TEXTILE TISSUE ENGINEERING FOR THE ANTERIOR CRUCIATE LIGAMENT

Silk could be an interesting material for anterior cruciate ligament (ACL) reconstruction. Sericin is usually removed to reduce immunogenicity and improve processability of Bombyx (B.) mori derived silk. Based on selected patterns, embroidering allows adaption of porosity and biomechanical properties of scaffolds for ACL tissue engineering. Previous studies with synthetic fibers including poly lactic acid (PLA) and PLA-co-caprolactone (P(LA-CL)) could confirm this. However, cell adhesion remains challenging. This project aims to identify an embroidered silk fibroin-based scaffold variant facilitating ACL tissue engineering. For removal of sericin, two different procedures were applied to the silk threads: a standard (“raw silk”) and a novel (“purified silk”) technique (DE102021118652A1). Both types of silk fibroin threads were used to embroider pure silk scaffolds or were combined with PLA-co-caprolactone (P(LA-CL)) fibers. Hence, four scaffold groups (“raw silk”,“raw silk/P(LA-CL)”, “purified silk”, “purified silk/P(LA-CL)”) were seeded with lapine cruciate ligament fibroblasts (LCL-Fb). Cytotoxicity was measured with scaffold extracts (MTS assay) and LCL and L929 fibroblasts (Fbs). LCL-Fb adherence, vitality, cytoskeletal and extracellular matrix proteins were monitored by immunolabelling and real-time PCR analysis. Glycosaminoglycan and DNA contents were measured. Scaffolds showed no cytotoxicity. LCL-Fb adherence on scaffolds differed, being low on raw silk and higher on raw silk/P(LA-CL) and highest on the purified silk and purified silk/P(LA-CL) scaffolds. Interestingly, the P(LA-CL) integration into the scaffold increased also the cytocompatibility of raw silk fibers. Cell survival on the scaffolds was high for the whole observation period (14 days). The focal adhesion component paxillin was abundantly expressed in cells on purified silk scaffolds underlining intimate cell material interaction and also typical ECM could be detected. GAG synthesis was confirmed. Gene expression of typical tendon related extracellular matrix components and markers could be detected on all four silk scaffold variants with high collagen expression in the purified silk at 14 days of culture. Purified silk fibroin threads are highly cytocompatible and represent a versatile material, suitable to prepare embroidered LCL-Fb carriers without the necessity of further functionalization.