(137b) Nanog Restores the Impaired Extracellular Matrix Synthesis and Mechanical Strength in Senescent Stem Cells

Organismal aging and cellular senescence alter the mechanical properties of tissues such as skin, aorta, and bone, while senescent cells is known to deposit less collagen and elastin. This may severely hinder tissue regeneration as well as any tissue engineering application.  Hence, there is a need to develop strategies to reverse the effects of senescence on Extracellular Matrix (ECM) molecule production. Previously, we discovered that ectopic expression of Nanog restored the contractile function of aged ovine Mesenchymal Stem Cells (MSC) [1]. Here we report that ectopic expression of Nanog can also restore mechanical properties and ECM deposition of human senescent cells. Human dermal Fibroblasts and Mesenchymal Stem Cells (MSC) were isolated from foreskin and hair follicle respectively and induced to senescence by serially passaging. To express Nanog, cells were transduced with a tetracycline-inducible system which allowed the expression of the transgene only in the presence of the tetracycline analogue, Doxycycline (Dox). Upon senescence cells were treated with DOX (LP NANOG) and the production of collagen and elastin were evaluated by Western blot and real time PCR and compared to Early passage (EP) and senescent cells which expressed GFP (Late Passage or LP). Our results show that senescence induces a significant reduction in the production of ECM molecules such as collagen3a1 and elastin. Interestingly, expression of NANOG in LP completely restored collagen and elastin production and restored the collagen content and mechanical properties of fibrin based tissue constructs. We also investigated the molecular signaling pathways underlying these observations and showed that NANOG synergized with TGFbeta to increase the ECM production. In addition, NANOG increased SMAD2 phosphorylation as well as the total levels of SMAD2 and 3, whereas knockdown of SMADs by shRNA or by chemical inhibition completely abolished the effect of NANOG on ECM production. In conclusion, our study provides a novel strategy to reverse the effects of senescence on ECM production and mechanical properties of tissues, which may have broad applications in tissue regeneration and anti-aging treatments.

1.              Han, J, Mistriotis, P, Lei, P, Wang, D, Liu, S, and Andreadis, ST (2012). Nanog reverses the effects of organismal aging on mesenchymal stem cell proliferation and myogenic differentiation potential. Stem cells 30: 2746-2759.