(549d) Cadherin-11 Directs Mesenchymal Stem Cell Differentiation and Regulates Extracellular Matrix Production and Mechanical Properties of Myogenic Tissues in-Vivo and in Vitro

Differentiation of mesenchymal stem cells (MSC) is affected by many soluble and insoluble signals in their local microenvironment. In addition to soluble growth factors, cell-ECM interactions and substrate mechanics have been implicated in stem cell lineage commitment. However, the mechanical and biochemical signals originating from cell-cell adhesion remain unexplored in this context. Recent studies implicated adherens junctions in the maintenance of embryonic stem cell self-renewal potential and during cellular reprogramming but the role of cell-cell interactions in MSC differentiation remains elusive. In this study we implicated Cadherin-11 as a deciding factor in directing stem cell differentiation into smooth muscle cells (SMC); production of ECM synthesis; and development of contractility in vitro and in vivo.

Cad11-FC, a chimeric homo-dimer consisting of CH2 and CH3 (Constant Heavy-chain) region of FCɣ was linked through the hinge region of the antibody to all five extracellular domains of Cadherin-11 and coated on IgG-bound hydrophobic plates to create a contact surface with exposed Cadherin-11 domains. This surface was used to bind cells selectively to Cadherin-11 and single out and study effects of Cadherin-11 engagement in Mesenchymal Stem Cells.Cad11-null (Cad11^-/-) mice and wild-type (WT) B6:129 F1 intercross mice were housed at Baylor College of Medicine under approval of the Baylor College of Medicine Institutional Animal Care and Use Committee. Bladders, aortas and skin were removed from 8-week old Cad11^-/- and WT old mice after being euthanized and evaluated for smooth muscle cell content, stress-tested for Young’s modulus, ultimate tensile strength and assayed for collagen and elastin content (by hydroxyl proline assay and ninhydin assay respectively).

 Using the Cad-11-FC surface we found that Cadherin-11 engagement is necessary for myogenic differentiation and promotes myogenic marker expression.  Lack of Cadherin-11 in differentiated MSCs diminished the αSMA levels and the contractility of fibrin based 3-D vascular media.  Similar events transpired in-vivo where smooth muscle containing organs of Cad11^-/- mice, namely bladder and artery have reduced contractile function, mechanical strength, collagen and elastin content . Further, we observed that Cadherin-11 affected the ECM levels, collagen through the ROCK-SRF pathway both in-vivo and in-vitro.

Overall, our novel data showed that Cadherin-11 is an important molecule involved in smooth muscle gene expression and function, as well as production of extra cellular matrix and contractility of smooth muscle organs. These finding are novel and implicate the role of cell-cell adhesion is stem cell fate decisions as well as in the function of muscle containing organs in vivo.