A recent physiological study established that hindlimb unloading of rats at 3 and 7 weeks inhibits healing of injured ligaments resulting in a badly aligned discontinuous collagen matrix. Using tissue from these rats we focused on the 3-week time point employing microarray analysis to identify what cellular processes or lack of processes could account for these observed deficiencies. We used the Affymetrix RG_U34A GeneChip and performed image analysis with Microarray Suite 5.0. For normalization we used the MAS global normalization protocol with a default target mean signal of 500. Gene expression in medial collateral ligament tissue under 4 different treatment conditions was measured: loaded control loaded wound healing unloaded control and unloaded wound healing. From our results it appears that unloaded tissue lags behind loaded tissue in its progression through the healing process and at 3 weeks is still engaged in the proliferative phase whereas loaded tissue is actively remodeling its collagen matrix.

Analysis of effect of hindlimb suspension and reloading on C57Bl/6 mouse soleus muscle. Experimental groups examined: -Control mice 14 days -Hindlimb suspension for 7 days -Hindlimb suspension for 7 days and subsequent reloading for 1 day -Hindlimb suspension for 7 days and subsequent reloading for 7 days

['"The annotation of the Affymetrix HTA 2.0 array was updated to optimise the detection of RNA in human skeletal muscle biopsy samples by removing invalid and low signal-high-variance probes (as for CDF GPL24047). The probes were then summarized into groups (probe-sets) reflecting either an ensembl full transcript identifier (FL-ENST, GPL24047) or just the probes targeting the 3\' UTR or the 5\' UTR of that particular ENST. Therefore, 3 different CDF were used to process the HTA 2.0 arrays in this study. Note that each CEL file was GC adjusted using APT while our custom CDF pipeline removes any probe that has >80% or <20% GC content (~50,000). The analysis was carried out only on the pairs of probe-sets i.e. FL-ENST vs 3\'UTR or FL-ENST vs 5\'UTR or 3\'UTR vs 5\'UTR. Dynamic muscle loading alters tissue phenotype reflecting altered metabolic and functional demands. In humans, heterogeneous adaptation to loading complicates identification of the underpinning molecular regulators. We present a within-person analysis strategy that reduced heterogeneity for changes in muscle mass by ~40% and employed a genome-wide transcriptome method that modeled each mRNA from coding exons and 3’/5’ untranslated (UTR) regions. Our strategy detected ~3-4 times more regulated genes than similarly sized studies, including substantial UTR-selective regulation that other methods would not detect. We discovered a core of 141 genes correlated to muscle growth validated from newly analyzed independent samples (n=100). Further validating these identified genes, via RNAi in primary muscle cells, we demonstrate that members of the core genes were regulators of protein synthesis e.g. Molecular Transducers of Physical Activity in Humans MoTrPAC. Employing proteome-constrained networks and pathway analysis revealed notable relationships with the molecular characteristics of human muscle aging and insulin sensitivity, as well as potential drug-therapies."']

Reduced skeletal loading leads to marked bone loss. Animal models of hindlimb suspension are widely used to assess alterations in skeleton during the course of complete unloading. More recently, the effects of partial unloading on the musculoskeletal system have been interrogated in mice and rats, revealing dose-dependent effects of partial weight bearing (PWB) on the skeleton and skeletal muscle. Here, we extended these studies to determine the structural and functional skeletal alterations in 14-week-old male Wister rats exposed to 20%, 40%, 70%, or 100% of body weight for 1, 2, or 4 weeks (n  equals 11–12/group). Using in vivo pQCT, we found that trabecular bone density at the proximal tibia declined in proportion to the degree of unloading and continued progressively with time, without evidence of a plateau by 4 weeks. Ex vivo measurements of trabecular microarchitecture in the distal femur by microcomputed tomography revealed deficits in bone volume fraction, 2 and 4 weeks after unloading. Histologic analyses of trabecular bone in the distal femur revealed the decreased osteoblast number and mineralizing surface in unloaded rats. Three-point bending of the femoral diaphysis indicated modest or no reductions in femoral stiffness and estimated modulus due to PWB. Our results suggest that this rat model of PWB leads to trabecular bone deterioration that is progressive and generally proportional to the degree of PWB, with minimal effects on cortical bone. This study derives results from the pQCT assay using tibia tissue.

Background SPARC is a matricellular protein involved in cell-matrix interactions. From expression patterns at the wound site and in vitro studies, SPARC has been implicated in the control of wound healing. Here we examined the function of SPARC in cutaneous wound healing using SPARC-null mice and dermal fibroblasts derived from them. Results In large (25 mm) wounds, SPARC-null mice showed a significant delay in healing as compared to wild-type mice (31 days versus 24 days). Granulation tissue formation and extracellular matrix protein production were delayed in small 6 mm SPARC-null wounds initially but were resolved by day 6. In in vitro wound-healing assays, while wild-type primary dermal fibroblasts showed essentially complete wound closure at 11 hours, wound closure of SPARC-null cells was incomplete even at 31 hours. Addition of purified SPARC restored the normal time course of wound closure. Treatment of SPARC-null cells with mitomycin C to analyze cell migration without cell proliferation showed that wound repair remained incomplete after 31 hours. Cell proliferation as measured by 3H-thymidine incorporation and collagen gel contraction by SPARC-null cells were not compromised. Conclusions A significant delay in healing large excisional wounds and setback in granulation tissue formation and extracellular matrix protein production in small wounds establish that SPARC is required for granulation tissue formation during normal repair of skin wounds in mice. A defect in wound closure in vitro indicates that SPARC regulates cell migration. We conclude that SPARC plays a role in wound repair by promoting fibroblast migration and thus granulation tissue formation.

Gene expression changes induced by acute skeletal muscle unloading which leads to physiological changes including muscle atrophy fibre-type switching and loss of ability to transition between lipid and glucose as energy source (metabolic inflexibility) was investigated by hind-limb suspension (HLS) treatment of Male ICR mice (28 x9632 g body wt; Harlan Indianapolis IN). Agilent Whole Mouse Genome Oligo Microarrays were utilised to examine the effects of HLS on mRNA expression profiles of the soleus muscle and the gastrocnemius muscle in the hindlimbs of freely ambulating control and 24h HLS treated mice.

The purpose of this study was to evaluate transcriptional changes in mouse spleens using a ground-based model for spaceflight. This model includes prolonged unloading and low-dose irradiation. Low-dose-rate gamma-radiation was delivered to 6-month old female C57BL/6J mice using 57Co plates (0.04 Gy) to simulate the radiation environment of spaceflight. Anti-orthostatic tail suspension was used to model the unloading fluid shift and physiological stress aspects of the microgravity component of spaceflight. Mice were hindlimb suspended and/or irradiated for 21 days. Mice were euthanized and spleens collected 7 days following treatment. RNA sequencing data was generated to assess transcriptional changes in these spleens.

Background Fracture healing slows with age. While 6-week-old rats regain normal bone biomechanics at 4 weeks after fracture, one-year-old rats require more than 26 weeks. The possible role of altered mRNA gene expression in this delayed union was studied. Closed mid-shaft femoral fractures were induced followed by euthanasia at 0 time (unfractured) or at 1, 2, 4 or 6 weeks after fracture in 6-week-old and 12-15-month-old Sprague-Dawley female rats. mRNA levels were measured for osteocalcin, type I collagen α1, type II collagen, bone morphogenetic protein (BMP)-2, BMP-4 and the type IA BMP receptor. Results For all of the genes studied, the mRNA levels increased in both age groups to a peak at one to two weeks after fracture. All gene expression levels decreased to very low or undetectable levels at four and six weeks after fracture for both age groups. At four weeks after fracture, the younger rats were healed radiographically, but not the older rats. Conclusions (1) All genes studied were up-regulated by fracture in both age groups. Thus, the failure of the older rats to heal promptly was not due to the lack of expression of any of the studied genes. (2) The return of the mRNA gene expression to baseline values in the older rats prior to healing may contribute to their delayed union. (3) No genes were overly up-regulated in the older rats. The slower healing response of the older rats did not stimulate a negative-feedback increase in the mRNA expression of stimulatory cytokines.

The advances in biomedicine over the past decade have provided revolutionary insights into molecules that mediate cell proliferation and differentiation. Findings on the complex interplay of cells, growth factors, matrix molecules and cell adhesion molecules in the process of tissue patterning have vitalized the revolutionary approach of bioregenerative medicine and tissue engineering. Here we review the impact of recent work in this interdisciplinary field on the treatment of musculoskeletal disorders. This novel concept combines the transplantation of pluripotent stem cells, and the use of specifically tailored biomaterials, arrays of bioactive molecules and gene transfer technologies to direct the regeneration of pathologically altered musculoskeletal tissues.

NASA s Rodent Research (RR) project is playing a critical role in advancing biomedical research on the physiological effects of space environments. Due to the limited resources for conducting biological experiments aboard the International Space Station (ISS) it is imperative to use crew time efficiently while maximizing high-quality science return. NASA s GeneLab project has as its primary objectives to 1) further increase the value of these experiments using a multi-omics systems biology-based approach and 2) disseminate these data without restrictions to the scientific community. The current investigation assessed viability of RNA DNA and protein extracted from archived RR-1 tissue samples for epigenomic transcriptomic and proteomic assays. During the first RR spaceflight experiment a variety of tissue types were harvested from subjects snap-frozen or RNAlater-preserved and then stored at least a year at -80C after return to Earth. They were then prioritized for this investigation based on likelihood of significant scientific value for spaceflight research. All tissues were made available to GeneLab through the bio-specimen sharing program managed by the Ames Life Science Data Archive and included mouse adrenal glands quadriceps gastrocnemius tibialis anterior extensor digitorum longus soleus eye and kidney. We report here protocols for and results of these tissue extractions and thus the feasibility and value of these kinds of omics analyses. In addition to providing additional opportunities for investigation of spaceflight effects on the mouse transcriptome and proteome in new kinds of tissues our results may also be of value to program managers for the prioritization of ISS crew time for rodent research activities.