Induction of Myofibroblastic Differentiation In Vitro by Covalently Immobilized Transforming Growth Factor-β 1

Growth factors are an important tool in tissue engineering. Bone morphogenetic protein-2 and transforming growth factor-β₁ (TGF-β₁) are used to provide bioactivity to surgical implants and tissue substitute materials. Mostly growth factors are used in soluble or adsorbed form. However, simple adsorption of proteins to surfaces is always accompanied by reduced stability and undefined pharmacokinetics. This study aims to prove that TGF-β₁ can be covalently immobilized to functionalized surfaces, maintaining its ability to induce myofibroblastic differentiation of normal human dermal fibroblasts. In vivo, fibroblasts differentiate to myofibroblasts (MFs) during soft tissue healing by the action of TGF-β₁. As surfaces for our experiments, we used slides bearing aldehyde, epoxy, or amino groups. For our in vitro cell culture experiments, we used the expression of α-smooth muscle actin as a marker for MFs after immunochemical staining. Using the aldehyde and the epoxy slides, we were able to demonstrate the activity of immobilized TGF-β₁ through a significant increase in MF differentiation rate. A simple immunological test was established to detect TGF-β₁ on the surfaces. This technology enables the creation of molecular “landscapes” consisting of several factors arranged in a distinct spatial pattern and immobilized on appropriate surfaces.