BMSC Sheets for Ligament Tissue Engineering

Abstract

The anterior cruciate ligament (ACL) has poor capabilities of healing. Currently, allografts or autografts are used to repair the injury site. But healing of the ACL following autograft or allograft reconstruction has been found slow. Thus, other methods like reconstruction of the ACL are being investigated. Most work in ligament tissue engineering has been done using a system of seeding biodegradable polymer scaffolds with single cell suspensions. The cell sources are mostly from Bone Marrow Derived Mesenchymal Stem Cells (BMSCs) or ligament fibroblasts. These cells would have to attach directly to the scaffolds and begin the process of proliferating, secreting ECM and other factors that would enhance the growth rate. This method is inefficient as many cells are lost during the seeding process due to the lack of ample site to adhere onto within the porous scaffold structure. When cells are cultured to confluence in vitro, they connect with each other through ECM and cell-to-cell adhesion molecules. With enzymatic digestion such as trypsinization, ECM proteins and cell-to-cell adhesion proteins are disrupted to allow the cells to be dissociated. Harvesting the entire cell sheet would avoid this disruptive process and preserve all ECM as well as cell-to cell adhesion proteins, as it does not experience the enzymatic dissociation process. With the help of the preserved ECM and cell-to-cell adhesion proteins, the cell sheet maintains cellular viability and functionality and can also adhere easily onto biodegradable scaffolds or other layers of cell sheets to form three-dimensional structures with suitable topology and mechanical properties. These unique aspects make the cell sheet technology a promising candidate for tissue engineering. The proposed project intends to investigate the growth of a cell sheet beginning with BMSCs to study the collagen deposition, cell sheet viability, cell sheet thickness and gene expression to determine the suitability of BMSC sheets for ligament tissue engineering.