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

## TL;DR

A hydrogel containing sulforaphane, a compound from cruciferous vegetables, significantly prolonged skin graft survival in mice by reducing immune rejection.

## Contribution

A thermosensitive hydrogel delivering sulforaphane was developed and shown to reduce immune cell activation and prolong allograft survival in a mouse model.

## Key findings

- GS treatment reduced immune cell activation and delayed acute rejection in skin transplant mice.
- Subcutaneous GS injections prolonged allograft survival to over 14 days in 80% of cases.
- GS-treated dendritic cells showed reduced activation of costimulatory markers in vitro.

## Abstract

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.