The loss of renal dendritic cells and activation of host adaptive immunity are long-term effects of ischemia/reperfusion injury following syngeneic kidney transplantation
2012; Elsevier BV; Volume: 81; Issue: 10 Linguagem: Inglês
10.1038/ki.2011.458
ISSN1523-1755
AutoresKikumi S. Ozaki, Shoko Kimura, Michael A. Nalesnik, Rita M. Sico, Matthew Zhang, Shinya Ueki, Mark A. Ross, Donna B. Stolz, Noriko Murase,
Tópico(s)Organ Transplantation Techniques and Outcomes
ResumoIschemia/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 green fluorescent protein (GFP) transgenic rat kidney transplantation was performed with and without 24-h 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 caused 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. 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 green fluorescent protein (GFP) transgenic rat kidney transplantation was performed with and without 24-h 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 caused 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. Although significant improvements have been achieved in early transplant outcomes, progressive deterioration of renal allograft function and late allograft loss remain as major impediments to long-term successful kidney transplantation (KTx), with little clinical progress for many years.1.Meier-Kriesche H.U. Schold J.D. Srinivas T.R. et al.Lack of improvement in renal allograft survival despite a marked decrease in acute rejection rates over the most recent era.Am J Transplant. 2004; 4: 378-383Crossref PubMed Scopus (977) Google Scholar,2.Kasiske B.L. Gaston R.S. Gourishankar S. et al.Long-term deterioration of kidney allograft function.Am J Transplant. 2005; 5: 1405-1414Crossref PubMed Scopus (102) Google Scholar Late graft loss typically associates with progressive renal dysfunction, proteinuria, and hypertension, and is accompanied by histopathological findings of interstitial fibrosis, tubular atrophy, vascular occlusive changes, and glomerulosclerosis.2.Kasiske B.L. Gaston R.S. 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Making global transplantation pathology standards truly global.Am J Transplant. 2007; 7: 2834Crossref PubMed Scopus (2) Google Scholar The incidence of IF/TA is as high as 50% of kidney transplants at 1 year, 70% at 2 year, and nearly universal after 10 year of KTx.7.Nankivell B.J. Borrows R.J. Fung C.L. et al.The natural history of chronic allograft nephropathy.N Engl J Med. 2003; 349: 2326-2333Crossref PubMed Scopus (1660) Google Scholar, 8.Bosmans J.L. Ysebaert D.K. Verpooten G.A. Chronic allograft nephropathy: what have we learned from protocol biopsies?.Transplantation. 2008; 85: S38-S41Crossref PubMed Scopus (35) Google Scholar, 9.Seron D. Moreso F. Protocol biopsies in renal transplantation: prognostic value of structural monitoring.Kidney Int. 2007; 72: 690-697Abstract Full Text Full Text PDF PubMed Scopus (73) Google Scholar As there is neither an effective therapy, nor proven preventive strategies, IF/TA and late graft loss remain as a significant clinical problem in the field. Ischemia/reperfusion injury (I/R) of the kidney graft is a leading cause of late graft loss and earlier development of IF/TA. Because of the current shortage of organs for transplantation, the donor pool has been expanded with the use of marginal donors (e.g., old donors, non-heart beating donors, grafts with prolonged cold storage), and grafts from these donors have a higher incidence of severe cold I/R injury and subsequent IF/TA development. During the acute phase, renal I/R injury presents a cascade of inflammatory events involving multiple interconnected factors, including peritubular capillary endothelial cell injury and disturbances of microvascular circulation, production and release of reactive oxygen species and inflammatory mediators, and extravasation of host inflammatory cells. However, the mechanisms of ongoing fibroinflammatory changes in the late phase of I/R injury are yet to be identified. Dendritic cells (DCs) function in and interact between the innate and adaptive arms of the immune system. In the normal kidney, DCs together with macrophages are major constituents of the renal mononuclear phagocyte system, and widely distributed throughout the interstitium.10.Steptoe R.J. Patel R.K. Subbotin V.M. et al.Comparative analysis of dendritic cell density and total number in commonly transplanted organs: morphometric estimation in normal mice.Transpl Immunol. 2000; 8: 49-56Crossref PubMed Scopus (46) Google Scholar, 11.Soos T.J. Sims T.N. Barisoni L. et al.CX3CR1+ interstitial dendritic cells form a contiguous network throughout the entire kidney.Kidney Int. 2006; 70: 591-596Abstract Full Text Full Text PDF PubMed Scopus (243) Google Scholar, 12.Kaissling B. Le Hir M. The renal cortical interstitium: morphological and functional aspects.Histochem Cell Biol. 2008; 130: 247-262Crossref PubMed Scopus (146) Google Scholar These populations represent substantial heterogeneity and plasticity, and studies aiming the distinction of two populations based on cell surface markers have shown complicated pictures.13.Li L. 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Although renal DCs have been shown to have key roles in many renal diseases,14.Woltman A.M. de Fijter J.W. Zuidwijk K. et al.Quantification of dendritic cell subsets in human renal tissue under normal and pathological conditions.Kidney Int. 2007; 71: 1001-1008Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar, 17.John R. Nelson P.J. Dendritic cells in the kidney.J Am Soc Nephrol. 2007; 18: 2628-2635Crossref PubMed Scopus (67) Google Scholar, 18.Hochheiser K. Tittel A. Kurts C. Kidney dendritic cells in acute and chronic renal disease.Int J Exp Pathol. 2011; 92: 193-201Crossref PubMed Scopus (33) Google Scholar little is known about their function during KTx-induced I/R injury and the subsequent chronic inflammatory immune reactions leading to IF/TA. Several previous studies have aimed to determine in vivo functional roles of renal mononuclear phagocytes, in particular DCs, in various kidney disease models by actively eliminating DCs with liposome clodronate or using the CD11c-DTR mouse, and showed contradictory results. Renal DCs are protective in cisplatin-induced acute kidney injury19.Tadagavadi R.K. Reeves W.B. Renal dendritic cells ameliorate nephrotoxic acute kidney injury.J Am Soc Nephrol. 2010; 21: 53-63Crossref PubMed Scopus (120) Google Scholar and nephrotoxic nephritis.20.Scholz J. Lukacs-Kornek V. Engel D.R. et al.Renal dendritic cells stimulate IL-10 production and attenuate nephrotoxic nephritis.J Am Soc Nephrol. 2008; 19: 527-537Crossref PubMed Scopus (101) Google Scholar On the contrary, they are proinflammatory and detrimental in obstructive nephropathy21.Kitamoto K. Machida Y. 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Hamilton-Williams E.E. et al.Kidney dendritic cell activation is required for progression of renal disease in a mouse model of glomerular injury.J Clin Invest. 2009; 119: 1286-1297Crossref PubMed Scopus (176) Google Scholar, 25.Hochheiser K. Engel D.R. Hammerich L. et al.Kidney dendritic cells become pathogenic during crescentic glomerulonephritis with proteinuria.J Am Soc Nephrol. 2011; 22: 306-316Crossref PubMed Scopus (67) Google Scholar In the model of renal warm ischemia, cell population(s) that are depleted by liposome clodronate have protective roles,26.Kim M.G. Boo C.S. Ko Y.S. et al.Depletion of kidney CD11c+ F4/80+ cells impairs the recovery process in ischaemia/reperfusion-induced acute kidney injury.Nephrol Dial Transplant. 2010; 25: 2908-2921Crossref PubMed Scopus (72) Google Scholar whereas the same liposome clodronate-depleted population(s) or CD11c+ cells depleted in CD11c-DRT mouse are shown to be detrimental.13.Li L. Okusa M.D. Macrophages, dendritic cells, and kidney ischemia-reperfusion injury.Semin Nephrol. 2010; 30: 268-277Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar, 27.Dong X. Swaminathan S. Bachman L.A. et al.Resident dendritic cells are the predominant TNF-secreting cell in early renal ischemia-reperfusion injury.Kidney Int. 2007; 71: 619-628Abstract Full Text Full Text PDF PubMed Scopus (275) Google Scholar, 28.Day Y.J. Huang L. Ye H. et al.Renal ischemia-reperfusion injury and adenosine 2A receptor-mediated tissue protection: role of macrophages.Am J Physiol Renal Physiol. 2005; 288: F722-F731Crossref PubMed Scopus (225) Google Scholar These conflicting outcomes might be due to different experimental settings or functions of non-DC populations, as these DC deletion methods are not completely specific for DCs.21.Kitamoto K. Machida Y. Uchida J. et al.Effects of liposome clodronate on renal leukocyte populations and renal fibrosis in murine obstructive nephropathy.J Pharmacol Sci. 2009; 111: 285-292Crossref PubMed Scopus (110) Google Scholar, 29.Probst H.C. Tschannen K. Odermatt B. et al.Histological analysis of CD11c-DTR/GFP mice after in vivo depletion of dendritic cells.Clin Exp Immunol. 2005; 141: 398-404Crossref PubMed Scopus (210) Google Scholar, 30.Bennett C.L. Clausen B.E. DC ablation in mice: promises, pitfalls, and challenges.Trends Immunol. 2007; 28: 525-531Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar However, contradictory results in these experiments could be explained by the different roles of kidney-resident DCs and locally recruited systemic DCs, and by the difficulty to differentiate two DC populations in these studies, as both the populations could be influenced by the depletion methods. We hypothesized that renal graft–resident DCs and infiltrating host DCs might have different functional roles in acute innate and subsequent chronic phases of renal I/R injury. Accordingly, using the green fluorescent protein (GFP) transgenic rat KTx model, the aim of this study was to understand the roles of kidney-resident DCs by examining the alteration of renal DCs in the early and late phases of renal I/R injury, and by characterizing recruited host DCs and other host cells. To characterize kidney-resident DCs, naïve rat kidney leukocytes were analyzed by flow cytometry (FCM) and immunohistochemistry (IHC). FCM of isolated renal CD45+ cells revealed that the major leukocyte population in normal kidneys was CD11b/c+ cells, followed by NK cells, T cells, and NKT cells (Figure 1a). IHC of naïve kidney showed that CD11b/c+ cells form a contiguous network throughout the entire kidney interstitium (Figure 1c, upper), suggesting that these cells were relevant to renal DCs as previously reported both in mice and in humans.10.Steptoe R.J. Patel R.K. Subbotin V.M. et al.Comparative analysis of dendritic cell density and total number in commonly transplanted organs: morphometric estimation in normal mice.Transpl Immunol. 2000; 8: 49-56Crossref PubMed Scopus (46) Google Scholar, 11.Soos T.J. Sims T.N. Barisoni L. et al.CX3CR1+ interstitial dendritic cells form a contiguous network throughout the entire kidney.Kidney Int. 2006; 70: 591-596Abstract Full Text Full Text PDF PubMed Scopus (243) Google Scholar, 12.Kaissling B. Le Hir M. The renal cortical interstitium: morphological and functional aspects.Histochem Cell Biol. 2008; 130: 247-262Crossref PubMed Scopus (146) Google Scholar, 14.Woltman A.M. de Fijter J.W. Zuidwijk K. et al.Quantification of dendritic cell subsets in human renal tissue under normal and pathological conditions.Kidney Int. 2007; 71: 1001-1008Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar Further analysis of CD11b/c+ renal DCs showed that they expressed CD4, CD86, and MHC class II, but were negative for CD62L (Figure 1b). Subpopulation (∼10%) of CD11b/c+ renal DCs also expressed CD103, which were scarcely found in the interstitium (Figure 1c, lower). These results indicate the presence of two subsets of DCs, predominant CD103-CD11b/c+ and minor 103+CD11b/c+ populations, in naïve rat kidneys. Orthotopic syngeneic KTx was conducted using GFP transgenic rats as recipients and wild type (WT) as donors with static cold storage of kidney grafts for 24h in UW (University of Wisconsin) solution (24h-CS group). Donor and recipient leukocytes in the kidney grafts were analyzed with a comparison to control grafts that were transplanted immediately (no-CS group). Robust mRNA upregulation for tumor necrosis factor-α (TNF-α), interleukin (IL)-6, inducible nitric oxide synthase, and IL-10 at 3h after transplantation was seen in 24h-CS grafts, as we have previously reported31.Neto J.S. Nakao A. Kimizuka K. et al.Protection of transplant-induced renal ischemia-reperfusion injury with carbon monoxide.Am J Physiol Renal Physiol. 2004; 287: F979-F989Crossref PubMed Scopus (179) Google Scholar, 32.Nakao A. Faleo G. Shimizu H. et al.Ex vivo carbon monoxide prevents cytochrome P450 degradation and ischemia/reperfusion injury of kidney grafts.Kidney Int. 2008; 74: 1009-1016Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar, 33.Faleo G. Neto J.S. Kohmoto J. et al.Carbon monoxide ameliorates renal cold ischemia-reperfusion injury with an upregulation of vascular endothelial growth factor by activation of hypoxia-inducible factor.Transplantation. 2008; 85: 1833-1840Crossref PubMed Scopus (64) Google Scholar (Figure 2a). In contrast, no-CS grafts showed negligible mRNA levels for these mediators (Figure 2a). In addition, host neutrophil infiltration was significantly increased in 24h-CS grafts, whereas they were only occasionally seen in no-CS grafts at 12h after KTx (Figure 2b). At 4 weeks after KTx, no-CS grafts showed CCr levels comparable with those of normal unoperated animals (1.65±0.3ml/min), whereas 24h-CS grafts showed significantly reduced CCr levels (0.26±0.2ml/min) with considerable proteinuria.33.Faleo G. Neto J.S. Kohmoto J. et al.Carbon monoxide ameliorates renal cold ischemia-reperfusion injury with an upregulation of vascular endothelial growth factor by activation of hypoxia-inducible factor.Transplantation. 2008; 85: 1833-1840Crossref PubMed Scopus (64) Google Scholar Histopathological analyses of 24h-CS grafts at 10 weeks revealed patchy areas of chronic changes comprising tubular atrophy, interstitial fibrosis, chronic inflammation, and lymphocytic infiltration, relevant to changes that were described as IF/TA (Figure 3a). No evidence of arteritis was seen. In contrast, in the control no-CS grafts, the glomeruli, tubules, and vessels in general appeared unremarkable. Masson's Trichrome stain revealed significantly increased fibrotic area in 24h-CS grafts (Figure 3a). Immunofluorescent stain also showed intense α-smooth muscle actin expression in 24h-CS grafts at 10 weeks, whereas control no-CS grafts showed marginal α-smooth muscle actin expression. Active proinflammatory and profibrotic reactions in 24h-CS kidney grafts at 10 weeks were confirmed with real-time polymerase chain reaction. mRNA levels for inflammatory cytokines, as well as regulated upon activation normal T-cell expressed, and presumably secreted and IL-10 were significantly increased in 24h-CS than in no-CS grafts (Figure 3b). Transforming growth factor-β, a key mediator in the progression of fibrosis, and collagen-1 also remarkably increased in 24h-CS grafts. These results indicated that acute innate I/R injury resulted in progressive fibroinflammatory changes in syngeneic kidney grafts. To investigate the roles of renal DCs in acute I/R injury and the development of chronic fibroinflammatory changes in the WT to GFP KTx model, kidney-resident GFP- DCs were analyzed at early (3, 12h) and late (4, 10 weeks) time points by FCM of graft CD45+ cells. Percentages of donor leukocytes (GFP-CD45+) started to decrease after KTx, and the reduction was significantly more in 24h-CS than in no-CS grafts. At 10 weeks, only 11.3±4.9% of leukocytes in 24h-CS grafts were donor phenotype, whereas 46.3±10.2% in no-CS grafts (Figure 4a). The reduction of donor leukocytes was mainly due to progressive decreases of GFP-CD11b/c+ renal DCs, the major leukocyte population in native kidneys, and at 10 weeks, frequencies of GFP-CD11b/c+ renal DCs were markedly lower in 24h-CS than in no-CS grafts (Figure 4b). These results indicate that I/R injury in 24h-CS grafts resulted in nearly total loss of graft renal DCs, while GFP- renal DCs were maintained in no-CS grafts. Interestingly, further analysis of GFP-CD11b/c+ renal DCs revealed that the CD103-CD11b/c+ DC subset disappeared from 24h-CS, but not from no-CS, grafts. In contrast, CD103+CD11b/c+ renal DCs disappeared from both 24h-CS and no-CS grafts, regardless of I/R injury (Figure 4c), suggesting different functional roles of CD103+ and CD103- kidney DC populations. Concurrently, at 10 weeks, significant numbers of host GFP+CD11b/c+ cells were found in 24h-CS grafts compared with no-CS grafts. Particularly, host CD103+CD11b/c+ DCs were significantly higher in 24h-CS than in no-CS grafts (19.6±2.0 vs. 6.7±1.9%; Figure 4c). IHC at 10 weeks revealed that GFP-CD11b/c+ DCs were maintained and homogenously distributed in the interstitium of no-CS grafts (Figure 5a–c). In contrast, these renal DCs were not detected in 24h-CS grafts, and abundant GFP+CD11b/c+ host cells were found among inflammatory infiltrates (Figure 5d–f). Host CD11b/c+ cells could include monocytes, macrophages, DCs, and neutrophils; however, neutrophils (naphthol+ or RP-1+) were rare at 10 weeks (data not shown), indicating that infiltrating host CD11b/c+ cells in 24h-CS grafts at 10 weeks were mostly DC and monocyte/macrophage populations. In IHC, host GFP+CD11b/c+ cells were found among inflammatory infiltrates and did not localize to peritubular area to replace the original renal DCs (Figure 5e), suggesting that functions of host GFP+CD11b/c+ cells were different from those of kidney-resident DCs. As renal DCs have been shown to produce TNF-α in the mouse warm I/R injury model,27.Dong X. Swaminathan S. Bachman L.A. et al.Resident dendritic cells are the predominant TNF-secreting cell in early renal ischemia-reperfusion injury.Kidney Int. 2007; 71: 619-628Abstract Full Text Full Text PDF PubMed Scopus (275) Google Scholar we examined whether renal-resident graft DCs and/or host infiltrating DCs produced TNF-α in KTx-induced I/R injury. TNF-α production was exclusively seen on CD11b/c+ cells. At 12h in 24h-CS grafts, both GFP- renal DCs and GFP+CD11b/c+ host infiltrates produced TNF-α, and their frequencies were higher in host GFP+CD11b/c+ cells (Figure 4d). At 10 weeks, 20.4±2.8% of host CD11b/c+ cells produced TNF-α, whereas remaining small fractions (5.3±1.2%) of donor renal DCs were positive for TNF-α. TNF-α–producing renal DCs were CD103- subtype. In conjunction with the alteration in DC populations, GFP+ host leukocytes infiltrated kidney grafts after KTx, and percentages of host cells were significantly higher in 24h-CS than in control no-CS grafts as early as 3h after KTx. GFP+ host cells in 24h-CS grafts further increased with time, and nearly all of graft leukocytes became host phenotype by 10 weeks, while no-CS grafts showed significantly less GFP+ host cells (88.7±4.9 vs. 53.7±10.2%; Figure 6a). Increases of GFP+ host infiltration into kidney grafts were confirmed in tissue sections, and 24h-CS grafts showed abundant GFP+ cells at 10 weeks (Figure 6b). FCM analysis of host infiltrates during early and late phases of I/R injury revealed significant increase of CD3+ T-cell frequencies in 24h-CS grafts at 4 and 10 weeks compared with control no-CS kidney grafts (Figure 6c). IHC with anti-CD3 mAb also confirmed numerous GFP+CD3+ cells among infiltrates in 24h-CS grafts at 10 weeks (Figure 6d). Characterization of CD3+ cells in kidney grafts revealed gradual increases of CD4+ T cells with I/R injury. At 10 weeks, infiltrating GFP+ host T cells in 24h-CS grafts were dominated by CD4+ T cells with significantly higher CD4/CD8 ratios, compared with those in no-CS grafts (1.8±0.4 vs. 0.7±0.2; Figure 7a and b). Majority of GFP+CD3+ cells were CD62L negative and expressed low molecular weight CD45 isoforms, indicating that they were effector or effector-memory phenotype T cells (Figure 7a). Function of T cells was analyzed by their capability to produce interferon (IFN)-γ. CD3+ cells producing IFN-γ were mostly GFP-donor cells at 3h of I/R injury, but quickly shifted to GFP+ host T cells at 12h. At 10 weeks, one third of GFP+ host T cells were able to produce IFN-γ. Frequencies of IFN-γ–producing host T cells were similar among CD4+ and CD8+ T cells (Figure 7c). Renal I/R injury, which occurs in some degree in every transplant graft, is a significant deleterious factor responsible for early poor graft function as well as for late graft loss due to chronic inflammation and fibrosis, characterized as IF/TA. To understand the mechanisms by which acute I/R injury results in continual adaptive immune responses, the current study focused on graft renal DC alteration and host DC infiltration during acute and late phases of KTx-induced renal I/R injury. DCs are known to have crucial roles in regulating normal and abnormal immune functions. Numerous studies have described the roles of DCs in lymphoid tissues during steady-state as well as various disease conditions; however, relatively little is known about the roles of tissue-resident DCs, particularly in the kidney. Previous histopathological studies show that normal kidney DCs form a contiguous network throughout the entire interstitium and create an anatomic surveillance network to sense and respond to substances diffusing into the kidney.11.Soos T.J. Sims T.N. Barisoni L. et al.CX3CR1+ interstitial dendritic cells form a contiguous network throughout the entire kidney.Kidney Int. 2006; 70: 591-596Abstract Full Text Full Text PDF PubMed Scopus (243) Google Scholar, 12.Kaissling B. Le Hir M. The renal cortical interstitium: morphological and functional aspects.Histochem Cell Biol. 2008; 130: 247-262Crossref PubMed Scopus (146) Google Scholar, 14.Woltman A.M. de Fijter J.W. Zuidwijk K. et al.Quantification of dendritic cell subsets in human renal tissue under normal and pathological conditions.Kidney Int. 2007; 71: 1001-1008Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar In vitro analyses of isolated renal DCs have shown that they are in immature status (low costimulatory function) and possess full phagocytic ability.10.Steptoe R.J. Patel R.K. Subbotin V.M. et al.Comparative analysis of dendritic cell density and total number in commonly transplanted organs: morphometric estimation in normal mice.Transpl Immunol. 2000; 8: 49-56Crossref PubMed Scopus (46) Google Scholar These studies certainly have established the location and phenotypes of renal DCs; however, in vivo functional roles of renal DCs are not defined. Using the WT to GFP transgenic rat KTx model, which enabled us to differentiate donor kidney-resident DCs from recruited host DCs, we demonstrate here an early loss of GFP- donor renal DCs and progressive GFP+ host DC infiltration into the kidney grafts with I/R injury. At 4–10 weeks after initial I/R injury, the majority of donor renal DCs disappear from 24h-CS grafts, and CD11b/c+ cells in these kidney grafts become nearly totally GFP+ host phenotype, which are located among inflammatory infiltrates, and do not form the interstitial network. In contrast, control grafts without I/R injury maintain the interstitial network of donor phenotype renal DCs for 10 weeks with significantly less host DC infiltration. These results suggest that kidney-resident DCs and recruited systemic DCs have different functional roles. Infiltrating host DCs promote fibroinflammatory reactions, whereas renal-resident DCs might have protective roles in regulating chronic inflammation and infiltration of host DCs. Although further investigation is needed, renal-resident DCs could be involved in the control of renal microenvironment and regulation of adaptive immune responses. We have identified two subpopulations of renal DCs in normal rat kidneys, predominant CD103-CD11b/c+ and minor CD103+CD11b/c+ DCs, and they behave differently in responding to KTx-induced renal I/R injury. GFP-CD103+ DCs quickly disappear from both 24h-CS and control no-CS grafts, regardless of injury. In contrast, GFP-CD103- DCs are maintained in no-CS grafts, but disappear from 24h-CS grafts with I/R injury. Recent studies show that DCs exhibit distinct functional roles depending on CD103 (integrin αE) expression; CD103- DCs are highly qualified to perform innate mechanisms such as antigen clearance and chemokine-mediated attraction of leukocytes. In contrast, CD103+ DCs are primarily involved in cross-presentation of self or foreign antigens after migrating to draining lymph nodes.34.del Rio M.L. Bernhardt G. Rodriguez-Barbosa J.I. et al.Developmen
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