23.3.10 - Engineering the Damaged Cartilage Interface to Direct Stem Cell Behavior
- J. Patel (Philadelphia, US)
- J. Patel (Philadelphia, US)
- C. Loebel (Philadelphia, US)
- B. Wise (Philadelphia, US)
- J. Carey (Philadelphia, US)
- J. Burdick (Philadelphia, US)
- R. Mauck (Philadelphia, US)
Abstract
Purpose
Cartilage defects compromise tissue function, and often propagate and progress to osteoarthritis. The purpose of this study was to establish a microenvironment at the damaged interface that recruits and directs cells, with the goal of forming a living fibrous barrier to restore biomechanical function and prevent matrix loss.
Methods and Materials
Methacrylated hyaluronic acid (MeHA) was modified to include aldehydes (adhesiveness to tissue), FITC peptides (visualization), and fibronectin-mimicking peptides (RGD; for cellular adhesion). Bovine cartilage plugs were either defected or defected and digested in order to mimic focal defects (ND) and degenerated defects (D), respectively, and subject to biomaterial application and cross-linking (0, 5, 15 min). Engineered tissues were seeded with bovine mesenchymal stem cells (MSCs) and adhesion was evaluated at 24hr. The fibrogenic properties of these attached cells were evaluated by the presence of alpha-smooth muscle actin (ASMA) fibers at 7d. Finally, matrix production by adherent cells was visualized by the incorporation of azidohomoalanine (AHA) in place of L-methionine into newly synthesized proteins.
Results
The biomaterial diffused into and formed an integrated tissue-gel composite with cartilage, allowing for MSC attachment to the damaged interface (Fig 1A). Focal adhesion staining (Fig 1B) showed that biomaterial application and cross-linking increased the number of adhesions and adhesion area per cell (Fig 1C). Biomaterial with cross-linking (15 minutes) promoted fibrogenesis of MSCs in both focally defected and degenerated tissues (Fig 2A), with a greater number of ASMA positive cells (Fig 2B). Finally, increased matrix production was observed by cells cultured on engineered cartilage surfaces (Fig 2C/D).
Conclusion
This study demonstrated the ability of a modified HA biomaterial to form an integrated environment at the cartilage defect interface, enhancing the attachment, response, and matrix production of MSCs. Future studies will evaluate the ability of a living barrier to form and restore cartilage biomechanics in vitro and in vivo.