Role of Collagen Content and Architecture in the Load Bearing Capabilities of Tissue-Engineered Cartilage

A promising treatment for damaged cartilage is to replace it with tissue-engineered (TE) cartilage. However, the insufficient load-bearing capacity of today’s TE cartilage is an important limiting factor in its clinical application. In native cartilage, collagen fibers resist tension and proteoglycans (PG’s) attract water through osmotic pressure and resist its flow, which allows cartilage to withstand high compressive forces. One of the main challenges for tissue engineering of mechanically stable cartilage is therefore to find the cues to create an engineered tissue with an ultrastructure similar to that of native tissue. Currently, it is possible to tissue engineer cartilage with almost native PG content but collagen reaches only 1/4 of the native content [1]. Furthermore, the specific depth dependent arcade-like organization of collagen in native cartilage (i.e. vertical fibers in the deep zone and horizontal fibers in the superficial zone), which is optimized for distributing loads, has not been addressed in TE’d cartilage. However, the relative importance of matrix component content and collagen network architecture to the mechanical performance of TE cartilage is poorly understood, perhaps because this would require substantial effort on time consuming and labor-intensive experimental studies. The aim of this study is to explore if it is sufficient to produce a tissue with abundant proteoglycans and/or collagen, or whether reproducing the specific arcade-like collagen network in the implant is essential to develop sufficient load-bearing capacity, using a numerical approach.