The localisation of inflammatory cells and expression of associated proteoglycans in response to implanted chitosan

Implantation of a foreign material almost certainly results in the formation of a fibrous capsule around the implant however, mechanistic events leading to its formation are largely unexplored. Mast cells are an inflammatory cell type known to play a role in the response to material implants, through the release of pro-inflammatory proteases and cytokines from their α-granules following activation. This study examined the in vivo and in vitro response of mast cells to chitosan, through detection of markers known to be produced by mast cells or involved with the inflammatory response. Mast cells, identified as Leder stained positive cells, were shown to be present in response to material implants. Additionally, the mast cell receptor, c-kit, along with collagen, serglycin, perlecan and chondroitin sulphate were detected within the fibrous capsules, where distribution varied between material implants. In conjunction, rat mast cells (RBL-2H3) were shown to be activated following exposure to chitosan as indicated by the release of β-hexosaminidase. Proteoglycan and glycosaminoglycans produced by the cells showed similar expression and localisation when in contact with chitosan to when chemically activated. These data support the role that mast cells play in the inflammatory host response to chitosan implants, where mediators released from their α-granules impact on the formation of a fibrous capsule by supporting the production and organisation of collagen fibres.