[Osteogenesis induced by the combination of growth factor, fibrin glue and coral; towards a substitute of autologous bone graft. An experimental study on the rabbit]

A triple mixture of TGF-beta, fibrin glue and natural coral skeleton granules (madreporic calcium carbonate) was tested in a rabbit bilateral cranioplasty model. Three-dimensional CT scan and histomorphometry demonstrated that, at one month and at two months, this association produced significantly more bone tissue than other associations, especially growth factor or coral alone. The rate of mineralization was significantly increased bilaterally in all animals having received TGF-beta. Coral resorption was also accelerated by growth factor and was replaced by histologically normal bone after two months. We emphasize the potentiation of TGF-beta by fibrin glue and natural coral skeleton and its potential application as a bone substitute.

Potentiation of transforming growth factor (TGF-beta 1) by natural coral and fibrin in a rabbit cranioplasty model

The association of a biodegradable material and a growth factor could be of clinical value for treating bone defects. We therefore tested the association of transforming growth factor beta (TGF-beta 1) in fibrin glue and coral granules to heal skull defects in rabbits. Adult rabbits underwent a double trepanation symmetrically in both parietal bones. Using histomorphometry, we compared bone repair after 1 month in control animals (n = 5) and in animals treated with either TGF-beta 1 as a single injection of 1 microgram in methylcellulose (n = 5) or in fibrin glue (n = 5), or with coral granules in fibrin glue (n = 4) or with coral granules and TGF-beta 1 1 microgram in fibrin glue (n = 5). We measured the diameter of the remaining defect and the surface of the bone growth. TGF-beta 1 without coral in either methyl cellulose or fibrin induced a partial closure of the defect as assessed by a significant decrease in the defect diameter, compared with the control group. However, the association of TGF-beta 1 in fibrin and coral induced an area of the bone growth higher than in any other groups (P < 0.05). Two months after surgery, this triple association induced a better healing of the defect than coral alone or control group. In each group treated with TGF-beta 1, the mineralization rate was increased not only at the treated side but also in the contralateral defect which was untreated, suggesting a diffusion of the growth factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Biologic, histologic and densitometric effects of oral risedronate on bone in patients with multiple myeloma

Recent studies have shown that treatment with bisphosphonates could be effective against the myelomatous skeletal deterioration. However, the mechanisms of action of these drugs in multiple myeloma (MM) have been poorly studied. In the present study, 11 patients with MM and bone lesions were treated orally with 30 mg/day of risedronate for 6 months, and monitored for 6 additional months. Mean serum calcium decreased from day 4, with a concomitant increase in circulating levels of PTH (1-84) and 1,25-(OH)2D. These parameters reached their nadir on day 7 and returned to baseline value during the treatment period. Markers of bone resorption, pyridinoline and deoxypyridinoline decreased from day 7; they were at 50% and 78% of their basal value at the end of treatment and follow-up periods, respectively. A significant reduction of estimates of bone formation (serum alkaline phosphatase and osteoclacin) appeared at month 3 and persisted for the remainder of the 9-month period. Histomorphometric analysis showed a significant reduction of activation frequency, number of osteoclasts and erosion depth. Bone turnover was high at baseline, and normal after treatment, without mineralisation defects. Mean wall thickness was not different before and after treatment. Spinal bone mineral density measured by dual energy X-ray absorptiometry increased (5.3%) at the end of treatment. We conclude that oral risedronate in multiple myeloma induces a noticeable and rapid inhibition of bone resorption.

Peripheral monocyte culture supernatants of menopausal women can induce bone resorption: involvement of cytokines

Increased bone resorption is a mechanism contributing to bone loss in the postmenopausal period. Cytokines are involved in osteoclastic differentiation and, therefore, may play a role in the regulation of bone resorption. Several previous works showed the implication of interleukin-1 (IL-1), IL-6, and tumor necrosis factor-alpha (TNF alpha) in the modulation of bone remodeling. This study determines the concomitant production of the three cytokines and tests the bone-resorbing activity of peripheral monocyte supernatants. Four groups of women were studied: premenopausal women (n = 13; mean age, 47 +/- 0.9 yr), untreated postmenopausal women (n = 21; mean age, 52 +/- 0.6 yr), postmenopausal women treated with estrogens (n = 14; mean age, 54.2 +/- 1.1 yr), or postmenopausal women treated with ethanehydroxydiphosphonate (n = 12; mean age, 53.2 +/- 2 yr). Assignment to clinical groups was verified by plasma FSH and estradiol determinations. Lumbar spine bone mineral density was significantly higher in the premenopausal women group than in the three postmenopausal groups. Peripheral blood monocytes were cultured for 48 h with 20% autologous plasma, and after stimulation with lipopolysaccharides. IL-1, IL-6, and TNF alpha levels were measured by RIA in the monocyte surpernatants. The three cytokines were highly correlated to each other, IL-1 with IL-6 (r = 0.76; P < 0.001), IL-1 with TNF alpha (r = 0.89; P < 0.001), and IL-6 with TNF alpha (r = 0.89; P < 0.001). The mean levels of the three cytokines could not be compared because of the variations in the values. However, a trend toward lower levels in the three cytokines was noted in estrogen-treated women compared to the untreated postmenopausals. The bone-resorbing activity of monocyte supernatants, assessed by fetal long bone-resorbing assay, increased in untreated postmenopausal compared to that in premenopausal women (1.22 +/- 0.08 vs. 0.87 +/- 0.11; P < 0.05). In estrogen-treated patients, this activity decreased to premenopausal levels (0.89 +/- 0.04 vs. 0.87 +/- 0.11; P = NS). The resorbing activity was correlated to IL-1 (r = 0.28; P = 0.03), IL-6 (r = 0.52; P < 0.01), and TNF alpha (r = 0.48; P < 0.01). The addition of cytokine inhibitors and IL-1 receptor antagonist and TNF alpha antibodies to the supernatant bone culture medium induced a significant decrease in the calcium release. Those data show the involvement of several cytokines in the bone resorption process after estrogen deficiency.

Polymerase chain reaction analysis of parathyroid hormone-related protein gene expression in breast cancer patients and occurrence of bone metastases

Parathyroid hormone-related protein (PTHrP) is associated with the syndrome of humoral hypercalcemia of malignancy. A high incidence of positive staining for PTHrP is observed in breast cancer and positivity is more frequent in patients who develop bone metastases. We assessed the presence of PTHrP mRNA by using the polymerase chain reaction in 38 normocalcemic breast cancer patients with long-term follow-up (minimum, 5 years) selected for the presence or absence of later bone metastasis development. In all the patients except one, the PTHrP gene was expressed in the breast tumor. The level of amplified PTHrP complementary DNA was inversely related to age (P < 0.02) and positively related to the proportion of invaded nodes (P < 0.02) but was not related to the other usual prognostic factors. The level of PTHrP mRNA was not different between the group of patients without recurrence or metastases (n = 11) and the group of patients who later developed metastases in soft tissues (n = 10). By contrast, patients who subsequently developed bone metastases (n = 17) showed higher PTHrP gene expression than patients in the other two groups (P < 0.001). This study suggests that strong PTHrP gene expression in breast tumors is associated with the onset of bone metastases.

Bone cytokines

Cytokines and growth factors are important in bone tissue as mediators of cell-to-cell and matrix-to-cell communication. Cytokines also locally mediate the effects of several hormones on bone cells. Indeed, calciotropic hormones modulate the bone-cell production rate of these factors and, conversely, can change the number of receptors for these hormones on bone cells. Most cytokines are active in bone, but the existence of a bone-specific cytokine is still questioned. Recent work has searched for estradiol modulation of osteoblastic cytokine acting on osteoclast differentiation. In mice, increased interleukin-6 production by osteoblasts is responsible for increased bone resorption occurring after ovariectomy. Interleukin-6 could also be an autocrine or paracrine factor in the pathogenesis of increased resorption occurring in giant cell tumor or in Paget's disease. During osteoporosis and age-related bone changes, modifications of the production of insulin-like growth factor I or of one of its binding proteins could be responsible for low bone formation. Interrelationships between cytokines and hormones can affect the action of parathyroid hormone-related peptide on bone cells. The field of implication of cytokines in metabolic bone disease is growing.

Influence of calcium and vitamin D deficient diet on calcitonin gene expression in the ultimobranchial cells of the developing chicken

Recently hatched chickens were fed a vitamin D and calcium deficient diet for 4 weeks. Calcitonin (CT) biosynthesis in the ultimobranchial glands (UBG) was studied during the treatment by means of in situ hybridization of specific CT mRNAs and immunocytochemical detection of the CT intracellular stores. Circulating CT levels were measured by radioimmunoassay. Within 1 week of the start of treatment, the deficient animals had significantly lowered plasma calcium concentrations and a dramatic fall of plasma CT levels, but the UBGs were not much affected. From week 2 to week 4, the UBG underwent a gradual atrophy. The tissue became lacunar due to the presence of an abnormally developed cystic component. Although calcemia returned to normal at week 4, the cellular endocrine cords were dramatically reduced, corresponding to the undetectable circulating CT levels. However, the UB glands always contained persistent CT-secreting cells, mainly at the periphery of the tissue or in contact with enlarged parathyroid tissue inclusions. These endocrine UB cells contained large amounts of hybridizable CT mRNA and immunodetectable stores of the mature hormone, and their ultrastructural features were quite unaffected compared to normal ones. Thus, we conclude that, in the chicken, severe calcium malnutrition led to a striking reduction of CT biosynthesis in the UB glands by decreasing the number of secretory cells and not by triggering modifications of the biosynthetic activity of the UB endocrine cells.

[Bone demineralization and cytokines]

Cytokines are secreted by several cell types in the bone microenvironment. These peptides act on bone cells by a paracrine or autocrine mechanism and play an important role, although not completely clarified, in the regulation of bone remodeling. Postmenopausal osteoporosis could be due to a local overproduction of some osteoclast-stimulating cytokines in response to estrogen deficiency. During chronic inflammatory joint diseases, such as rheumatoid arthritis, synovial cells produce large amounts of cytokines leading to increased local bone resorption and juxta-articular bone destructions. The local action of cytokines is also involved for interactions between tumoral cells and bone cells. These are secreted by the tumoral (metastatic or hemopoietic) cells, bone marrow cells, bone cells, or even could be released from the bone matrix during bone resorption. Recent progress in our knowledge in the field of cytokines have improved the understanding of the pathogenesis of these diseases and let hope future promising developments for more specific treatments.

Bone hypertrophy and trabecular generation in Paget's disease and in fluoride-treated osteoporosis

The replacement of lost trabeculae characteristic of postmenopausal osteoporosis is problematic, since a biological pathway has not been established for trabecular regeneration de novo in the healthy, intact, mature skeleton. Possible pathways for trabecular replacement may occur under pathological conditions, in particular those associated with bone hypertrophy. The topography of trabecular hypertrophy was compared in two groups of subjects with disease- or treatment-induced osteosclerosis following a period of atrophy. In Paget's disease and fluoride-treated osteoporosis a thickening of rarefied trabeculae in both was associated in Paget's disease only with an increase in the trabecular number and the transformation of a discontinuous arrangement into a more continuous network. The sequence seems to be a progression of intratrabecular resorption normally attendant upon a period of trabecular thickening. The failure of fluoride-treated bone in this respect, due to the unusual stability of the fluorotic skeleton, may provide insight to more effective anabolic regimens.

Bone mastocytosis. A report of nine cases with a bone histomorphometric 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.

[Bone involvement in primary oxalosis. Study of 20 cases]

The authors report 20 cases of primary oxalosis with bone involvement, late revealed in adults in 19 cases. They have studied the clinical, radiological and histological manifestations of this bone oxalosis. 19 cases had an end stage chronic renal failure, either treated by maintenance hemodialysis, or by renal (or liver-renal) graft. 17 patients complained of bone pain after starting hemodialysis; 3 had vertebral crush fractures, and 1 multiple spontaneous fractures. Diffuse bone sclerosis (with a homogeneous pattern on axial skeleton and a patchy appearance on the peripherical skeleton), bone translucency, subperiosteal phalangeal resorption were the main radiological symptoms. Oxalate crystals surrounded by a giant cells granuloma were always observed on bone biopsy (16 cases). Bone resorption was observed in 9 cases, hyperparathyroidism in 14 cases and osteomalacia in 7 cases. Hyperparathyroidism does'nt explain all the clinical and radiological manifestations (especially bone resorption). Bone resorption as other radiological and clinical manifestations can be found without hyperparathyroidism and can increase despite parathyroidectomy; so, bone resorption seems to be partly due to the granulomatous reaction around oxalate crystals rather than hyperparathyroidism.

Decreased DNA synthesis by cultured osteoblastic cells in eugonadal osteoporotic men with defective bone formation

To determine the osteoblastic dysfunction that may be involved in the pathophysiology of osteoporosis in men we have compared histomorphometric indices of bone formation with in vitro characteristics of osteoblastic cells isolated from the trabecular bone surface in 23 untreated men with eugonadal osteoporosis. In most patients (n = 14), trabecular bone loss resulted from decreased bone formation evidenced by a lower than normal osteoblast surface, double tetracycline labeled surface, bone formation rate, and mean wall thickness. In these patients, DNA synthesis by cultured osteoblastic cells was altered. The peak of [3H]thymidine incorporation into DNA, the maximal DNA synthesis, and the area under the curve of cell proliferation were lower than the values in normal bone cells from age-matched controls. Parameters of bone cell growth were decreased in correlation with the extent of actively bone forming surfaces. By contrast, in patients (n = 9) with normal histomorphometric indices of bone formation, bone cell proliferation in vitro was not different from normal. Parameters of osteoblastic differentiation in vitro such as osteocalcin production and alkaline phosphatase activity were normal in the two groups of patients. This study shows that the trabecular bone loss resulting from defective bone formation in eugonadal osteoporotic men is associated with a lower than normal proliferative capacity of osteoblastic cells lining the trabecular bone surface.

Relationship between the number of resorbing cells and the amount resorbed in metabolic bone disorders

The relationship between bone-resorbing cells, assessed by the presence of tartrate-resistant acid phosphatases (TRAP) and morphologic indices of bone resorption, was determined in 29 osteoporotic patients (14 postmenopausal females and 15 males) and 15 dialyzed patients. The number of TRAP-positive cells per unit of cancellous bone area (N.Oc/B.Ar) was higher in dialyzed patients than in those with osteoporosis (16.8 +/- 15.3 versus 4.95 +/- 2.86, p less than 0.05). The amount of bone resorbed at the basic multicellular unit level was estimated by calculating eroded area containing TRAP cells per bone area (E.Ar+/BA). This novel parameter was similar in dialyzed and in osteoporotic patients (41,700 +/- 28,400 versus 32,300 +/- 24,600). In contrast, trabecular spacing (Tb.Sp) was identical in both metabolic bone diseases. Trabecular width (169 +/- 38 versus 127 +/- 32 microns, p less than 0.05) and bone area were higher in dialyzed than in osteoporotic patients. N.Oc/B.Ar was significantly related to E.Ar+/BA in dialyzed (r = 0.76, p less than 0.05) but not in osteoporotic patients. Tb.Sp was significantly correlated to N.Oc/B.Ar and to the number of TRAP-positive cell nuclei per B.Ar (r = 0.44, p less than 0.05) in osteoporotic but not in dialyzed patients. This last result shows that in overt osteoporosis with thin trabeculae, trabecular spacing is related to the number of resorbing cells. In contrast, the spacing of thick trabeculae in dialysis osteodystrophy is not dependent on the number of osteoclasts.

Cyclosporin-A in vitro decreases bone resorption, osteoclast formation, and the fusion of cells of the monocyte-macrophage lineage

We studied the in vitro effect of cyclosporin-A (CyA) on bone resorption using a fetal rat long bone-resorbing assay. CyA inhibited both PTH-stimulated and unstimulated bone resorption. The inhibitory effect of CyA on basal resorption was dose dependent, and it was more pronounced during the second period (less than or equal to 0.1 microgram/ml) of culture (days 5-7) than during the first period (days 2-4). A cytotoxic effect was ruled out by the absence of decrease in [3H]thymidine incorporation into bones up to a concentration of 5 micrograms/ml CyA. Histomorphometry performed after 4 and 7 days of culture showed that CyA (1 microgram/ml) decreased the number of osteoclasts per bone section after 7 days of culture (23.5 +/- 4.0 vs. 41.7 +/- 2.9 osteoclasts/bone section; P less than 0.05), but not after 4 days (25.6 +/- 3.3 vs. 23.0 +/- 2.5). These data suggested an effect of CyA on osteoclastic differentiation rather than on the function of mature osteoclasts. We further assessed the mechanisms of the inhibitory effect of CyA on osteoclastic differentiation in order to determine 1) the level of this action (proliferation and/or fusion of osteoclast precursors), and 2) if this action is direct or indirect. Autoradiographic studies were performed on bone sections after incubation of bones with [3H]thymidine for the last 48 h of culture. CyA decreased slightly but significantly the percentage of labeled nuclei per osteoclast and the number of osteoclasts containing at least one labeled nucleus (20.2 +/- 0.7 vs. 33.2 +/- 3.5; P less than 0.02). Moreover the number of nuclei per osteoclast was decreased after 7 days in CyA-treated bones (2.4 +/- 0.05 vs. 3.0 +/- 0.1; P less than 0.02). Taken together these results demonstrate that CyA slightly decreased the proliferation of osteoclast precursors, but markedly decreased their fusion. Similar effects were observed in cultures of rat marrow macrophages. CyA (1 microgram/ml) inhibited the fusion of macrophages into multinucleated cells elicited by 1 nM 1,25-dihydroxyvitamin D3, but had only a slight effect on the proliferation of these cells, as assessed by autoradiography. CyA also inhibited the formation of multinucleated cells and the fusion index in long term cultures of human cord blood monocytes, a cellular model for osteoclastic differentiation. By contrast, CyA had no effect on the formation of myotubes by fusion of cultured mononucleated rat myoblasts.(ABSTRACT TRUNCATED AT 400 WORDS)

Human umbilical cord blood monocytes express calcitonin receptors in culture in the presence of 1,25 dihydroxyvitamin D

Calcitonin (CT) is a potent inhibitor of bone resorption and there are abundant CT receptors on mature osteoclasts. The relationship between osteoclast precursors and monocyte lineage is far from clear. We recently showed that human cord monocytes in culture, by contrast to adult monocytes, develop some features of osteoclast precursors. We therefore assessed the presence of CT receptors on monocytes. We could not demonstrate any CT receptors on adult monocytes. By contrast, we observed in cultured cord monocytes increased cAMP production in presence of CT. This cAMP response was observed after a 2-week culture and only in the presence of 10(-9) M 1,25-dihydroxyvitamin D. After a 3-week culture, CT 10(-9) to 10(-6) M increased cAMP production dose dependently from 10(-9) M; however the curve was shallower than the one observed in a control CT receptor positive tumoral cell line, MCF7. 125I sCT bound specifically to cord monocytes cultured during 3 weeks; apparent dissociation constant (Kd) was 3.3 +/- 2.2 10(-10) M and average receptor number was 5.1 +/- 0.4 10(4)/cell. On autoradiography all the cells, whether mono or multinucleated, were labeled with 125sCT. One or 2-h exposure to salmon CT did not induce cell contraction. In conclusion, CT receptors can be induced on newborn cord monocytes in the presence of 1,25-dihydroxyvitamin D. This observation shows that osteoclasts and fetal monocytes share a common membrane determinant.

The effect of sodium fluoride on trabecular architecture

The effect of sodium fluoride therapy on iliac trabecular bone has been studied in 15 patients with primary osteoporosis by comparing bone biopsies taken before and after two years of treatment. A marked increase in bone volume (43%) was observed, which was attributable to an increase in trabecular thickness (46%) rather than their number. Because the trabecular bone surface, the trabecular number, the bone volume/trabecular width ratio, and the trabecular terminus number do not change significantly after fluoride treatment, we conclude that fluoride does not induce the de novo generation of trabeculae, nor does it restore trabecular connectivity despite the restoration of bone mass. These data suggest that the restoration of skeletal mass with fluoride may not lead to a comparable decrease in the risk of future fracture.

[Renal osteodystrophy: aluminium and secondary hyperparathyroidism]

Aluminium-related osteodystrophy results in osteomalacia or in the so-called aplastic bone. In this particular bone disease bone cells activities are distinctly reduced but there is no disorder of bone mineralization. Aluminium exerts a direct toxic effect on bone tissue, notably on osteoblasts which are always strongly depressed in case of major aluminium overload. Aluminium-related osteopathy is regularly accompanied by low levels of parathormone due to accumulation of aluminium in the parathyroid glands. Parathormone modulates the bone aluminium overload: hyperparathyroidism "protects" bones against the deleterious effect of aluminium, whereas aluminium deposit in bone increase after parathyroidectomy. The respective roles played by low parathormone levels and by aluminium deposits in aplastic bone lesions is difficult to determine since hypoparathyroidism itself can probably cause the aplastic osteopathy. The role of parathormone stands out more clearly now that in patients under dialysis the bone aluminium overload has markedly decreased. Many patients with aplastic bone (initially described in aluminium poisoning) show no aluminium deposits in bones but have, for some unknown reason, a normal or even low parathormone level. The clinical course of this type of osteopathy remains to be determined, but there seems to be no reason to worry since numerous patient are asymptomatic. Preventing secondary hyperparathyroidism while refraining from prescribing aluminium hydroxide is the principal therapeutic objective in osteodystrophy of haemodialysis patients.

Stress fractures of the lower limbs in osteoporotic patients treated with fluoride

We report clinical and bone morphometric findings in 18 osteoporotic patients who experienced stress fractures during fluoride therapy. Patients were treated with either sodium fluoride (n = 15), or sodium monofluorophosphate (n = 3). Oral calcium supplementation was given in 11 patients, and vitamin D in 13. Stress fractures occurred after 17.1 +/- 10.3 months of therapy (range: 5-41 months). Atraumatic sudden pain in a lower limb bone extremity, normal initial roentgenogram, high 99technetium uptake on early bone scan, and a 3 to 4 week delay in linear bone condensation area at the same site were characteristics of stress fracture. The most frequent sites were the tibial metaphysis (n = 13), femoral neck (n = 10), and calcaneus (n = 4). Biochemical data showed increased plasma alkaline phosphatase levels in 11 patients, and mild renal failure in 2. Bone histomorphometry was performed on an iliac crest specimen in 10 patients at the time of the stress fracture. Trabecular bone volume was normal, and formation parameters were increased. Features of osteomalacia were encountered in only 2 patients with decreased renal function. Trabecular resorption was increased, as assessed by the osteoclastic surface (1.01 +/- 1.15% bone surface), and the number of osteoclasts (0.44 +/- 0.49 per mm2 bone section). The clinical course was favorable in all patients who stopped fluoride, although 5 patients who continued the treatment had either completion of femoral neck stress fractures to hip fractures (n = 2), or recurrent stress fractures (n = 2), or both (n = 1). Fluoride appears to be a key factor in the pathogenesis of stress fractures, and may be associated with increased trabecular resorption in some treated patients.

Formation of multinucleated cells with osteoclast precursor features in human cord monocytes cultures

A common lineage between monocytes and osteoclasts has been suggested but not yet proved, and an osteoclast precursor might be an immature cell of the monocyte-macrophage family. We therefore compared the ability of cord blood and adult monocytes in long-term culture to differentiate toward osteoclasts. Both adult and cord monocytes were cultured for 3 weeks in the presence of 20% horse serum. The proportion of multinucleated cells formed was influenced by 1,25(OH)2D3 in cord, but not in adult monocyte cultures: 10(-9)M 1,25(OH)2D3 increased multinucleated cells from 13 +/- 2 to 26 +/- 1% of total cells in cord monocyte cultures. The formation of multinucleated cells in cord monocyte cultures, in the presence of 10(-9) M 1,25(OH)2D, was decreased by salmon calcitonin (dose dependently from 10(-8) to 10(-6) M) and increased by 1-34 parathormone (100 ng/ml). None of these hormones induced any modification of the proportion of multinucleated cells formed in adult monocytes culture. Specific antigens on the membrane of the cells obtained after 3 weeks culture in the presence of 10(-9) M 1,25(OH)2D3 were assessed by immunocytochemistry. The respective proportion of adult and cord labeled cells was 64 +/- 11 vs. 63 +/- 6% with Leu M5 (specific for monocyte) and 68 +/- 7 vs. 30 +/- 10% (P less than 0.05) with the anti-HLA DR antibody. The monoclonal antibody 23C6 is specific to the vitronectin receptor, which is highly expressed by osteoclasts--41 +/- 2% of the cells in cord monocyte cultures--but none in the adult monocytes culture were labeled with 23C6 at the end of the culture period.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of calcitonin administration on young pig trabecular bone remodeling

Ten-week-old pigs were treated with 4 different treatment schedules of porcine calcitonin for 2 months. Groups C1 and C4 received continuous treatment: C1 had daily IM injections (4 IU/kg/BW (body weight) each injection), and C4 was infused with a minipump implanted subcutaneously delivering 4 IU/kg/BW/day. Groups C2 and C3 received intermittent calcitonin treatment (each injection 4 IU/kg/BW): C2 was given 1 out of every four days, C3 was injected 5 consecutive days out of 20 days. The total dosage received in C1 versus C4 and C2 versus C3 were the same. Results were evaluated by histomorphometry after double tetracycline labeling on iliac trabecular bone. Resorption surfaces were decreased in groups C2, C3 and C4, but bone volume, osteoclast surfaces, and interstitial bone thickness were not modified in any group receiving calcitonin. Osteoblast and mineralizing surfaces were increased in group C2, C3 and C4. Plasma 1,25-dihydroxyvitamin D concentration and bone formation rate were increased in groups C2 and C4. Plasma immunoreactive parathyroid hormone levels and parathyroid weights were not increased in any treated groups. In conclusion, 2-month calcitonin treatment did not decrease the amount of bone resorbed in growing pigs. Continuous calcitonin infusion and intermittent calcitonin administration induced an increase in the extent of active bone formation which might be in part dependent on an increased production of 1,25 dihydroxyvitamin D.