Steady and oscillatory fluid flows produce a similar osteogenic phenotype

Mechanical loading induces positive changes in the skeleton due to direct effects on bone cells, which may include regulation of transcription factors that support osteoblast differentiation and function. Flow effects on osteoblast transcription factors have generally been evaluated after short exposures. In this work, we assayed flow effects on osteogenic genes at early and late time points in a preosteoblast (CIMC-4) cell line and evaluated both steady and oscillatory flows. Four hours of steady unidirectional flow decreased the level of RANKL mRNA 53 ± 7% below that of nonflowed cells, but increases in Runx2 and osterix mRNA (44 ± 22% and 129 ± 12%, respectively) were significant only after 12-19 h of continuous flow. Late flow effects on RANKL and osterix were also induced by an intermittent flow-rest protocol (four cycles of 1 h on/1 h off + overnight rest). Four hours of oscillatory flow decreased RANKL mRNA at this early time point (63 ± 2%) but did not alter either osterix or Runx2. When oscillatory flow was delivered using the intermittent flow-rest protocol, Runx2 and osterix mRNA increased significantly (85 ± 19% and 161 ± 22%, respectively). Both β-catenin and ERK1/2, known to be involved in RANKL regulation, were rapidly activated by steady flow. Inhibition of flow-activated ERK1/2 prevented the increase in osterix mRNA but not Runx2; Runx2 phosphorylation was increased by flow, an effect which likely contributes to osterix induction. This work shows that both steady and oscillatory fluid flows can support enhancement of an osteogenic phenotype.

Mechanical signal influence on mesenchymal stem cell fate is enhanced by incorporation of refractory periods into the loading regimen

Mechanical signals of both low and high intensity are inhibitory to fat and anabolic to bone in vivo, and have been shown to directly affect mesenchymal stem cell pools from which fat and bone precursors emerge. To identify an idealized mechanical regimen which can regulate MSC fate, low intensity vibration (LIV; <10 microstrain, 90 Hz) and high magnitude strain (HMS; 20,000 microstrain, 0.17 Hz) were examined in MSC undergoing adipogenesis. Two x twenty minute bouts of either LIV or HMS suppressed adipogenesis when there was at least a 1h refractory period between bouts; this effect was enhanced when the rest period was extended to 3h. Mechanical efficacy to inhibit adipogenesis increased with additional loading bouts if a refractory period was incorporated. Mechanical suppression of adipogenesis with LIV involved inhibition of GSK3β with subsequent activation of β-catenin as has been shown for HMS. These data indicate that mechanical biasing of MSC lineage selection is more dependent on event scheduling than on load magnitude or duration. As such, a full day of rest should not be required to "reset" the mechanical responsiveness of MSCs, and suggests that incorporating several brief mechanical challenges within a 24h period may improve salutary endpoints in vivo. That two diverse mechanical inputs are enhanced by repetition after a refractory period suggests that rapid cellular adaptation can be targeted.

Indomethacin promotes adipogenesis of mesenchymal stem cells through a cyclooxygenase independent mechanism

Regulation of mesenchymal stem cell (MSC) lineage selection is important for the generation of bone mass. Inhibition of cyclooxygenase-2 (COX2) may increase adipogenesis at the cost of decreasing osteoprogenitor output. Here we investigated the role of COX2 and its products during MSC differentiation. Indomethacin stimulated adipogenesis (increased aP2, adiponectin and lipid droplets) of CH310T1/2 stem cells as well as marrow-derived MSCs to a degree similar to the PPARγ2 ligand, rosiglitazone. Unlike rosiglitazone, indomethacin significantly upregulated PPARγ2 expression. Indomethacin and the COX2 specific inhibitor celecoxib suppressed PGE2 production, but celecoxib did not induce adipogenesis. As well, addition of PGE2 failed to reverse indomethacin induced adipogenesis, indicating that indomethacin's effects were prostaglandin independent. In MSCs over-expressing PPARγ2 and RXRα, indomethacin did not increase PPAR-induced transcription, while rosiglitazone and 15d-PGJ2 did (1.7- and 1.3-fold, respectively, P < 0.001). We considered whether indomethacin might directly affect C/EBPβ proximally to PPARγ2 induction. Indomethacin significantly increased C/EBPβ expression and protein within 24 h of addition. These results indicate that indomethacin promotes adipogenesis by increasing C/EBPβ and PPARγ2 expression in a prostaglandin-independent fashion. This effect of indomethacin is pertinent to potential deleterious effects of this commonly used anti-inflammatory drug on bone remodeling and tissue healing.

Mechanical activation of β-catenin regulates phenotype in adult murine marrow-derived mesenchymal stem cells

Regulation of skeletal remodeling appears to influence the differentiation of multipotent mesenchymal stem cells (MSC) resident in the bone marrow. As murine marrow cultures are contaminated with hematopoietic cells, they are problematic for studying direct effects of mechanical input. Here we use a modified technique to isolate marrow-derived MSC (mdMSC) from adult mice, yielding a population able to differentiate into adipogenic and osteogenic phenotypes that is devoid of hematopoietic cells. In pure mdMSC populations, a daily strain regimen inhibited adipogenic differentiation, suppressing expression of PPARγ and adiponectin. Strain increased β-catenin and inhibition of adipogenesis required this effect. Under osteogenic conditions, strain activated β-catenin signaling and increased expression of WISP1 and COX2. mdMSC were also generated from mice lacking caveolin-1, a protein known to sequester β-catenin: caveolin-1((-/-)) mdMSC exhibited retarded differentiation along both adipogenic and osteogenic lineages but retained mechanical responses that involved β-catenin activation. Interestingly, caveolin-1((-/-)) mdMSC failed to express bone sialoprotein and did not form mineralized nodules. In summary, mdMSC from adult mice respond to both soluble factors and mechanical input, with mechanical activation of β-catenin influencing phenotype. As such, these cells offer a useful model for studies of direct mechanical regulation of MSC differentiation and function.

A case report of right ventricular mass

Primary Cardiac tumors are uncommon during infancy and childhood. Myxomas originating in the right ventricles are even less common in paediatric patient. Our patient baby Rani, 3 months of age presented with shortness of breath and chest indrawing. Antenatal history and delivery was uneventful. The baby was under weight and also malnourished but there was no cyanosis and clubbing. Her respiratory rate was 25/minute. On precordium examination, first heart sound (S1) was normal but pulmonary component of second heart sound (P2) was soft. There was an ejection systolic murmur (Grade-3/6) in the left upper para-sternal area. Chest X-ray revealed cardiomegaly. Echocardiogram revealed a large mass (11x10mm) in the right ventricle, dynamically obstructing the right ventricular out-flow tract and compressing the left ventricle. There was a Tricuspid regurgitation (Grade-2) and moderate pulmonary hypertension (PASP-50 mmHg).

Correlation of platelet count and acute ST-elevation in myocardial infarction

The role of platelets in the pathogenesis of ST-elevation myocardial infarction (STEMI) has been substantiated by studies that demonstrated significant clinical benefits associated with antiplatelet therapy. Initial platelet counts in Acute Myocardial Infarction (AMI) may be a useful adjunct for identifying those patients who may or may not respond to fibrinolytic agents. Patient with acute STEMI has variable level of platelet count and with higher platelet count have poor in hospital outcome. There are many predictors of poor outcome in Acute Myocardial Infarction (AMI) like cardiac biomarkers (Troponin I, Troponin T and CK-MB), C-Reactive Protien (CRP) and WBC (White Blood Cell) counts. Platelet count on presentation of STEMI is one of them. Higher platelet count is associated with higher rate of adverse clinical outcome in ST-Elevation Myocardial Infarction (STEMI), like heart failure, arrhythmia, re-infarction & death. So, categorization of patient with STEMI on the basis of platelet counts may be helpful for risk stratification and management of these patients.

Mechanical loading regulates NFATc1 and beta-catenin signaling through a GSK3beta control node

Mechanical stimulation can prevent adipogenic and improve osteogenic lineage allocation of mesenchymal stem cells (MSC), an effect associated with the preservation of beta-catenin levels. We asked whether mechanical up-regulation of beta-catenin was critical to reduction in adipogenesis as well as other mechanical events inducing alternate MSC lineage selection. In MSC cultured under strong adipogenic conditions, mechanical load (3600 cycles/day, 2% strain) inactivated GSK3beta in a Wnt-independent fashion. Small interfering RNA targeting GSK3beta prevented both strain-induced induction of beta-catenin and an increase in COX2, a factor associated with increased osteoprogenitor phenotype. Small interfering RNA knockdown of beta-catenin blocked mechanical reduction of peroxisome proliferator-activated receptor gamma and adiponectin, implicating beta-catenin in strain inhibition of adipogenesis. In contrast, the effect of both mechanical and pharmacologic inhibition of GSK3beta on the putative beta-catenin target, COX2, was unaffected by beta-catenin knockdown. GSK3beta inhibition caused accumulation of nuclear NFATc1; mechanical strain increased nuclear NFATc1, independent of beta-catenin. NFATc1 knockdown prevented mechanical stimulation of COX2, implicating NFATc1 signaling. Finally, inhibition of GSK3beta caused association of RNA polymerase II with the COX2 gene, suggesting transcription initiation. These results demonstrate that mechanical inhibition of GSK3beta induces activation of both beta-catenin and NFATc1 signaling, limiting adipogenesis via the former and promoting osteoblastic differentiation via NFATc1/COX2. Our novel findings suggest that mechanical loading regulates mesenchymal stem cell differentiation through inhibition of GSK3beta, which in turn regulates multiple downstream effectors.

Food choice among homebound older adults: motivations and perceived barriers

OBJECTIVES

The purpose of this paper is to identify: motivations and perceived barriers associated with food choices made by homebound older adults; whether motivations and perceived barriers vary according to social demographic characteristics; and whether motivations and perceived barriers are associated with dietary quality.

DESIGN

This was an observational study using standard interview methods where participants were administered a questionnaire and completed three 24-hour dietary recalls.

SETTING

Participants were interviewed in their homes.

PARTICIPANTS

185 homebound older adults were included.

MEASUREMENT

Motivations were assessed using a modification of The Food Choice Questionnaire and perceived barriers were assessed using the Vailas Food Enjoyment Questionnaire. Participants answered questions regarding social demographic characteristics. Dietary quality measures of adequate intakes of calories, protein, vitamin D, and vitamin B12 were obtained from the three 24-hour dietary recalls.

RESULTS

Mean age was 78.9; 80% were female; and 36% were African American. Key motivations in food choice included sensory appeal, convenience, and price. Key barriers included health, being on a special diet, and being unable to shop. These varied little by social demographics, except for age. Dietary quality varied according to different motivations and barriers.

CONCLUSION

Food choices are based upon a complex interaction between the social and environmental context, the individual, and the food. Efforts to change eating behaviors, especially community-based interventions involving self-management approaches, must carefully take into account individuals' self-perceived motivations and barriers to food selection. Incorporating foods that are tasty, easy to prepare, inexpensive, and that involve caregivers are critical for successful interventions.

Mechanical strain inhibits adipogenesis in mesenchymal stem cells by stimulating a durable beta-catenin signal

The ability of exercise to decrease fat mass and increase bone mass may occur through mechanical biasing of mesenchymal stem cells (MSCs) away from adipogenesis and toward osteoblastogenesis. C3H10T1/2 MSCs cultured in highly adipogenic medium express peroxisome proliferator-activated receptor gamma and adiponectin mRNA and protein, and accumulate intracellular lipid. Mechanical strain applied for 6 h daily inhibited expression of peroxisome proliferator-activated receptor gamma and adiponectin mRNA by up to 35 and 50%, respectively, after 5 d. A decrease in active and total beta-catenin levels during adipogenic differentiation was entirely prevented by daily application of mechanical strain; furthermore, strain induced beta-catenin nuclear translocation. Inhibition of glycogen synthase kinase-3beta by lithium chloride or SB415286 also prevented adipogenesis, suggesting that preservation of beta-catenin levels was important to strain inhibition of adipogenesis. Indeed, mechanical strain inactivated glycogen synthase kinase-3beta, which was preceded by Akt activation, indicating that strain transmits antiadipogenic signals through this pathway. Cells grown under adipogenic conditions showed no increase in osteogenic markers runt-related transcription factor (Runx) 2 and osterix (Osx); subsequent addition of bone morphogenetic protein 2 for 2 d increased Runx2 but not Osx expression in unstrained cultures. When cultures were strained for 5 d before bone morphogenetic protein 2 addition, Runx2 mRNA increased more than in unstrained cultures, and Osx expression more than doubled. As such, mechanical strain enhanced MSC potential to enter the osteoblast lineage despite exposure to adipogenic conditions. Our results indicate that MSC commitment to adipogenesis can be suppressed by mechanical signals, allowing other signals to promote osteoblastogenesis. These data suggest that positive effects of exercise on both fat and bone may occur during mesenchymal lineage selection.

Beta-catenin levels influence rapid mechanical responses in osteoblasts

Mechanical loading of bone initiates an anabolic, anticatabolic pattern of response, yet the molecular events involved in mechanical signal transduction are not well understood. Wnt/beta-catenin signaling has been recognized in promoting bone anabolism, and application of strain has been shown to induce beta-catenin activation. In this work, we have used a preosteoblastic cell line to study the effects of dynamic mechanical strain on beta-catenin signaling. We found that mechanical strain caused a rapid, transient accumulation of active beta-catenin in the cytoplasm and its translocation to the nucleus. This was followed by up-regulation of the Wnt/beta-catenin target genes Wisp1 and Cox2, with peak responses at 4 and 1 h of strain, respectively. The increase of beta-catenin was temporally related to the activation of Akt and subsequent inactivation of GSK3beta, and caveolin-1 was not required for these molecular events. Application of Dkk-1, which disrupts canonical Wnt/LRP5 signaling, did not block strain-induced nuclear translocation of beta-catenin or up-regulation of Wisp1 and Cox2 expression. Conditions that increased basal beta-catenin levels, such as lithium chloride treatment or repression of caveolin-1 expression, were shown to enhance the effects of strain. In summary, mechanical strain activates Akt and inactivates GSK3beta to allow beta-catenin translocation, and Wnt signaling through LRP5 is not required for these strain-mediated responses. Thus, beta-catenin serves as both a modulator and effector of mechanical signals in bone cells.

Volkmann sign of non-ischaemic origin

This paper presents six cases who had a contracture of the long flexor tendons of the fingers and exhibited Volkmann's sign due to a chronic abscess or cysticercosis in the belly of the flexor digitorum profundus. All of them were treated conservatively, with full functional recovery in all the cases and with no recurrence.

The role of nitric oxide in the mechanical repression of RANKL in bone stromal cells

Both mechanical loading and nitric oxide (NO) have positive influences on bone mass. NO production is induced by mechanical strain via upregulation of eNOS mRNA and protein, the predominant NOS in adult bone. At the same time, strain causes decreased expression of RANKL, a factor critical for osteoclastogenesis. In this study, we harvested primary stromal cells from wild-type (WT) and eNOS(-/-) mice to test whether induction of NO by mechanical strain was necessary for transducing mechanical inhibition of RANKL. We found that strain inhibition of RANKL expression was prevented by NOS inhibitors (L-NAME and L-NMMA) in WT stromal cells. Surprisingly, stromal cells from eNOS(-/-) mice showed significant mechanical repression of RANKL expression (p<0.05). Mechanical strain still increased NO production in the absence of eNOS, and was abolished by SMTC, a specific nNOS inhibitor. nNOS mRNA and protein expression were increased by strain in eNOS(-/-) but not in WT cells, revealing that nNOS was mechanically sensitive. When NO synthesis was blocked with either SMTC or siRNA targeting nNOS in eNOS(-/-) cells however, strain still was able to suppress RANKL expression by 34%. This indicated that strain suppression of RANKL can also occur through non-NO dependent pathways. While our results confirm the importance of NO in the mechanical control of skeletal remodeling, they also suggest alternative signaling pathways by which mechanical force can produce anti-catabolic effects on the skeleton.

Caveolin-1 knockout mice have increased bone size and stiffness

The skeletal phenotype of the cav-1(-/-) mouse, which lacks caveolae, was examined. muCT and histology showed increased trabecular and cortical bone caused by the gene deletion. Structural changes were accompanied by increased mechanical properties. Cell studies showed that cav-1 deficiency leads to increased osteoblast differentiation. These results suggest that cav-1 helps to maintain osteoblast progenitors in a less differentiated state.

INTRODUCTION

The absence of caveolin-1 in cellular membranes causes dysregulated signaling. To understand the role of the caveolar microdomain in bone homeostasis, we examined the skeletal phenotype of 5- and 8-wk-old cav-1(-/-) mice.

MATERIALS AND METHODS

High-resolution microCT imaging showed a region-specific effect of cav-1 deficiency on the skeleton. At 5 wk, cav-1(-/-) mice had increased epiphyseal bone volume (+58.4%, p = 0.05); at 8 wk, metaphyseal bone volume was increased by 77.4% (p = 0.008). Cortical bone at the femoral mid-diaphysis showed that the periosteal area of cav-1(-/-) mice significantly exceeded that of cav-1(+/+) mice by 23.9% and 16.3% at 5 and 8 wk, respectively, resulting in increased mechanical properties (I(max): +38.2%, p = 0.003 and I(mi): +23.7%, p = 0.03).

RESULTS

Histomorphometry complemented microCT results showing increased bone formation rate (BFR) at trabecular and cortical sites at 5 wk, which supported findings of increased bone at 8 wk in cav-1(-/-) mice. Formal mechanical testing of the femoral diaphysis confirmed increased bone structure: stiffness increased 33% and postyield deflection decreased 33%. Stromal cells from cav-1(-/-) marrow showed a 23% increase in von Kossa-positive nodules; osteoclastogenesis was also modestly increased in cav-1-deficient marrow. Knockdown of cav-1 with siRNA in wildtype stromal cells increased alkaline phosphatase protein and expression of osterix and Runx2, consistent with osteoblast differentiation.

CONCLUSIONS

These data suggest that cav-1 helps to maintain a less differentiated state of osteoblast progenitor cells, and the absence of cav-1 causes bone to mature more rapidly. Caveolin-1 may thus be a target for altering skeletal homeostasis.