THE TRANSCRIPTOME OF ENDOTHELIAL PATHOLOGY: RELEVANCE TO ANTIBODY-MEDIATED MICROCIRCULATION INJURY

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1 THE TRANSCRIPTOME OF ENDOTHELIAL PATHOLOGY: RELEVANCE TO ANTIBODY-MEDIATED MICROCIRCULATION INJURY Introduction Banu Sis, MD, FRCPC University of Alberta, Edmonton, AB, Canada In solid organ transplantation, two forms of allograft rejection have been recognized: T- cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR). The destructive power of alloantibody was first recognized in 1960s as hyperacute rejection due to preformed donor specific antibody (DSA) at time of transplantation (1). However, the problem of ABMR post transplantation remained unrecognized for decades. In early 1990s, Halloran et al. (2;3) identified cases of acute rejection of kidney allografts that were associated with anti-hla DSA. These rejections were more severe than TCMR, were resistant to therapy, and were associated with endothelial injury in the microcirculation and vasculitis (2-4). This observation was then followed by discovery of C4d (a split product of component C4) staining in allograft tissues as evidence of antibody acting on endothelium, which linked antibodies to graft pathology (5;6). After another decade, late graft losses and histology of chronic graft injury were related to C4d and DSA (7-10). ABMR has been demonstrated in kidney, heart, pancreas and lung allografts, and is not restricted to presensitized patients (11-18). Acute C4d+ ABMR has since been reported to occur in about 7% of conventional kidney transplant recipients and in 20 30% of biopsies with acute rejection, and in 20-48% of positive cross-match patients (14;19-21). Diagnosis of ABMR currently requires the simultaneous presence of diffuse C4d staining, DSA, and histopathologic evidence of tissue injury (22;23). C4d+ ABMR can occur early or late post transplant and can be acute or chronic. The morphology of acute ABMR in kidney include peritubular capillaritis; glomerulitis; fibrin thrombi; infarction; and occasionally fibrinoid necrosis of arteries or acute tubular injury (4;22;24). Features of chronic C4d+ ABMR are variable, but include transplant glomerulopathy (TG) (7;10;23;25), multilayering of the peritubular capillary basement membrane, and scarring of parenchymal tissue (7;10;11;23). However, more than 50% of TG with alloantibodies are C4d-negative (10;26), suggesting that C4d is insensitive for chronic ABMR. Thus true incidence of chronic ABMR remains unknown. Microcirculation endothelium is the main target of ABMR Although alloantibodies play major roles in rejection, the precise mechanisms by which alloantibodies cause allograft injury, dysfunction, and loss are not well understood. On the other hand, it is well recognized that the endothelium in microcirculation is the main target of ABMR (16;27-29). Antibody ligation to HLA or blood antigens expressed on the endothelium can initiate activation of the complement system, recruitment of leukocytes (causing vascular 1

2 inflammation), and facilitation of NK-cell-mediated or monocyte/macrophage-mediated cytotoxicity. Together, these reactions to alloantibodies can result in endothelial damage, loss of vascular integrity, and increased coagulation (19;30-33). Antibodies and complement components can alter gene expression in endothelial cells or inflammatory cells via Fc receptors and complement receptors, which further remodel the lesions of ABMR that compromise graft function. The current diagnostic criterion of C4d staining does not identify many kidneys that are failing due to ABMR Detecting which renal transplants are at risk for antibody-mediated deterioration is an unmet need. Anti- HLA antibodies develop in 25% of renal transplant recipients and are associated with increased graft failure (34), but have low predictive value for graft loss. ABMR is a major cause of late kidney transplant failure (35). Data from two major transplant centres independently indicated that most late kidney transplant losses have a specific etiology that is not idiopathic fibrosis or drug toxicity (35;36). We recently studied phenotypes of late failed grafts (after 1 year) in a prospective study of 173 conventional kidney transplants (35). In this study, the Banff diagnostic categories (23;37;38) (the current gold standard for the assessment of kidney transplant biopsies) could not explain many of the graft losses. Conversely, if histologic changes in microcirculation and presence of anti-hla alloantibodies were used to define ABMR (regardless of the presence of C4d), 63% of the late kidney failures were attributed to antibody-mediated microcirculation injury, of which many were C4d-negative and thus were missed by the current Banff diagnostic criteria, suggesting that detection of this phenotype requires new diagnostic criteria. Microarrays of kidney allograft biopsies decipher molecular burden of ABMR: Microarrays of prospective and unselected kidney transplant biopsies that sampled the entire population of renal transplants with clinical difficulties, provided novel insights in understanding the molecular phenotype of ABMR in the allograft tissue when compared with other diseases (39;40). a. Increased endothelial gene expression Recognizing the key role of endothelial changes in ABMR, we hypothesized that altered expression of endothelial genes in biopsies from patients with alloantibody would identify kidneys incurring antibody-mediated damage. In the Transplant Transcriptome Project at the University of Alberta, we studied 173 consecutive renal transplant biopsies for acute or chronic renal dysfunction and/or proteinuria. A study of the literature identified 119 endothelialassociated transcripts (ENDATs), and we used microarrays to determine expression of these transcripts (40). Mean ENDAT expression was increased in all rejection cases; however, their expression was selectively higher in C4d+ ABMR biopsies than in TCMR. ENDAT scores correlated with DSA and histopathologic lesions of ABMR, but not lesions of TCMR. 2

3 Many individual ENDATs were increased C4d+ ABMR and predicted future graft loss. The expression of VWF, EDN1, CAV1 (caveolin 1), CDH5 (cadherin 5), CDH13 (cadherin 13), PALMD, PECAM1, SELE, FY (Duffy blood group), RHOJ, SOX7, SOX18, THBD (thrombomodulin), and MALL (BENE; interacts with CAV1) was higher in ABMR than in TCMR biopsies (40). The increased expression of endothelial genes in ABMR with microarrays was confirmed by RT-PCR. The biology underlying increased ENDAT expression could include a number of processes, including endothelial activation, repair, and/or angiogenesis. For example, seven ENDATs elevated in C4d+ ABMR (VWF, MCAM, CDH5, SELE, PECAM1, CD34, CAV1) are associated with endothelial activation and endothelial cell-cell interactions (30;41). KLF4 (Kruppel-like factor 4), another ENDAT elevated in ABMR, is a regulator of endothelial activation and has anti-inflammatory and anti-thrombotic effects on endothelium (42). SOX7 and SOX18, other endothelial transcripts that increased in ABMR, play redundant roles in endothelial differentiation and some members of SOX family i.e. SOX18 are involved in postnatal angiogenesis in mice (43). b. Increased Ifn-γ effects Interferon-gamma (Ifn-γ), presumably from antigen-triggered effector T cells, plays a major role in allograft rejection. Both ABMR and TCMR biopsies showed high expression of Ifn-γ induced transcripts i.e. CXCL11, CXCL9, CCL5 (RANTES) (39;40). Ifn-γ induces expression of many genes in the donor tissue and in host infiltrating cells, inducing chemokines such as Cxcl9, Cxcl10, CXL11 and MHC class Ia (HLA-A, HLA-B), class Ib (e.g. HLA-E), and class II (HLA-DP, -DQ, and -DR) (44;45). Ifn-γ secreted by T cells and/or NK cells is essential for induction of class I and class II antigens on endothelium (45). Increased major histocompability antigens on endothelium by Ifnγ, increases antibody ligation to endothelium and thus makes antibodies more effective in inducing graft inflammation and injury. c. Leukocytes, platelets, and Fc Receptors are involved in antibody-mediated graft injury Microvascular inflammation (capillaritis, glomerulitis) is the typical histopathological feature of ABMR and is associated with DSA (46). Leukocyte recruitment to the allograft capillaries can be mediated by complement split products (C3a, C5a), activated endothelial cells, and activated platelets. There is recent evidence that complement-independent mechanisms can also trigger microvascular inflammation: Yamakuchi et al (47) showed that alloantibody against class I triggers endothelial exocytosis by the release of VWF and externalization of P-selectin in vitro in the absence of complement, but this requires cross-linking of two Fab portions of IgG. The same group also showed that alloantibody induces VWF expression and platelet adhesion to microvessels in mouse skin allografts (33). Released VWF is a prothrombotic molecule that can mediate platelet aggregation. P-selectin, whereas, is a cell adhesion molecule expressed on activated endothelium and platelets, that triggers the initial stages of leuokocyte trafficking. 3

4 Antibody-dependent cellular cytotoxicity can damage/kill endothelial cells coated by alloantibodies. NK cells, monocytes/macrophages, and other leukocytes have surface receptors for the Fc portion of IgG. In particular, FcγRIII (CD16) binding to IgG causes release of cytotoxic granules (perforin, granzymes) from NK cells that in turn triggers apoptosis of the target cell (19;48). Endothelial gene expression studies led to discovery of C4d negative ABMR Kidneys with high intragraft expression of ENDATs and circulating antibody showed lesions of ABMR (capillaritis, glomerulitis, TG, and fibrosis/atrophy) and poor outcome (40). Many of these active ABMR cases were missed: Only 40% of kidneys with high ENDAT expression and chronic ABMR or graft loss was diagnosed by C4d positivity. However, high ENDAT expression was not an indicator of graft damage or eventual graft loss in patients that lacked anti-hla antibodies. We grouped patients according to increased ENDAT score ( E ), HLA antibody positivity ( A ), and C4d positivity ( C ). Of 161 kidneys, 13 were AEC, 37 AE, 21 E only, 50 A only and 40 with no AEC. AEC and AE kidneys were associated with increased TG, scarring and poor survival. Survival did not differ significantly between AEC and AE; thus; C4d positivity did not have an additional adverse prognostic impact over high ENDAT with antibodies. However, kidneys with only E or only A did not show increased TG, scarring or graft loss, compared to kidneys with no AEC (40). We conclude that ENDAT changes in renal transplants occur in rejection and in other forms of renal injury (infections, ischemic injury), but their impact on TG and graft loss is principally in patients with antibodies. High ENDAT expression with the presence of antibodies predicts graft loss with higher sensitivity (77% vs. 31%) and slightly lower specificity (71% vs. 94%) than the presence of C4d. These results were validated in independent set of 82 kidney grafts. Therefore, high renal endothelial transcript expression in patients with circulating alloantibody is a proven indicator of active antibody-mediated allograft damage and poor graft outcome (40). Most C4d negative ABMR biopsies demonstrated chronic ABMR pathology (TG). However, our recent analyses show that there are some C4d negative biopsies with DSA, high ENDAT expression, and acute ABMR lesions in the absence of TCMR or other pathology (unpublished data). Thus C4d negative acute ABMR probably occurs, and its incidence is yet to be determined. Supporting this point, 49% of sensitized kidney transplant patients developed subclinical C4d negative ABMR (capillaritis plus glomerulitis plus DSA) (versus 31% C4d+ ABMR) at 3-month protocol biopsies, who later developed increased fibrosis, capillaritis, TG, and low graft function at 1-year (49). Conclusion Microarrays of kidney allograft biopsies defined molecular features of ABMR and detected a new group of C4d negative active ABMR with endothelial transcript changes, chronic graft injury, and failure. Thus, complement-independent mechanisms also probably operate in 4

5 ABMR. Recent molecular data show that C4d staining has low sensitivity for detecting active ABMR. Measuring endothelial gene expression in biopsies from kidneys with alloantibody is a sensitive and specific method to diagnose ABMR and predict graft outcomes. Reference List (1) Kissmeyer-Nielsen F, Olsen S, Peterson VP, Fjeldborg O. Hyperacute rejection of kidney allografts associated with pre-existing humoral antibodies against donor cells. Lancet 1966; 2: (2) Halloran PF, Wadgymar A, Ritchie S, Falk J, Solez K, Srinivasa NS. The significance of the anticlass I antibody response. I. Clinical and pathologic features of anti-class I-mediated rejection. Transplant 1990; 49(1): (3) Halloran PF, Schlaut J, Solez K, Srinivasa NS. The significance of the anti-class I response II. Clinical and pathologic features of renal transplants with anti-class I-like antibody. Transplant 1992; 53: (4) Trpkov K, Campbell P, Pazderka F, Cockfield S, Solez K, Halloran PF. Pathologic features of acute renal allograft rejection associated with donor-specific antibody. Transplant 1996; 61: (5) Feucht HE, Felber E, Gokel MJ, Hillebrand G, Nattermann U, Brockmeyer C et al. Vascular deposition of complement-split products in kidney allografts with cell-mediated rejection. Clin Exp Immunol 1991; 86(3): (6) Feucht HE, Schneeberger H, Hillebrand G, Burkhardt K, Weiss M, Riethmüller G et al. Capillary deposition of C4d complement fragment and early renal graft loss. Kidney Int 1993; 43: (7) Mauiyyedi S, Pelle PD, Saidman S, Collins AB, Pascual M, Tolkoff-Rubin NE et al. Chronic humoral rejection: identification of antibody-mediated chronic renal allograft rejection by C4d deposits in peritubular capillaries. J Am Soc Nephrol 2001; 12(3): (8) Regele H, Bohmig GA, Habicht A, Gollowitzer D, Schillinger M, Rockenschaub S et al. Capillary deposition of complement split product C4d in renal allografts is associated with basement membrane injury in peritubular and glomerular capillaries: a contribution of humoral immunity to chronic allograft rejection. J Am Soc Nephrol 2002; 13(9): (9) Vongwiwatana A, Gourishankar S, Campbell PM, Solez K, Halloran PF. Peritubular capillary changes and C4d deposits are associated with transplant glomerulopathy but not IgA nephropathy. Am J Transplant 2004; 4(1): (10) Sis B, Campbell PM, Mueller T, Hunter C, Cockfield SM, Cruz J et al. Transplant glomerulopathy, late antibody-mediated rejection and the ABCD tetrad in kidney allograft biopsies for cause. Am J Transplant 2007; 7(7):

6 (11) Colvin RB. Antibody-mediated renal allograft rejection: diagnosis and pathogenesis. J Am Soc Nephrol 2007; 18(4): (12) Reed EF, Demetris AJ, Hammond E, Itescu S, Kobashigawa JA, Reinsmoen NL et al. Acute antibody-mediated rejection of cardiac transplants. J Heart Lung Transplant 2006; 25(2): (13) McKenna RM, Takemoto SK, Terasaki PI. Anti-HLA antibodies after solid organ transplantation. Transplant 2000; 69(3): (14) Mauiyyedi S, Colvin RB. Humoral rejection in kidney transplantation: new concepts in diagnosis and treatment. Current Opinion in Nephrology and Hypertension 2002; 11(6): (15) Miller GG, Destarac L, Zeevi A, Girnita A, McCurry K, Iacono A et al. Acute humoral rejection of human lung allografts and elevation of C4d in bronchoalveolar lavage fluid. Am J Transplant 2004; 4(8): (16) Rodriguez ER, Skojec DV, Tan CD, Zachary AA, Kasper EK, Conte JV et al. Antibody-mediated rejection in human cardiac allografts: evaluation of immunoglobulins and complement activation products c4d and c3d as markers. Am J Transplant 2005; 5(11): (17) Drachenberg CB, Odorico J, Demetris AJ, Arend L, Bajema IM, Bruijn JA et al. Banff schema for grading pancreas allograft rejection: working proposal by a multi-disciplinary international consensus panel. Am J Transplant 2008; 8(6): (18) Girnita AL, Lee TM, McCurry KR, Baldwin WM, III, Yousem SA, Detrick B et al. Anti-human leukocyte antigen antibodies, vascular C4d deposition and increased soluble c4d in broncho-alveolar lavage of lung allografts. Transplant 2008; 86(2): (19) Colvin RB, Smith RN. Antibody-mediated organ-allograft rejection. Nat Rev Immunol 2005; 5(10): (20) Haas M, Rahman MH, Racusen LC, Kraus ES, Bagnasco SM, Segev DL et al. C4d and C3d staining in biopsies of ABO- and HLA-incompatible renal allografts: Correlation with histologic findings. Am J Transplant 2006; 6(8): (21) Kraus ES, Parekh RS, Oberai P, Lepley D, Segev DL, Bagnasco S et al. Subclinical rejection in stable positive crossmatch kidney transplant patients: incidence and correlations. Am J Transplant 2009; 9(8): (22) Racusen LC, Colvin RB, Solez K, Mihatsch MJ, Halloran PF, Campbell PM et al. Antibodymediated rejection criteria - an addition to the Banff 97 classification of renal allograft rejection. Am J Transplant 2003; 3(6): (23) Solez K, Colvin RB, Racusen LC, Sis B, Halloran PF, Birk PE et al. Banff '05 Meeting report: Differential diagnosis of chronic allograft injury and elimination of chronic allograft nephropathy ('CAN'). Am J Transplant 2007; 7(3): (24) Mauiyyedi S, Crespo M, Collins AB, Schneeberger EE, Pascual MA, Saidman SL et al. Acute humoral rejection in kidney transplantation: II. Morphology, immunopathology, and pathologic classification. J Am Soc Nephrol 2002; 13(3): (25) Feucht HE, Opelz G. The humoral immune response towards HLA class II determinants in renal transplantation [review]. Kidney Int 1996; 50:

7 (26) Gloor JM, Sethi S, Stegall MD, Park WD, Moore SB, Degoey S et al. Transplant glomerulopathy: Subclinical incidence and association with alloantibody. Am J Transplant 2007; 7(9): (27) Jin YP, Jindra PT, Gong KW, Lepin EJ, Reed EF. Anti-HLA class I antibodies activate endothelial cells and promote chronic rejection. Transplant 2005; 79(3 Suppl):S19-S21. (28) Regele H, Bohmig GA. Tissue injury and repair in allografts: novel perspectives. Current Opinion in Nephrology and Hypertension 2003; 12(3): (29) Minami K, Murata K, Lee CY, Fox-Talbot K, Wasowska BA, Pescovitz MD et al. C4d deposition and clearance in cardiac transplants correlates with alloantibody levels and rejection in rats. Am J Transplant 2006; 6(5 Pt 1): (30) Valujskikh A, Heeger PS. Emerging roles of endothelial cells in transplant rejection. Curr Opin Immunol 2003; 15(5): (31) Baldwin WM, III, Kasper EK, Zachary AA, Wasowska BA, Rodriguez ER. Beyond C4d: other complement-related diagnostic approaches to antibody-mediated rejection. Am J Transplant 2004; 4(3): (32) Baldwin W.M. I, Larsen CP, Fairchild RL. Innate immune responses to transplants: a significant variable with cadaver donors. Immunity 2001; 14: (33) Morrell CN, Murata K, Swaim AM, Mason E, Martin TV, Thompson LE et al. In vivo plateletendothelial cell interactions in response to major histocompatibility complex alloantibody. Circ Res 2008; 102(7): (34) Terasaki PI, Ozawa M. Predicting kidney graft failure by HLA antibodies: a prospective trial. Am J Transplant 2004; 4(3): (35) Einecke G, Sis B, Reeve J, Mengel M, Campbell PM, Hidalgo LG et al. Antibody-mediated microcirculation injury is the major cause of late kidney transplant failure. Am J Transplant 2009; 9(11): (36) El Zoghby ZM, Stegall MD, Lager DJ, Kremers WK, Amer H, Gloor JM et al. Identifying specific causes of kidney allograft loss. Am J Transplant 2009; 9(3): (37) Solez K, Colvin RB, Racusen LC, Haas M, Sis B, Mengel M et al. Banff 07 classification of renal allograft pathology: updates and future directions. Am J Transplant 2008; 8(4): (38) Racusen LC, Solez K, Colvin RB, Bonsib SM, Castro MC, Cavallo T et al. The Banff 97 working classification of renal allograft pathology. Kidney Int 1999; 55(2): (39) Mueller TF, Einecke G, Reeve J, Sis B, Mengel M, Jhangri.G. et al. Microarray analysis of rejection in human kidney transplants using pathogenesis-based transcript sets. Am J Transplant 2007; 7(12): (40) Sis B, Jhangri G, Bunnag S, Allanach K, Kaplan B, Halloran PF. Endothelial gene expression in kidney transplants with alloantibody indicates antibody-mediated damage despite lack of C4d staining. Am J Transplant 2009; 9(10):

8 (41) Hermant B, Bibert S, Concord E, Dublet B, Weidenhaupt M, Vernet T et al. Identification of proteases involved in the proteolysis of vascular endothelium cadherin during neutrophil transmigration. J Biol Chem 2003; 278(16): (42) Hamik A, Lin Z, Kumar A, Balcells M, Sinha S, Katz J et al. Kruppel-like factor 4 regulates endothelial inflammation. J Biol Chem 2007; 282(18): (43) Cermenati S, Moleri S, Cimbro S, Corti P, Del Giacco L, Amodeo R et al. Sox18 and Sox7 play redundant roles in vascular development. Blood 2008; 111(5): (44) Famulski KS, Einecke G, Reeve J, Ramassar V, Allanach K, Mueller T et al. Changes in the transcriptome in allograft rejection: IFN-γ induced transcripts in mouse kidney allografts. Am J Transplant 2006; 6(6): (45) Goes N, Urmson J, Hobart M, Halloran PF. The unique role of interferon-gamma in the regulation of MHC expression on arterial endothelium. Transplant 1996; 62(12): (46) Hidalgo LG, Campbell PM, Sis B., Einecke G, Mengel M, Chang J et al. De novo donor specific antibody at the time of kidney transplant biopsy associates with microvascular pathology and late graft failure. Am J Transplant 2009; 9(11): (47) Yamakuchi M, Kirkiles-Smith NC, Ferlito M, Cameron SJ, Bao C, Fox-Talbot K et al. Antibody to human leukocyte antigen triggers endothelial exocytosis. Proc Natl Acad Sci U S A 2007; 104(4): (48) Lee CY, Lotfi-Emran S, Erdinc M, Murata K, Velidedeoglu E, Fox-Talbot K et al. The involvement of FcR mechanisms in antibody-mediated rejection. Transplant 2007; 84(10): (49) Loupy A, Suberbielle-Boissel C, Hill GS, Lefaucheur C, Anglicheau D, Zuber J et al. Outcome of subclinical antibody-mediated rejection in kidney transplant recipients with preformed donorspecific antibodies. Am J Transplant 2009; 9(11):