Received for publication: 2.10.2012; Accepted in revised form: 5.10.2012. Nephrol Dial .... The main cause of graft loss in the long term is the death of the patient ...
4. Wang W, Pang L, Palade P. Angiotensin II upregulates Cav1.2 protein expression in cultured arteries via endothelial H2O2 production. J Vasc Res 2011; 48: 67–78 5. McCurley A, Pires PW, Bender SB, Aronovitz M, Zhao MJ, Metzger D, Chambon P, Hill MA, Dorrance AM, Mendelsohn ME, Jaffe IZ. Direct regulation of blood pressure by smooth muscle cell mineralocorticoid receptors. Nat Med 2012; 18: 1429–1433
REFERENCES 1. Pearce D, Bhargava A, Cole TJ. Aldosterone: its receptor, target genes, and actions. Vitam Horm 2003; 66: 29–76 2. Ronzaud C, Loffing J, Bleich M, Gretz N, Gröne HJ, Schütz G, Berger S. Impairment of sodium balance in mice deficient in renal principal cell mineralocorticoid receptor. J Am Soc Nephrol 2007; 18: 1679–1687 3. Levy DG, Rocha R, Funder JW. Distinguishing the antihypertensive and electrolyte effects of eplerenone. J Clin Endocrinol Metab 2004; 89: 2736–2740
Received for publication: 2.10.2012; Accepted in revised form: 5.10.2012
Nephrol Dial Transplant (2013) 28: 1362–1370 doi: 10.1093/ndt/gfs606 Advance Access publication 24 January 2013
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Clinical and histological predictors of long-term kidney graft survival 1
Pierre Galichon1,2,3,
Urgences Néphrologiques et Transplantation Rénale, Hôpital Tenon,
Assistance Publique des Hôpitaux de Paris, Paris, France,
Yi-Chun Xu-Dubois3,4, 1
Serge Finianos , Alexandre Hertig1,2,3
2
Université Pierre et Marie Curie—Paris 6, Paris, France,
3
INSERM UMR S702, Paris, France and
4
Service de Santé Publique, Hôpital Tenon, Assistance Publique des
Hôpitaux de Paris, Paris, France
and Eric Rondeau1,2,3*
Keywords: clinical marker, graft survival, pathology, prognosis
Correspondence and offprint requests to: Eric Rondeau; E-mail: eric.rondeau@tnn.aphp.fr
A B S T R AC T
INTRODUCTION
Renal transplantation is the best option for patients with endstage renal disease (ESRD), but its half-life is limited to a decade. Clinical and histological markers measurable within the first year of transplantation can be used to predict its outcome. These markers are important for selecting kidneys for transplantation, for identifying the main causes of late allograft loss, for therapeutic decisions and as surrogate markers in therapeutic trials. ‘Basal state’ markers, such as age, glomerular filtration rate and fibrotic lesions, are highly predictive of allograft loss, showing that early and stable pathological mechanisms contribute considerably to this loss. On the other hand, some more dynamic predictors such as treatment, recurrence of the initial disease, inflammation and epithelial phenotypic changes offer clinicians and researchers opportunities to influence the fate of allografts.
Renal transplantation is the best treatment for advanced chronic renal failure. It offers a better quality of life than haemodialysis, and significantly improves patient survival. It also dramatically reduces the long-term cost of medical care for these patients. However, prolonged immunosuppression is associated with several side effects, which may alter both graft and patient survival. Overall, in patients who are suitable for transplantation, renal transplantation offers a better benefit–risk ratio than dialysis. Various clinical and histological predictors of long-term kidney graft survival have been identified, and in some cases, they can be used to intervene in order to prolong the survival of the graft or of the patient. In other cases, they are simply markers that can be used in therapeutic trials as early surrogate markers for long-term efficacy.
© The Author 2013. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.
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Graft survival rates are currently in the range of 90–95 at 1year post-transplant, 80 at 5 years and 50% at 10–11 years for cadaveric donor kidneys. The results are even better for kidneys from living donors, reaching ∼100 at 1 year, 90 at 5 years and 50% at 17–18 years, at least when living-related donors are used [1]. Excellent survival rates have also been reported in living-unrelated donors, such as spouses, indicating that the quality of kidney graft and the limited cold ischaemia time are major factors in determining the duration of the transplant. Conversely, antibody-mediated graft injury is associated with a reduced survival in patients with donorspecific antibodies or in patients receiving a graft from a donor with incompatible ABO blood group and insufficient immunosuppression [2]. In France, as in the USA, outcomes have improved over time, and the half-lives of both kidney grafts and patients have increased significantly since the 1980s, although the rate of improvement is now slowing. There are some disparities between different ethnic groups [3]. These improved results are related to a decrease in early graft failure during the first year post-transplantation, and also to a limited but significant decrease in the annual rate of graft attrition in the long term. This phenomenon has been observed for grafts from standard criteria deceased donors, whether black or nonblack, but also for grafts from living donors [1]. C A U S E S O F G R A F T LO S S I N T H E LO N G T E R M During the early post-transplantation phase and during the first year, graft loss is not infrequent, and may occur in 0–10%
F I G U R E 1 : Long-term kidney graft survival in France according to the time of transplantation [5].
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of the cases [1, 3]. Surgical complications and acute rejection are the most frequent causes [4]. In the long term, i.e. after the first year, the decrease in graft survival follows a fairly linear pattern (Figure 1), with a slope that has only slowly improved over the past 20 years, even though substantial progress has been made in the management of immunosuppression, cardiovascular risk factors and cancers [5]. The main cause of graft loss in the long term is the death of the patient with a functioning graft. Chronic allograft dysfunction associated with a progressive decline in the glomerular filtration rate (GFR) is the second most frequent cause. It has been shown recently that 50% of cases of graft loss at 1 year were due to patient death [4], while interstitial fibrosis and tubular atrophy (IFTA) and transplant glomerulopathy accounted for only 6% of graft loss. In contrast, at 5 years, in the same trials, death, IFTA and transplant glomerulopathy accounted for 46, 15 and 13% of graft loss, respectively (Table 1). However, the slow onset of the disease and the multiplicity of possible insults make a precise aetiological diagnosis challenging. Histological diagnoses, such as IFTA, transplant glomerulopathy, recurrence of initial disease and infectious diseases, such as pyelonephritis or BK virus nephropathy, are frequently associated [6]. It is difficult to determine which of these injuries has led to the graft loss, and whether others also contributed. It might be more relevant to consider the respective contribution of various synergistic risk factors to allograft loss rather than attempting to identify the main or most specific cause of allograft loss. Thus, the role of cyclosporine nephrotoxicity has recently been questioned, because it has seldom been specifically diagnosed as the main factor for allograft loss. We have no sensitive and specific diagnostic marker for cyclosporine toxicity, but this does not necessarily mean that it does not significantly contribute to allograft loss in many cases.
G R A F T A N D P AT I E N T S U R V I VA L A F T E R R E N A L T R A N S P L A N TAT I O N
Table 1. Factors associated with increased long-term chronic allograft injury
Table 2. Mechanisms and risks factors for IFTA
Donor factors
Immune mechanisms
Deceased (versus living)
Acute rejection (humoral, cellular)
Higher age
HLA mismatches
Vascular cause of death
Positive panel-reactive antibodies
Decreased nephron mass
Previous transplantation
Increased ischaemic time
Under-immunosuppression, non-compliance
Delayed graft function
Non-immune mechanisms
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Recipient factors
Cold ischaemia time
Higher age
Acute tubular necrosis and delayed graft function
African-American ethnicity
Calcineurin inhibitors
Diabetes mellitus
Reduced renal mass
HLA mismatch
Donor age
Presence of panel-reactive antibodies
Hypertension
Hypertension
Diabetes
Poor compliance with treatment
Hyperlipidaemia
Renal function
Proteinuria
Higher creatininaemia or increase in serum creatinine between 6 and 12 months
Pyelonephritis
Lower GFR or decrease in GFR between 6 and 12 months
glomerulopathy, which is characterized by significant proteinuria, and chronic allograft injury, characterized by progressive fibrosis of the kidney tissue and a decline in renal function [4]. Both immune and non-immune mechanisms are involved in these changes, as summarized in Table 2. Acute cellular and humoral rejection episodes are significant risk factors for rapid tissue injury and fibrosis; they may be related to human leucocyte antigen (HLA) mismatching, immunized recipients with donor-specific antibodies (DSAs) or non-compliance. Delay before treating acute rejection is also a risk factor for more severe graft injury and sequelae. Chronic humoral rejection, usually with transplant glomerulopathy, is another form of graft rejection that compromises the long-term survival of the graft [7]. A rise in the serum creatinine level may not always be observed, and protocol or surveillance biopsies performed at different times after transplantation have demonstrated that infraclinical graft injury can also develop silently over several days or weeks, and may result in kidney fibrosis and renal failure [2]. The main bon-immunological risk factors for chronic allograft dysfunction are calcineurin-inhibitor nephrotoxicity, advanced donor age, uncontrolled high blood pressure in the recipient, diabetes, dyslipidemia, BK virus nephropathy and repeated pyelonephritis [6].
Proteinuria >800 mg/24 h Doppler ultrasound resistive index ≥0.80 Renal events Acute rejection, especially vascular rejection and late rejection BK virus nephropathy CNI toxicity Recurrent disease Graft pyelonephritis Renal histology in first year Subclinical rejection Nephrocalcinosis Arteriolar hyalinosis Interstitial fibrosis Tubular atrophy Transplant glomerulopathy C4d binding Recurrent or de novo glomerulonephritis
C L I N I C A L P R E D I C T O R S O F LO N G - T E R M G R A F T S U R V I VA L
So, apart from the death of a patient with a functioning graft, the main situations leading to graft loss are transplant
These predictors are listed in Table 1. Some of them are related to recipient characteristics, including the time on 1364
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dialysis before being registered on the transplant waiting list, initial nephropathy, panel-reactive antibodies and older age at transplantation. All these factors are significantly and independently associated with 5-year, non-censored, graft survival. Concerning the donor, old age, vascular causes of death, hypertension, alcohol consumption, diabetes and high body mass index are significantly and independently associated with worse 5-year graft survival [6].
of their kidneys developed DGF). Remarkably, in these selected patients, delayed graft function was frequently caused by insults other than increased CIT: in 43% of the donors, the DGF occurred in the kidney with the shorter CIT, implying that other causes of DGF might have influenced the outcome in these patients in the selected population. In transplants from living donors, poor early graft function is infrequent but can occur in ∼10–15% of cases. In a recent retrospective study, Hellegering et al. [15] reported incidences of slow graft function and delayed graft function of 9.3 and 4.4%, respectively. The rejection-free survival and the longterm graft survival were worse for patients with poor early graft function than for those with immediate graft function. Role of the immunosuppressive regimen Immunosuppressive regimens also have an impact on the long-term prognosis of transplantation. Recent analysis of the United Network of Organ Sharing registry data shows that induction immunosuppression improved long-term graft and patient outcome for most organ transplants [16]. Depleting agents (alemtuzumab and rabbit antithymocyte globulin), especially when combined with steroids, were more effective than non-depleting agents (basiliximab and daclizumab) in preventing renal graft failure. Immunosuppressive regimens were also evaluated in the long term. Recent evidence was provided showing that the combination of tacrolimus and mycophenolate mofetil was more favourable than either tacrolimus/ sirolimus or cyclosporine/sirolimus with regard to acute rejection episodes and mean GFR during the first 36 months [17]. However, there was no significant difference between these regimens with regard to the actuarial graft survival at 8-year post-transplant. The chronic use of calcineurin inhibitors (CNI) is also associated with decreased GFR in the long term, and in some studies, with an increased risk of graft failure after 10 years of transplantation [18]. To prevent such deleterious long-term effects, CNI-sparing regimens have been proposed, and shown to produce a significant improvement of renal function at 1 or 3 years, but no significant change in the long-term graft survival [19].
Effect of cold ischaemia time and delayed graft function Delayed graft function (DGF) has been reported to be associated with an increased risk for acute rejection and for an inferior graft survival [12, 13]. DGF is multifactorial, but the cold ischaemia time is one of its major determinants. In previous studies, the cold ischaemia time (CIT) has been reported to have a negative impact on both early graft function and long-term graft survival, suggesting that ischaemia-reperfusion injury may not recover completely and that long-term chronic damage ensues. More recently, a large analysis of the national Scientific Registry of Transplant Recipients data between 2000 and 2009 showed that the adjusted odds ratios of DGF were significantly higher when CIT was longer (>1, 5, 10 and 15 h) than for shorter CIT transplants [14]. Unexpectedly, graft survival in paired donor transplants with shorter or longer CIT values were similar. It would, therefore, seem that in most of the cases the CIT-induced DGF no longer has a significant long-term impact on the graft outcome, and that consequently the long distance sharing of kidneys can be promoted. This study may, however, not be devoid of an important bias: only patients with discordant DGF were included in the analysis (70% of donors were excluded because either both or neither
Glomerular filtration rate at 1-year post-transplant. After transplantation, acute rejection episodes, anti-HLA immunization, anticalcineurin treatment, urinary tract infections, noncompliance, uncontrolled hypertension and proteinuria have all been shown to impact the long-term prognosis. In a recent major analysis of the United States Renal Data System (USRDS) for kidney transplant recipients (1995–2004), the data from 87 575 patients with >1-year graft survival were used to construct an accurate model of long-term graft survival [20]. The model was validated in the cohort of the BENEFIT and BENEFIT-EXT trials. The multivariate Cox regression analyses describing the relative hazards of all-cause graft loss in relation to baseline (1 year) factors among recipients of each donor type [standard criteria donor (SCD) and extended criteria donor (ECD)] are summarized in Table 3. All-cause graft loss was strongly predicted by the estimated glomerular filtration rate (eGFR) measured at 1-year post-transplant in the 1365 Predictors of kidney graft survival
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Effect of age The influence of the ages of the recipient and the donor has been recently re-analysed by Veroux et al. [8]. Elderly recipients had significantly lower graft (death-censored) and patient survival than younger patients, and donor age >65 years was associated with a higher risk of graft loss whatever the age of the recipient. This study fails to show any benefit of transplantation during the first 5 years when compared with dialysis in patients who were older than 65 and had received a kidney from a donor >65 years old. However, other studies show that older recipients may suffer fewer immunological graft losses [9], and even display better death-censored graft survival, suggesting that the effect of recipient age may be modified by other factors [10]. Age is also an important factor in living donor (LD) transplantation. Increasing living donor age has been shown to be associated with lower donor kidney function before transplantation. After transplantation, older donor age is associated with poorer kidney function and higher proteinuria in the recipients at 1 year, with a lower graft survival beyond 4 years, especially when the donor was over 60 [3, 11]. The impact of living donor age on graft survival was observed particularly >4 years post-transplant, and was influenced by recipient age: in younger recipients (3 g/day, and acute cellular rejection or IFTA for proteinuria levels of between 150 and 3000 mg/day. Even low levels of proteinuria (150–500 mg/day) are associated with lower graft survival and thus warrant attention [23]. For patients with nephrotic-range proteinuria, the risk of graft failure was 19 times greater than that in patients without proteinuria. After taking into account the other potential confounding variables, several studies indicate that, on average, patients with proteinuria have a 3-fold greater risk of graft failure. Moreover, both cardiovascular and non-cardiovascular deaths are increased in patients with proteinuria [22, 24]. Recent studies using the urinary protein–creatinine ratio confirm these findings, and indicate that spot measures of proteinuria can be used for renal transplant monitoring [25].
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Cause of ESRD
Recipient variables
Donor variables
H I S T O LO G I C A L P R E D I C T O R S O F LO N G T E R M G R A F T S U R V I VA L Histological analysis is the gold standard for evaluating the status of a kidney graft, and it is used for both diagnostic and prognostic purposes. It can be performed on a routine or surveillance basis, known as a protocol biopsy, at day 0, and day 30 or 3 months or 1 year. It can also be performed in response to a cause such as proteinuria or a decline in renal function. Histological markers of acute and chronic kidney injury have been identified, and the Banff classification is now widely used to describe and quantify the various histological lesions.
USRDS sample. When compared with an eGFR of 60 mL/ min/1.73 m2, the risk of graft loss increased exponentially as the eGFR decreased, reaching a 2-fold increase in the risk for an eGFR of 30, and an 8-fold increase in the risk for an eGFR of 15 mL/min/1.73 m2. In both SCD and in ECD transplant recipients, the other factors associated with the increased risk of all-cause graft loss included end-stage renal disease (ESRD) due to hypertension, prior transplant status, panel-reactive
Fibrotic lesions and prognosis Glomerular, tubulo-interstitial and vascular fibrosis on zero-hour biopsies have all been described as predictors of late outcome [26]. On later biopsies at 3 months [27], 6 months [28], 1 year [29] and 2 years, chronic lesions such as allograft glomerulopathy (cg), interstitial fibrosis (ci) and tubular 1366
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Fibrogenic graft injury After transplantation, the kidney graft is the target of several simultaneous or serial injuries all of which may promote graft fibrosis and reduce graft survival. Among the main kidney injuries that are known to have an impact on long-term graft survival, one has to consider initial ischaemia/ reperfusion, acute cellular rejection, antibody-mediated rejection (AMR), calcineurin-inhibitor toxicity, bacterial acute pyelonephritis, BK virus nephropathy and recurrence of the initial disease. To find out whether these markers of injury have a long-term predictive value calls for longitudinal studies that have not been always performed. Acute cellular rejection is a factor of graft failure [4]. However, acute cellular rejection no longer predicts allograft survival now that current treatments make a full recovery possible [34]. Subclinical acute rejection, which can only be identified by surveillance biopsies, may be associated with a poor outcome if left untreated [35]. The Banff score classifies biopsies with inflammation (i) ≥ 2 and tubulitis (t) ≥ 2 as acute cellular rejection, but i1 and t1 scores are also predictive, especially, if they are combined with other markers of injury. Borderline changes (defined by t > 0 without a diagnosis of acute rejection) are associated with a poorer outcome [36], and with a positive response to antirejection therapy in the context of allograft dysfunction. Mild or focal interstitial inflammation may only lead to a poorer outcome when associated with tubulitis [37]. Finally, Banff’s i-score evaluation excludes fibrotic and sub-capsular areas in order to enhance diagnostic specificity, but the total i-score is a better predictor of the renal outcome than Banff’s i-score [38]. Thus, raw tubular and interstitial inflammation scores are more informative than the diagnosis of rejection they are used to establish. BK virus nephropathy, which may simulate acute rejection, is also associated with a poor outcome because once diagnosed, little can be done to limit disease progression. Similarly, it has been shown that acute bacterial pyelonephritis induces inflammatory changes in the graft, and may later promote graft fibrosis, and a decline in renal function [4]. 1367
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Antibody-mediated injury is now identified using peritubular capillaritis, C4d staining and DSAs. Unlike the thresholds used for diagnosis, C4d staining predicts allograft long-term survival, even though only minimally positive, and isolated C4d staining predicts the response to increased immunosuppression [2, 39]. Microvascular inflammation (suggestive of acute AMR), peritubular capillary basement membrane multilayering and glomerular double contours (suggestive of chronic allograft glomerulopathy) are associated with a poor outcome independently of C4d staining [2, 7, 40]. Effective therapies are still lacking for use in these situations. Infraclinical AMR has been found during routine biopsies, and various treatments, including increased immunosuppression, rituximab, eculizumab and plasma exchange, have sometimes proved effective [7]. However, prospective therapeutic trials are needed to evaluate the impact of treating these patients on the long-term graft outcome (incidence of transplant glomerulopathy, overt AMR and graft loss). Clearly, new early markers of AMR, i.e. endothelial activation markers, are needed, since it seems likely that low-grade AMR, either alone or in combination with acute cellular rejection, is under-diagnosed at present. There is no specific marker for calcineurin-inhibitor nephrotoxicity, which makes it tricky to diagnose. However, treatment with calcineurin inhibitors is associated with an increase in interstitial fibrosis, vacuolization of tubular cells and arteriolar hyalinosis. During the early phase of transplantation, the combination of ischaemia/reperfusion and CNI treatment may also promote the development of fibrogenic markers and late graft fibrosis. Calcineurin-inhibitor overexposure is associated with greater allograft dysfunction and loss. No histological lesion is specific to calcineurininhibitor nephrotoxicity, but cyclosporine treatment is strongly associated in the long term with a higher incidence of arteriolar hyalinosis, and with a poorer outcome than CNI-free treatment [18]. Some diseases frequently recur after transplantation; this happens in ∼10% of cases of small vessel vasculitis, in ∼30% of cases for idiopathic membranous nephropathy, membranoproliferative glomerulonephritis, focal segmental glomerulosclerosis, lupus nephritis and diabetic nephropathy and in up to 60% of cases for IgA nephropathy, Henoch Schönlein purpura, mixed cryoglobulinemic nephritis and atypical haemolytic uraemic syndrome [41–43]. The prognostic value of these recurrences depends considerably on the type of disease. IgA nephropathy, idiopathic membranous nephropathy and diabetic nephropathy recurrences do not significantly impact graft outcome, whereas focal and segmental glomerulosclerosis, type-2 membranoproliferative glomerulonephritis, and small vessel vasculitis recurrences have a poor prognosis. Atypical haemolytic uraemic syndrome recurrences had a very poor prognosis, but this may now have dramatically improved with the availability of targeted complement inhibitors. There is a need for other predictors that could be used to track any situation of progressive injury of the renal allograft, regardless of the aetiology involved. Epithelial to mesenchymal transition markers can be expressed in various renal situations,
atrophy (ct) used in the Banff classification were also found to be predictive of the outcome. Interestingly, interstitial fibrosis can be quantified by computerized morphometric techniques using special (collagen III or Sirius red) or standard (Masson’s Trichrome) staining at 6 months, and provides a better predictor of long-term renal function than the Banff classification [28, 30]. Another parameter, the mean glomerular volume on renal biopsy is a surrogate marker for total renal mass (being inversely correlated with the total number of glomeruli in the kidney), and correlates with graft loss [31]. Yet, this ‘baseline’ approach does not differentiate between ongoing aggressions and finished ones. Indeed, a molecular inflammatory phenotype on 6-week biopsies is relevant to past aggressions, rather than to the future course [32]. Similarly, in a study evaluating interstitial fibrosis on 1-year biopsies, fibrosis combined with inflammation was found to be predictive of long-term outcome, whereas fibrosis alone was not [33]. We still need to identify early markers of kidney injuries that promote long-term fibrosis and graft loss.
F I G U R E 2 : Markers of epithelial-to-mesenchymal transition in kidney allografts. On serial sections, normal tubular epithelial cells (*) are
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stained slightly at the basolateral pole by anti-β-catenin antibodies in immunohistochemistry, and not by anti-vimentin antibodies. In contrast, activated epithelial cells, which undergo the mesenchymal differentiation, show diffuse cytoplasmic staining for β-catenin and de novo expression of vimentin (arrows).
including renal transplantation [44]. Epithelial-to-mesenchymal transition (EMT) has been proposed as a mechanism for renal fibrosis, and, although this is debated, it is accepted that some renal epithelial cells switch to a mesenchymal phenotype in pathological situations [7, 45]. As far as we are aware, there is no situation in which renal fibrosis appears without the concurrent expression of EMT markers [44, 46, 47]. We and others have shown that the expression on 3-month protocol biopsies of the EMT markers vimentin, β-catenin and CD44 is associated with all the main factors of allograft dysfunction (i. e. cold ischaemia time, inflammation and calcineurin-inhibitor nephropathy) [48–52], and that they are independent predictors of an increase in interstitial fibrosis and a decrease in graft function [53] (Figure 2). EMT markers on 3-month protocol biopsies provide information on the prognosis of the renal allograft. In a retrospective study, we have shown that the presence of EMT markers during cyclosporine treatment predicts an amelioration of renal function after cyclosporine cessation [52]. A prospective study evaluating the value of EMT markers to optimize the therapeutic choice between everolimus and cyclosporin is currently ongoing (CERTITEM, #NCT01079143). Although not specific to a particular aetiology, its extreme sensitivity makes it a very useful tool for detecting at-risk situations before irreversible lesions occur. EMT is particularly promising for detecting fibrogenic situations that call for a change in therapy. Conversely, the absence of EMT markers will suggest that no modification of the treatment is needed to prevent allograft dysfunction. The nature of the therapeutic modification will, however, depend on other criteria, such as the presence or absence of inflammation in the graft (suggesting the need for enhancing immunosuppression or decrease calcineurin inhibitors, respectively). EMT markers thus qualify as some of the best predictors of renal outcome in renal transplantation, applicable to the general context of transplantation and highly dynamic. However, epithelial to mesenchymal transition markers still have to show that they predict renal allograft survival beyond predicting fibrosis and decline in function.
P R E D I C T I O N O F LO N G - T E R M A L LO G R A F T S U R V I VA L U S I N G M O L E C U L A R A P P R O AC H E S There is increasing evidence that allograft failure results from the combined impact of several injuries. Clinical and histological approaches have sought to highlight the independent value of risk factors, but are confronted by the problem of thresholds (e.g. DSA level or histological inflammation score). Recent studies have revealed promising molecular approaches involving microarrays and providing large-scale, systematic data that make it possible to characterize patterns of gene expression rather than single markers. These techniques are outside the scope of this paper, and their contribution has been detailed elsewhere [26]. In a nutshell, this molecular information has been shown to be more effective than the usual histological techniques for diagnosing subtle renal injuries (e.g. differentiating between deceased donor and LD kidneys). These genome-wide techniques have been validated on patients sorted by pathological classification, and now need to be scaled down to single (or only a few) markers, and to the context of a single patient. The use of urinary markers for this purpose has aroused a strong interest, as they have the added advantage of being non-invasive [54]. However, the published markers (for predicting acute rejection in particular) still lack sufficient diagnostic power to be used in clinical practice, and we look forward to having better markers and/or technical improvements in this field. In conclusion, several clinical and histological markers have been shown to strongly predict the long-term kidney graft outcome, especially donor age and recipient age, renal function at 1-year post-transplantation, proteinuria at 3 months or 1 year, donor-specific antibodies, IFTA combined with inflammatory infiltrates and transplant glomerulopathy. Importantly, death with a functioning graft accounts for ∼50% of long-term graft loss, indicating that we need to improve the prevention of cardiovascular diseases and infections, which are the main causes of patient death in the long term. In addition, deathcensored graft loss is mainly related to chronic allograft injury 1368
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FUNDING Pierre Galichon recieved funding from Agence de la Biomedecine, Societe Francophone de Transplantation and Societe de Nephrologie.
C O N F L I C T O F I N T E R E S T S TAT E M E N T None declared.
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resulting in IFTA and a progressive decline in renal function. Its various mechanisms need to be understood in greater detail before we can hope for earlier and more effective intervention. EMT markers seem to be useful for identifying this condition at an early stage, and helping to choose appropriate immunosuppressive treatment in order to prevent the progression of graft fibrosis.
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Received for publication: 26.6.2012; Accepted in revised form: 12.12.2012
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