(776c) Novel Role of Cadherin 11 in Extracellular Matrix Synthesis and Muscular Physiology

Cell-cell adhesion through cadherins has been identified as an important player in stem cell fate decisions. Recently, our lab study has recognized that Cadherin 11 (CDH11) is intimately involved in the process of MSC to smooth muscle cell (SMC) differentiation, and further that engagement of cadherin 11 is a significant event in the regulation of extra cellular matrix (ECM) synthesis. Here we report on the mechanism of CDH11 mediated ECM synthesis and furthermore, we provide in vivo data supporting our in vitro results and link our findings on cellular differentiation to tissue organization, muscle function and neuromuscular physiology. Aorta, bladder and skin were obtained from 8-week old mice (Cdh11^-/- and WT-wildtype) and tested for mechanical properties. shRNA targeting CDH11 was used in human dermal fibroblasts to study the effect of CDH11 deficiency. An engineered surface immobilized with a fusion protein containing extracellular CDH11 with the Fc domain (CDH11-Fc) was used as a tool to study immediate downstream effects and identify the mechanism of ECM production following CDH11 engagement. To study the effect of CDH11 on muscle function in-vivo, 6-month-old male Cdh11^-/- and WT (n=12) were acclimated to assessment protocols, and then assessed bi-monthly over a 6-month period. Assessments includes an inverted grid hanging test and overnight activity wheel monitoring. Body composition (total body fat and lean mass) was also measured by quantitative magnetic resonance.

 We demonstrate that CDH11 regulates collagen and elastin synthesis and thereby contributes to tissue integrity both in vivo using a Cdh11^-/- mouse model and in vitro using knockdown studies as well as gain of function approaches. We also identified the underlying mechanism and discovered that CDH11 engagement leads to swift and direct activation of both the TGF-β1 and ROCK pathways. This is followed by activation of transcription factors, MRTF-A and MYOCD leading to expression of collagen and elastin genes. In summary, our findings indicate that cell-cell contact by cadherin-11 is a novel regulator of ECM synthesis. Notably, these findings have important implications in skeletal muscle function and overall physical strength of the mice. In tests of physical endurance, Cdh11^-/- mice failed to maintain their body position in an inverted grid hanging test, failing in just 10 seconds as compared to WT (1-3 minutes). Furthermore, Cdh11^-/- mice have little to no activity wheel usage in contrast to control mice. Finally, our data also indicate that Cdh11^-/- mice have significantly higher body fat relative to WT as well as lower lean mass.

 Overall, we discovered a novel role for Cadherin-11 in ECM synthesis and tissue structure and identified the underlying mechanism involving direct TGF-β and ROCK activation. Notably, CDH11-mediated molecular events are linked to changes in muscle mass and organization, ultimately affecting neuromuscular function and physiology.