Chronic rejection and its risk factors

Pattern of organ remodeling in chronic non-communicable diseases is due to endogenous regulations and falls under the category of Kauffman's self-organization: A case of arterial neointimal pathology

Clinical diagnosis is based on analysis of pathologic findings that may result in perceived patterns. The same is true for diagnostic pathology: Pattern analysis is a foundation of the histopathology-based diagnostic system and, in conjunction with clinical and laboratory findings, forms a basis for the classification of diseases. Any histopathology diagnosis is based on the explicit assumption that the same diseased condition should result in formation of the same (or highly similar) morphologic patterns in different individuals; it is a standard approach in microscopic pathology, including that of non-communicable chronic diseases with organ remodeling. During fifty years of examining diseased tissues under microscopy, I keep asking the same question: Why is a similarity of patterns expected for chronic organ remodeling? For infection diseases, xenobiotic toxicity and deficiencies forming an identical pathologic pattern in different individuals is understandable and logical: The same infection, xenobiotic, or deficiency strikes the same target, which results in identical pathology. The same is true for Mendelian diseases: The same mutations lead to the same altered gene expressions and the same pathologic pattern. But why does this regularity hold true for chronic diseases with organ remodeling? Presumable causes (or risk factors) for a particular chronic disease differ in magnitude and duration between individuals, which should result in various series of transformations. Yet, mysteriously enough, pathological remodeling in a particular chronic disease always falls into a main dominating pattern, perpetuating and progressing in a similar fashion in different patients. Furthermore, some chronic diseases of different etiologies and dissimilar causes/risk factors manifest as identical or highly similar patterns of pathologic remodeling. HYPOTHESIS: I hypothesize that regulations governing a particular organ's chronic remodeling were selected in evolution as the safest response to various insults and physiologic stress conditions. This hypothesis implies that regulations directing diseased chronic remodeling always preexist but normally are controlled; this control can be disrupted by a diverse range of non-specific signals, liberating the pathway for identical pathologic remodeling. This hypothesis was tested in an analysis of arterial neointimal formation, the identical pathology occurring in different diseases and pathological conditions: graft vascular disease in organ transplantation, in-stent restenosis, peripheral arterial diseases, idiopathic intimal hyperplasia, Kawasaki disease, coronary atherosclerosis and as reaction to drugs. The hypothesis suggests that arterial intimal cells are poised between only two alternative pathways: the pathway with controlled intimal cell proliferation or the pathway where such control is disrupted, ultimately leading to the progressive neointimal pathology. By this property the arterial neointimal formation constitutes a special case of Kauffman's self-organization. This new hypothesis gives a parsimonious explanation for identical pathological patterns of arterial remodeling (neointimal formation), which occurs in diseases of different etiologies and due to dissimilar causes/risk factors, or without any etiology and causes/risk factors at all. This new hypothesis also suggests that regulation facilitating intimal cell proliferation cannot be overwritten or annulled because this feature is vital for arterial differentiation, cell renewal, and integrity. This hypothesis suggests that studying numerous, and likely interchangeable, non-specific signals that disrupt regulation controlling intimal cell proliferation is unproductive; instead, a study of the controlling regulation(s) itself should be a priority of our research.

Interplay between immune responses to HLA and non-HLA self-antigens in allograft rejection

Recent studies strongly suggest an increasing role for immune responses against self-antigens (Ags) which are not encoded by the major histocompatibility complex in the immunopathogenesis of allograft rejection. Although, improved surgical techniques coupled with improved methods to detect and avoid sensitization against donor human leukocyte antigen (HLA) have improved the immediate and short term function of transplanted organs. However, acute and chronic rejection still remains a vexing problem for the long term function of the transplanted organ. Immediately following organ transplantation, several factors both immune and non immune mechanisms lead to the development of local inflammatory milieu which sets the stage for allograft rejection. Traditionally, development of antibodies (Abs) against mismatched donor HLA have been implicated in the development of Ab mediated rejection. However, recent studies from our laboratory and others have demonstrated that development of humoral and cellular immune responses against non-HLA self-Ags may contribute in the pathogenesis of allograft rejection. There are reports demonstrating that immune responses to self-Ags especially Abs to the self-Ags as well as cellular immune responses especially through IL17 has significant pro-fibrotic properties leading to chronic allograft failure. This review summarizes recent studies demonstrating the role for immune responses to self-Ags in allograft immunity leading to rejection as well as present recent evidence suggesting there is interplay between allo- and autoimmunity leading to allograft dysfunction.

Improving donor organ function-cold to warm preservation

This paper explores the evolution of organ preservation methods from cold preservation to the more sophisticated method of warm preservation. Both methods are detailed, and the benefits and limitations of both methods are discussed.

Analysis of arterial intimal hyperplasia: review and hypothesis

BACKGROUND

Despite a prodigious investment of funds, we cannot treat or prevent arteriosclerosis and restenosis, particularly its major pathology, arterial intimal hyperplasia. A cornerstone question lies behind all approaches to the disease: what causes the pathology?

HYPOTHESIS

I argue that the question itself is misplaced because it implies that intimal hyperplasia is a novel pathological phenomenon caused by new mechanisms. A simple inquiry into arterial morphology shows the opposite is true. The normal multi-layer cellular organization of the tunica intima is identical to that of diseased hyperplasia; it is the standard arterial system design in all placentals at least as large as rabbits, including humans. Formed initially as one-layer endothelium lining, this phenotype can either be maintained or differentiate into a normal multi-layer cellular lining, so striking in its resemblance to diseased hyperplasia that we have to name it "benign intimal hyperplasia". However, normal or "benign" intimal hyperplasia, although microscopically identical to pathology, is a controllable phenotype that rarely compromises blood supply. It is remarkable that each human heart has coronary arteries in which a single-layer endothelium differentiates early in life to form a multi-layer intimal hyperplasia and then continues to self-renew in a controlled manner throughout life, relatively rarely compromising the blood supply to the heart, causing complications requiring intervention only in a small fraction of the population, while all humans are carriers of benign hyperplasia. Unfortunately, this fundamental fact has not been widely appreciated in arteriosclerosis research and medical education, which continue to operate on the assumption that the normal arterial intima is always an "ideal" single-layer endothelium. As a result, the disease is perceived and studied as a new pathological event caused by new mechanisms. The discovery that normal coronary arteries are morphologically indistinguishable from deadly coronary arteriosclerosis continues to elicit surprise.

CONCLUSION

Two questions should inform the priorities of our research: (1) what controls switch the single cell-layer intimal phenotype into normal hyperplasia? (2) how is normal (benign) hyperplasia maintained? We would be hard-pressed to gain practical insights without scrutinizing our premises.

Chronic allograft nephropathy uniformly affects recipients of cadaveric, nonidentical living-related, and living-unrelated grafts

BACKGROUND

Chronic allograft nephropathy (CAN) remains a major barrier to long-term allograft survival. The authors retrospectively compared the development of CAN in recipients of cadaveric (CAD), living-related donor (LRD), and living-unrelated donor (LURD) transplants at their center.

METHODS

The authors retrospectively examined the impact of various factors on the incidence of CAN using univariate and multivariate proportional hazards analysis in a single-center kidney transplant population.

RESULTS

Between 1 January 1990 and 31 May 2000, 2,140 kidney-alone transplants were performed at the authors' center. The overall 5-year incidence of biopsy-proven CAN was 12.2% (n=203). Risk factors for CAN included the number of transplants (P=0.0001), acute rejection (P=0.0001), panel reactive antibody (P=0.0001), discharge creatinine (P=0.0001), 1-year creatinine (P=0.0015), delayed graft function (P=0.007), total human leukocyte antigen (HLA)-B and -DR mismatches (P=0.0005), recipient age (P=0.003), black donor race (P=0.001), black recipient race (0.0457), donor age (P=0.0053), cold storage time (P=0.019), and cytomegalovirus infections (P=0.002). Interestingly, although the LRD HLA-identical recipients had a significantly lower incidence of CAN (P=0.0015), the incidence of CAN in CAD and HLA-nonidentical LRD recipients did not differ. Graft survival was significantly worse in CAD recipients compared with all other groups (P<0.001).

CONCLUSIONS

These results demonstrate the importance of immunologic and nonimmunologic factors on the development of CAN. The disparities in overall graft survival, despite the similarities in CAN rates, suggests that other factors, in addition to CAN, influence the increase in graft loss in CAD transplant recipients.

Donor-derived circulating endothelial cells after kidney transplantation

BACKGROUND

In solid-organ transplantation, the allograft vasculature, in particular the endothelium, is prone to injury inflicted by peritransplantational and posttransplantational factors. Previously, we have shown that circulating endothelial cells (cEC) can be detected in the peripheral blood of kidney allograft recipients and are often associated with acute rejection and active infections with human cytomegalovirus. In the present study we hypothesized that cEC after kidney transplantation are of donor origin, thus reflecting transplantation-related damage to the allograft endothelium.

METHODS

Using hydraulic micromanipulation equipment, we isolated single cEC (n=153) from the peripheral blood of nine kidney allograft recipients at various time points after transplantation. We demonstrated the origin of these cells (donor or recipient) by typing their HLA-DRB alleles by single-cell, genomic, nested polymerase chain reaction.

RESULTS

The majority (71.8%) of cEC were of donor origin and could be detected up to 141 days after onset of acute rejection episodes. Although less frequent (28.2%), recipient-type cEC were detected in the same time course as donor-type cEC.

CONCLUSION

We conclude that posttransplantational injury to the allograft endothelium is reflected by the presence of donor-derived cEC in the blood.

Platelet-endothelial cell adhesion molecule-1 (CD31) expression on donor endothelial cells attenuates the development of transplant arteriosclerosis

BACKGROUND

Platelet-endothelial cell adhesion molecule(PECAM)-1 (CD31) is expressed on the surface of endothelial cells, platelets, monocytes, neutrophils, and certain T-cell subsets. Treatment of endothelial cells with anti-PECAM-1 antibody inhibits leukocyte transmigration. This study was designed to test the hypothesis that, in transplantation, the absence of PECAM-1 expression on donor endothelial cells would reduce the number of leukocytes transmigrating into the allograft, thereby attenuating the development of transplant arteriosclerosis.

METHODS

PECAM-1 and PECAM (C57BL/6/H2 ) abdominal aortic allografts were transplanted into BALB/c (H2 ) recipients; syngeneic grafts were used as controls. Aortic grafts were analyzed by performing morphometry, immunohistochemistry, and quantitative reverse transcriptase-polymerase chain reaction for the detection of intragraft cytokine mRNA production.

RESULTS

Intimal proliferation was exacerbated in PECAM-1 grafts (57+/-5% for PECAM-1 vs. 36+/-6% for PECAM-1; <0.005; n=6). The absence of PECAM-1 expression on donor endothelial cells did not reduce the overall number of graft-infiltrating cells significantly but instead resulted in a significant increase in infiltration by macrophages (F4/80 cells), leading to significantly elevated intragraft mRNA expression of inducible nitric oxide synthase. During the development of transplant arteriosclerosis, PECAM-1 donor endothelial cells were replaced by recipient PECAM-1 endothelial cells, a process that occurred only in the allogeneic situation. Endothelial replacement commenced 14 days after transplantation and was complete by day 30.

CONCLUSIONS

These data suggest that PECAM-1 expression by donor endothelial cells attenuates the development of transplant arteriosclerosis, possibly by affecting macrophage infiltration.

Cold storage preservation and warm ischaemic injury to isolated arterial segments: endothelial cell injury

Injury to endothelial cells is thought to be important to the development of the vascular lesion of chronic rejection. It was the aim of this study to develop a semiquantitative method to assess endothelial injury in arterial grafts and to document the injury produced by cold storage preservation and additional warm ischaemia. Twelve- and 24-h cold preservation of rat aortic segments, together with an additional 1 h of warm ischaemia, were assessed. Electron micrographs of representative endothelial cells were scored for cytoplasmic, nuclear and mitochondrial injury. The overall injury score was obtained by addition of the individual scores. Storage for up to 24 h in University of Wisconsin (UW) and Terasaki did not produce any injury. Twenty-four hours of storage in Euro-Collins resulted in endothelial cell death. Injury occurred after 12 h of storage in Ross, Collins and normal saline, and the injury increased following 24 h of storage. One hour of warm ischaemia did not increase the injury. Injury to endothelial cells varies with the preservation solution used and the time of cold storage, so that both the type of solution and the storage time should be taken into account in clinical studies looking at the influence of cold ischaemia time and graft outcome.

Kinetics of transplant arteriosclerosis in MHC-Class I mismatched and fully allogeneic mouse aortic allografts

INTRODUCTION

Transplant arteriosclerosis is still the major complication for long-term allograft survival in clinical transplantation. The aim of our study was to investigate the impact of MHC disparity on the kinetics of the development of transplant arteriosclerosis.

METHODS

MHC-class I mismatched CBK (H2k+Kb) or fully allogeneic C57BL/10 (H2b) aortic allografts were transplanted into CBA.CA (H2k) recipients; syngeneic grafts were used as controls. Aortic grafts were analyzed on days 7, 14, and 30 after transplantation by performing morphometry, immunohistochemistry and quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) for the detection of intragraft cytokine mRNA production. Donor specific alloantibody production was measured by FACS analysis.

RESULTS

Intimal proliferation developed more rapidly in fully allogeneic grafts (direct and indirect allorecognition by CD4+ T cells) compared to MHC-class I mismatched grafts (indirect allorecognition only by CD4+ T cells) (day 7: 6+/-7 vs. 2+/-3%; day 14: 17+/-8 vs. 5+/-1%; day 30: 65+/-5 vs. 38+/-7% (C57BL/10 vs. CBK). However, by day 60, the level of intimal proliferation in the MHC-class I mismatched grafts was equivalent to that observed with fully allogeneic grafts on day 30. There was also a marked delay in the kinetics of graft infiltration by CD4+, CD8+, CD11b+, and CD40+ leukocytes and alloantibody production when CD4+ T cells were only activated via indirect presentation (MHC-class I mismatched grafts). Expression of interferon-gamma, interleukin-2, and interleukin-4 correlated with the kinetics of leukocyte infiltration, whereas interleukin-10, interleukin-12p40, iNOS, and TGF-beta1 showed a distinct pattern of expression.

CONCLUSIONS

These data demonstrate that the degree of MHC incompatibility between donor and recipient markedly influences the kinetics of the development of transplant arteriosclerosis. The onset of disease was delayed when grafts were mismatched for only MHC-class I antigens, but ultimately reached the same levels as seen in fully allogeneic grafts. The pattern of leukocyte infiltration and the kinetics of cytokine production suggest that in the MHC-class I mismatched grafts CD4+ T cells responding via the indirect pathway might play an important role in the development of transplant arteriosclerosis.

Pediatric cardiac transplantation: management issues

Pediatric heart transplantation is an effective therapeutic modality for children with end-stage heart disease. The overall survival of young heart recipients is very good: 89% to 92% one year survival. Survival data for the long term indicates that pediatric heart recipients have a very good chance of living for decades. Advances in immunosuppression have lent optimism for the future. There are now alternatives in induction, maintenance, and acute rejection therapy. Immunosuppressants are more specific in action and prevent and treat allograft rejection with less toxic side effects and decreased morbidity. Acute rejection and infection are early complications that reduce in incidence significantly after six months post-transplant. Graft coronary artery disease continues to be the most significant hurdle to long-term survival. Currently there is a plateau in the number of heart transplants performed annually. Lack of available pediatric donors plays a large role in the paucity of pediatric transplants. This review focuses on the key management issues involved in the care of the pediatric heart transplant recipient and incorporates the experiences and protocols of the Stanford University Pediatric Heart Transplant Program.

Increased dietary salt accelerates chronic allograft nephropathy in rats

BACKGROUND

Chronic allograft nephropathy (CAN), a major problem in renal transplantation, is related to both alloantigen-dependent and -independent processes. Because dietary salt intake modulated glomerular production of transforming growth factor-beta, which has been shown to play an important role in CAN, we hypothesized that dietary salt would directly enhance renal injury in a rodent model of CAN.

METHODS

Dietary NaCl was increased from 1.0% (normal) to 8.0% in a group of Fisher/Lewis rats 25 days following orthotopic renal transplantation and was continued until 16 weeks after transplantation.

RESULTS

Blood pressure, which was recorded using radiotelemetry in the first eight-weeks post-transplantation, did not differ between the groups, but allograft recipients on the 8.0% NaCl diet rapidly demonstrated increased urinary albumin excretion. Renal function determined by dynamic functional imaging was worse in allograft recipients on the 8.0% NaCl diet by six weeks following transplantation. Histologic examination at 16 weeks confirmed a significant increase in allograft damage in the 8.0% NaCl group compared with allografts from rats on 1.0% NaCl diet. These findings included glomerulosclerosis and tubulointerstitial injury that consisted of fibrosis, tubular atrophy and dilation, intratubular casts, and tubular epithelial cell damage. Small arteries and arterioles did not show evidence of damage from hypertension or other abnormality.

CONCLUSIONS

In this model of CAN, renal allograft dysfunction preceded hypertension and was accelerated significantly by an increase in dietary salt.

Intragraft interleukin-4 mRNA expression after short-term CD154 blockade may trigger delayed development of transplant arteriosclerosis in the absence of CD8+ T cells

BACKGROUND

It has recently been shown that, although anti-CD154 induces CD4+ T-cell tolerance, it is unable to prevent allograft rejection mediated by CD8+ T cells. We have also shown that anti-CD154 monotherapy does not protect the graft from the development of transplant arteriosclerosis even in the absence of CD8+ T cells. This study was designed to investigate and characterize possible mechanisms responsible for the development of transplant arteriosclerosis after CD154 blockade in the absence of CD8+ T cells.

METHODS

C57BL/6 (H2b) recipients received a fully MHC-mismatched BALB/c donor aorta (H2d). Animals were either treated with anti-CD154 monoclonal antibody (mAb) in the presence or absence of CD8 T cells. Histology, morphometric measurements, immunohistochemistry, and the production of alloantibodies (IgM, IgG1, IgG2a) were analyzed on days 14, 30, and 50 after transplantation. Cytokine production within the graft was investigated by competitive reverse transcription-polymerase chain reaction on day 14.

RESULTS

Combined treatment with anti-CD154 and a depleting CD8 mAb resulted in a delay in the development of transplant arteriosclerosis (intimal proliferation: 33+/-10% vs. 67+/-11% untreated control, day 30) but ultimately did not prevent its progression (intimal proliferation: 55+/-10% vs. 78+/-9% untreated control, day 50). Although there was a significant decrease in the number of CD4+, CD11b+, and CD40+ graft-infiltrating cells and a reduction in the formation of donor-specific IgG1 alloantibodies in recipients treated with anti-CD154 and anti-CD8 mAbs, mRNA for interleukin (IL)-4 was increased, suggesting a shift in the intragraft cytokine profile towards a Th2-like pattern.

CONCLUSIONS

Our data provide evidence that short-term CD154 blockade is insufficient to prevent transplant arteriosclerosis, even in combination with CD8+ T-cell depletion. Moreover, the increased expression of the Th2 cytokine interleukin-4 within the graft may be responsible for the development of transplant arteriosclerosis in the long term.

Hypercholesterolemia is associated with increased kidney graft loss caused by chronic rejection in male patients with previous acute rejection

BACKGROUND

Whereas acute rejection is the main risk factor for the occurrence of chronic rejection, mechanisms in addition to the donor-specific immune response probably contribute to late allograft failure. In this study, we investigated the possible role of hypercholesterolemia in the incidence of chronic kidney graft loss.

METHODS

By using the actuarial method, we retrospectively analyzed the long-term loss of cadaveric kidney grafts in patients who had a functioning graft at 1 year and had received a transplant and undergone cyclosporin A therapy in our center between 1983 and 1997.

RESULTS

As observed previously, patients with acute rejection during the 1st posttransplant year (n=198) had significantly higher actuarial graft loss at 10 years compared with those free of acute rejection (n=244). In patients free of acute rejection at 1 year, hypercholesterolemia (> or =250 mg/dl) had no impact on graft loss at 10 years. On the contrary, in patients with previous acute rejection, those with hypercholesterolemia (n=59) had a higher immunological (36.0% vs. 19.2%; P<0.01) and overall (50.0% vs. 25.3%; P<0.01) graft loss at 10 years compared with patients with serum cholesterol <250 mg/dl (n=139). Among patients with 1st year acute rejection, hypercholesterolemia was associated with a significant increase in graft loss in male but not in female recipients. Multivariate analysis confirmed that hypercholesterolemia was an independent risk factor for chronic graft loss in male patients (P<0.05).

CONCLUSION

Hypercholesterolemia is an independent risk factor for kidney graft loss from chronic rejection in male patients with previous acute rejection. Correction of hypercholesterolemia could help to reduce kidney graft loss caused by chronic rejection in this category of patients.

Targeting of the chemokine receptor CCR1 suppresses development of acute and chronic cardiac allograft rejection

Although mononuclear cell infiltration is a hallmark of cellular rejection of a vascularized allograft, efforts to inhibit rejection by blocking leukocyte-endothelial cell adhesion have proved largely unsuccessful, perhaps in part because of persistent generation of chemokines within rejecting grafts. We now provide, to our knowledge, the first evidence that in vivo blockade of specific chemokine receptors is of therapeutic significance in organ transplantation. Inbred mice with a targeted deletion of the chemokine receptor CCR1 showed significant prolongation of allograft survival in 4 models. First, cardiac allografts across a class II mismatch were rejected by CCR1(+/+) recipients but were accepted permanently by CCR1(-/-) recipients. Second, CCR1(-/-) mice rejected completely class I- and class II-mismatched BALB/c cardiac allografts more slowly than control mice. Third, levels of cyclosporin A that had marginal effects in CCR1(+/+) mice resulted in permanent allograft acceptance in CCR1(-/-) recipients. These latter allografts showed no sign of chronic rejection 50-200 days after transplantation, and transfer of CD4(+) splenic T cells from these mice to naive allograft recipients significantly prolonged allograft survival, whereas cells from CCR1(+/+) mice conferred no such benefit. Finally, both CCR1(+/+) and CCR1(-/-) allograft recipients, when treated with a mAb to CD4, showed permanent engraftment, but these allografts showed florid chronic rejection in the former strain and were normal in CCR1(-/-) mice. We conclude that therapies to block CCR1/ligand interactions may prove useful in preventing acute and chronic rejection clinically.