Bioinformatics and Molecular Approaches for the Construction of Biological Artificial Cartilage

Osteoarthritis (OA) is one of the leading causes of disability in the United States, afflicting over 27 million Americans and imposing an economic burden of more than $128 billion each year (1, 2). OA is characterized by progressive degeneration of articular cartilage together with sub-chondral bone remodeling and synovial joint inflammation. Currently, OA treatments are limited, and inadequate to restore the joint to its full functionality.

Over the years, progresses have been made to create biologic cartilage substitutes. However, the repair of degenerated cartilage remains challenging due to its complex architecture and limited capability to integrate with surrounding tissues. Hence, there exists a need to create not only functional chondral constructs, but functional osteochondral constructs, which could potentially enhance affixing properties of cartilage implants utilizing the underlying bone. Furthermore, the molecular mechanisms driving chondrogenesis are still not fully understood. Therefore, detailed transcriptomic profiling would bring forth the progression of not only genes, but gene entities and networks that orchestrate this process.

Bone-marrow derived mesenchymal stem cells (MSCs) are routinely utilized to create cartilage constructs in vitro for the study of chondrogenesis. In this work, we set out to examine the underlying mechanisms of these cells, as well as the intricate gene correlation networks over the time course of lineage development. We first asked the question of how transforming growth factors are determining MSC differentiation, and subsequently utilized genetic engineering to manipulate this pathway to create an osteochondral construct. Next, we performed high-throughput next-generation sequencing to profile the dynamics of MSC transcriptomes over the time course of chondrogenesis. Bioinformatics analyses of these big data have yielded a multitude of information: the chondrogenic functional module, the associated gene ontologies, and finally the elucidation of GRASLND and its crucial function in chondrogenesis. We extended our results with a detailed molecular characterization of GRASLND and its underlying mechanisms. We showed that GRASLND could enhance chondrogenesis, and thus proposed its therapeutic use in cartilage tissue engineering as well as in the treatment of OA.