric analysis was done by using NIH software (image J) and Adobe Photoshop software for image masking into black and white for volume calculation. Determination of BMD was performed by DEXA SCAN (Model HORIZON A). The detection sections included the central skeleton's three areas- anteroposterior lumbar (L1-L4) spine, proximal femur (femoral neck), and distal radius. Results A total of 46 patients on maintenance hemodialysis were included. Thirty-one (67.39%) were male, and the mean age was 34.43 ± 12.5 years. Amongst the study population, 60.87% (28) patients had osteopenia, 19.57%(9) patients had osteoporosis, and 19.57%(9) patients had normal BMD. Out of 46, four biopsies were inconclusive, 50% (21) had adynamic bone disease, 19.05%(8) had high turnover bone disease, 19.05%(8) had high mixed uremic osteodystrophy and 11.9%(5) patients had normal parameters. Among biochemical parameters, serum iPTH, ALP, and calcium had a significant association with bone turnover. BMD was significantly associated with age. However, it had no significant association with dialysis vintage, sex, or the type of renal osteodystrophy. Static bone histomorphometric parameters were not significantly associated with the T score. Conclusion PTH, ALP, and serum calcium were significantly associated with bone turnover. Adynamic bone disease was the most common renal osteodystrophy. BMD was not significantly associated with static bone histomorphometric parameters in our study.

Age-related changes in densitometry and histomorphometry of long bone during the pubertal growth spurt in male rats.

Because experimental studies to determine the developmental toxicity of exposure to various substances in children are impossible, many studies use immature male rats. This study aimed to provide normative data for longitudinal bone growth with age during the puberty in male rats. In order to evaluate long bone growth and mineralization we examined bone size and bone density by dual-energy X-ray absorptiometry, analyzed histomorphometry of the growth plate, and serum hormone levels relevant to bone growth from postnatal day (PD)20 to PD60. The length and weight of long bones increased strongly by PD40, and no further increase was observed after PD50. On the other hand, tibial growth plate height decreased sharply after PD50 along with a reduction in the number of cells and columns, which was probably responsible for the absence of further lengthening of long bones. Parameters related to bone formation such as bone area ratio, and the thickness and number of trabeculae, also increased significantly between PD40 and PD50. Furthermore, serum levels of IGF-1 peaked at PD30 and testosterone increased rapidly on and after PD40, when IGF-1 levels were going down. These changes may participate in the parallel increase in mineral acquisition, as well as lengthening of long bones. Our findings provide comprehensive data for changes in bone density, histomorphometry of long bones, and hormone levels relevant to bone growth during the growth spurt. This will be useful for planning animal toxicological studies, particularly for deciding on the appropriate age of animals to use in given experiments.