Sulforaphane-Loaded Hydrogel Prolongs Fully MHC-Mismatched Skin Allograft Survival

Despite immunosuppression, acute rejection (AR) is still a common setback among transplantation patients and is a risk factor for graft survival. Sulforaphane (SFN), a phytochemical present in crucifers, has been shown to have anti-inflammatory and immunoregulatory properties, yet its influences on immune cell activation as well as in graft survival are still unknown. Thus, the aim was to evaluate SFN's effect, and to improve efficacy, efficiency, and availability, it was incorporated into thermosensitive polymeric hydrogels, to prevent AR in skin transplant (Tx) model mice. A thermosensitive hydrogel containing SFN (0.1%) and hyaluronic acid (HA) (0.5%) dispersed in a poloxamer matrix (PL407 at 20% w/v) was developed (GS-PL407 20%, HA and SFN) and characterized as a liquid-viscous hydrogel. The fully MHC-incompatible skin Tx procedure was performed by using donor skin Balb/c mice, transplanted into C57BL/6 recipient mice. The cytotoxicity test of GS was performed using in vitro assays with bone marrow-derived dendritic cells (BMDC). Treatment of BMDC with GS for 24 h presents no cytotoxicity. Untreated allograft mice present 100% of graft loss at day 9 post Tx. Remarkably, subcutaneous GS injection every 3 days promoted 80% of allograft survival for more than 14 days when compared with untreated recipients (p < 0.001). Histological analysis showed a lower level of inflammatory cells in the skin Tx of GS-treated mice. Flow cytometry analysis of draining lymph nodes at day 5 post Tx revealed that GS treatment reduced the frequency of DC and subtypes and function of the CD4⁺ T cells. In vitro GS-treated lipopolysaccharide-activated BMDC present less activation of costimulatory markers. Taken together, GS treatment reduced immune cell activation, postponing AR onset and prolonging allograft survival in Tx animals. This strategy highlights the role of SFN as a promising candidate for further studies in organ transplantation experiments and being tested combined with current immunosuppression protocols.