Tsang Hai Huang

Ultrasound stimulates cyclooxygenase-2 expression and increases bone formation through integrin, focal adhesion kinase, phosphatidylinositol 3-kinase, and Akt pathway in osteoblasts.

It has been shown that ultrasound (US) stimulation accelerates fracture healing in animal models and in clinical studies. Here we found that US stimulation transiently increased the surface expression of α2, α5, β1, and β3 integrins in cultured osteoblasts, as shown by flow cytometric analysis and immunofluorescence staining. US stimulation increased prostaglandin E2 formation and the protein and mRNA levels of cyclooxygenase-2 (COX-2). At the mechanistic level, anti-integrin α5β1 and αvβ3 antibodies or rhodostomin, a snake venom disintegrin, attenuated the US-induced COX-2 expression. Phosphatidylinositol 3-kinase (PI3K) inhibitors 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride (LY294002) and wortmannin also inhibited the potentiating action of US. US stimulation increased the phosphorylation of focal adhesion kinase (FAK), extracellular signal-regulated kinases (ERK), p85 subunit of PI3K, and serine 473 of Akt. COX-2 promoter activity was enhanced by US stimulation in cells transfected with pCOX2-Luc. Cotransfection with dominant-negative mutant of FAK(Y397F), p85(Δp85), Akt(K179A), or ERK2(K52R) inhibited the potentiating action of US on COX-2 promoter activity. Expression of mineralized nodule was lower in dominant-negative mutants of FAK, p85, and Akt-transfected clones than in vector-transfected control cells. Taken together, our results provide evidence that US stimulation increases COX-2 expression and promotes bone formation in osteoblasts via the integrin/FAK/PI3K/Akt and ERK signaling pathway.

Endurance treadmill running training benefits the biomaterial quality of bone in growing male Wistar rats

This study investigated the effects of endurance running training on the bones of growing rats. Thirty-two male Wistar rats (7 weeks old) were assigned to a sedentary control group (CON, n = 10), a continuous endurance running group (CEN, n = 10), or an intermittent endurance running group (IEN, n = 12). After an 8-week training period, both exercise groups had significantly less body weight (BW) gain but higher aerobic capacity, shown by increased muscle citrate synthase (CS) activity. Bone area (BA), areal bone mineral density (aBMD), and bone mineral content (BMC) were measured by dual-energy Xray absorptiometry (DXA) in the total femur and sections of femora. Except for showing a significantly higher aBMD in total femora, the CON group was only slightly and nonsignificantly higher in other DXA measurements. In tissue weight measurements, the CON group showed a nonsignificantly higher tissue dry weight (P = 0.146), but a significantly lower tissue water content ratio (WCR, %) as compared to the exercise group. Despite having nonsignificantly lower long bone cross-sectional parameters, both exercise groups showed significantly better biomaterial properties, as measured by a three-point bending test. In extrinsic analysis, femora of the two exercise groups showed no difference in bending load and stiffness, but were significantly higher in post-yield bending energy and total ultimate bending energy (P < 0.05). Similar phenomena were revealed in tissue-level measurements; the CEN and IEN groups were significantly higher in ultimate toughness and post-yield toughness (P < 0.05). Higher post-yield energy shown by two exercise groups implied a change in bone matrix organization. In conclusion, this study demonstrated that two endurance treadmill training modes benefit bone, with subjects showing better tissue biomaterial properties without significantly increasing aBMD, BMC, or bone dimension. Further study would be valuable to investigate the effects of endurance running on other components of bone, such as organization of bone matrix and its relationship with bone biomaterial properties.

Bone Morphogenetic Proteins Signal Via SMAD and Mitogen-activated Protein (MAP) Kinase Pathways at Distinct Times during Osteoclastogenesis

Background: BMPs affect osteoclastogenesis in vitro, but the effects of BMP signaling on osteoclastogenesis in vivo are not well understood. Results: Conditional deletion of BMPRII in osteoclasts results in reduced osteoclastogenesis, resulting in increased bone. Conclusion: BMP signaling is required for proper bone remodeling in vivo. Significance: Identifying factors affecting osteoclast differentiation increase understanding of bone remodeling regulation in vivo. To investigate the role of bone morphogenetic protein (BMP) signaling in osteoclastogenesis in vivo, we eliminated BMPRII in osteoclasts by creating a BMPRIIfl/fl;lysM-Cre mouse strain. Conditional knock-out (cKO) mice are osteopetrotic when compared with WT controls due to a decrease in osteoclast activity. Bone marrow macrophages (BMMs) isolated from cKO mice are severely inhibited in their capacity to differentiate into mature osteoclasts in the presence of M-CSF and receptor activator of NF-κB (RANK) ligand. We also show that BMP noncanonical (MAPK) and canonical (SMAD) pathways are utilized at different stages of osteoclast differentiation. BMP2 induces p38 phosphorylation in pre-fusion osteoclasts and increases SMAD phosphorylation around osteoclast precursor fusion. Phosphorylation of MAPKs was decreased in differentiated BMMs from cKO animals. Treating BMMs with the SMAD inhibitor dorsomorphin confirms the requirement for the canonical pathway around the time of fusion. These results demonstrate the requirement for BMP signaling in osteoclasts for proper bone homeostasis and also explore the complex signaling mechanisms employed by BMP signaling during osteoclast differentiation.

Onion decreases the ovariectomy-induced osteopenia in young adult rats

It has been suggested that fruit and vegetable consumption are associated with good bone health. Onion, in particular, has been verified in its efficacy in bone resorption activity. In this study, we further investigated the effects of an onion-containing diet on ovariectomy-induced bone loss using methods of serum marker assay, histomorphometric analysis and biomechanical tests. Sixty-four female Wistar rats (14-week-old) with sham operations or ovariectomy were assigned to 6 groups: CON, sham-operated control group; OVX, ovariectomized group; ALN, ovariectomized rats treated with alendronate (1 mg/kg/day, p.o.); and 3% ON, 7% ON and 14% ON, ovariectomized rats fed with diets containing 3%, 7% and 14% (wt/wt) onion powder, respectively. Animals were sacrificed after a six-week treatment course. In the serum marker assay, alendronate and all three onion-enriched diets significantly decreased serum calcium level (p<0.05). Both 14% ON group and the ALN group even showed similarly lower level of serum osteocalcin (p<0.05), suggesting a down-regulation of bone turnover. The histomorphometric analysis showed that ovariectomy markedly decrease bone trabeculae. The ALN and 14% ON rats were 80% and 46% higher, respectively, in BV/TV than the OVX rats (p<0.05), and the rats fed with onion-enriched food showed a lesser ovariectomy-induced bone loss in a dose-dependent manner. Additionally, both ALN and 14% ON groups had significantly more trabecular number, less separated trabeculae, and fewer osteoclasts (p<0.05), but the protective efficacy from the 14% onion-enriched diet was slightly inferior to that of alendronate. Ovariectomy also significantly decreased tissue weight and biomechanical strength in the OVX group (p<0.05). The ALN and 14% ON groups equivalently showed a lesser decrease in tissue weight, though the difference was not significant. On the other hand, both the ALN and 14% ON groups represented similar biomaterial properties of femurs, and both reduced the ovariectomy-induced decrease in bending load and bending energy (p<0.05). The present study further verified that an onion-enriched diet could counteract ovariectomy-induced bone loss and deterioration of biomechanical properties.

Water solution of onion crude powder inhibits RANKL-induced osteoclastogenesis through ERK, p38 and NF-κB pathways

SummaryOnion powder has been reported to decrease the ovariectomy-induced bone resorption of rats. However, the molecular mechanism of onion powder on the bone cells has not been reported. Here, we report that water solution of onion crude powder decreases the osteoclastogenesis from co-cultures of bone marrow stromal cells and macrophage cells. Additionally, water solution of onion crude powder inhibits the RANKL-induced ERK, p38 and NF-κB activation in macrophages. In summary, our data showed that onion powder may benefit bone through an anti-resorption effect on the osteoclasts.IntroductionA nutritional approach is important for both prevention and treatment of osteoporosis. Onion has been reported to decrease the ovariectomy-induced bone resorption. However, the functional effects of onion on the cultured osteoclasts and osteoblasts remain largely unknown. Here, we found that water solution of onion crude powder markedly inhibited the receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclastogenesis through ERK, p38 and NF-κB pathways. Other studies were also designed to investigate the potential signaling pathways involved in onion-induced decrease in osteoclastogenesis.MethodsThe osteoclastogenesis was examined using the TRAP staining method. The MAPKs and NF-κB pathways were measured using Western blot analysis. A transfection protocol was used to examine NF-κB activity.ResultsWater solution of onion crude powder inhibited the RANKL plus M-CSF-induced osteoclastic differentiation from either bone marrow stromal cells or from RAW264.7 macrophage cells. Treatment of RAW264.7 macrophages with RANKL could induce the activation of ERK, p38 and NF-κB that was inhibited by water solution of onion crude powder. On the other hand, it did not affect the cell proliferation and differentiation of human cultured osteoblasts.ConclusionsOur data suggest that water solution of onion crude powder inhibits osteoclastogenesis from co-cultures of bone marrow stromal cells and macrophage cells via attenuation of RANKL-induced ERK, p38 and NF-κB activation.

Ultrasound stimulates MMP‐13 expression through p38 and JNK pathway in osteoblasts

It has been shown that ultrasound (US) stimulation accelerates fracture healing, bone maturation, and remodeling in the animal models and in clinical studies. One of the major factor involves in remodeling process is matrix metalloproteinases (MMPs) such as MMP‐13 that has been shown to degrade the native interstitial collagens in several tissues. Here we found that US stimulation increased the secretion of MMP‐13 in cultured rat osteoblasts, as shown by zymographic analysis. US stimulation also increased the mRNA level of MMP‐13, c‐Fos, and c‐Jun. Cycloheximide (an inhibitor of protein translocation) and actinomycin D (an inhibitor of gene transcription) did not inhibit the MMP‐13, c‐Fos, and c‐Jun mRNA expression, suggesting that such expression does not require de novo protein synthesis and not change their stabilities. p38 inhibitor, SB203580 or JNK inhibitor, SP600125 but not ERK inhibitor, PD98059 attenuated the US‐induced MMP‐13, c‐Fos, and c‐Jun expression; these results were further substantiated by transfecting with the dominant negative mutants of p38 or JNK. The binding of c‐Fos and c‐Jun to the AP‐1 element on the MMP‐13 promoter and the enhancement of AP‐1 luciferase activity was enhanced by US stimulation. Taken together, our results provide evidence that US stimulation increases MMP‐13 expression through p38 and JNK signaling pathway to regulate bone remodeling. J. Cell. Physiol. 215: 356–365, 2008.

A Methionine-Restricted Diet and Endurance Exercise Decrease Bone Mass and Extrinsic Strength but Increase Intrinsic Strength in Growing Male Rats

Dietary methionine restriction (MR) has been suggested to be comparable to endurance exercise with respect to its beneficial effects on health. To further investigate the effects of MR and endurance exercise on growing bone, 7-wk-old male Sprague-Dawley rats were fed different l-methionine (Met)-containing diets with or without endurance exercise intervention (Ex; 0.86% Met, 0.52% Met, 0.17% Met, 0.86% Met-Ex, 0.52% Met-Ex, and 0.17% Met-Ex groups). After an 8-wk intervention period, exercise-trained rats had a 9.2% lower body weight (BW) than did sedentary rats (P < 0.05). Additionally, 0.17% Met-fed rats had 32% lower BW when compared with rats fed the other 2 diets (P < 0.05). Serum osteocalcin was lower in the 0.17% Met-Ex group compared with the other 2 exercise groups and the 0.17% Met group (P < 0.05). Serum concentrations of C-terminal telopeptide of type 1 collagen were lower in exercise-trained and 0.17% Met-fed rats than in sedentary rats and rats fed the other 2 diets (P < 0.05 for both). Rats fed the 0.17% Met diet had lower trabecular bone volume, bone mineralization activities, and bone mineral content (BMC; e.g., total, cortical, and spongy BMC) and bone mineral density (BMD; e.g., total and spongy BMD) indices compared with rats fed the other 2 diets (P < 0.05). Exercise-trained rats also had lower bone mineralization activity, trabecular osteoclast density, total BMC, cortical BMC, and total BMD compared with sedentary rats (P < 0.05). In total BMD, only the 0.17% Met-Ex group had values lower than the other 2 exercise groups and the 0.17% Met group (P < 0.05). Compared with rats fed the other 2 diets and sedentary rats, the femora of 0.17% Met-fed and exercise-trained rats, respectively, had smaller size and/or lower extrinsic strength but enhanced intrinsic biomechanical properties (P < 0.05). The results indicate that MR and endurance exercise caused lower whole bone mass, size, and/or strength but might enhance intrinsic bone strength.

The first international mini-symposium on methionine restriction and lifespan.

It has been 20 years since the Orentreich Foundation for the Advancement of Science, under the leadership Dr. Norman Orentreich, first reported that low methionine (Met) ingestion by rats extends lifespan (Orentreich et al., 1993). Since then, several studies have replicated the effects of dietary methionine restricted (MR) in delaying age-related diseases (Richie et al., 1994; Miller et al., 2005; Ables et al., 2012; Sanchez-Roman and Barja, 2013). We report the abstracts from the First International Mini-Symposium on Methionine Restriction and Lifespan held in Tarrytown, NY, September 2013. The goals were (1) to gather researchers with an interest in MR and lifespan, (2) to exchange knowledge, (3) to generate ideas for future investigations, and (4) to strengthen relationships within this community. The presentations highlighted the importance of research on cysteine, growth hormone (GH), and ATF4 in the paradigm of aging. In addition, the effects of dietary restriction or MR in the kidneys, liver, bones, and the adipose tissue were discussed. The symposium also emphasized the value of other species, e.g., the naked mole rat, Brandts bat, and Drosophila, in aging research. Overall, the symposium consolidated scientists with similar research interests and provided opportunities to conduct future collaborative studies (Figure 3).

Dietary restrictions, bone density, and bone quality.

Caloric restriction (CR), protein restriction (PR), and specific amino acid restriction (e.g., methionine restriction (MR)) are different dietary interventions that have been confirmed with regard to their comprehensive benefits to metabolism and health. Based on bone densitometric measurements, weight loss induced by dietary restriction is known to be accompanied by reduced areal bone mineral density, bone mass, and/or bone size, and it is considered harmful to bone health. However, because of technological advancements in bone densitometric instruments (e.g., high‐resolution X‐ray tomography), dietary restrictions have been found to cause a reduction in bone mass/size rather than volumetric bone mineral density. Furthermore, when considering bone quality, bone health consists of diverse indices that cannot be fully represented by densitometric measurements alone. Indeed, there is evidence that moderate dietary restrictions do not impair intrinsic bone material properties, despite the reduction in whole‐bone strength because of a smaller bone size. In the present review, we integrate research evidence from traditional densitometric measurements, metabolic status assays (e.g., energy metabolism, oxidative stresses, and inflammatory responses), and biomaterial analyses to provide revised conclusions regarding the effects of CR, PR, and MR on the skeleton.

Methionine restriction alters bone morphology and affects osteoblast differentiation

Methionine restriction (MR) extends the lifespan of a wide variety of species, including rodents, drosophila, nematodes, and yeasts. MR has also been demonstrated to affect the overall growth of mice and rats. The objective of this study was to evaluate the effect of MR on bone structure in young and aged male and female C57BL/6J mice. This study indicated that MR affected the growth rates of males and young females, but not aged females. MR reduced volumetric bone mass density (vBMD) and bone mineral content (BMC), while bone microarchitecture parameters were decreased in males and young females, but not in aged females compared to control-fed (CF) mice. However, when adjusted for bodyweight, the effect of MR in reducing vBMD, BMC and microarchitecture measurements was either attenuated or reversed suggesting that the smaller bones in MR mice is appropriate for its body size. In addition, CF and MR mice had similar intrinsic strength properties as measured by nanoindentation. Plasma biomarkers suggested that the low bone mass in MR mice could be due to increased collagen degradation, which may be influenced by leptin, IGF-1, adiponectin and FGF21 hormone levels. Mouse preosteoblast cell line cultured under low sulfur amino acid growth media attenuated gene expression levels of Col1al, Runx2, Bglap, Alpl and Spp1 suggesting delayed collagen formation and bone differentiation. Collectively, our studies revealed that MR altered bone morphology which could be mediated by delays in osteoblast differentiation.