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Research Containing: Bone formation

Could the effect of modeled microgravity on osteogenic differentiation of human mesenchymal stem cells be reversed by regulation of signaling pathways?

by on 9 June 2015in Biology & Biotechnology No comment

Microgravity (MG) results in a reduction in bone formation. Bone formation involves osteogenic differentiation from mesenchymal stem cells (hMSCs) in bone marrow. We modeled MG to determine its effects on osteogenesis of hMSCs and used activators or inhibitors of signaling factors to regulate osteogenic differentiation. Under osteogenic induction, MG reduced osteogenic differentiation of hMSCs and decreased the expression of osteoblast gene markers. The expression of Runx2 was also inhibited, whereas the expression of PPARgamma2 increased. MG also decreased phosphorylation of ERK, but increased phosphorylation of p38MAPK. SB203580, a p38MAPK inhibitor, was able to inhibit the phosphorylation of p38MAPK, but did not reduce the expression of PPARgamma2. Bone morphogenetic protein (BMP) increased the expression of Runx2. Fibroblast growth factor 2 (FGF2) increased the phosphorylation of ERK, but did not significantly increase the expression of osteoblast gene markers. The combination of BMP, FGF2 and SB203580 significantly reversed the effect of MG on osteogenic differentiation of hMSCs. Our results suggest that modeled MG inhibits the osteogenic differentiation and increases the adipogenic differentiation of hMSCs through different signaling pathways. Therefore, the effect of MG on the differentiation of hMSCs could be reversed by the mediation of signaling pathways.

Related URLs:
http://ovidsp.ovid.com/ovidweb.cgi?T=JS&CSC=Y&NEWS=N&PAGE=fulltext&D=emed8&AN=2007294544
http://sfxhosted.exlibrisgroup.com/mayo?sid=OVID:embase&id=pmid:&id=doi:10.1515%2FBC.2007.082&issn=1431-6730&isbn=&volume=388&issue=7&spage=755&pages=755-763&date=2007&title=Biological+Chemistry&atitle=Could+the+effect+of+modeled+microgravity+on+osteogenic+differentiation+of+human+mesenchymal+stem+cells+be+reversed+by+regulation+of+signaling+pathways%3F&aulast=Zheng&pid=%3Cauthor%3EZheng+Q.%3C%2Fauthor%3E&%3CAN%3E2007294544%3C%2FAN%3E

Simulated microgravity alters multipotential differentiation of rat mesenchymal stem cells in association with reduced telomerase activity

by on 9 June 2015in Biology & Biotechnology No comment

Microgravity is one of the most important characteristics in space flight. Exposure to microgravity results in extensive physiological changes in humans. Bone loss is one of the changes with serious consequences: however. the mechanism retains unclear. As the origin of osteoprogenitors, mesenchymal stein cells (MSCs) may play an important role in it. After cultured under simulated microgravity (in a rotary cell culture system, RCCS), MSCs were stained using oil red O to identify adipocytes. The mRNA level of bone morphogenetic protein (BMP)-2 and peroxisome proliferators-activated receptor (PPAR) gamma 2 was determined by RT-PCR. Otherwise, MSCs were induced to osteogenic differentiation after microgravity culture, and then the activity of alkaline phosphatase (ALP) was determined by PNPP and the content of osteocalcin (OC) by ELISA. Furthermore, the telomerase activity in MSCs was measured by TRAP. The results showed that simulated microgravity inhibited osteoblastic differentiation and induced adipogenic differentiation accompanied by the change of gene expression of BMP-2 and PPAR gamma 2 in MSCs. Meanwhile, the telomerase activity decreased significantly in MSCs under simulated microgravity. The reduced bone formation in space flight may partly be due to the altered potential differentiation of MSCs associated with telomerase activity which plays a key role in regulating the lifespan of cell proliferation and differentiation. Therefore. telomerase activation/replacement may act as a potential countermeasure for microgravity-induced bone loss. (C) 2008 Elsevier Ltd. All rights reserved.

Related URLs:
<Go to ISI>://WOS:000259409100033

Adaptation of the Skeletal System During Long-Duration Spaceflight

by on 9 June 2015in Biology & Biotechnology No comment

This review will highlight evidence from crew members flown on space missions >90 days to suggest that the adaptations of the skeletal system to mechanical unloading may predispose crew members to an accelerated onset of osteoporosis after return to Earth. By definition, osteoporosis is a skeletal disorder—characterized by low bone mineral density (BMD) and structural deterioration—that reduces the ability of bones to resist fracture under the loading of normal daily activities. “Involutional” or age-related osteoporosis is readily recognized as a syndrome afflicting the elderly population because of the insipid and asymptomatic nature of bone loss that does not typically manifest as fractures until after age ∼60. It is not the thesis of this review to suggest that spaceflight-induced bone loss is similar to bone loss induced by metabolic bone disease; rather this review draws parallels between the rapid and earlier loss in females that occurs with menopause and the rapid bone loss in middle-aged crew members that occurs with spaceflight unloading and how the cumulative effects of spaceflight and ageing could be detrimental, particularly if skeletal effects are totally or partially irreversible. In brief, this report will provide detailed evidence that long-duration crew members, exposed to the weightlessness of space for the typical long-duration (4–6 months) mission on Mir or the International Space Station, (1) display bone resorption that is aggressive, that targets normally weight-bearing skeletal sites, that is uncoupled to bone formation, and that results in areal BMD deficits that can range between 6 and 20% of preflight BMD; (2) display compartment-specific declines in volumetric BMD in the proximal femur (a skeletal site of clinical interest) that significantly reduces its compressive and bending strength and may account for the loss in hip bone strength (i.e., force to failure); (3) recover BMD over a post-flight time period that exceeds spaceflight exposure but for which the restoration of whole bone strength remains an open issue and may involve structural alteration; and (4) display risk factors for bone loss—such as the negative calcium balance and down-regulated calcium-regulating hormones in response to bone atrophy—that can be compounded by the constraints of conducting mission operations (inability to provide essential nutrients and vitamins). The full characterization of the skeletal response to mechanical unloading in space is not complete. In particular, countermeasures used to date have been inadequate, and it is not yet known whether more appropriate countermeasures can prevent the changes in bone that have been found in previous flights. Knowledge gaps related to the effects of prolonged (≥6 months) space exposure and to partial gravity environments are substantial, and longitudinal measurements on crew members after spaceflight are required to assess the full impact on skeletal recovery.

Related URLs:
http://dx.doi.org/10.1007/s12018-008-9012-8

Modeled Microgravity disrupts integrin expression and function during osteoblastogenesis of human mesenchymal stem cells

by on 9 June 2015in Biology & Biotechnology No comment

Spaceflight leads to reduced bone mineral density in weight bearing bones that is primarily attributed to a reduction in bone formation. We have previously demonstrated severely reduced osteoblastogenesis of human mesenchymal stem cells (hMSC) following 7 days culture in modeled microgravity (MMG). One potential mechanism for reduced osteoblastic differentiation is disruption of type I collagen (Col I)-integrin interactions and reduced integrin signaling. Integrins are heterodimeric transmembrane receptors that bind extracellular matrix (ECM) proteins and produce signals essential for proper cellular function, survival, and differentiation. Therefore, we investigated the effects of MMG on integrin expression and function in hMSC. We demonstrate that 7 days of culture in MMG leads to reduced expression of the ECM protein, Col I. Conversely, MMG consistently increases Col I-specific alpha2 and beta1 integrin protein expression. Despite this increase in integrin subunit expression, autophosphorylation of adhesion-dependent kinases, focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (PYK2), is significantly reduced. Activation of Akt protein kinase (Akt) is unaffected by the reduction in FAK activation. However, reduced downstream signaling via the Ras-mitogen activated protein kinase (MAPK) pathway is evidenced by a reduction in Ras and extracellular signal-related protein kinase (ERK) activation. Taken together, our findings indicate that MMG decreases integrin/MAPK signaling, which likely contributes to the observed reduction in osteoblastogenesis.

Related URLs:
<Go to ISI>://WOS:000186080500854

The use of murine embryonic stem cells, alginate encapsulation, and rotary microgravity bioreactor in bone tissue engineering

by on 9 June 2015in Biology & Biotechnology No comment

The application of embryonic stem cells (ESCs) in bone tissue engineering and regenerative medicine requires the development of suitable bioprocesses that facilitate the integrated, reproducible, automatable production of clinically-relevant, scaleable, and integrated bioprocesses that generate sufficient cell numbers resulting in the formation of three-dimensional (3D) mineralised, bone tissue-like constructs. Previously, we have reported the enhanced differentiation of undifferentiated mESCs toward the osteogenic lineage in the absence of embryoid body formation. Herein, we present an efficient and integrated 3D bioprocess based on the encapsulation of undifferentiated mESCs within alginate hydrogels and culture in a rotary cell culture microgravity bioreactor. Specifically, for the first 3 days, encapsulated mESCs were cultured in 50% (v/v) HepG2 conditioned medium to generate a cell population with enhanced mesodermal differentiation capability followed by osteogenic differentiation using osteogenic media containing ascorbic acid, β-glycerophosphate and dexamethasone. 3D mineralised constructs were generated that displayed the morphological, phenotypical, and molecular attributes of the osteogenic lineage, as well mechanical strength and mineralised calcium/phosphate deposition. Consequently, this bioprocess provides an efficient, automatable, scalable and functional culture system for application to bone tissue engineering in the context of macroscopic bone formation.

Related URLs:
http://ovidsp.ovid.com/ovidweb.cgi?T=JS&CSC=Y&NEWS=N&PAGE=fulltext&D=emed9&AN=2008550758
http://sfxhosted.exlibrisgroup.com/mayo?sid=OVID:embase&id=pmid:&id=doi:10.1016%2Fj.biomaterials.2008.07.028&issn=0142-9612&isbn=&volume=30&issue=4&spage=499&pages=499-507&date=2009&title=Biomaterials&atitle=The+use+of+murine+embryonic+stem+cells%2C+alginate+encapsulation%2C+and+rotary+microgravity+bioreactor+in+bone+tissue+engineering&aulast=Hwang&pid=%3Cauthor%3EHwang+Y.-S.%3C%2Fauthor%3E&%3CAN%3E2008550758%3C%2FAN%3E

IMPACT OF OSTEOCLAST PRECURSORS SUBJECTED TO RANDOM POSITIONING MACHINE ON OSTEOBLASTS

by on 9 June 2015in Biology & Biotechnology No comment

Osteoblast-osteoclast interaction plays an important role in the bone remodeling. During long duration space flight, astronauts undergo serious bone loss mainly due to the disruption of equivalence between bone formation and bone resorption. Osteoclast precursors often operate under the control of osteoblasts. However, here we show that the osteoclast precursors could in turn influence osteoblasts. RAW264.7 cells, the murine osteoclast precursors, were treated in the simulated weightlessness produced by a Random Positioning Machine (RPM). After 72 h, conditioned mediums (CM) by the RAW264.7 cells from RPM (RCM) or static control (CCM) were collected and were used to culture osteoblastic-like MC3T3-E1 cells. The results showed that the RCM culture inhibited cell viability and slightly altered cell cycle, but the morphology of the MC3T3-E1 cells was not changed by RCM compared to that of CCM. Furthermore, the intracellular ALP level, NO release and expression of osteoblastic marker genes were all down-regulated by RCM culture. These results suggest that osteoclast precursors subjected to RPM exert negative regulation on osteoblasts.

Related URLs:
<Go to ISI>://WOS:000310159000027

MOLECULAR THERAPIES FOR DISUSE OSTEOPOROSIS

by on 9 June 2015in Biology & Biotechnology No comment

Microgravity causes changes in physiological systems that are both detrimental to human health and valuable for biomedical research. Some of the most pronounced and long-term changes occur in skeletal tissue, which experiences a profound and rapid wasting. Finding a countermeasure to the bone atrophy associated with weightlessness is necessary before long-duration human space exploration can be possible. However, these physiological changes can also be exploited as a biomedical model for osteoporosis, offering an extreme environment in which therapeutics can be tested and mechanisms examined. Utilizing space as a biomedical test-bed has been done on several flights: STS-41, 52, 57, 60, 62, 63, 77 and 108, the aims and results of which will be briefly summarized. The rational for spaceflight serving as a biomedical test-bed is that microgravity exposure (and resulting changes in the spacecraft environment) causes an accelerated model for biomedical disorders experienced, often as a result of the normal aging process, here on Earth. The most common target system for these flights was skeletal, with the goal of mimicking osteoporosis, but immune dysfunction, wound healing and muscle atrophy were also studied. Most recently (STS-108, December 2001), the biotechnology company Amgen examined the ability of osteoprotegerin (OPG) to mitigate the osteoporosis caused by microgravity. OPG is a protein that is critical to the differentiation and activation of bone resorbing osteoclasts. Amgen is developing OPG as a treatment for osteoporosis and the bone loss associated with metastatic bone cancer. Over the 12-day flight, the mice experienced a decline in bone strength (15-20% relative to ground controls) that was greater than that of ground-based disuse models. The mechanical testing data was complimented by serum, mRNA and histological analyses that indicated a decline in bone formation and an increase in bone resorption in addition to an inhibition of mineralization. OPG mitigated the decline in mechanical strength by preventing the increase in resorption and maintaining mineralization.

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