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Increased migration of antigen presenting cells to newly-formed lymphatic vessels in transplanted kidneys by glycol-split heparin

Background

Chronic renal transplant dysfunction is characterized by loss of renal function and tissue remodeling, including chronic inflammation and lymph vessel formation. Proteoglycans are known for their chemokine presenting capacity. We hypothesize that interruption of the lymphatic chemokine–proteoglycan interaction interferes with the lymphatic outflow of leukocytes from the renal graft and might decrease the anti-graft allo-immune response.

Methods

In a rat renal chronic transplant dysfunction model (female Dark-Agouti to male Wistar Furth), chemokines were profiled by qRT-PCR in microdissected tubulo-interstitial tissue. Disruption of lymphatic chemokine–proteoglycan interaction was studied by (non-anticoagulant) heparin-derived polysaccharides in vitro and in renal allografts. The renal allograft function was assessed by rise in plasma creatinine and urea.

Results

Within newly-formed lymph vessels of transplanted kidneys, numerous CD45⁺ leukocytes were found, mainly MHCII⁺, ED-1^-, IDO^-, HIS14^-, CD103^- antigen presenting cells, most likely representing a subset of dendritic cells. Treatment of transplanted rats with regular heparin and two different (non-)anticoagulant heparin derivatives revealed worsening of kidney function only in the glycol-split heparin treated group despite a two-fold reduction of tubulo-interstitial leukocytes (p<0.02). Quantitative digital image analysis however revealed increased numbers of intra-lymphatic antigen-presenting cells only in the glycol-split heparin group (p<0.01). The number of intra-lymphatic leukocytes significantly correlates with plasma creatinine and urea, and inversely with creatinine clearance.

Conclusions

Treatment of transplanted rats with glycol-split heparin significantly increases the number of intra-lymphatic antigen presenting cells, by increased renal diffusion of lymphatic chemokines, thereby increasing the activation and recruitment of antigen presenting cells towards the lymph vessel. This effect is unwanted in the transplantation setting, but might be advantageous in e.g., dendritic cell vaccination.

The loss of renal dendritic cells and activation of host adaptive immunity are long-term effects of ischemia/reperfusion injury following syngeneic kidney transplantation

Ischemia/reperfusion injury associated with kidney transplantation induces profound acute injury, influences early graft function and affects long-term graft outcomes. To determine whether renal dendritic cells play any role during initial innate ischemia/reperfusion injury and the subsequent development of adaptive immune responses, we studied the behavior and function of renal graft and host infiltrating dendritic cells during early and late phases of renal ischemia/reperfusion injury. Wild type to GFP-transgenic rat kidney transplantation was performed with and without 24 hours cold storage. Ischemia/reperfusion injury in cold stored grafts resulted in histopathological changes of interstitial fibrosis and tubular atrophy by 10 weeks accompanied by upregulation of mRNAs of mediators of interstitial fibrosis and inflammation. In normal rat kidneys we identified two populations of renal dendritic cells, predominant CD103⁻CD11b/c⁺ and minor CD103⁺CD11b/c⁺ cells. After transplantation without cold storage, grafts maintained CD103⁻ but not CD103⁺ GFP-negative renal dendritic cells for 10 weeks. In contrast, both cell subsets disappeared from cold stored grafts, which associated with a significant GFP-expressing host CD11b/c⁺ cell infiltration that included CD103⁺ dendritic cells with a TNF-α producing phenotype. These changes in graft/host dendritic cell populations were associated with progressive infiltration of host CD4⁺ T cells with effector/effector-memory phenotypes and IFN-γ secretion. Thus, renal graft ischemia/reperfusion injury causes graft dendritic cell loss and was associated with progressive host dendritic cell and T cell recruitment. Renal resident dendritic cells might function as a protective regulatory network.