Search

Tissue-resident γδ T cells form the first line of defense at barrier surfaces where they survey host tissue for signs of stress or damage. Following recognition of injury, γδ T cells play a crucial role in the wound-healing response through the production of growth factors and cytokines that promote proliferation in surrounding epithelial cells. To initiate this response, γδ T cells require interactions with a variety of epithelial-expressed costimulatory molecules in addition to primary signaling through their TCR. In the epidermis these signals include the coxsackie and adenovirus receptor (CAR), histocompatibility antigen 60c (H60c), and plexin B2, which interact with γδ T cell-expressed junctional adhesion molecule-like protein (JAML), NKG2D, and CD100, respectively. Here we identify heat shock protein family A member 8 (Hspa8) and ICAM-1 as two additional keratinocyte-expressed costimulatory molecules for epidermal resident γδ T cells (termed DETC). These molecules were rapidly up-regulated in the epidermis following wounding in both mouse and human tissue. Both Hspa8 and ICAM-1 had a costimulatory effect on DETC, inducing proliferation, CD25 up-regulation, and IL-2 production. We also provide evidence that DETC can be activated through the potential ICAM-1 and Hspa8 receptors LFA-1 and CD316. Finally, knockdown of Hspa8 in keratinocytes reduced their ability to activate DETC in culture and ICAM-1−/− mice exhibited impaired rates of healing in skin-organ culture suggesting a role for these proteins in the DETC-mediated damage response. Together with previous work on CAR, H60c, and plexin B2, these results add to a picture of a complex keratinocyte wound signature that is required for efficient DETC activation.

Chronic wounds represent a growing clinical problem for which limited treatment strategies exist. Defects in immune cell-mediated healing play an important role in chronic wound development, presenting an attractive clinical target in the treatment of chronic wounds. However, efforts to improve healing through the application of growth factors and cytokines have been limited by the rapid degradation and diffusion of these molecules in the wound environment. In this study we sought to overcome the challenge of rapid diffusion through the development of a hydrogel delivery system in which protein cargo can be released into the wound environment at a constant and tunable rate. This system was used to deliver the intercellular adhesion molecule-1 (ICAM-1) in order to target endogenous cells upstream of growth factor and cytokine production and circumvent the issue of their rapid degradation. We demonstrated that our delivery system was able to release cargo at different and highly controllable rates and thereby improved cargo retention in the wound environment. Additionally, treatment with ICAM-1 in the delivery system improved healing in both ICAM-1-deficient mice and an aged mouse model of delayed healing, highlighting a potential clinical benefit for this protein in the treatment of chronic wounds.