The Use of Autogenous Bone Mixed with a Biphasic Calcium Phosphate in a Maxillary Sinus Floor Elevation Procedure with a 6-Month Healing Time: A Clinical, Radiological, Histological and Histomorphometric Evaluation

Background: In this study it is evaluated whether autogenous bone mixed with biphasic calcium phosphate (BCP) used in a maxillary sinus floor elevation (MSFE) leads to improved bone formation. Materials and methods: In five patients a unilateral MSFE was performed. Histological and histomorphometric analyses were performed on bone biopsies that were obtained 6 months after MSFE during dental implant surgery. Results: The average vital bone volume was 29.9% of the total biopsy (BV/TV, SD ± 10.1) of which 7.1% was osteoid (OV/BV, SD ± 4.8). The osteoid surface (OS/BS) covered 26.0% (SD ± 13.4) of the bone surface. The BS/TV covered 4.7 mm2/mm3 (SD ± 2.3). Compared with previous studies the analyses showed a difference for trabecular thickness (Tb.Th.) and osteoid surface (OS/BS), but not for BV/TV, OV/BV and the number of osteoclasts. Conclusion: MSFE with autogenous bone mixed with BCP shows an amount of newly formed bone that is comparable with the findings from the previously published 6-month study with pure BCP. However, a better distribution of the new bone over the entire biopsy was observed.

Bone Histomorphometry in Young Patients With Type 2 Diabetes is Affected by Disease Control and Chronic Complications

Context Type 2 diabetes mellitus (T2DM) is associated with an increased risk of fractures. No study has evaluated the correlation of bone histomorphometry (BH) parameters with glycemic control and presence of chronic complications (CCs) in premenopausal women with T2DM. Objectives To evaluate BH and correlate them with the degree of glycemic control and presence of CCs. Design, settings, and patients This was a cross-sectional study conducted at a tertiary medical center. Twenty-six premenopausal women with T2DM were divided into groups with glycated hemoglobin HbA1c < 7% (good control, GC; n = 10) and HbA1c > 7% (poor control, PC; n = 16), and further subdivided into groups with (n = 9) and without (n = 17) CCs. BH parameters (bone volume [bone volume per total volume, BV/TV], trabecular thickness [Tb.Th], trabecular number [Tb.N], trabecular separation [Tb.Sp], osteoid thickness [O.Th], osteoid surface [osteoid surface per bone surface, OS/BS]), mineralizing surface [MS/BS], bone formation rate [BFR]), mineral apposition rate [MAR]) as well as serum pentosidine (PEN) and insulin-like growth factor (IGF)-1 were measured. The BH data were compared among the groups and with a BH control group (control group, CG, n = 15) matched by age, sex, and race. Results BV/TV was increased in GC (P < .001) and PC (P = .05) groups and O.th (P = .03) was smaller in the PC group than in the CG. A comparison of the groups with and without CCs with the CG showed in the group with CCs, O.Th was smaller(P = .01) and BV/TV similar to the CG (P = .11). HbA1c correlated negatively with O.Th (P = .02) and OS/BS (P = .01). There was no correlation of BH to PEN and IGF-1. Conclusion BH in premenopausal patients with T2DM is affected by disease control and chronic complications.

Petunidin, a B-ring 5′-O-Methylated Derivative of Delphinidin, Stimulates Osteoblastogenesis and Reduces sRANKL-Induced Bone Loss

Several lines of evidence suggest that oxidative stress is one of the key pathogenic mechanisms of osteoporosis. We aimed to elucidate the bone protective effects of petunidin, one of the most common anthocyanidins, considering its potent antioxidative activity. Petunidin (>5 μg/mL) significantly inhibited osteoclastogenesis and downregulated c-fos, Nfatc1, Mmp9, Ctsk, and Dc-stamp mRNA expression in RAW264.7 cells. Conversely, petunidin (>16 μg/mL) stimulated mineralized matrix formation and gene expression of Bmp2 and Ocn, whereas it suppressed Mmp13, Mmp2, and Mmp9 mRNA expression and proteolytic activities of MMP13 and MMP9 in MC3T3-E1 cells. Micro-CT and bone histomorphometry analyses of sRANKL-induced osteopenic C57BL/6J mice showed that daily oral administration of petunidin (7.5 mg/kg/day) increased bone volume to tissue volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), the ratio of osteoid volume to tissue volume (OV/TV), osteoid thickness (O.Th), the ratio of osteoid surface to bone surface (OS/BS), the ratio of osteoblast surface to bone surface (Ob.S/BS), and the number of osteoblast per unit of bone surface (N.Ob/BS), and decreased trabecular separation (Tb.Sp), the ratio of eroded surface to bone surface (ES/BS), the ratio of osteoclast surface to bone surface (Oc.S/BS), and number of osteoclast per unit of bone surface (N.Oc/BS), compared to untreated mice. Furthermore, histological sections of the femurs showed that oral administration of petunidin to sRANKL-induced osteopenic mice increased the size of osteoblasts located along the bone surface and the volume of osteoid was consistent with the in vitro osteoblast differentiation and MMP inhibition. These results suggest that petunidin is a promising natural agent to improve sRANKL-induced osteopenia in mice through increased osteoid formation, reflecting accelerated osteoblastogenesis, concomitant with suppressed bone resorption.

Sweet Bones: The Pathogenesis of Bone Alteration in Diabetes

Diabetic patients have increased fracture risk. The pathogenesis underlying the status of bone alterations in diabetes mellitus is not completely understood but is multifactorial. The major deficits appear to be related to a deficit in mineralized surface area, a decrement in the rate of mineral apposition, deceased osteoid surface, depressed osteoblast activity, and decreased numbers of osteoclasts due to abnormal insulin signaling pathway. Other prominent features of diabetes mellitus are an increased urinary excretion of calcium and magnesium, accumulation of advanced glycation end products, and oxidative stress leading to sweet bones (altered bone’s strength, metabolism, and structure). Every diabetic patient should be assessed for risk factors for fractures and osteoporosis. The pathogenesis of the bone alterations in diabetes mellitus as well as their molecular mechanisms needs further study.

gp130 in late osteoblasts and osteocytes is required for PTH-induced osteoblast differentiation

Parathyroid hormone (PTH) treatment stimulates osteoblast differentiation and bone formation, and is the only currently approved anabolic therapy for osteoporosis. In cells of the osteoblast lineage, PTH also stimulates the expression of members of the interleukin 6 (IL-6) cytokine superfamily. Although the similarity of gene targets regulated by these cytokines and PTH suggest cooperative action, the dependence of PTH anabolic action on IL-6 cytokine signaling is unknown. To determine whether cytokine signaling in the osteocyte through glycoprotein 130 (gp130), the common IL-6 superfamily receptor subunit, is required for PTH anabolic action, male mice with conditional gp130 deletion in osteocytes (Dmp1Cre.gp130f/f) and littermate controls (Dmp1Cre.gp130w/w) were treated with hPTH(1–34) (30 μg/kg 5× per week for 5 weeks). PTH dramatically increased bone formation in Dmp1Cre.gp130w/w mice, as indicated by elevated osteoblast number, osteoid surface, mineralizing surface, and increased serum N-terminal propeptide of type 1 collagen (P1NP). However, in mice with Dmp1Cre-directed deletion of gp130, PTH treatment changed none of these parameters. Impaired PTH anabolic action was associated with a 50% reduction in Pth1r mRNA levels in Dmp1Cre.gp130f/f femora compared with Dmp1Cre.gp130w/w. Furthermore, lentiviral-Cre infection of gp130f/f primary osteoblasts also lowered Pth1r mRNA levels to 16% of that observed in infected C57/BL6 cells. In conclusion, osteocytic gp130 is required to maintain PTH1R expression in the osteoblast lineage, and for the stimulation of osteoblast differentiation that occurs in response to PTH.

Influence of Gastrectomy on Cortical and Cancellous Bones in Rats

The aim of the present study was to examine the influence of gastrectomy (GX) on cortical and cancellous bones in rats. Twenty male Sprague-Dawley rats were randomized into the two groups of 10 animals each: a sham operation (control) group and a GX group. Seven weeks after surgery, the bone mineral content and density (BMC and BMD, resp.) and the mechanical strength of the femur were determined, and bone histomorphometric analyses were performed on the tibia. GX induced decreases in the BMC, BMD, ultimate force, work to failure, and stiffness of the femoral distal metaphysis and the BMC, BMD, and ultimate force of the femoral diaphysis. GX induced a decrease in cancellous bone mass, characterized by an increased osteoid thickness, osteoid surface, osteoid volume, and bone formation. GX also induced a decrease in cortical bone mass, characterized by increased endocortical bone resorption. The GX induced reductions in the bone mass and strength parameters were greater in cancellous bone than in cortical bone. The present study showed that the response of bone formation, resorption, and osteoid parameters to GX and the degree of GX-induced osteopenia and the deterioration of bone strength appeared to differ between cortical and cancellous bones in rats.

Effect of paricalcitol and cinacalcet on serum phosphate, FGF-23, and bone in rats with chronic kidney disease

Calcimimetics activate the calcium-sensing receptor (CaR) and reduce parathyroid hormone (PTH) by increasing the sensitivity of the parathyroid CaR to ambient calcium. The calcimimetic, cinacalcet, is effective in treating secondary hyperparathyroidism in dialysis patients [chronic kidney disease (CKD 5)], but little is known about its effects on stage 3–4 CKD patients. We compared cinacalcet and paricalcitol in uremic rats with creatinine clearances “equivalent” to patients with CKD 3–4. Uremia was induced in anesthetized rats using the 5/6th nephrectomy model. Groups were 1) uremic control, 2) uremic + cinacalcet (U+Cin; 15 mg·kg−1·day−1 po for 6 wk), 3) uremic + paricalcitol (U+Par; 0.16 μg/kg, 3 × wk, ip for 6 wk), and 4) normal. Unlike U+Par animals, cinacalcet promoted hypocalcemia and marked hyperphosphatemia. The Ca × P in U+Cin rats was twice that of U+Par rats. Both compounds suppressed PTH. Serum 1,25-(OH)2D3 was decreased in both U+Par and U+Cin rats. Serum FGF-23 was increased in U+Par but not in U+Cin, where it tended to decrease. Analysis of tibiae showed that U+Cin, but not U+Par, rats had reduced bone volume. U+Cin rats had similar bone formation and reduced osteoid surface, but higher bone resorption. Hypocalcemia, hyperphosphatemia, low 1,25-(OH)2D3, and cinacalcet itself may play a role in the detrimental effects on bone seen in U+Cin rats. This requires further investigation. In conclusion, due to its effects on bone and to the hypocalcemia and severe hyperphosphatemia it induces, we believe that cinacalcet should not be used in patients with CKD without further detailed studies.

Transgenic Expression of 11β-Hydroxysteroid Dehydrogenase Type 2 in Osteoblasts Reveals an Anabolic Role for Endogenous Glucocorticoids in Bone

Glucocorticoid excess leads to bone loss, primarily by decreasing bone formation. However, a variety of in vitro models show that glucocorticoids can promote osteogenesis. To elucidate the role of endogenous glucocorticoids in bone metabolism, we developed transgenic (TG) mice in which a 2.3-kb Col1a1 promoter fragment drives 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) expression in mature osteoblasts. 11β-HSD2 should metabolically inactivate endogenous glucocorticoids in the targeted cells, thereby reducing glucocorticoid signaling. The inhibitory effect of 300 nm hydrocortisone on percent collagen synthesis was blunted in TG calvariae, demonstrating that the transgene was active. Collagen synthesis rates were lower in TG calvarial organ cultures compared with wild-type. Trabecular bone parameters measured by microcomputed tomography were reduced in L3 vertebrae, but not femurs, of 7- and 24-wk-old TG females. These changes were also not seen in males. In addition, histomorphometry showed that osteoid surface was increased in TG female vertebrae, suggesting that mineralization may be impaired. Our data demonstrate that endogenous glucocorticoid signaling is required for normal vertebral trabecular bone volume and architecture in female mice.

A Histomorphometric Evaluation of Heparin-Induced Bone Loss After Discontinuation of Heparin Treatment in Rats

Although it is well established that long-term heparin therapy causes osteoporosis, it is unknown whether heparin-induced bone loss is reversible when heparin treatment is stopped. To address this question, we randomized rats to once daily subcutaneous injections of either unfractionated heparin (1.0 U/g or 0.5 U/g) or saline for 28 days and then followed the rats for an additional 28 days off treatment. Based on histomorphometric analysis of the distal third of the right femur proximal to the epiphyseal growth plate, 1.0 U/g heparin caused a 30% loss in cancellous bone volume over the first 28 days. This was accompanied by a 137% increase in osteoclast surface and a 60% decrease in both osteoblast and osteoid surface. One month after cessation of heparin treatment, no recovery in these parameters was observed. Similarly, serum levels of alkaline phosphatase, a biochemical marker of bone formation, which continued to decrease over the course of heparin treatment, showed no signs of recovery in the subsequent 28 days off treatment. To explore the mechanism responsible for the prolonged effect of heparin on bone, we repeated the experiment giving 125I-labeled heparin in place of unlabeled heparin.125I-labeled heparin was found to accumulate in bone during the course of its administration, and be retained in bone for at least 56 days after stopping heparin treatment. These findings suggest that heparin-induced osteoporosis is not rapidly reversible because heparin is sequestered in bone for an extended period.

A Histomorphometric Evaluation of Heparin-Induced Bone Loss After Discontinuation of Heparin Treatment in Rats

Although it is well established that long-term heparin therapy causes osteoporosis, it is unknown whether heparin-induced bone loss is reversible when heparin treatment is stopped. To address this question, we randomized rats to once daily subcutaneous injections of either unfractionated heparin (1.0 U/g or 0.5 U/g) or saline for 28 days and then followed the rats for an additional 28 days off treatment. Based on histomorphometric analysis of the distal third of the right femur proximal to the epiphyseal growth plate, 1.0 U/g heparin caused a 30% loss in cancellous bone volume over the first 28 days. This was accompanied by a 137% increase in osteoclast surface and a 60% decrease in both osteoblast and osteoid surface. One month after cessation of heparin treatment, no recovery in these parameters was observed. Similarly, serum levels of alkaline phosphatase, a biochemical marker of bone formation, which continued to decrease over the course of heparin treatment, showed no signs of recovery in the subsequent 28 days off treatment. To explore the mechanism responsible for the prolonged effect of heparin on bone, we repeated the experiment giving 125I-labeled heparin in place of unlabeled heparin.125I-labeled heparin was found to accumulate in bone during the course of its administration, and be retained in bone for at least 56 days after stopping heparin treatment. These findings suggest that heparin-induced osteoporosis is not rapidly reversible because heparin is sequestered in bone for an extended period.