ABSTRACT
Scaffoldless engineered 3D skeletal muscle tissue created from satellite cells offers the potential to replace muscle tissue that is lost due to severe trauma or disease. Transforming growth factor-beta 1 (TGF-ß1) plays a vital role in mediating migration and differentiation of satellite cells during the early stages of muscle development. Additionally, TGF-ß1 promotes collagen type I synthesis in the extracellular matrix (ECM) of skeletal muscle, which provides a passive elastic substrate to support myofibres and facilitate the transmission of force. To determine the role of TGF-ß1 in skeletal muscle construct formation and contractile function in vitro, we created tissue-engineered 3D skeletal muscle constructs with varying levels of recombinant TGF-ß1 added to the cell culture medium. Prior to the addition of TGF-ß1, the primary cell population was composed of 75% Pax7-positive cells. The peak force for twitch, tetanus and spontaneous force were significantly increased in the presence of 2.0 ng/ml TGF-ß1 when compared to 0, 0.5 and 1.0 ng/ml TGF-ß1. Visualization of the cellular structure with H&E and with immunofluorescence staining for sarcomeric myosin heavy chains and collagen type I showed denser regions of better organized myofibres in the presence of 2.0 ng/ml TGF-ß1 versus 0, 0.5 and 1.0 ng/ml. The addition of 2.0 ng/ml TGF-ß1 to the culture medium of engineered 3D skeletal muscle constructs enhanced contractility and extracellular matrix organization.
