Introduction: The endothelial glycocalyx alters immune reactions and glycosaminoglycans (GAGs) in the glycocalyx bind chemokines that attract immune cell invasion. Prior work has implicated heparan sulfation and disaccharide content in acute rejection after transplantation. Myxomavirus encodes a broad-spectrum chemokine modulating protein, M-T7 that reduces aortic allograft vasculopathy and renal allograft rejection in rodent models. We investigated the effects of conditional endothelial deficiency of the primary heparin sulfate modifying enzyme (N-deacetylase-N-sulfotransferase-1, Ndst1-/-) on renal allograft transplants.
Methods: Donor kidneys from C57Bl/6J mice (WT, Ndst1+/+) or Ndst1-/- mice were transplanted into Balb/C mice with normal Ndst1 expression. Rejection was assessed in recipients of WT and Ndst1-/- donor allografts, and compared to M-T7 treatment in WT kidney transplants at 10-day follow up.
Results: Recipients of Ndst1-/- donor organs treated with saline (N=9 mice; P<0.012) and WT donor organs treated with M-T7 (N=7; P<0.009) had significantly reduced acute rejection compared to those with WT donor organs given saline treatments at 10 days follow up. Saline treated Ndst1-/- donors had equal reductions in pathological scores for acute rejection compared to M-T7 treated WT donors. Analysis of heparan (HS) and chondroitin sulfate (CS) disaccharide content demonstrated significant correlations with suppressed rejection. In non-transplanted kidneys Ndst1-/- mice treated with saline and M-T7 treated WT had significantly reduced disaccharide, D0S6 (P<0.046 and P<0.004). Extraction of disaccharides from formalin fixed renal allografts at 10 days post-transplant again detected altered D0S6 (P<0.02). CD3+ T cell invasion in transplanted kidneys were reduced in Ndst1-/- grafts (P<0.0001) and with M-T7 treatment (P<0.0001) (N=12). Gene expression in inflammatory NFκB and JAK STAT pathways was also altered (P<0.05).
Conclusion: Modulation of donor organ heparn sulfate alone and inhibition of GAG/chemokine interactions are equally effective at inhibiting early transplant rejection. Targeted modification of HS disaccharide D0S6 in allograft transplants may provide a new therapeutic approach to preventing rejection.