Regulation of bone formation

A Case of Hypercalcemia and Acute Kidney Injury Caused by Adrenal Insufficiency

Hypercalcemia is a common electrolyte disturbance, most frequently caused by hyperparathyroidism or malignancy, though it can also arise from adrenal insufficiency, creating diagnostic challenges. We present a case of a 78-year-old male patient with stage 3b chronic kidney disease due to immunoglobulin A nephropathy who exhibited altered mental status following dehydration caused by a five-day episode of diarrhea. The patient presented with hypercalcemia and acute kidney injury. His history of adrenal insufficiency had been managed with glucocorticoid replacement. Dehydration and inability to take oral medications led to exacerbation of adrenal insufficiency, worsening his hypercalcemia. Routine causes of hypercalcemia, such as hyperparathyroidism and malignancy, were ruled out. Treatment with intravenous prednisolone and fluid replacement gradually improved serum calcium and mental status, with normalization by the seventh hospital day. This case highlights the importance of timely glucocorticoid therapy in managing adrenal insufficiency-related hypercalcemia and the complex mechanisms involved, including decreased glomerular filtration rate and increased calcium reabsorption.

A Case of Acute Adrenal Insufficiency: A Rare but Possible Cause of Hypercalcemia

A 30-year-old woman presented with a 15-day history of epigastric pain, nausea, vomiting, asthenia, and weight loss. On admission, hypercalcemia was reported with a negative etiologic workup (including no primary hyperparathyroidism, malignancy, or vitamin D toxicity). Fluid replacement did not improve her hypercalcemia. We performed a blood ionogram and assessed the adrenocortical function, which showed that her serum cortisol was decreased, her adrenocorticotropic hormone (ACTH) was elevated, and anti-21 hydroxylase antibodies were positive. We established the diagnosis of autoimmune primary acute adrenal insufficiency. The patient was treated with hydrocortisone. Shortly after initiating the treatment, her serum calcium levels returned to normal and her symptoms improved.

This case report highlights the fact that even though adrenal insufficiency is an uncommon etiology of hypercalcemia, it should not be totally ignored, especially since hypercalcemia can sometimes be indicative of adrenal impairment.

An in vitro / in vivo release test of risedronate drug loaded nano-bioactive glass composite scaffolds

Three-dimensional (3D) matrices scaffolds play a noteworthy role in promoting cell generation and propagation. In this study, scaffolds prepared from chitosan/polyvinyl alcohol loaded with/without an osteoporotic drug (risedronate) and nano-bioactive glass (nBG) have been developed to promote healing of bone defects. The scaffolds were characterized by scanning electron microscopy (SEM), porosity test as well as mechanical strength. The pattern of drug release and ability to promote the proliferation of Saos-2osteosarcoma cells had also been reported. Osteogenic potential of the scaffolds was evaluated by testing their effect on healing critical-sized dog's mandibular bone defects. Increasing chitosan and nBG in the porous scaffolds induced decrease in drug release, increased the scaffold's strength and supported their cell proliferation, alkaline phosphatase (ALP) activities, as well as increased calcium deposition. Histological and histomorphometric results demonstrated newly formed bone trabeculae inside critical-sized mandibular defects when treated with scaffolds. Trabecular thickness, bone volume/tissue volume and the percentage of mature collagen fibers increased in groups treated with scaffolds loaded with 10% nBG and risedronate or loaded with 30% nBG with/without risedronate compared with those treated with non-loaded scaffolds and empty control groups. These findings confirmed the potential osteogenic activity of chitosan/polyvinyl alcohol-based scaffolds loaded with risedronate and nBG.

Interplay between mineral crystallinity and mineral accumulation in health and postmenopausal osteoporosis

Osteoporosis is characterized by an imbalance between bone formation and resorption rates, resulting in bone loss. For ethical reasons, effects of antiosteoporosis drugs are compared against patients receiving vitamin D and calcium supplementation which is a mild antiresorptive regimen. Bone formation may be resolved into two phases: the initial formation of mineral crystals (primary nucleation) and the subsequent mineral accumulation (secondary nucleation and mineral growth) on them. In this study, we used Raman microspectroscopic analysis of iliac crest biopsies from healthy females (N = 108), postmenopausal osteoporosis patients receiving vitamin D and calcium supplementation (PMOP-S; N = 66), and treatment-naïve postmenopausal osteoporosis patients (PMOP-TN; N = 12) to test the hypothesis that at forming trabecular surfaces, mineral maturity / crystallinity of the youngest crystallites associates with the amount of subsequent mineral accumulation. The surfaces of analysis were chosen based on the presence of fluorescent double labels, defining three distinct tissue ages. The results indicated that when adjusted for age and tissue age, there were no differences in amount of mineral formed between healthy females and either PMOP-S or PMOP-TN, while both PMOP-S and PMOP-TN had larger crystallites compared to healthy females. Moreover, significant differences existed between PMOP-S and PMOP-TN in size of initial crystals formed as well as rate of mineral accumulation and maturation. These findings suggest an additional mechanism that may contribute to the decreased mineral content evident in PMOP, and provide a potential target for the development of new interventions. STATEMENT OF SIGNIFICANCE: We used Raman microspectroscopic analysis of iliac crest biopsies from healthy females and postmenopausal osteoporosis patients (PMOP) receiving placebo to test the hypothesis that at forming trabecular surfaces, mineral maturity / crystallinity (MMC) of the youngest crystallites associates with the amount of subsequent mineral accumulation. This can affect bone mechanical properties as larger crystallites have been shown to result in compromised mechanical attributes; and larger crystallites grow slower compared to smaller ones. The results of the present analysis indicate that increased MMC of the youngest formed mineral may contribute to the bone mineral loss evident in PMOP and the accompanying increased fracture risk independently of bone turnover rate.

The role of vitamin D in sarcoidosis

After the initial description of extrarenal synthesis of 1,25-dihydroxyvitamin D (1,25-(OH)₂D) three decades ago, extensive progress has been made in unraveling the immunomodulatory roles of vitamin D in the pathogenesis of granulomatous disorders, including sarcoidosis. It has been shown that 1,25-(OH)₂D has dual effects on the immune system, including upregulating innate immunity as well as downregulating the autoimmune response. The latter mechanism plays an important role in the pathogenesis and treatment of sarcoidosis. Vitamin D supplementation in patients with sarcoidosis has been hampered owing to concerns about the development of hypercalcemia and hypercalciuria given that extrarenal 1-α hydroxylase is substrate dependent. Recently, a few studies have cast doubt over the mechanisms underlying the development of hypercalcemia in this population. These studies demonstrated an inverse relationship between the level of vitamin D and severity of sarcoidosis. Consequently, clinical interest has been piqued in the use of vitamin D to attenuate the autoimmune response in this disorder. However, the development of hypercalcemia and the attendant detrimental effects are real possibilities. Although the average serum calcium concentration did not change following vitamin D supplementation, in two recent studies, hypercalciuria occurred in one out of 13 and two out of 16 patients. This review is a concise summary of the literature, outlining past work and newer developments in the use of vitamin D in sarcoidosis. We feel that larger-scale placebo-controlled randomized studies are needed in this population. Since the current first-line treatment of sarcoidosis is glucocorticoids, which confer many systemic adverse effects, and steroid-sparing immunosuppressant treatment options carry additional risks of adverse effects, adjunct management with vitamin D in combination with potent anti-osteoporotic medications could minimize the risk of glucocorticoid-induced osteoporosis and modulate the immune system to attenuate disease activity in sarcoidosis.

Inorganic Self-Assembled Bioactive Artificial Proto-Osteocells Inducing Bone Regeneration

Since the discovery of osteoinduction in the early 20th century, innovative biomaterials with osteoinductive potential have emerged as candidates for bone repair. Recently, artificial protocell models have demonstrated great potential for tissue regeneration. Herein, we developed artificial bioactive proto-osteocells by self-assembly of biodegradable biphasic-phosphate particles in the form of aqueous bone morphogenetic protein 2 (BMP2)-containing Pickering emulsions in corn oil to fulfill the release of BMP2 with controlled and local efficacy. These artificial proto-osteocells have the advantage of (1) being directly injected into the target location to avert reported side effects of BMP2, minimizing surgical complications, (2) exhibiting the capability of osteoinduction as shown in both in vitro and in vivo models, and (3) demonstrating calcific deposition locally by utilizing the biodegradable calcium phosphate shell. The efficiency of BMP2 within the artificial proto-osteocells showed 25 times greater bone-inducing potential when compared to the control. This study demonstrates for the first time a new strategy toward utilizing material-based artificial proto-osteocells to tackle medical issues in bone tissue repair and regeneration.

Embryology of the craniocervical junction and posterior cranial fossa, part II: Embryogenesis of the hindbrain

Although pathology of the hindbrain and its derivatives can have life altering effects on a patient, a comprehensive review on its embryology is difficult to find in the peer-reviewed medical literature. Therefore, this review article, using standard search engines, seemed timely. The embryology of the hindbrain is complex and relies on a unique timing of various neurovascular and bony elements. Derailment of these developmental processes can lead to a wide range of malformations such as the Chiari malformations. Therefore, a good working knowledge of this embryology as outlined in this review of the hindbrain is important for those treating patients with involvement of this region of the central nervous system. Clin. Anat. 31:488-500, 2018. © 2018 Wiley Periodicals, Inc.

Alterations in intervertebral disc composition, matrix homeostasis and biomechanical behavior in the UCD-T2DM rat model of type 2 diabetes

Type 2 diabetes (T2D) adversely affects many tissues, and the greater incidence of discogenic low back pain among diabetic patients suggests that the intervertebral disc is affected too. Using a rat model of polygenic obese T2D, we demonstrate that diabetes compromises several aspects of disc composition, matrix homeostasis, and biomechanical behavior. Coccygeal motion segments were harvested from 6-month-old lean Sprague-Dawley rats, obese Sprague-Dawley rats, and diabetic obese UCD-T2DM rats (diabetic for 69 ± 7 days). Findings indicated that diabetes but not obesity reduced disc glycosaminoglycan and water contents, and these degenerative changes correlated with increased vertebral endplate thickness and decreased endplate porosity, and with higher levels of the advanced glycation end-product (AGE) pentosidine. Consistent with their diminished glycosaminoglycan and water contents and their higher AGE levels, discs from diabetic rats were stiffer and exhibited less creep when compressed. At the matrix level, elevated expression of hypoxia-inducible genes and catabolic markers in the discs from diabetic rats coincided with increased oxidative stress and greater interactions between AGEs and one of their receptors (RAGE). Taken together, these findings indicate that endplate sclerosis, increased oxidative stress, and AGE/RAGE-mediated interactions could be important factors for explaining the greater incidence of disc pathology in T2D.

High prevalence of metabolic syndrome in a mestizo group of adult patients with primary hyperparathyroidism (PHPT)

BACKGROUND

Primary hyperparathyroidism (PHPT) and metabolic syndrome (MS) have been independently related to cardiovascular morbidities, however this association is still controversial. Mexican population has a high prevalence of metabolic syndrome, however its frequency seems to be even higher than expected in patients with PHPT.

METHODS

We retrospectively reviewed the charts of patients that underwent parathyroidectomy for PHPT in a referral center and used the criteria from the National Cholesterol Educational Program (NCEP)/Adult Treatment Panel III (ATP III) to define MS before surgery. We compared the characteristics between the patients with and without MS.

RESULTS

60 patients were analyzed, 77% were female and 72% had a single parathyroid adenoma. MS was present in 59% of the patients, this group was significantly older (57 vs. 48 years, p = 0.01) and they had lower iPTH (115 vs. 161 ng/ml, p = 0.017). Other parameters did not show differences.

CONCLUSIONS

MS is frequent in our population diagnosed with primary hyperparathyroidism, adverse cardiovascular parameters are common and significant differences in calcium metabolism compared to the non-MS group are present.

Calcium-deficiency assessment and biomarker identification by an integrated urinary metabonomics analysis

BACKGROUND

Calcium deficiency is a global public-health problem. Although the initial stage of calcium deficiency can lead to metabolic alterations or potential pathological changes, calcium deficiency is difficult to diagnose accurately. Moreover, the details of the molecular mechanism of calcium deficiency remain somewhat elusive. To accurately assess and provide appropriate nutritional intervention, we carried out a global analysis of metabolic alterations in response to calcium deficiency.

METHODS

The metabolic alterations associated with calcium deficiency were first investigated in a rat model, using urinary metabonomics based on ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry and multivariate statistical analysis. Correlations between dietary calcium intake and the biomarkers identified from the rat model were further analyzed to confirm the potential application of these biomarkers in humans.

RESULTS

Urinary metabolic-profiling analysis could preliminarily distinguish between calcium-deficient and non-deficient rats after a 2-week low-calcium diet. We established an integrated metabonomics strategy for identifying reliable biomarkers of calcium deficiency using a time-course analysis of discriminating metabolites in a low-calcium diet experiment, repeating the low-calcium diet experiment and performing a calcium-supplement experiment. In total, 27 biomarkers were identified, including glycine, oxoglutaric acid, pyrophosphoric acid, sebacic acid, pseudouridine, indoxyl sulfate, taurine, and phenylacetylglycine. The integrated urinary metabonomics analysis, which combined biomarkers with regular trends of change (types A, B, and C), could accurately assess calcium-deficient rats at different stages and clarify the dynamic pathophysiological changes and molecular mechanism of calcium deficiency in detail. Significant correlations between calcium intake and two biomarkers, pseudouridine (Pearson correlation, r = 0.53, P = 0.0001) and citrate (Pearson correlation, r = -0.43, P = 0.001), were further confirmed in 70 women.

CONCLUSIONS

To our knowledge, this is the first report of reliable biomarkers of calcium deficiency, which were identified using an integrated strategy. The identified biomarkers give new insights into the pathophysiological changes and molecular mechanisms of calcium deficiency. The correlations between calcium intake and two of the biomarkers provide a rationale or potential for further assessment and elucidation of the metabolic responses of calcium deficiency in humans.

Glucocorticoid-induced osteoporosis in children with 21-hydroxylase deficiency

21-Hydroxylase deficiency (21-OHD) is the most common cause of congenital adrenal hyperplasia (CAH), resulting from deletions or mutations of the P450 21-hydroxylase gene (CYP21A2). Children with 21-OHD need chronic glucocorticoid (cGC) therapy, both to replace congenital deficit in cortisol synthesis and to reduce androgen secretion by adrenal cortex. GC-induced osteoporosis (GIO) is the most common form of secondary osteoporosis that results in an early, transient increase in bone resorption accompanied by a decrease in bone formation, maintained for the duration of GC therapy. Despite the conflicting results in the literature about the bone status on GC-treated patients with 21-OHD, many reports consider these subjects to be at risk for osteoporosis and fractures. In bone cells, at the molecular level, GCs regulate various functions including osteoblastogenesis, osteoclastogenesis, and the apoptosis of osteoblasts and osteocytes. In this paper, we focus on the physiology and biosynthesis of endogenous steroid hormones as well as on the effects of GCs on bone cells, highlighting the pathogenetic mechanism of GIO in children with 21-OHD.

Retinoic acid regulates commitment of undifferentiated mesenchymal stem cells into osteoblasts and adipocytes

Evidence indicates that the balance between osteoblastogenesis and adipogenesis of mesenchymal stem cells (MSCs) is regulated by several hormones, growth factors, and their downstream signaling cascades. Previous studies suggest that retinoic acid (RA) plays a role in osteoblastogenesis and adipogenesis. However, it is unknown whether RA regulates commitment of MSCs into osteoblasts and adipocytes. In this study, we investigated the role of RA in differentiation of MSCs using the C3H10T1/2 cell line. RA stimulated activity and expression of alkaline phosphatase (ALP) and upregulated activity of the ALP gene promoter. The effects of RA were further enhanced by bone morphogenetic protein 2 (BMP2) and resultant Smad signaling. Furthermore, overexpression of Runx2 and Msx2, critical transcription factors for bone formation and BMP2-dependent osteoblastogenesis, enhanced RA-dependent ALP activity. In view of these findings, RA likely stimulates osteoblast differentiation through the BMP2-Smad-Runx2/Msx2 pathway. In contrast, RA markedly inhibited BMP2-induced adipocyte differentiation, suppressing expression of peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT/enhancer-binding protein (C/EBP)α and C/EBPδ, and inhibiting adipogenic function of C/EBPβ, C/EBPδ, and PPARγ. In conclusion, our data suggest that RA regulates commitment of MSCs into osteoblasts and adipocytes by controlling transcriptional regulators.

Concentrated bovine milk whey active proteins facilitate osteogenesis through activation of the JNK-ATF4 pathway

Concentrated fractions of low molecular weight whey proteins (1-30 kDa), that is concentrated bovine milk whey active proteins (CBP), have been found to enhance bone formation in both in vivo and clinical studies, but the underlying mechanisms are poorly understood. In this study, we found that CBP promoted osteoblastic differentiation in normal human osteoblasts, and determined the involvement of the c-jun NH2-terminal kinase (JNK)-activating transcription factor 4 (ATF4) pathway. We observed that alkaline phosphatase activity and mineralization were significantly induced by CBP treatment. In addition, mRNA expression of ATF4 was intensely elevated in CBP-treated osteoblasts, indicating that the late-phase events of differentiation were promoted. We found that CBP activated the phosphorylation of JNK and extracellular signal-regulated kinase (ERK). Furthermore, pathway analyses using the various signaling pathway-specific inhibitors revealed that JNK activation, but not ERK activation, is essential for CBP-induced mineralization and ATF4 expression. Our results indicate that the JNK-mediated ATF4 pathway is required for CBP-promotive osteogenesis.

Human mesenchymal stem cell differentiation to the osteogenic or adipogenic lineage is regulated by AMP-activated protein kinase

AMP-activated protein kinase (AMPK) is an energy-sensing kinase that has recently been shown to regulate the differentiation of preadipocytes and osteoblasts. However, the role of AMPK in stem cell differentiation is largely unknown. Using in vitro culture models, the present study demonstrates that AMPK is a critical regulatory factor for osteogenic differentiation. We observed that expression and phosphorylation of AMPK were increased during osteogenesis in human adipose tissue-derived mesenchymal stem cells (hAMSC). To elucidate the role of AMPK in osteogenic differentiation, we investigated the effect of AMPK inhibition or knockdown on mineralization of hAMSC. Compound C, an AMPK inhibitor, reduced mineralized matrix deposition and suppressed the expression of osteoblast-specific genes, including alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), and osteocalcin (OCN). Knockdown of AMPK by shRNA-lentivirus infection also reduced osteogenesis. In addition, inhibition or knockdown of AMPK during osteogenesis inhibited ERK phosphorylation, which is required for osteogenesis. Interestingly, inhibition of AMPK induced adipogenic differentiation of hAMSC, even in osteogenic induction medium (OIM). These results provide a potential mechanism involving AMPK activation in osteogenic differentiation of hAMSC and suggest that commitment of hAMSC to osteogenic or adipogenic lineage is governed by activation or inhibition of AMPK, respectively.

Infrared assessment of bone quality: a review

BACKGROUND

Bone strength depends on both bone quantity and quality. The former is routinely estimated in clinical settings through bone mineral density measurements but not the latter. Bone quality encompasses the structural and material properties of bone. Although its importance is appreciated, its contribution in determining bone strength has been difficult to precisely quantify partly because it is multifactorial and requires investigation of all bone hierarchical levels. Fourier transform infrared spectroscopy provides one way to explore these levels.

QUESTIONS/PURPOSES

The purposes of our review were to (1) provide a brief overview of Fourier transform infrared spectroscopy as a way to establish bone quality, (2) review the major bone material parameters determined from Fourier transform infrared spectroscopy, and (3) review the role of Fourier transform infrared microspectroscopic analysis in establishing bone quality.

METHODS

We used the ISI Web of Knowledge database initially to identify articles containing the Boolean term "infrared" AND "bone." We then focused on articles on infrared spectroscopy in bone-related journals.

RESULTS

Infrared spectroscopy provides information on bone material properties. Their microspectroscopic versions allow one to establish these properties as a function of anatomic location, mineralization extent, and bone metabolic activity. It provides answers pertaining to the contribution of mineral to matrix ratio, mineral maturity, mineral carbonate substitution, and collagen crosslinks to bone strength. Alterations of bone material properties have been identified in disease (especially osteoporosis) not attainable by other techniques.

CONCLUSIONS

Infrared spectroscopic analysis is a powerful tool for establishing the important material properties contributing to bone strength and thus has helped better understand changes in fragile bone.

Bone material properties in actively bone-forming trabeculae in postmenopausal women with osteoporosis after three years of treatment with once-yearly Zoledronic acid

Zoledronic acid (ZOL), a third-generation aminobisphosphonate, showed pronounced antifracture efficacy in a phase III clinical trial [Health Outcomes and Reduced Incidence with Zoledronic Acid Once Yearly-Pivotal Fracture Trial (HORIZON-PFT)] when administered yearly (5-mg infusions of ZOL), producing significant reductions in morphometric vertebral, clinical vertebral, hip, and nonvertebral fractures by 70%, 77%, 41%, and 25%, respectively, over a 3-year period. The purpose of this study was to analyze the biopsies obtained during the HORIZON clinical trial (152 patients, 82 ZOL and 70 placebo) by means of Raman microspectroscopy (a vibrational spectroscopic technique capable of analyzing undecalcified bone tissue with a spatial resolution of approximately 0.6 µm) to determine the effect of ZOL therapy on bone material properties (in particular mineral/matrix ratio, lamellar organization, carbonate and proteoglycan (based on spectral identification of glycosaminoglycan) content, and mineral maturity/crystallinity) at similar tissue age (based on the presence of tetracycline double labels). The results indicated that while ZOL administration increased the mineral/matrix ratio compared with placebo, it also resulted in mineral crystallites with a quality profile (based on carbonate content and maturity/crystallinity characteristics) of younger (with respect to tissue age) bone. Since the comparisons between ZOL- and placebo-treated patients were performed at similar tissue age at actively forming bone surfaces, these results suggest that ZOL may be exerting an effect on bone matrix formation in addition to its well-established antiresorptive effect, thereby contributing to its antifracture efficacy.

Bone health should be an important concern in the care of patients affected by 21 hydroxylase deficiency

Osteoporosis has been an understandable concern for children and adult patients with congenital adrenal hyperplasia (CAH) who may receive or have received supraphysiological doses of glucocorticoids. Some previous reports on bone mineral density (BMD) in adult CAH patients showed no significant differences in BMD between patients with CAH and controls, but others have found lower BMD in CAH patients. In reports documenting the BMD reduction, this outcome has been attributed to an accumulated effect of prolonged exposure to excess glucocorticoids during infancy and childhood. We recently conducted a trial to establish the role of the total cumulative glucocorticoid dose on BMD. We established for the first time that there was a negative relationship between total cumulative glucocorticoid dose and lumbar and femoral BMD. Women might benefit from the preserving effect of estrogens compared to men. BMI (Body Mass Index) also appeared to protect patients from bone loss. In light of this, physicians should bear in mind the potential consequences of glucocorticoids on bone and therefore adjust the treatment and improve clinical and biological surveillance from infancy. Furthermore, preventive measures against corticosteroid-induced osteoporosis should be discussed right from the beginning of glucocorticoid therapy.

Metabolic control and future opportunities for growth regulation

The last 10 years have seen a significant expansion in the scope of attempts to manipulate the growth of animals (Buttery, Lindsay and Haynes, 1986). The expansion of interest has been driven by a number of factors, both economic and theoretical. At the economic level the need to develop energetically and economically efficient strategies of animal production has been coupled with a renewed awareness of the implications for human health of excessive intakes of saturated fats. Emphasis then has switched from the maximization of weight gain as an end in itself towards a need to promote protein deposition at any given intake and, at the same time, to reduce the fat content of meat and meat products. These twin objectives might be achieved by one of three strategies: the promotion of protein deposition alone, because at any given rate of weight gain this will tend to minimize the rate of fat deposition (the so-called repartitioning effect); the reduction of fat gain (an approach that has received particularly close attention by those concerned primarily with human obesity); or ideally the simultaneous promotion of protein accretion and depression of that of fat.

Osteoblast differentiation is functionally associated with decreased AMP kinase activity

Osteoblasts, originating from mesenchymal stem cells, play a pivotal role in bone formation and mineralization. Several transcription factors including runt-related transcription factor 2 (Runx2) have been reported to be essential for osteoblast differentiation, whereas the cytoplasmic signal transduction pathways controlling the differentiation process have not been fully elucidated. AMP-activated protein kinase (AMPK) is a serine-threonine kinase generally regarded as a key regulator of cellular energy homeostasis, polarity, and division. Recent lines of evidence have indicated that the activity of the catalytic alpha subunit of AMPK is regulated through its phosphorylation by upstream AMPK kinases (AMPKKs) including LKB1. Here, we explored the role of AMPK in osteoblast differentiation using in vitro culture models. Phosphorylation of AMPKalpha was significantly decreased during osteoblastic differentiation in both primary osteoblasts and MC3T3-E1, a mouse osteoblastic cell line. Conversely, the terminal differentiation of primary osteoblasts and MC3T3-E1 cells, represented by matrix mineralization, was significantly inhibited by glucose restriction and stimulation with metformin, both of which are known activators of AMPK. Matrix mineralization of MC3T3-E1 cells was also inhibited by the forced expression of a constitutively active form of AMPKalpha. Metformin significantly inhibited gene expression of Runx2 along with osteoblast differentiation markers including osteocalcin (Ocn), bone sialo protein (Bsp), and osteopontin (Opn). Thus, our present data indicate that differentiation of osteoblasts is functionally associated with decreased AMPK activity.

Impact of total cumulative glucocorticoid dose on bone mineral density in patients with 21-hydroxylase deficiency

OBJECTIVE

It remains controversial whether long-term glucocorticoids are charged of bone demineralization in patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency. The aim of this study was to know whether cumulative glucocorticoid dose from the diagnosis in childhood to adulthood in patients with CAH had a negative impact on bone mineral density (BMD).

DESIGN

This was a retrospective study.

METHODS

Thirty-eight adult patients with classical and non-classical CAH were included. BMD was measured in the lumbar spine and femoral neck. Total cumulative glucocorticoid (TCG) and total average glucocorticoid (TAG) doses were calculated from pediatric and adult files.

RESULTS

We showed a difference between final and target heights (-0.82+/-0.92 s.d. for women and -1.31+/-0.84 s.d. for men; P<0.001). Seventeen patients (44.7%) had bone demineralization (35.7% of women and 70% of men). The 28 women had higher BMD than the 10 men for lumbar (-0.26+/-1.20 vs -1.25+/-1.33 s.d.; P=0.02) and femoral T-scores (0.21+/-1.30 s.d. versus -1.08+/-1.10 s.d.; P=0.007). In the salt-wasting group, women were almost significantly endowed with a better BMD than men (P=0.053). We found negative effects of TCG, TAG on lumbar (P<0.001, P=0.002) and femoral T-scores (P=0.006, P<0.001), predominantly during puberty. BMI was protective on BMD (P=0.006).

CONCLUSION

The TCG is an important factor especially during puberty for a bone demineralization in patients with 21-hydroxylase deficiency. The glucocorticoid treatment should be adapted particularly at this life period and preventive measures should be discussed in order to limit this effect.

Hormonal regulation of bone growth and remodelling

Many systemic and local hormones influence bone growth and remodelling. These include calcium regulating hormones, systemic growth regulators and local growth factors. Parathyroid hormone (PHT) is a potent stimulator of osteoclastic bone resorption and a direct inhibitor of osteoblastic collagen synthesis. However, intermittent low-dose PTH administration can increase bone formation in vivo. PTH may act indirectly via local factors. It has been shown to increase prostaglandin E2 (PGE2) and transforming growth factor beta (TGF-beta) release from bone. Both PGE2 and TGF-beta have complex effects on bone metabolism and are likely to be physiological regulators of bone remodelling. Oestradiol has been shown to inhibit bone resorption in vivo but not in vitro. While there is evidence for oestrogen receptors in cultured bone cells, the effect could still be indirect. Oestradiol can inhibit bone PGE2 release in an in vivo-in vitro model in the rat. Glucocorticoids are potent inhibitors of bone formation and inhibit PGE2 and interleukin 1 production both in vivo and in vitro. While many regulatory factors affect prostaglandin production in bone, the complex effects of PGE2 on bone metabolism make it difficult to predict the ultimate response. The major effects of PGE2 are stimulation of bone formation and resorption and an increase in bone turnover. However, opposite effects can occur at certain times and concentrations. Interactions among these factors could explain some physiological, pathological, and therapeutic responses in skeletal tissue.

Osteoporosis

Effective therapies are available for the patient who has arthritic osteoporosis. The approach is critical to ensure an optimal quality of life in these individuals who suffer with a disease that is clearly treatable.

Vanadium and bone development: putative signaling pathwaysThis paper is one of a selection of papers published in this Special issue, entitled Second Messengers and Phosphoproteins—12th International Conference

Vanadium is a trace element present in practically all cells in plants and animals. It exerts interesting actions in living systems. At pharmacological doses, vanadium compounds display relevant biological actions such as mimicking insulin and growth factors as well as having osteogenic activity. Some vanadium compounds also show antitumoral properties. The importance of vanadium in bone arises from the studies developed to establish the essentiality of this element in animals and humans. Bone tissue, where the element seems to play an important role, accumulates great amounts of vanadium. This paper reviews the physiology of osteoblasts, the involvement of different growth factors on bone development, and the effects of vanadium derivatives on the skeletal system of animal models and bone-related cells. Two cellular lines are discussed in particular; one derived from a rat osteosarcoma (UMR106) and the other is a nontransformed osteoblast cell line (MC3T3-E1). The effects of different growth factors and their mechanisms of action in these cellular lines are reviewed. These models of osteoblasts are especially useful in understanding the intracellular signaling pathways of vanadium derivatives in hard tissues. Vanadium uses an intricate interplay of intracellular mechanisms to exert different biochemical and pharmacological actions. The effects of vanadium derivatives on some cellular signaling pathways related to insulin are compiled in this review. The comprehension of these intracellular signaling pathways may facilitate the design of vanadium compounds with promising therapeutic applications as well as the understanding of secondary side effects derived from the use of vanadium as a therapeutic agent.

Osteoporosis

Bone is a complex organ which contains an organic matrix which serves as scaffolding, includes mineral as calcium distributed in a pattern providing structure and serves as an ion reservoir for the body. Throughout life it dynamically changes in response to changes in activity, body mass, and weight bearing. It is important to define patients at risk for bone loss, since accrued bone loss leading to osteoporosis in the older population of both men and women is unacceptable. There are many different therapies including biphosphonates which can decrease loss of bone and decrease fracture risk in patients who already have had sustained a fracture. Newer therapies such as parathyroid hormone may improve the fracture risk even more than biphosphonates over a shorter period of time.

Association between primary hyperparathyroidism and increased body weight: a meta-analysis

Although primary hyperparathyroidism is frequently asymptomatic, it has been associated with an increased prevalence of hypertension, insulin resistance, dyslipidemia, cardiovascular mortality, and cancer. Previously we reported that patients with primary hyperparathyroidism are heavier than age-matched controls. Increased body weight could contribute to the association between primary hyperparathyroidism and these extraskeletal complications. We searched MEDLINE for English language studies published between 1975 and 2003 that reported body weight or body mass index in subjects with primary hyperparathyroidism and a healthy age- and sex-comparable eucalcemic control group. Seventeen eligible studies were identified. Subjects with primary hyperparathyroidism were 3.34 kg (95% confidence interval, 1.97-4.71; P < 0.00001) heavier than controls in 13 studies reporting body weight. In four studies reporting body mass index, subjects with primary hyperparathyroidism had an increased body mass index of 1.13 kg/m(2) (-0.29 to 2.55; P = 0.12) compared with controls. Standard mean difference analysis showed that subjects with primary hyperparathyroidism had an increased weight or body mass index of 0.3 sd (0.19-0.40; P < 0.00001) compared with controls. We conclude that patients with primary hyperparathyroidism are heavier than their eucalcemic peers, and that increased body weight may contribute to the reported associations between primary hyperparathyroidism and some extraskeletal complications.

Cell lines and primary cell cultures in the study of bone cell biology

Bone is a metabolically active and highly organized tissue consisting of a mineral phase of hydroxyapatite and amorphous calcium phosphate crystals deposited in an organic matrix. Bone has two main functions. It forms a rigid skeleton and has a central role in calcium and phosphate homeostasis. The major cell types of bone are osteoblasts, osteoclasts and chondrocytes. In the laboratory, primary cultures or cell lines established from each of these different cell types provide valuable information about the processes of skeletal development, bone formation and bone resorption, leading ultimately, to the formulation of new forms of treatment for common bone diseases such as osteoporosis.

Elevated bone resorption markers in a patient with hypercalcemia associated with post-partum thyrotoxicosis and hypoadrenocorticism due to pituitary failure

A 36-yr-old woman began to suffer from headache, anorexia and general fatigue at 35 weeks' gestation. About 2 or 3 months after the delivery, fever, tachycardia and generalized musculoskeletal disorder appeared. Thereafter, they worsened rapidly, accompanied by a disturbance of consciousness and hypercalcemia. Thyrotoxicosis, due to a post-partum thyroiditis, and glucocorticoid deficiency, due to a pituitary failure, probably associated with lymphocytic hypophysitis, were also observed. All the symptoms and hypercalcemia disappeared after the glucocorticoid replacement therapy and the normalization of thyroid hormone levels. Serum and urinary bone resorption markers, such as urine pyridinoline (U-Pyr), urine deoxypyridinoline (U-DPD), urine amino-terminal telopeptide of type I collagen (U-NTx) and serum carboxy-terminal telopeptide of type I collagen (ICTP), were extremely high at the hypercalcemic state. In this case, they were 10 to 20 times higher than the normal upper limits, and then markedly decreased in a normocalcemic state, thereby showing an extreme acceleration of bone resorption in a state of both thyrotoxicosis and glucocorticoid deficiency.

Prominent Tc-99m MIBI skeletal uptake in renal osteodystrophy: a possible role for whole-body scanning

Renal osteodystrophy is a process whereby renal failure causes profound bone disease. Effects on bone include osteosclerosis, osteomalacia, osteoporosis, pathologic fractures, aseptic necrosis of the hips, and bone pain. The authors present a case of renal osteodystrophy with intense Tc-99m 2-methoxy isobutyl isonitrile (MIBI) radiotracer uptake in the mandible and propose that Tc-99m MIBI may have a potential role in diagnosing renal osteodystrophy.

The influence of culture conditions on extracellular matrix proteins synthesized by osteoblasts derived from rabbit bone marrow

The influence of culture conditions on the extracellular matrix (ECM) protein expressions of rabbit bone marrow stromal cells has been studied. The focus was on the effects of two kinds of sera, fetal calf serum (FCS) and Ultroser, on cells treated with dexamethasone. The induction of osteoblastic differentiation by dexamethasone addition is confirmed, particularly when cells are cultured in FCS. Bone marrow stromal cells produce alkaline phosphatase positive CFU-F and produce ECM with some mineralized nodules. Analysis by means of two-dimensional gel electrophoresis showed important changes in the composition of ECM proteins after dexamethasone treatment. Overexpression, underexpression, and new synthesized proteins were observed. The most significant modification was linked to the synthesis of four new proteins visible in the acidic area with a low molecular weight of around 17 kDa. These proteins did not correspond to those ECM proteins known to be induced by dexamethasone. Moreover, the effect of dexamethasone on osteoblastic differentiation induction appears very limited when cells are cultured in Ultroser compared to FCS. The protein pattern with Ultroser is different to that obtained with FCS. Cells cultured in Ultroser synthesized no new protein. The different behavior of cells according to the type of medium used is discussed in terms of the osteogenic factors present in the two different sera.

Bone metabolism in childhood rheumatic disease

There is an increasing appreciation among physicians about the importance of bone health in children as a potential modifiable risk factor for development of osteoporosis later in life. Many unanswered questions about normal pediatric bone health make the treatment and clinical investigation of bone disease in children with chronic rheumatic diseases challenging. Understanding normal bone biology along with the epidemiology and diagnosis of osteoporosis is the key to the understanding of the potential for abnormal bone metabolism in the juvenile rheumatic diseases.

Reduced spinal bone mineral density in adolescents of an Ultra-Orthodox Jewish community in Brooklyn

OBJECTIVES

Bone mass increases throughout childhood, with maximal bone mass accrual rate occurring in early to mid-puberty and slowing in late puberty. Prevention of osteoporosis and its morbidities depends primarily on the establishment of adequate peak bone mass. Physical activity, calcium intake, and vitamin D stores (from sunlight conversion of precursors of vitamin D and to a lesser degree from dietary intake) are vital determinants of bone mineral density (BMD). BMD is further controlled by genetic and environmental factors that are poorly understood. Observance of ultra-Orthodox Jewish customs may have a negative effect on the factors that promote bone health, and there have been anecdotal reports of higher fracture rates in this population. The ultra-Orthodox Jewish lifestyle encourages scholarly activity in preference to physical activity. Additionally, modest dress codes and inner-city dwelling reduce sunlight exposure. Orthodox Jews do not consume milk products for 6 hours after meat ingestion, leading to potentially fewer opportunities to consume calcium. Foods from the milk group are some of the best sources of dietary calcium. Our aims are to examine BMD in a group of healthy ultra-Orthodox Jewish adolescents in an urban community and to attempt to correlate it to physical activity and dietary factors.

DESIGN AND METHODS

We recruited 50 healthy, ultra-Orthodox Jews, ages 15 to 19 years (30 males and 20 females). None were taking corticosteroids or had evidence of malabsorption. All girls were postmenarchal and nulliparous. Pubic hair Tanner stage for boys and breast Tanner stage for girls were determined. Weight and height standard deviation scores were calculated. Calcium, phosphorus, protein, vitamin D, and calorie intake were assessed using a comprehensive food questionnaire referring to what has been eaten over the last year. Hours per week of weight-bearing exercise and walking were determined. Serum levels of calcium, intact parathyroid hormone (PTH), 25 hydroxyvitamin D (25[OH]D) and 1,25 dihydroxyvitamin D (1,25[OH](2)D) were measured. Lumbar spine (L) BMD was assessed by dual energy radiograph absorptiometry. The pediatric software supplied by Lunar Radiation Corporation, which contains gender- and age-specific norms, provided a z score for the lumbar BMD for each participant. L2 to L4 bone mineral apparent density (BMAD) was calculated from L2 to L4 BMD.

RESULTS

BMD of L2 to L4 was significantly decreased compared with age/sex-matched normative data: mean z score was -1.25 +/- 1.25 (n = 50). The mean L2 to L4 BMD z score +/- standard deviation was -1.71 +/- 1.18 for boys and -0.58 +/- 1.04 for girls. Eight boys (27%) had L2 to L4 BMD z scores <-2.5, which defines osteoporosis in adulthood. Twenty-seven adolescents (54%), 16 boys and 11 girls, had Tanner stage V. Two participants (4%) had delayed development of Tanner stage V. Mean consumption of calcium by participants under 19 years old was 908 +/- 506 mg/day (n = 46), which is lower than the adequate intake of 1300 mg/day for this age. The consumption of phosphorus was 1329 +/- 606 mg/day, and the consumption of vitamin D was 286 +/- 173 IU/day (n = 50). The mean serum 25(OH)D level was 18.4 +/- 7.6 ng/mL, and the mean serum 1,25(OH)(2)D level was 71.1 +/- 15.7 pg/mL (n = 50). Boys had significantly higher serum levels of 1,25(OH)(2)D than did girls (74.9 +/- 16.46 pg/mL vs 65.25 +/- 12.8 pg/mL, respectively). The serum levels of PTH, calcium, and protein were (mean +/- standard deviation): 33 +/- 16 pg/mL, 9.5 +/- 0.69 mg/dL, and 7.8 +/- 0.6 g/dL, respectively (n = 50). L2 to L4 BMD z score had positive correlation with walking hours (r = 0.4). L2 to L4 BMD z score had negative correlation with serum level of 1,25(OH)(2)D )r = -0.33; n = 50). We could not find significant correlation between L2 to L4 BMD z scores for the entire cohort and any of calcium, vitamin D, phosphorus, or protein intake. However, the L2 to L4 BMD z scores of boys had positive correlation with calcium, phosphorus, and protein intake (r = 42, r = 44, and r = 43, respectively). After adjustment for Tanner stage, boys who had Tanner stage V (n = 16) had stronger positive correlation between L2 to L4 BMD z scores and calcium and protein intake (r = 0.55 and r = 0.57, respectively), as was the correlation between L2 to L4 BMD z score and weight-bearing activity and walking hours (r = 0.77 and r = 0.72, respectively; n = 16). By multiple regression analysis with stepwise selection, sex, walking hours, weight-standard deviation scores, and serum PTH predicted 54% of the variability in L2 to L4 BMD z score. Sex, walking hours, and age predicted 65% of the variability in L2 to L4 BMAD.

CONCLUSIONS

Lumbar BMD is significantly decreased in ultra-Orthodox Jewish adolescents living in an urban community. Boys had profoundly lower spinal BMD than did girls. Previous studies have introduced estrogen as a critical factor in bone mineralization. (ABSTRACT TRUNCATED)

Expression of extracellular calcium-sensing receptor in human osteoblastic MG-63 cell line

We have previously shown the expression of the extracellular calcium (Ca2+o)-sensing receptor (CaR) in osteoblast-like cell lines, and others have documented its expression in sections of murine, bovine, and rat bone. The existence of the CaR in osteoblasts remains controversial, however, since some studies have failed to document its expression in the same osteoblast-like cell lines. The goals of the present study were twofold. 1) We sought to determine whether the CaR is expressed in the human osteoblast-like cell line, MG-63, which has recently been reported by others not to express this receptor. 2) We investigated whether the CaR, if present in MG-63 cells, is functionally active, since most previous studies have not proven the role of the CaR in mediating known actions of Ca2+o on osteoblast-like cells. We used immunocytochemistry and Western blotting with the specific, affinity-purified anti-CaR antiserum 4637 as well as Northern blot analysis and RT-PCR using a riboprobe and PCR primers specific for the human CaR, respectively, to show readily detectable CaR protein and mRNA expression in MG-63 cells. Finally, we employed the patch-clamp technique to show that an elevation in Ca2+o as well as the specific, allosteric CaR activator NPS R-467 (0.5 microM), but not its less active stereoisomer NPS S-467 (0.5 microM), activate an outward K+ channel in MG-63 cells, strongly suggesting that the CaR in MG-63 cells is not only expressed but is functionally active.

Extracellular calcium sensing and extracellular calcium signaling

The cloning of a G protein-coupled extracellular Ca(2+) (Ca(o)(2+))-sensing receptor (CaR) has elucidated the molecular basis for many of the previously recognized effects of Ca(o)(2+) on tissues that maintain systemic Ca(o)(2+) homeostasis, especially parathyroid chief cells and several cells in the kidney. The availability of the cloned CaR enabled the development of DNA and antibody probes for identifying the CaR's mRNA and protein, respectively, within these and other tissues. It also permitted the identification of human diseases resulting from inactivating or activating mutations of the CaR gene and the subsequent generation of mice with targeted disruption of the CaR gene. The characteristic alterations in parathyroid and renal function in these patients and in the mice with "knockout" of the CaR gene have provided valuable information on the CaR's physiological roles in these tissues participating in mineral ion homeostasis. Nevertheless, relatively little is known about how the CaR regulates other tissues involved in systemic Ca(o)(2+) homeostasis, particularly bone and intestine. Moreover, there is evidence that additional Ca(o)(2+) sensors may exist in bone cells that mediate some or even all of the known effects of Ca(o)(2+) on these cells. Even more remains to be learned about the CaR's function in the rapidly growing list of cells that express it but are uninvolved in systemic Ca(o)(2+) metabolism. Available data suggest that the receptor serves numerous roles outside of systemic mineral ion homeostasis, ranging from the regulation of hormonal secretion and the activities of various ion channels to the longer term control of gene expression, programmed cell death (apoptosis), and cellular proliferation. In some cases, the CaR on these "nonhomeostatic" cells responds to local changes in Ca(o)(2+) taking place within compartments of the extracellular fluid (ECF) that communicate with the outside environment (e.g., the gastrointestinal tract). In others, localized changes in Ca(o)(2+) within the ECF can originate from several mechanisms, including fluxes of calcium ions into or out of cellular or extracellular stores or across epithelium that absorb or secrete Ca(2+). In any event, the CaR and other receptors/sensors for Ca(o)(2+) and probably for other extracellular ions represent versatile regulators of numerous cellular functions and may serve as important therapeutic targets.

Risk of inadequate bone mineralization in diseases involving long-term suppression of dairy products

BACKGROUND

Eighty percent of peak bone mass should be achieved from birth through adolescence. An adequate calcium intake is essential, and it is advisable that 60% of the recommended calcium allowance be dairy calcium. This study was conducted to examine bone mineral content (BMC) in patients with diseases that usually involve long-term suppression of dairy products.

METHODS

Thirty patients, aged 2 to 14 years (mean, 7 years), 10 with late-onset, genetically induced lactose intolerance, 7 with cow's milk protein allergy, 3 with short-bowel syndrome, and 10 with hypercholesterolemia were involved in the study. They were receiving various dietary regimens for periods longer than 2 years: 14 patients received special formulas for children (lactose-free cow's milk formula, highly hydrolyzed cow's milk protein formula, soy protein isolate formula), 4 patients received liquid soy beverages, 6 patients received skim milk (1% fat), and 6 patients had exclusion of dairy products. Bone mineral density (BMD) was assessed by dual-energy x-ray absorptiometry.

RESULTS

Nine patients had osteoporosis, 6 had osteopenia, and 15 had results within normal ranges. Overall, the group had a standard deviation score of -1.3 (osteopenia). The statistical correlation between the BMD value and the percentage intake of recommended daily allowance (RDA) of dairy (or substitute) calcium (in milligrams per day) was highly significant (P < 0.0001, r = 0.89).

CONCLUSIONS

All patients with diseases involving total or partial withdrawal from milk products for a prolonged period are a group at potential risk of defective bone mineralization and should be monitored through BMD assessment.

Prostaglandin E2-induced up-regulation of c-fos messenger ribonucleic acid is primarily mediated by 3',5'-cyclic adenosine monophosphate in MC3T3-E1 osteoblasts

The mechanism by which the proto-oncogene, c-fos, is up-regulated in response to PGE2 in the mouse osteoblastic (MC3T3-E1) cell line was investigated using RT-PCR. c-fos messenger RNA up-regulation by dmPGE2 is rapid, starting 10 min post stimulation, and transient. The specific protein kinase A (PKA) inhibitor, H89, inhibited c-fos induction. Moreover, down-regulation of protein kinase C (PKC) activity by chronic TPA treatment had no effect on the induction of c-fos by dmPGE2. We conclude that up-regulation of c-fos by dmPGE2 is primarily dependent on PKA in MC3T3-E1 osteoblasts. In S49 lymphoma wild-type but not S49 cyc- cells, which are deficient in cAMP signaling, dmPGE2 up-regulates c-fos and increases cell growth compared with unstimulated cells. Thus in S49 lymphoma cells, c-fos induction by PGE2 is also dependent on cAMP signaling. The minimal c-fos promoter region required for dmPGE2-induced expression was identified by transfecting c-fos promoter deletion constructs coupled to the chloramphenicol acetyltransferase (CAT) reporter gene into Vero cells. Transfection of a plasmid containing 99 bp c-fos proximal promoter was sufficient to direct c-fos/CAT expression following stimulation with dmPGE2. Because induction of c-fos is mediated by cAMP, these data are consistent with activation of c-fos via the CRE/ATF cis element.

Identification of a novel parathyroid hormone-responsive gene in human osteoblastic cells

Parathyroid hormone (PTH) is a potent stimulator of osteoblastic cell function in vitro and bone resorption and formation in vivo; however, the details of the molecular mechanism(s) responsible for PTH action and the regulation of gene expression in response to PTH remain unknown. In this study, we employed an mRNA differential display (DRD) approach to examine the initial events in gene expression in human osteoblast-like SaoS-2/B10 cells exposed to 10(-7) mol/L bPTH(1-34). This approach identified several differentially regulated mRNA species, including a novel paired-class homeobox protein, osteoblast-specific factor-2 (OSF-2), and a unique clone with no known sequence homology (clone G18). G18 is a previously unidentified human gene, expressed in a wide variety of human tissues, including heart, brain, placenta, skeletal muscle, and kidney, and is regulated by PTH in osteoblastic cells in vitro. This mRNA appears to be the product of a single gene, which is alternatively spliced to produce multiple transcript sizes observed in several tissues, except bone and bone-derived cells, in which a single predominant approximately 1.8 kb transcript is observed. Our study has identified several genes that have expression altered significantly by treatment with bPTH(1-34), and which may provide insight into the immediate effects of PTH on osteoblast-like cells and ultimately on the mechanism of action and bioactivity of PTH.

Functional hierarchy between two OSE2 elements in the control of osteocalcin gene expression in vivo

Osteocalcin gene expression is initiated perinatally and is restricted to mature osteoblasts and odontoblasts. Because their pattern of expression is highly restricted, the osteocalcin genes are excellent tools to study osteoblast-specific gene expression. To define the mechanisms of osteocalcin cell-specific gene expression in vivo, we generated transgenic mice harboring deletion mutants of the promoter region of OG2, one of the mouse osteocalcin genes. We show here that only 647 base pairs of this promoter are sufficient to confer cell-specific and time-specific expression to a reporter gene in vivo. This promoter fragment contains two copies of OSE2. This osteoblast-specific cis-acting element binds Osf2, a recently characterized osteoblast-specific transcription factor (Ducy, P., Zhang, R., Geoffroy, V., Ridall, A. L., and Karsenty, G. (1997) Cell 89, 747-754). We also demonstrate that the proximal OSE2 element is critical to confer an osteoblast-specific, developmentally regulated pattern of expression to a reporter gene. The other OSE2 element, located more upstream and presenting a lower affinity for Osf2, affects only weakly OG2 promoter activity. These data demonstrate the crucial role of Osf2 in controlling osteocalcin gene expression. Since osteocalcin synthesis is a hallmark of the differentiated osteoblast phenotype, these results suggest that, beyond its developmental function, Osf2 is also required for the maintenance of the osteoblast phenotype postnatally.

Bone mineral density in prepubertal and in adolescent and young adult patients with the salt-wasting form of congenital adrenal hyperplasia

OBJECTIVE

To evaluate bone mineral density (BMD) in prepubertal and in adolescent and young adult patients with the salt-wasting form of congenital adrenal hyperplasia (CAH).

DESIGN

A relationship between bone mineral content and risk for osteoporotic fractures has been observed in adulthood. Infancy, childhood, and adolescence are critical periods for skeletal mineralization; thus, chronic diseases may impair bone mass peaking, particularly if children and adolescents are overexposed to glucocorticoids, as may occur in patients with CAH. Lumbar L2-L4 BMD values were measured by dual x-ray absorptiometry and compared with those of 471 age- and sex-matched controls.

PATIENTS

Thirty-three patients with the salt-wasting form of CAH were studied. Sixteen (10 girls and 6 boys; age range, 1.5 to 8.3 years) were prepubertal and 17 (13 women and 4 men; age range, 17.1 to 28.2 years) were adolescent and young adults who had reached final height and had presented normal pubertal development and normal gonadal function thereafter. The average doses of hydrocortisone (mg/m body surface/day) received from diagnosis in the neonatal period to BMD evaluation were 21.2 +/- 2.2 and 22.3 +/- 2.6, respectively.

RESULTS

Mean BMD Z score values were 0.16 +/- 1.01 in prepubertal patients and 0.06 +/- 1.02 in adolescent and young adult patients with no statistically significant differences with age- and sex-matched controls. Mean height Z score values were -0.03 +/- 1.13 in prepubertal patients and -1.13 +/- 0.62 in adolescent and young adult patients with significant differences between the latter and their respective age- and sex-matched controls.

CONCLUSION

Long-term glucocorticoid therapy does not impair bone mass peaking in CAH patients with normal gonadal function, even though their adult height values are low.

TGF-beta 1, TGF-beta 2, and TGF-beta 3 exhibit distinct patterns of expression during cranial suture formation and obliteration in vivo and in vitro

Cranial sutures function as bone growth centers while themselves remaining unossified. Rat frontonasal sutures become obliterated by neonatal day 21 (N21), while coronal sutures do not fuse over the life of the animal. Coronal sutures induced to undergo osseous obliteration in vitro after removal of the dura mater were found to require soluble, heparin-binding factors present in dura mater to resist osseous obliteration. Transforming growth factor beta 1 (TGF-beta 1), beta 2, and beta 3, heparin-binding factors known to regulate bone cell proliferation and differentiation, were considered likely candidates. The presence and distribution of these factors in calvarial tissues both in vivo and in vitro were established by immunohistochemical analysis, while reverse transcription followed by polymerase chain reaction (RT/PCR) was employed to determine the presence of transcripts for these factors in mRNA isolated from microdissected dura mater. Results indicated that the presence of TGF-beta 1 and TGF-beta 2 were associated with developing coronal and frontonasal sutures, and that the continued presence of these factors was associated with osseous obliteration of the frontonasal suture. However, increased TGF-beta 3 immunoreactivity was associated with the coronal suture remaining unossified. RT/PCR demonstrated the presence of transcripts for TGF-beta 1, beta 2, and beta 3 in dural tissues isolated from rat calvaria. These data support the notion of a role for TGF-beta s in regulating cranial suture morphogenesis and establish the in vitro model as a valid system for examining mechanisms by which growth factors regulate both suture morphogenesis and bone growth at the suture site.

Chick osteocyte-derived protein inhibits osteoclastic bone resorption

In order to investigate the role of osteocytes in bone resorption, we examined the homogenate and conditioned medium from purified chick calvarial osteocytes in a pit-formation assay using unfractionated bone cells from mice. The osteocyte homogenate markedly inhibited pit formation, whereas the conditioned medium of osteocytes had no effect. This inhibitory activity was not the result of cytotoxicity of the homogenate. A novel bone-resorption-inhibitory protein was purified from collagenase-digested chick calvarial fragments enriched in osteocytes. The inhibitory protein, of molecular mass 18.5 kDa, showed significant dose-dependent inhibition of pit formation by unfractionated bone cells from mice and rabbits, and by human giant tumour cells. This protein also inhibited the bone-resorbing activity of purified osteoclasts in the pit-formation assay in the absence of other effector cells. Microinjection of the protein into osteoclasts caused disruption of the podosomes in the cells. The N-terminal 25-amino-acid sequence of the protein showed 68% identity to a part of Rho-GTP-dissociation inhibitor. Thus chick calvarial osteocytes may be involved in the regulation of bone resorption by osteoclasts.

Effects of the calciotrophic peptides calcitonin and parathyroid hormone on prostate cancer growth and chemotaxis

BACKGROUND

The most common site of metastases in prostate cancer is the skeleton and occurs in 70-80% of patients with prostate carcinoma. Calciotrophic peptides are important in the growth and development of normal bone matrix.

METHODS

Three human prostate carcinoma cells lines, DU-145, PC-3, and LNCaP, were exposed to varying concentrations of parathyroid hormone (PTH) or calcitonin (CT). Cell proliferation and chemotaxis were assessed.

RESULTS

Proliferation increased in LNCaP cells in a dose-dependent manner following treatment with PTH. Proliferation was not altered in PC-3 cells in response to PTH. Proliferation was decreased in DU-145 and PC-3 cells and increased in LNCaP cells after treatment with CT. Cell chemotaxis was increased in the presence of PTH in DU-145 and PC-3 cells compared to vehicle-treated controls.

CONCLUSIONS

The combined proliferation and chemotaxis data suggest that PTH has a dual role in prostate carcinoma resulting in an increase in the number and migration of selected prostate cancer cells. With CT, chemotaxis was unchanged in the DU-145 and PC-3 cells and significantly elevated in the LNCaP cell line. The calciotrophic hormones, PTH and CT, may play an integral role in the regulation of prostate cell growth and metastases.

Biomechanical analysis of the effects of single high-dose vitamin D3 on fracture healing in a healthy rabbit model

In a previous ultrastructural study, the benefit of a single high dose of vitamin D3 on fracture healing in a healthy animal model was demonstrated. This study examined the biomechanical consequences of applying a single high dose of vitamin D3 in a healthy rabbit model subsequent to femoral fracture. The fracture load, the values of energy absorbed until fracture and the flexural rigidity values of the vitamin D group were significantly higher than the corresponding ones of the control group in the case of fracture. On the other hand, for intact bones, those values did not differ significantly between the two groups. It was concluded that single high-dose vitamin D3 application had positive effects on fracture healing in a healthy animal model, as far as the parameters related to mechanical strength are concerned.