Project description:We investigated calcaneal tendon extracellular matrix (ECM) remodeling after gastrocnemius muscle injury using a rat model. Wistar rats were randomly divided into four groups: control group (C; animals that were not exposed to muscle injury) and harvested at different time points post gastrocnemius muscle injury (3, 14 and 28 days) for gene expression analysis. qRT-PCR was performed using TaqMan Universal PCR Master Mix system (Applied Biosystems, CA, USA - Cat. 4304437).
Project description:Cross-talk between skeletal muscle and tendon is important for tissue homeostasis. Whereas the skeletal muscle response to tendon injury has been well-studied, to the best of our knowledge the tendon response to skeletal muscle injury has been neglected. Thus, we investigated calcaneal tendon extracellular matrix (ECM) remodeling after gastrocnemius muscle injury using a rat model. Wistar rats were randomly divided into four groups: control group (C; animals that were not exposed to muscle injury) and harvested at different time points post gastrocnemius muscle injury (3, 14, and 28 days) for gene expression, morphological, and biomechanical analyses. At 3 days post injury, we observed mRNA-level dysregulation of signaling pathways associated with collagen I accompanied with disrupted biomechanical properties. At 14 days post injury, we found reduced collagen content histologically accompanied by invasion of blood vessels into the tendon proper and an abundance of peritendinous sheath cells. Finally, at 28 days post injury, there were signs of recovery at the gene expression level including upregulation of transcription factors related to ECM synthesis, remodeling, and repair. At this time point, tendons also presented with increased peritendinous sheath cells, decreased adipose cells, higher Young's modulus, and lower strain to failure compared to the uninjured controls and all post injury time points. In summary, we demonstrate that the calcaneal tendon undergoes extensive ECM remodeling in response to gastrocnemius muscle injury leading to altered functional properties in a rat model. Tendon plasticity in response to skeletal muscle injury merits further investigation to understand its physiological relevance and potential clinical implications.
Project description:Partial tendon-to-bone interface (TBI) injuries heal in a mechanically inferior manner and redevelop healthy uninjured tissue morphology. The origin of the cells involved in tendon-to-bone healing remains unknown. We employed a rigorous approach to evaluate if mouse skeletal stem cells (mSSC) play a role in tendon-to-bone healing after partial-injury. Using fluorescence-activated cell sorting we identified that found that they are present within the TBI. Using a TBI-injury rainbow lineage tracing mouse model, we demonstrated that injury-responsive cells within the TBI and calcaneus proliferate polyclonally following partial-tendon injury at the TBI. These injury-responsive clonal cells express skeletal marker SP7. We quantified the differences in mSCC frequency after TBI-injury and found that mSSC respond to injury with a higher frequency and have associated changes in gene expression, with the specific down-regulation of the TGFβ signaling pathway. Exogenous delivery of TGFβ after injury was found to reduce the mSSC response after injury. These findings suggest that mSSC may facilitate tendon-to-bone healing by downregulating TGFβ signaling within the mSSC niche.
Project description:Injury was induced in the left Achilles tendon by needle puncture. Rats were sacrificed 4 and 21 days post injury. Shams, in which the tendon was isolated but not punctured, were included as controls. Serum was collected post-mortem and RNAseq used to identify differentially expressed ncRNAs.
Project description:The rat tendon injury models were established and divided into three groups: normal control group, injury model group, and celecoxib + lactoferrin treatment group. Then, RNA sequencing and differential expression analysis were performed for samples from injury model group and celecoxib + lactoferrin treatment group on day 14. Next, autophagy/hypoxia/ferroptosis/pyroptosis-related genes retrieved from the corresponding databases and related literatures were downloaded to obtain the genes associated with autophagy/hypoxia/ferroptosis/pyroptosis. Subsequently, functional annotation, protein-protein interaction (PPI) network and transcriptional regulatory network construction for these genes were performed.
Project description:Intralesional mesenchymal stem cell (MSC) therapy has improved tissue architecture and reinjury rates in equine tendon injury; however, the mechanisms by which they promote repair are still being investigated. Therefore, the objectives of this study were to determine how the predominate pro-inflammatory cytokines present in a surgically induced model of equine tendon injury modulate MSC gene and protein expression.