Loss of Tenomodulin Results in Reduced Self-Renewal and Augmented Senescence of Tendon Stem/Progenitor Cells

Abstract

Tenomodulin (Tnmd) is a well-known gene marker for the tendon and ligament lineage, but its exact functions in these tissues still remain elusive. In this study, we investigated Tnmd loss of function in mouse tendon stem/progenitor cells (mTSPC) by implicating a previously established Tnmd knockout (KO) mouse model. mTSPC were isolated from control and Tnmd KO tail tendons and their stemness features, such as gene marker profile, multipotential, and self-renewal, were compared. Immunofluorescence and reverse transcriptase-polymerase chain reaction analyses for stem cell-, tenogenic-, osteogenic-, and chondrogenic-related genes confirmed their stemness and lineage specificity and demonstrated no profound differences between the two genotypes. Multipotential was not significantly affected since both cell types differentiated successfully into adipogenic, osteogenic, and chondrogenic lineages. In contrast, self-renewal assays validated that Tnmd KO TSPC exhibit significantly reduced proliferative potential, which was also reflected in lower Cyclin D1 levels. When analyzing possible cellular mechanisms behind the observed decreased self-renewability of Tnmd KO TSPC, we found that cellular senescence plays a major role, starting earlier and cumulating more in Tnmd KO compared with control TSPC. This was accompanied with augmented expression of the cell cycle inhibitor p53. Finally, the proliferative effect of Tnmd in TSPC was confirmed with transient transfection of Tnmd cDNA into Tnmd KO TSPC, which rescued their proliferative deficit. Taken together, we can report that loss of Tnmd affects significantly the self-renewal and senescence properties, but not the multipotential of TSPC.

TGFβ and FGF promote tendon progenitor fate and act downstream of muscle contraction to regulate tendon differentiation during chick limb development

“…TNMD is considered as a late tendon marker in chick and mouse embryos, and is expressed during the differentiation and muscledependent phase of limb tendon development (reviewed by Dex et al, 2016). Tnmd mutant mice display an altered structure of collagen fibrils, and reduced self-renewal and increased senescence of tendon progenitors, in post-natal tendons (Docheva et al, 2005;Alberton et al, 2015). TNMD was expressed in SCX-positive tendons in E9 chick limbs (Fig.…”

Tendon Functional Extracellular Matrix

“…Their role, increasing water content in these regions, provides resistance to compression 27 . The glycoproteins found in tendon include molecules such as lubricin 28 , tenascin-C, collagen oligomeric matrix component 29 (COMP) and tenomodulin 30 . Elastic fibres, composed of elastin, fibrillins 1 and 2, as well as other elastic fibre-associated molecules are also present 31; 32 .…”

TENOgenic MODULating INsider factor: systematic assessment on the functions of tenomodulin gene

“…Lastly, a Tnmd knockout mouse model study revealed that loss of Tnmd results in reduced proliferation and earlier onset of senescence in TSPCs (Alberton et al 2015). The study compared tenogenic markers in both genotypes of which no differences were observed, except for the absence of Tnmd transcript in mutant mice.…”