Decreased Osteoblast Activity Research Articles

Developing In Vivo Model for Studying Mechanisms of Osteoblast Suppression in Multiple Myeloma.

Multiple myeloma (MM) is an incurable neoplastic disease characterized by an accumulation of plasma cells in bone marrow. Osteolytic bone lesions are the major source of morbidity in MM patients and are associated with bone pain and fractures and hypercalcemia. The bone lesions result from increased osteoclastic bone destruction in areas adjacent to the myeloma cells. New bone formation that normally happens at sites of previous bone resorption still occurs in early stages of the disease but is absent in advanced MM. Although the molecular basis for the increased osteoclastic activity has been intensely investigated, the basis for the decreased osteoblast activity is just beginning to be understood. Recently, inhibitors of WNT signaling pathway, Dickkorpf1 (DKK1) and secreted Frizzle-Related Protein-2 (sFRP2) have been identified as factors involved in osteoblast suppression in MM. In addition, IL-3 and IL-7 are increased in plasma of MM patients and suppress osteoblastogenesis in cell culture models. However, the role of those factors in the osteoblastic activity in MM patients is unclear. Studies in patients are confounded by cytotoxic therapy as well as bisphosphonates, which are standard therapy for MM patients. Therefore, preclinical in vivo models are required to delineate the mechanisms responsible for the profound osteoblast suppression in MM. We have developed a mouse model of myeloma bone disease in which genetically modified myeloma cells can be selectively ablated without the confounding effects of cytotoxic therapies and allows us to tract the growth of MM cells. The 5TGM1 cell line which is the most common version of murine MM, was stably transfected with the thymidine kinase (TK) gene from herpes simplex virus, which permits eradication of myeloma cells with ganciclovir, as well as GFP and luciferase genes to detect the presence of MM cells. One ug/ml ganciclovir treatment in culture results in 100% death of the transfected 5TGM1 cells in 4 days. Importantly, ganciclovir treatment of primary marrow cell cultures had no effect on growth and differentiation of osteoblast and hematopoietic progentitors. Co-culturing of primary marrow cells with 5TGM1 expressing TK has no bystander effect on osteoblast differentiation with ganciclovir treatment. Subcutaneously implanted 5TGM1 cells into SCID mice were eradicated by intraperitoneal injection of 20mg/kg ganciclovir/d for 2 weeks. The dose of ganciclovir did not affect osteoblast differentiation of primary marrow culture from the mice treated with ganciclovir. Then we injected the 5TGM1 cells into tibia of SCID nude mice (n=4 per group). After measuring the increase of serum IgG2b level, half of the mice were treated with ganciclovir for 2 weeks and the other with saline. Our preliminary data show that osteogenic cultures of bone marrow from the ganciclovir treated mice had significantly higher alkaline phosphatase activity than cultures derived from the saline treated group (p=0.03). In addition, the ganciclovir treated mice had tendency of higher trabecular bone volume than the saline-treated group (p=0.08). These results demonstrate that this model should be useful for studying mechanisms of osteoblast suppression in MM.

Zinc-Finger Transcription Factor Odd-Skipped Related 2 Is One of the Regulators in Osteoblast Proliferation and Bone Formation

We report that Osr2 is one of the regulators of osteoblast function, because dominant-negative Osr2 transgenic mice exhibited decreased osteoblast activity and delayed mineralization in calvarial and tibial bone tissues. Our results indicate that Osr2 functions in regulation of osteoblast proliferation. Molecular mechanisms that control bone formation have received attention with increasing knowledge related to genetic control of osteoblast differentiation. The odd-skipped related (Osr) gene is a zinc-finger transcription factor recently suggested to be involved in bone formation, although little is known about its role. To elucidate the in vivo function of Osr2, we generated transgenic mice overexpressing dominant-negative Osr2. In this study, N-terminal-deleted Osr2 was found to act as a dominant-negative mutant toward both Osr1 and Osr2. Dominant-negative Osr2 (Osr2DeltaN) transgenic mice showed delayed mineralization in calvarial and cortical bone tissues. Furthermore, soft X-ray analysis of transgenic mice bones revealed distinctly increased radiolucency. Examinations of newborn Osr2DeltaN transgenic mice skeletons stained with alcian blue and alizarin red showed reduced intensities in the skull and skeletal elements. Morphologically, calvariae and tibias of Osr2DeltaN transgenic mice were composed of markedly thinner parietal and cortical bones and lower numbers of osteoblastic cells on bone surfaces, indicating a reduced proliferation of osteoblasts. Furthermore, calvarial osteoblasts obtained from Osr2DeltaN transgenic mice showed highly attenuated osteoblast differentiation and proliferation, confirming that Osr2 is needed for osteogenesis. Finally, results of Runx2-deficient cell assays suggested that Osr2 induces alkaline phosphatase (ALP) expression, but to a lesser degree than Runx2-expressing cells. Our genetic observations showed that the Osr2 gene plays a key role in osteoblastic cell proliferation.

Leptin Inhibits Bone Formation Not Only in Rodents, but Also in Sheep

This study examines the effect of long-term ICV administration of leptin in ewes. We found that central application significantly decreased osteoblast activity as measured by serum analysis as well as by histomorphometry, resulting in decreased trabecular bone volume. These data provide additional evidence that bone formation and therefore bone remodeling is at least in part centrally controlled. Genetic studies in mice have identified leptin as a potent inhibitor of bone formation acting through the central nervous system and unraveled the central nature of bone mass control and its disorders. Although these studies have radically enhanced our understanding of skeletal physiology because they have established a hypothalamic regulation of bone remodeling through the sympathetic nervous system, controversy remains about the physiological relevance of these observations because leptin's effect on bone after intracerebroventricular (ICV) application has only been shown in mice. To address whether leptin has a role in regulating bone mass beyond rodents, we treated ewes with long-term ICV application of leptin and analyzed the bone phenotype after a treatment period of 3 months. Three groups of corriedale sheep were compared: (1) control entire (control), (2) ovariectomy (OVX) and ICV application of cerebrospinal fluid (CSF); and (iii) OVX and ICV application of leptin (leptin). Analysis included histomorphometric characterization of iliac crest, spine and femur by histology and biomechanical testing and measurement of bone turnover parameters in serum and urine. Central application of leptin decreased bone formation by 70% and mineralizing surface (MS/BS, 39.4 +/- 3.3% versus 16.1 +/- 2.1%) significantly (p < 0.01). Whereas OVX increased osteoclast indices and urinary cross-lap excretion by two and three times, respectively, serum parameters of osteoblast activity were significantly reduced by ICV application of leptin (p < 0.01). Consequently, ewes treated with leptin were osteopenic (iliac crest BV/TV entire, 22.7 +/- 1.3%; CSF, 18.9 +/- 2.4%; leptin, 12.4 +/- 2.6%), whereas bone torsional failure load reflecting the cortex of the tibia was not yet changed after 3 months of treatment (p < 0.01). Taken together, these data suggest that leptin controls bone formation after ICV application, leading to reduction of trabecular bone mass in sheep. Most importantly, however, they show that the central regulation of bone formation is not limited to rodents, but is also found in large animals, providing further evidence that bone remodeling in vertebrates is centrally controlled.

Fhl2 deficiency results in osteopenia due to decreased activity of osteoblasts

Osteoporosis is one of the major health problems today, yet little is known about the loss of bone mass caused by reduced activity of the bone-forming osteoblasts. Here we show that mice deficient for the transcriptional cofactor four and a half LIM domains 2 (Fhl2) exhibit a dramatic decrease of bone mass in both genders. Osteopenia is caused by a reduced bone formation rate that is solely due to the diminished activity of Fhl2-deficient osteoblasts, while their number remains unchanged. The number and activity of the bone-resorbing cells, the osteoclasts, is not altered. Enforced expression of Fhl2 in differentiated osteoblasts boosts mineralization in cell culture and, importantly, enhances bone formation in transgenic animals. Fhl2 increases the transcriptional activity of runt-related transcription factor 2 (Runx2), a key regulator of osteoblast function, and both proteins interact in vitro and in vivo. In summary, we present Fhl2-deficient mice as a unique model for osteopenia due to decreased osteoblast activity. Our data offer a novel concept to fight osteoporosis by modulating the anabolic activity of osteoblasts via Fhl2.

FIAT represses ATF4-mediated transcription to regulate bone mass in transgenic mice

We report the characterization of factor inhibiting activating transcription factor 4 (ATF4)–mediated transcription (FIAT), a leucine zipper nuclear protein. FIAT interacted with ATF4 to inhibit binding of ATF4 to DNA and block ATF4-mediated transcription of the osteocalcin gene in vitro. Transgenic mice overexpressing FIAT in osteoblasts also had reduced osteocalcin gene expression and decreased bone mineral density, bone volume, mineralized volume, trabecular thickness, trabecular number, and decreased rigidity of long bones. Mineral homeostasis, osteoclast number and activity, and osteoblast proliferation and apoptosis were unchanged in transgenics. Expression of osteoblastic differentiation markers was largely unaffected and type I collagen synthesis was unchanged. Mineral apposition rate was reduced in transgenic mice, suggesting that the lowered bone mass was due to a decline in osteoblast activity. This cell-autonomous decrease in osteoblast activity was confirmed by measuring reduced alkaline phosphatase activity and mineralization in primary osteoblast cultures. These results show that FIAT regulates bone mass accrual and establish FIAT as a novel transcriptional regulator of osteoblastic function.

NATURALLY OCCURRING SECONDARY NUTRITIONAL HYPERPARATHYROIDISM IN CATTLE EGRETS (BUBULCUS IBIS) FROM CENTRAL TEXAS

Naturally occurring secondary nutritional hyperparathyroidism is described in the nestlings of two colonies of cattle egrets (Bubulcus ibis) from Central Texas (Bryan and San Antonio, Texas, USA). Nestlings from a third colony (Waco, Texas, USA) were collected in a subsequent year for comparison. Birds from the first two colonies consistently had severe osteopenia and associated curving deformities and folding fractures of their long bones. These birds also had reduced bone ash, increased osteoclasia, a marked decrease in osteoblast activity, variable lengthening and shortening of the hypertrophic zone of the epiphyseal cartilage, decreased and disorganized formation of new bone, and a marked hypertrophy and hyperplasia of the parathyroid glands as compared to birds collected from the third colony. Fibrous osteodystrophy was found in all of the birds from San Antonio and Bryan. Evidence of moderate to severe calcium deficiency was also identified in 33% of the cattle egrets collected from Waco. Gut contents of affected chicks contained predominately grasshoppers and crickets; vertebrate prey items were absent from the Bryan birds. Grasshoppers and crickets collected from fields frequented by the adult egrets in 1994 had 0.12-0.28% calcium and 0.76-0.81% phosphorus. Pooled grasshoppers and crickets collected during a subsequent wet early spring averaged 0.24% calcium and 0.65% phosphorus. Although the phosphorus content of the insect prey was adequate for growth, calcium was approximately one-third the minimum calcium requirement needed for growth for other species of birds. It was postulated that cattle egrets breeding in Central Texas have expanded their range into habitat that contains less vertebrate prey, and as a result, many nestling egrets are being fed diets that contain suboptimal calcium. Therefore, in years where vertebrate prey is scarce and forage for insect prey is reduced in calcium, nestling egrets are at risk for developing secondary nutritional hyperparathyroidism.

Bone Loss Induced by Dietary Magnesium Reduction to 10% of the Nutrient Requirement in Rats Is Associated with Increased Release of Substance P and Tumor Necrosis Factor-α

Dietary Mg intake has been linked to osteoporosis. Previous studies have demonstrated that severe Mg deficiency [0.04% of nutrient requirement (NR)] results in osteoporosis in rodent models. We assessed the effects of more moderate dietary Mg restriction (10% of NR) on bone and mineral metabolism over a 6-mo experimental period in rats. At 2, 4 and 6 mo, serum Mg, Ca, parathyroid hormone (PTH), 1,25-dihydroxy-vitamin D, alkaline phosphatase, osteocalcin and urine pyridinoline were measured. Femurs and tibiae were collected for measurement of mineral content, microcomputerized tomography, histomorphometry, and immunocytochemical localization. By 2 mo, profound Mg deficiency had developed as assessed by marked hypomagnesemia and up to a 51% reduction in bone Mg content. These features continued through 6 mo of study. Serum Ca was slightly but significantly higher in Mg-deficient rats than in controls at all time points. At 2 mo, serum PTH was elevated in Mg-deficient rats but was significantly decreased at 6 mo in contrast to control rats in which PTH rose. Serum 1,25-dihydroxy-vitamin D was significantly lower than in controls at 4 and 6 mo. A significant fall in both serum alkaline phosphatase and osteocalcin suggested decreased osteoblast activity. Histomorphometry demonstrated decreased bone volume and trabecular thickness. This was confirmed by microcomputerized tomography analysis, which also showed that trabecular volume, thickness and number were significantly lower in Mg-deficient rats. Increased bone resorption was suggested by an increase in osteoclast number over time compared with controls as well as surface of bone covered by osteoclasts and eroded surface, but there was no difference in osteoblast numbers. The increased bone resorption may be due to an increase in TNF-alpha because immunocytochemical localization of TNF-alpha in osteoclasts was 199% greater than in controls at 2 mo, 75% at 4 mo and 194% at 6 mo. The difference in TNF-alpha may be due to substance P, which was 250% greater than in controls in mononuclear cells at 2 mo and 266% at 4 mo. These data demonstrated that a Mg intake of 10% of NR in rats causes bone loss that may be secondary to the increased release of substance P and TNF-alpha.

Reversible skeletal abnormalities in gamma-glutamyl transpeptidase-deficient mice.

Gamma-glutamyl transpeptidase (GGT) is a widely distributed ectopeptidase responsible for the degradation of glutathione in the gamma-glutamyl cycle. This cycle is implicated in the metabolism of cysteine, and absence of GGT causes a severe intracellular decrease in this amino acid. GGT-deficient (GGT-/-) mice have multiple metabolic abnormalities and are dwarf. We show here that this latter phenotype is due to a decreased of the growth plate cartilage total height resulting from a proliferative defect of chondrocytes. In addition, analysis of vertebrae and tibiae of GGT-/- mice revealed a severe osteopenia. Histomorphometric studies showed that this low bone mass phenotype results from an increased osteoclast number and activity as well as from a marked decrease in osteoblast activity. Interestingly, neither osteoblasts, osteoclasts, nor chondrocytes express GGT, suggesting that the observed defects are secondary to other abnormalities. N-acetylcysteine supplementation has been shown to reverse the metabolic abnormalities of the GGT-/- mice and in particular to restore the level of IGF-1 and sex steroids in these mice. Consistent with these previous observations, N-acetylcysteine treatment of GGT-/- mice ameliorates their skeletal abnormalities by normalizing chondrocytes proliferation and osteoblastic function. In contrast, resorbtion parameters are only partially normalized in GGT-/- N-acetylcysteine-treated mice, suggesting that GGT regulates osteoclast biology at least partly independently of these hormones. These results establish the importance of cysteine metabolism for the regulation of bone remodeling and longitudinal growth.

Prévention et traitement de l’ostéoporose cortisonique

Purpose. – Corticosteroid induced osteoporosis (CIO) is the most frequent complication of long-term corticosteroid therapy, and the most frequent cause of secondary osteoporosis. New data from biological, epidemiological and therapeutic studies provide basis for optimal management of this bone disease. Main points. – Corticosteroids are responsible for both quantitative and qualitative deleterious effects on bone, through their effect on bone cells, mainly on osteoblasts (with both a decrease in osteoblast activity and an increase in apoptosis). Epidemiological studies have shown an increased risk of fractures related to CIO, even for low doses, and during the first 6 months of treatment. Relative risk is 1.3 and 2.6 for peripheral and vertebral fractures respectively. Bone mineral density, measured by dual-energy X-ray absorptiometry, is decreased at spine and hip; the risk of fracture is higher in CIO as compared to post-menopausal osteoporosis, for a similar bone density. Prevention of CIO needs the use of the minimal efficacious dose, and treatment of calcium, vitamin D and gonadal hormones insufficiencies. Patients at risk of fracture, as post-menopausal women with prevalent fractures, should receive a bisphosphonate. Perspective. – It may be possible to reduce the fracture risk in patients on long-term corticosteroid therapy.

Steroid-induzierte Osteoporose: Pathogenese und therapeutische Konsequenzen

Many chronic inflammatory diseases require treatment with steroids, however, a remarkable proportion of steroid-treated patients suffer from osteoporosis as major complication after longterm treatment. Steroid-induced osteoporosis represents one of the most important secondary causes of osteoporosis. The pathogenesis is complex, there exists evidence that steroids cause a reduction of circulating testosterone and estrogen concentration and adversely affect calcium balance. The most important mechanism is a decrease in osteoblastic activity. As a consequence loss of bone mineral density and increased risk of fracture develop. In spite of better understanding of the causal relationships preventive strategies were infrequently applied. If we care for patients with steroid therapy we have both to consider the problem of steroid-induced osteoporosis and to focus on strategies to evaluate patients at risk. The dosage of the steroid, life style factors (such as lack of exercise, alcohol consumption and smoking), menopausal status, low bone mineral density at baseline and previous osteoporotic fractures predispose for the manifestation of steroid-induced osteoporosis. Therapeutic decisions depend on risk factors of the individual patient. Supplementation of calcium and vitamin D is usually appropriate, and postmenopausal women should be offered hormone replacement therapy. The prescription of bisphosphonates is strongly recommended to patients at elevated risk.

Carnitine and dehydroepiandrosterone sulfate induce protein synthesis in porcine primary osteoblast-like cells.

Age-related bone loss eventually leads to osteopenia in men and women. The etiology of age-related bone loss is currently unknown; however, decreased osteoblast activity contributes to this phenomenon. In turn, osteoblast proliferation and function is dependent on energy production, thus the loss of energy production that occurs with age may account for the deficient osteoblast activity. Carnitine and dehydroepiandrosterone-sulfate (DHEAS), both of which decline with age, promote energy production through fatty acid metabolism. Thus, we hypothesized that carnitine and DHEAS would increase osteoblast activity in vitro. Accordingly, we measured the effect of carnitine and DHEAS on palmitic acid oxidation as a measure of energy production, and alkaline phosphatase (ALP) activity and collagen type I (COL) as indices of osteoblast function in primary porcine osteoblast-like cell cultures. Carnitine (10(-3) and 10(-1) M) but not DHEAS (10(-9), 10(-8), and 10(-7) M) increased carnitine levels within the cells. Carnitine alone and in combination with DHEAS increased palmitic acid oxidation. Both carnitine and DHEAS alone and in an additive fashion increased ALP activity and COL levels. These results demonstrate that in osteoblast-like cells in vitro, energy production can be increased by carnitine and osteoblast protein production can be increased by both carnitine and DHEAS. These data suggest that carnitine and DHEAS supplementation in the elderly may stimulate osteoblast activity and decrease age-related bone loss.

Decreased osteoblast activity in spontaneously diabetic rats. In vivo studies on the pathogenesis.

Diabetes in both humans and rats is accompanied by low bone formation, which is presumably caused by serum-borne factors. To explore its pathogenesis, we carried out experiments in diabetic and nondiabetic BB rats, using plasma osteocalcin concentrations (OC) as a marker for osteoblast activity. In nondiabetic rats, the i.v. infusion of glucose (30%, 4 d) did not change OC; s.c. insulin infusion (4 U/d, 14 d) reduced OC by 27% (p < 0.01). In diabetic rats, OC were decreased from the first day of glycosuria (71 +/- 5% of paired controls), declining exponentially to 24 +/- 3% after 5 wk. Insulin infusion (1, 2, and 3 U/d, 14 d) produced gradual restoration of OC. OC were better correlated with insulin-like growth factor-I (IGF-I) than with insulin levels in these experiments. OC were dramatically increased 4 d after adrenalectomy (ADX) in all diabetic rats (73 +/- 8 vs 22 +/- 4 micrograms/L before ADX; p < 0.001), but not if corticosterone was administered. Ligand blotting of IGF binding proteins showed a marked decrease in two bands (44-49 and 32-35 kDa) 10-14 d after diabetes onset; the density of these bands was increased, but not normalized after ADX. Thus, decreased osteoblast activity is present from the onset of diabetes, is dependent on endogenous corticosterone, and cannot be reproduced by hyperglycemia in nondiabetic rats.

Management of corticosteroid-induced osteoporosis. UK Consensus Group Meeting on Osteoporosis.

Corticosteroid therapy results in osteoporosis. There is a doubling in the risk of fracture in patients taking more than the equivalent of 7.5 mg day-1. The bone loss is most rapid from the axial skeleton, particularly during the 1st year of therapy. The most important mechanism for the bone loss is a decrease in osteoblastic activity. Preventative strategies should be targeted to patients with low bone-mineral density, especially if the dose of corticosteroids is likely to be high. Treatment strategies agreed on by the Consensus Panel included hormone replacement therapy and bisphosphonates, with monitoring of efficacy by bone densitometry.

The in vivo histology of an absorbable suture anchor: a preliminary report

Suture anchors are playing an increasingly important role in attaching tendons or ligaments to bone. Anchors are usually made of metallic or other nonbioabsorbable materials. The development of an absorbable suture anchor would provide a valuable tool for the surgeon; this characteristic would minimize the problems of anchor loosening, migration, interference with imaging studies, and the potential requirement for later implant removal. This study evaluated the in vivo histological response over time of the first generation Arthrex Expanding Suture Plug (ESP) (Arthrex Inc, Naples, FL). Suture anchors threaded with nonab- sorbable No. 2 braided polyester sutures were implanted into ram femurs and removed at various intervals over a period of 12 weeks. After preparation, histological study showed a gradual healing response in the bone tract. There was no evidence of an inflammatory infiltrate or foreign-body reaction during the 12 weeks of implantation. A normal bone callus appeared at the insertion tunnel site consistent with a fracture-healing response. Later, a fibrous membrane appeared at the junction of the implant and the bone tunnel. Over the 12 week interval, there was a decrease in osteoblastic activity and the appearance of cavernous vascular spaces in the superficial portions of the membrane near the periosteum. The ESP anchor composed of poly-L-lactic acid was well tolerated in the in vivo setting. Throughout the study, no substantial acute, chronic, or foreign-body reaction was observed. These observations are consistent with the expected in vivo behavior of poly-L-lactic acid. There is no reason to believe that the ESP composed of poly-L-lactic acid should cause a foreign body reaction.

Decreased mitogenic and osteogenic responsiveness of calvarial osteoblasts isolated from aged rats to basic fibroblast growth factor.

Osteoporosis seen in aged individuals is represented by the reduced bone mass most likely resulting from decreased bone formation by osteoblasts. To examine whether aging causes a decrease in osteoblast activity, calvarial osteoblasts were isolated from aged rats (AOB) and studied for the capacity of the cells to form mineralized bone-like nodules in comparison with that of fetal calvarial osteoblasts (FOB). There were no significant differences in basal mineralized bone-like nodule formation determined by quantifying the size of the nodules which were formed in the cultures of AOB and FOB. However, the responsiveness of AOB to growth factors was profoundly reduced. AOB showed only marginal increase in mineralized bone-like nodule formation and growth in response to basic fibroblast growth factor (bFGF). On the other hand, bFGF markedly promoted mineralized bone-like nodule formation and proliferation in FOB. These results suggest that decreased responsiveness to local osteotropic growth factors such as bFGF might account for the reduced bone formation by aged osteoblasts, which in turn leads to the loss of bone mass characteristic for senile osteoporosis.

Idiopathic osteoporosis during pregnancy

Among the idiopathic forms of osteoporosis, the one developing during pregnancy is the least common and scarcely studied. Poorly understood, it seems to stem from transient failure of calcitropic hormones and decreased osteoblast activity. A 25-year-old patient presented with coxofemoral pain during the last three months of pregnancy, followed by multiple vertebral compression fractures at postpartum. Laboratory, radiological, densitometric and histological examinations led to a diagnosis of idiopathic osteoporosis in pregnancy, once other causes of osteopenia had been ruled out. Bone densitometries performed 12 and 24 months later showed an increase in mineral density, thus demonstrating the self-limited nature of this entity.

Bone Mastocytosis A Report of Nine Cases With a Bone Histomorphometnc Study

Bone mastocytosis is characterized radiographically in some patients by diffuse osteosclerosis and in others by demineralization. The reason for these apparently conflicting bone features is unknown. Bone remodeling and marrow mastocytosis infiltration were studied in nine cases of mastocytosis with bone marrow involvement. Six men, ranging from 42 to 78 years of age, and three women, 43, 55, and 73 years old, comprised the series. Two patients had severe and diffuse osteosclerosis. Seven had diffuse demineralization, with crushed vertebrae in four, suggesting common osteoporosis. In three of the seven, cutaneous mastocytosis was absent. Bone biopsies were undecalcified and stained with toluidine blue. In the seven patients with demineralization, the number of marrow mastocytes was increased (154 +/- 24 versus 2 +/- 0.5/mm2 in normal postmenopausal osteoporosis). Mastocyte nodules covering 1-9% of the marrow area were present in all seven patients. These patients showed a significant increase in remodeling; bone formation rate was increased, coupled with a decrease in mean wall thickness. Concomitantly, osteoclast surfaces were increased, with an increased amount of bone resorbed. The two patients with diffuse osteosclerosis had a markedly different histology; mast cell infiltration was dramatically increased (mastocyte count greater than 1000/mm2) with diffuse marrow fibrosis. Bone volume was increased as well, and most of the bone was woven with an intratrabecular mineralization defect. High bone remodeling and decreased osteoblast activity can explain bone loss in mastocytosis with demineralization. Mastocytosis with osteosclerosis is characterized by a more extensive marrow mast-cell infiltration and fibrosis.

Influence of experimental liver injury on rat blood and alveolar bone under stress.

Experimental liver injury was induced to test rats with a daily injection of thioacetamide (ThAA). The doses used for intraperitoneal administrations were 50 mg/kg body weight. The loss of body weight in the 3-week test period was 15%. In the liver there was seen progressive changes which displayed cell necrosis and regeneration. The influence of ThAA on rat blood and serum was checked using standard biochemical assays consisting of the percentage of blood obtainable and the serum/blood ratio and analysis of serum alanine transferase, serum alkaline phosphatase, serum creatinine, and hydroxyproline in the acute, subacute, chronic, and necrotic stage of liver injury. With ThAA injections, the stimulated rate of glycosaminoglycan synthesis had its association to the serum calcium content. It decreased continuously as function of traumatization time. In the 3-week test period, histological findings show in the alveolar bone, around the teeth, when under occlusal stress and ThAA traumatization, the distinct decrease in osteoblastic activity and less osteoids indicating thus the decreased formation of new bone. Conspicuous osteoclastic resorption was also seen in the same area.

Radiology and histopathology of lameness in young cattle with secondary copper deficiency

The radiographical and histological lesions found in a natural outbreak of lameness in cattle, suffering form copper deficiency associated with high dietary molybdenum and sulphate, are described. Consistent lesions in the distal metacarpal or metatarsal growth plates were characterized radiographically by a widening of the physis with marked irregularity and fragmentation of the metaphysis. Microscopically, focal widenings of the growth plate consisted of tongues of uncalcified cartilage with delayed or impaired provisional calcification in the presence of active osteoblasts. It was concluded that molybdenum-induced copper deficiency in cattle is possibly not the same syndrome as primary copper deficiency of dogs, pigs and sheep, which is characterized by decreased osteoblast activity and osteoporosis.

Bone as a Tissue

This book reports papers read at the annual research conference at the Lankenau Hospital in October, 1958. Topics were osteoporosis, dynamics of calcium metabolism, ultrastructure of bone, and vitamin D, the parathyroids, citric acid, calcium, and phosphorous in relation to bone. Concepts on osteoporosis are well presented. In the osteoporosis that is so prominent a part of Cushing's syndrome, histologically (decalcified, stained bone sections) the upset in the balance of bone formation and destruction appears to be a decrease in osteoblastic activity, there being no increase in osteoclasis. This contrasts with the exaggeration of osteoclasis seen in renal failure and of both osteoblastic and osteoclastic activity in primary hyperparathyroidism. Cushing's syndrome from exogenous glucocorticoids is associated with hypercalcuria. Undecalcified cross-sections of cortical bone studied by microradiography and microautoradiography showed the osteoporosis of Cushing's to be morphologically similar to spontaneous senile osteoporosis. From the morphologic findings the lesion in osteoporosis appears