Project description:A tendon’s ordered extracellular matrix (ECM) is integral for transmitting force and highly prone to injury. Whether and how tendon cells, or tenocytes, embedded within this dense ECM mobilize and contribute to healing is unknown. Here, we identify a specialized Axin2+ tenocyte population in mouse and human tendons that remains latent in homeostasis yet serves as a major source of tendon progenitors during healing. We show that Axin2+ tenocytes readily expand in vitro and express stem cell markers. In vivo, Axin2+ cells are major functional contributors to repair: Axin2+ tenocytes de-differentiate, expand, and re-adopt a tenocyte fate post-injury. Specific loss of Wnt secretion in Axin2+ cells alters their stem cell identity and disrupts their activation upon injury, severely compromising healing. Our work highlights Axin2+ tenocytes as quiescent stem cells embedded in dense matrix, which are uniquely regulated in an autocrine manner and are central organizers of robust tendon healing.
Project description:Despite their important roles in the musculoskeletal system, tendon and ligaments are much less studied comparing to bone, cartilage and muscle. The lack of knowledge in tendon biology severely hinders the understanding of the etiologies of tendon related diseases and development of efficient clinical treatments. In mouse, Scx gene, encoding a Twist family bHLH transcription factor, is expressed in progenitors of all tendons and ligaments, as well as in mature tenocytes. Previous studies show that inactivation of Scx gene results in absence or severe hypoplastia of force transmitting tendons, with muscle anchoring tendons and ligaments are less affected. Here we report a set of ChIPseq data from E13.5 forelimbs of novel Scx-2xFlag tagged mice in which a Scx-Flag fusion protein is expressed recapitulating endogenous Scx expression, and a set of RNAseq data of Scx-GFP positive cells from E13.5 Scx wildtype, E15.5 Scx wildtype and homozygous mutant forelimbs. Using RNAseq and ChIPseq assays, we identify several genes exhibiting Scx-dependent tendon expression druing differentiation, with Scx binding peaks located within their promoter/enhancer regions. Thus these genes may play critical roles in mediating Scx regulated tendon cell differentiation. Our results provide new insights in the mechanisms of tendon development.
Project description:Little is understood about the roles of tendon cells during flexor tendon healing. To better understand tendon cell functions, the Scx-Cre mouse was crossed to the DTR mouse model to facilitate scleraxis lineage cell depletion prior to acute flexor tendon injury and repair. WT (cre-) and experimental (cre+) mice underwent complete transection and repair of the flexor digitorum longus tendon. Repaired tendons were harvested at 14 and 28 days post-repair for bulk RNA-Seq analysis to examine possible mechanisms driving differential healing due to Scx lineage cell depletion.
Project description:To investigate which mRNA and miRNA are involved in Dicer KO mouse tendon hypoplasticity, we performed RNA-seq and small RNA-seq using RNA from Achilles tendon of Cont (Dicer f/f), Scx HT (ScxCre/+ Knock In:Dicer +/+) and Dicer KO (ScxCre/+ Knock In:Dicer f/f) mice at 4 weeks of age. Achilles tendon from 4-week-old female mice was harvested, RNA was isolated using an RNA extraction kit. RNA libraries were generated and sequenced by K. K. DNAFORM (Tokyo, Japan). The libraries were sequenced by Illumina HISEQ4000 using Illumina provided protocol. Differential gene expression was analyzed with R Bioconductor DESeq2. We found that a large portion of tendon-fibroblast characteristic genes was downregulated in Dicer KO mice Achilles tendon compared to Cont and Scx HT.
Project description:We have undertaken a screen of mouse limb tendon cells in order to identify molecular pathways involved in tendon development. Mouse limb tendon cells were isolated based on Scleraxis (Scx) expression at different stages of development: E11.5, E12.5 and E14.5 Microarray comparisons were carried out between tendon progenitor and differentiated stages. Forelimbs from E11.5, E12.5 and E14.5 Scx-GFP embryos were collected and dissociated with trypsin to obtain cell suspensions. Scx-positive tendon cells were isolated by FACS. RNA was extracted and Fragmented biotin-labelled cRNA samples were hybridized on Affymetrix Gene Chip Mouse Genome 430 2.0 arrays.
Project description:We have undertaken a screen of mouse limb tendon cells in order to identify molecular pathways involved in tendon development. Mouse limb tendon cells were isolated based on Scleraxis (Scx) expression at different stages of development: E11.5, E12.5 and E14.5 Microarray comparisons were carried out between tendon progenitor and differentiated stages.
Project description:Purpose: Our lab has previously shown that Scleraxis (Scx) is require for proper valve development in vivo. In order to fully explore gene networks regulated by Scx during the vital stages of valve remodeling , high throughput RNA-squencing was performed. Results:There were a total of 18,810 genes were detected. A total of 864 genes were differentially expressed Scx null AVC regions: 645 being upregulated and 217 downregulated. In this data set, we include expression data from atrioventricular canal (AVC) regions from Scx null and wild-type littermate controls at embryonic day 15.5. A total of 6 samples were analyzed; 3 valve regions from E15.5 Scx-/- mice, and 3 from E15.5 Scx+/+ wild-type littermate controls. Differential expression read counts are ranked based on p-value (<0.05).
Project description:Tendons are dense connective tissues with relatively few cells which makes studying the molecular profile of the tissue challenging. There is not a consensus on the spatial location of various cell types within a tendon, nor the accompanying transcriptional profile. In the present study, we used two male rat patellar tendon samples for sequencing-based spatial transcriptomics to determine the gene expression profile. We integrated our data with a single cell dataset to predict the cell type composition of the patellar tendon as a function of location within the tissue. The spatial location of the predicated cell types suggested that there were two populations of tendon fibroblasts, one located in the tendon midsubstance, while the other localized with red blood cells, pericytes, and immune cells to the tendon peripheral connective tissue. Of the highest expressed spatially variable genes, there were multiple genes with known function in tendon: Col1a1, Col1a2, Dcn, Fmod, Sparc, and Comp. Further, a novel spatially regulated gene (AABR07000398.1) with no known function was identified. The spatial gene expression of tendon associated genes (Scx, Thbs4, Tnmd, Can, Bgn, Lum, Adamts2, Lox, Ppib, Col2a1, Col3a1, Col6a2) was also visualized. Both patellar tendon samples had similar expression patterns for all these genes. This dataset provides new spatial insights into gene expression in a healthy tendon.