A Speculative Role for Perlecan, an Instructive Multifunctional Proteoglycan with Matrix Stabilising and Cell Regulatory Properties in Anterior Cruciate Ligament Repair - Abstract
Purpose/aim of the study: To immunolocalize perlecan in anterior cruciate ligament (ACL) and review its potential to promote ACL repair. Materials and Methods: Perlecan immunolocalisations were undertaken with an antibody to perlecan domain IV (MAb A7L6), toluidine blue staining visualized ACL glycosaminoglycan. Primary ACL cells were cultured in monolayers, cellular morphologies were compared with meniscal, synovial fibroblast and articular chondrocytes from the same knee joints. Results: The ACL contained toluidine blue stained proteoglycan associated with linear arrays of fusiform cells between collagen fibre bundles and plumper cells in vascular channels. Perlecan interconnected aligned fusiform cells in collagenous regions and rounded cells in vascular channels. Prominent actin cytoskeletons in monolayer culture demonstrating a contractile phenotype similar to myofibroblasts. Discussion: This study showed perlecan interconnected strings of ACL cells in anteriomedial and posteriolateral collagenous bundles in the ACL connecting the tibia and femur providing rotational stability in the knee joint. Type I collagen (70-80%), elastin (5-6 %) and proteoglycans (2-5%) are major ACL components. A review of perlecan’s roles in matrix stabilisation, mechanotransduction, growth factor mediated cellular proliferation and differentiation and its co-localisation with elastin in tensional and weight bearing connective tissues suggest it has potential contributions to make in functional ACL repair. Recently developed methods that have provided improved immobilization and a stable repair environment conducive to ACL repair indicate that the roles of perlecan in ACL repair processes deserve evaluation based on its known functional properties in other tensional and weight bearing connective tissues.