Pericytes are contractile, motile cells that surround the capillary. Recent studies have shown that pericytes promoted joint fibrosis and induced subchondral bone angiogenesis, indicating the role of pericytes in osteoarthritis (OA). However, whether pericytes are involved in regulating inflammatory and catabolic response, as well as fibrotic repair of cartilage is still unclear. Here we used 2D and 3D models to investigate the communication of pericytes and chondrocytes under inflammatory osteoarthritis conditions.

CD34-CD146+ pericytes were isolated and sorted from human bone marrow. Human OA chondrocytes were isolated from OA joints. In 2D studies, monolayer cultured chondrocytes were treated +/- pericyte conditioned media, +/- 1ng/ml IL1β for 24h. In 3D studies, pericytes and chondrocytes were cultured within fibrin gel in 3D polyurethane scaffolds, separately or combined for 7 days, followed by treatment of +/- IL1β for another 7 days (Fig 2A). The inflammatory response, catabolic activity and expression of fibrosis markers of chondrocytes and pericytes were measured by ELISA and/or q-rtPCR.

Pericytes had weak inflammatory, catabolic and fibrotic response to IL1β (data not shown). The 2D study showed that pericyte conditioned media promoted inflammation, catabolism and fibrosis markers of chondrocytes, in the absence of IL1β treatment (Figure 1). However, study in 3D showed that coculture of chondrocytes and pericytes reduced the inflammatory and catabolic response of chondrocytes to IL1β and induced fibrosis markers in chondrocytes (Figure 2).

Pericytes are involved in regulating inflammatory response, catabolic response and fibrosis of chondrocytes. The opposite results from 2D and 3D experiments indicate the variety of the regulatory role of pericytes in the interaction with chondrocytes within different culture models. The underlying mechanism is under evaluation with on-going studies.

Acknowledgements

This study was funded by SINPAIN project, from European Union's Horizon Europe research and innovation programme under Grant Agreement NO. 101057778. Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them.

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