Determining alpha-smooth muscle actin expression in embryonic and mesenchymal stem cells of assorted mammals seeded in collagen scaffolds in vitro

Abstract

Healing by contraction is responsible for scarring in adults. Embryos heal by regeneration but the mechanism is unknown. Alpha-smooth muscle actin ([alpha]-SMA) is the protein responsible for contraction, thus determining if it is present in embryos which heal by regeneration will further our knowledge about the causes of regenerative healing. This thesis experimentally determined the presence of [alpha]-SMA in these cell types by the following procedure. Embryonic and mesenchymal stem cells of various species were cultured and seeded into collagen scaffolds. Contractile behavior was determined by measuring the diameter change of the scaffolds over time. Alpha-smooth muscle actin presence was determined by immunohistochemical evaluation. This study found that while all the cell types displayed alpha smooth muscle actin presence in monolayer, not every cell type contracted when seeded into the collagen scaffolds designed to mimic the in vivo environment. Specifically, the embryonic stem cells did not contract. Upon staining, the embryonic stem cell seeded scaffolds and several of the mesenchymal stem cell seeded scaffolds, which did contract, did not stain positive for [alpha]-SMA. These results imply that the embryonic scaffolds did not generate actin filament bundles, and that several of the mesenchymal stem cell seeded scaffolds were imaged after [alpha]-SMA expression in them ceased.