Effects of donor age and cell senescence on kidney allograft survival

Effects of cellular sensitization and donor age on acute rejection and graft function after deceased-donor kidney transplantation

BACKGROUND

Allografts from older donors may be more immunogenic than those from younger donors. Pretransplantation cellular sensitization may interact with advanced donor age to increase the risk of immune injury after deceased-donor kidney transplantation.

METHODS

The outcomes of 118 consecutive deceased-donor kidney transplant recipients with available pretransplantation donor-stimulated enzyme-linked immunosorbent spot (ELISPOT) assays for interferon gamma were analyzed retrospectively to determine the impact of cellular sensitization and other clinical variables, including donor age, on the incidence of acute rejection (AR) in the first year after deceased-donor transplantation and on estimated glomerular filtration rate 12 months after transplantation.

RESULTS

The incidence of AR was higher in patients with positive pretransplantation ELISPOT assays versus those with negative assays (36% vs. 14%, P=0.009). Logistic regression indicated that the combination of donor age 50 years or older and a positive pretransplantation ELISPOT assay was more strongly associated with AR (odds ratio, 12.1; confidence interval, 1.1-133) than either variable alone. Estimated glomerular filtration 12 months after transplantation was highest in ELISPOT-negative patients receiving kidneys from donors younger than 50 years and lowest in ELISPOT-positive recipients with donors 50 years or older.

CONCLUSION

The combination of advanced donor age and pretransplantation cellular sensitization increases the risk of AR and poor graft function after deceased-donor kidney transplantation beyond the risk associated with each factor alone.

Systematic review of mouse kidney transplantation

A mouse model of kidney transplantation was first described in 1973 by Skoskiewicz et al. Although the mouse model is technically difficult, it is attractive for several reasons: the mouse genome has been characterized and in many aspects is similar to man and there is a greater diversity of experimental reagents and techniques available for mouse studies than other experimental models. We reviewed the literature on all studies of mouse kidney transplantation to report the donor and recipient strain combinations that have been investigated and the resultant survival and histological outcomes. Some models of kidney transplantation have used the transplanted kidney as a life-supporting organ, however, in many studies the recipient mouse's native kidney has been left in situ. Several different combinations of inbred mouse strains have been reported, with varying degrees of injury, survival or tolerance because of haplotype differences. This model has been exceptionally useful as an investigational tool to understand multiple aspects of transplantation including acute rejection, cellular and humoral rejection mechanisms and their treatment. Furthermore, this model has been used to investigate disease mechanisms beyond transplant rejection including intrinsic renal disease and infection-associated pathology.

Aldosterone induces p21-regulated apoptosis via increased synthesis and secretion of tumour necrosis factor-α in human proximal tubular cells

1. Aldosterone has been shown to mediate p21-dependent cellular senescence in rat kidney proximal tubules in vivo and in cultured human proximal tubular cells. The p21-induced senescent cells express higher levels of apoptotic cytokines, such as tumour necrosis factor (TNF)-α compared with non-senescent cells. The aim of the present study was to investigate the hypothesis that aldosterone increases proximal tubular apoptosis by increasing the secretion of apoptosis-inducing factors through a p21-dependent mechanism. 2. Human proximal tubular cells were incubated with aldosterone (10 nmol/L) and cell senescence was detected by senescence-associated β-galactosidase staining and expression of p21. Apoptosis was analysed by terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling and annexin/propidium iodide staining, whereas p21 localization was determined by immunofluorescence. 3. Exposure of cells to aldosterone for 3 or 5 days increased senescence-associated β-galactosidase staining, p21 and TNF-α mRNA expression and secretion of TNF-α into the culture medium. These changes were abolished by gene silencing of p21. Aldosterone failed to increase the number of apoptotic cells on day 3, but did increase them on day 5. A neutralizing antibody against TNF-α prevented the aldosterone-induced apoptotic changes. Aldosterone did not affect localization of p21. 4. These findings indicate that aldosterone increases TNF-α synthesis and secretion in proximal tubular cells via p21/senescence-dependent cell phenotypic changes and that the TNF-α secreted plays an important role as a paracrine factor in mediating cell apoptosis, indicating a possible involvement in aldosterone-induced renal damage.

Comparing molecular assessment of implantation biopsies with histologic and demographic risk assessment

We hypothesized that measurement of previously defined acute kidney injury-induced transcripts at the time of implantation would add a new dimension to existing methods based on donor factors, histology and recipient factors. We analyzed microarray results from implantation biopsies taken after reperfusion from 70 kidneys from 53 deceased donors. We used two definitions of early dysfunction: serum creatinine > 265 umol/L at day 7 posttransplant; and dialysis in the first week. The strongest correlate with early dysfunction was the mean expression of 30 injury transcripts. Older donor and recipient age were associated with early dysfunction, but histologic lesions were not. Prediction was best when the injury transcript expression was combined with donor or recipient age, particularly in standard criteria donors. In contrast, although extended criteria donor kidneys had a high risk of early dysfunction, no variables tested, including injury transcripts, predicted risk significantly, probably because these kidneys were allocated preferentially to old, high risk recipients. The injury transcripts did not predict late function, which was mainly associated with donor age. Thus, measurement of injury-induced transcripts at the time of implantation improves the prediction of early kidney dysfunction, but risk prediction may fail when old kidneys are transplanted into old recipients.

From cellular senescence to age-associated diseases: the miRNA connection

Cellular senescence has evolved from an in-vitro model system to study aging in vitro to a multifaceted phenomenon of in-vivo importance as senescent cells in vivo have been identified and their removal delays the onset of age-associated diseases in a mouse model system. From the large emerging class of non-coding RNAs, miRNAs have only recently been functionally implied in the regulatory networks that are modified during the aging process. Here we summarize examples of similarities between the differential expression of miRNAs during senescence and age-associated diseases and suggest that these similarities might emphasize the importance of senescence for the pathogenesis of age-associated diseases. Understanding such a connection on the level of miRNAs might offer valuable opportunities for designing novel diagnostic and therapeutic strategies.

New insights on molecular mechanisms of renal aging

Long-term transplant outcome is importantly influenced by the age of the organ donor. The mechanisms how age carries out its pathophysiological impact on graft survival are still not understood. One major contributing factor for the observed poor performance of old donor kidneys seems in particular the age-related loss in renal regenerative capacity. In this review, we will summarize recent findings about the molecular basis of renal aging with specific focus on the potential role of somatic cellular senescence and mitochondrial aging in renal transplant outcome.

Synergistic effects of prolonged warm ischemia and donor age on the immune response following donation after cardiac death kidney transplantation

BACKGROUND

Organs from DCD (donation after cardiac death) donors are increasingly used for transplantation. The impact of advanced donor age and warm ischemia on the immune response of the recipient has not been studied. We developed a novel and clinically relevant model of DCD kidney transplantation and investigated the effects of donor age and prolonged warm ischemia on the recipient immune response after following DCD kidney transplantation.

METHODS

DCD grafts from young and old F-344 donor rats were engrafted into LEW recipients who were nephrectomized bilaterally after a short (20 minutes) or prolonged (45 minutes) warm ischemia time.

RESULTS

Analysis of the recipient's immune response early after transplantation showed an enhanced innate and adaptive immune response when old DCD kidneys were engrafted. Next, we studied DCD recipients with a supportive, contralateral native kidney in place, which allowed the recovery of the transplanted DCD kidney. Old DCD kidneys, demonstrated an impaired renal function associated with pronounced histomorphologic graft deterioration and an enhanced immune response by day 100 after transplantation. Interestingly, young DCD kidneys with a long warm ischemic time recovered from acute tubular necrosis and did not stimulate the long-term immune response.

CONCLUSION

Our observations emphasize that prolonged warm ischemic time and advanced donor age augment the immune response after transplantation of DCD grafts. These results provide an experimental model and a mechanistic framework of clinically relevant aspects in DCD donation.

Cellular senescence limits regenerative capacity and allograft survival

Long-term graft survival after kidney transplantation remains unsatisfactory and unpredictable. Interstitial fibrosis and tubular atrophy are major contributors to late graft loss; features of tubular cell senescence, such as increased p16(INK4a) expression, associate with these tubulointerstitial changes, but it is unknown whether the relationship is causal. Here, loss of the INK4a locus in mice, which allows escape from p16(INK4a)-dependent senescence, significantly reduced interstitial fibrosis and tubular atrophy and associated with improved renal function, conservation of nephron mass, and transplant survival. Compared with wild-type controls, kidneys from INK4a(-/-) mice developed significantly less interstitial fibrosis and tubular atrophy after ischemia-reperfusion injury. Consistently, mice that received kidney transplants from INK4a/ARF(-/-) donors had significantly better survival 21 days after life-supporting kidney transplantation and developed less tubulointerstitial changes. This correlated with higher proliferative rates of tubular cells and significantly fewer senescent cells. Taken together, these data suggest a pathogenic role of renal cellular senescence in the development of interstitial fibrosis and tubular atrophy and kidney graft deterioration by preventing the recovery from injury. Inhibiting premature senescence could have therapeutic benefit in kidney transplantation but has to be balanced against the risks of suspending antitumor defenses.

Accelerated senescence of renal tubular epithelial cells is associated with disease progression of patients with immunoglobulin A (IgA) nephropathy

The aim of this study is to determine the potential correlation between the accelerated senescence of renal tubular epithelial cells (RTECs) and the disease progression of patients with immunoglobulin A nephropathy (IgAN). A total of 108 IgAN patients with different Lee's pathologic grades were enrolled. Additionally, 18 patients with renal resection were recruited as controls. Cellular senescence was evaluated by senescence-associated β-galactosidase (SA-β-gal) staining and an immunohistochemical analysis of p21 and p16 protein expression. The expression of type III collagen (Col III) and fibronectin (FN) in renal interstitium and the levels of serum total and low-density lipoprotein (LDL) cholesterol, serum creatinine concentration (SCr), and 24-h urinary protein excretion were evaluated also. SA-β-gal staining and the expression of p16 and p21 were increased significantly in renal biopsy specimens obtained from grades I-II IgAN patients compared with controls (P < 0.05). The expression of these senescence-associated markers increased gradually with disease progression and correlated with the renal morphologic changes and the expression of Col III and FN in renal interstitium in IgAN patients. A correlation analysis showed that the expressions of p16, p21, and SA-β-gal staining were associated significantly with blood pressure and renal function (P < 0.05), but not with patient age, body mass index (BMI), LDL cholesterol level, or 24-h urinary protein value (P > 0.05). Our results indicated that the RTECs in IgAN patients exhibited features of accelerated senescence, which were unrelated to mechanisms associated with normal aging. Cellular senescence was associated closely with IgAN disease progression, which suggested the accelerated senescence of RTECs may contribute to this progression.

Pre-existing arteriosclerotic intimal thickening in living-donor kidneys reflects allograft function

BACKGROUND

Donor shortage is a serious problem worldwide and it is now debated whether kidneys from marginal donors are suitable for renal transplantation. Recent studies have shown that the findings of preimplantation kidney biopsy are useful to evaluate vasculopathy in the donated kidney, and may predict transplant outcomes in deceased- donor kidney transplantation. However, few studies have focused on the pathological findings of preimplantation biopsy in living-donor kidney transplantation. Therefore, we investigated whether arteriosclerotic vasculopathy in living-donor kidneys at the time of transplantation predicts the recipient's kidney function (allograft function) later in life.

METHODS

We retrospectively analyzed 75 consecutive adult living-donor kidney transplants performed at Kagawa University Hospital. Renal arteriosclerotic vasculopathy was defined according to the presence of fibrous intimal thickening in the interlobular artery.

RESULTS

Forty-one kidneys exhibited mild arteriosclerotic vasculopathy on preimplantation kidney biopsies. The decreases in estimated glomerular filtration rate after donation were similar in donors with or without renal arteriosclerotic vasculopathy. Pre-existing arteriosclerotic vasculopathy did not affect graft survival rate, patient survival rate or the incidence of complications. Recipients of kidneys with arteriosclerotic vasculopathy had lower allograft function at 1 and 3 years after transplantation than the recipients of arteriosclerosis-free kidneys with or without donor hypertension. In multivariate analysis, fibrous intimal thickening on preimplantation biopsy was predictive of reduced allograft function at 1 year after transplantation.

CONCLUSIONS

The present study demonstrated that mild arteriosclerotic vasculopathy in the donated kidney is an important pathological factor that reflects future impaired function of renal allografts from marginal donors.

Secreted klotho and chronic kidney disease

Soluble Klotho (sKl) in the circulation can be generated directly by alterative splicing of the Klotho transcript or the extracellular domain of membrane Klotho can be released from membrane-anchored Klotho on the cell surface. Unlike membrane Klotho which functions as a coreceptor for fibroblast growth factor-23 (FGF23), sKl, acts as hormonal factor and plays important roles in anti-aging, anti-oxidation, modulation of ion transport, and Wnt signaling. Emerging evidence reveals that Klotho deficiency is an early biomarker for chronic kidney diseases as well as a pathogenic factor. Klotho deficiency is associated with progression and chronic complications in chronic kidney disease including vascular calcification, cardiac hypertrophy, and secondary hyperparathyroidism. In multiple experimental models, replacement of sKl, or manipulated up-regulation of endogenous Klotho protect the kidney from renal insults, preserve kidney function, and suppress renal fibrosis, in chronic kidney disease. Klotho is a highly promising candidate on the horizon as an early biomarker, and as a novel therapeutic agent for chronic kidney disease.

Is cellular senescence important in pediatric kidney disease?

Somatic cellular senescence (SCS) describes the limited ability of cells to divide. Normally, SCS is associated with physiological aging, but evidence suggests that it may play a role in disease progression, even in young patients. Stressors such as acute injury or chronic inflammation may induce SCS, which in turn exhausts organ regenerative potential. This review summarizes what is known about SCS in the kidney with aging and disease. As most patients with chronic kidney disease (CKD) also develop cardiovascular complications, a second focus of this review deals with the role of SCS in cardiovascular disease. Also, as SCS seems to accelerate CKD and cardiovascular disease progression, developing strategies for new treatment options that overcome SCS or protect a patient from it represents an exciting challenge.

Gene expression changes are associated with loss of kidney graft function and interstitial fibrosis and tubular atrophy: diagnosis versus prediction

BACKGROUND

Loss of kidney graft function due to interstitial fibrosis (IF) and tubular atrophy (TA) is the most common cause of kidney allograft loss.

METHODS

One hundred one allograft tissues (26 samples with IF/TA, 17 normal allografts, and an independent biopsy group collected at 3 month [n=34] posttransplantation) underwent microarray analysis to identify early detection/diagnostic biomarkers of IF/TA. Profiling of 24 allograft biopsies collected at or after 9-month posttransplantation (range 9-18 months) was used for validation. Three-month posttransplantation biopsies were classified as IF/TA nonprogressors (group 1) or progressors (group 2) using graft function and histology at 9-month posttransplantation.

RESULTS

We identified 2223 differentially expressed probe sets between IF/TA and normal allograft biopsies using a Bonferroni correction. Genes up-regulated in IF/TA were primarily involved in pathways related to T-cell activation, natural killer cell-mediated cytotoxicity, and programmed cell death. A least absolute shrinkage and selection operator model was derived from the differentially expressed probe sets, resulting in a final model that included 10 probe sets and had 100% training set accuracy. The N-fold crossvalidated error was 2.4% (sensitivity 95.8% and specificity 100%). When 3-month biopsies were tested using the model, all the samples were classified as normal. However, evaluating gene expression of the 3-month biopsies and fitting a new penalized model, 100% sensitivity was observed in classifying the samples as group1 or 2. This model was evaluated in the sample set collected at or after 9-month posttransplantation.

CONCLUSIONS

An IF/TA gene expression signature was identified, and it was useful for diagnosis but not prediction. However, gene expression profiles at 3 months might predict IF/TA progression.

Consequences of transplant quality on chronic allograft nephropathy

Using kidneys from expanded-criteria donors to alleviate organ shortage has raised concern on reduced transplant outcomes. In this paper, we review how critical donor-related factors such as donor age, brain death, and consequences of ischemia-reperfusion injury (IRI) determine graft quality and impact chronic allograft nephropathy. We propose that combinatorial effects of organ-intrinsic features associated with increasing age and unspecific injuries related to brain death and IRI will impact innate and adaptive immune responses. Future research will need to explore avenues to optimize donor management, organ preservation, adapted immunosuppressive strategies, as well as modifications of the allocation of suboptimal allografts.

Favorable outcomes with machine perfusion and longer pump times in kidney transplantation: a single-center, observational study

BACKGROUND

Hypothermic machine perfusion (MP) preservation is used for all deceased donor kidney transplants at our center. Kidneys are placed in cold storage at retrieval, then transferred to MP on arrival. Because a lack of consensus regarding optimal use of MP still exists, we evaluated the overall impact of using MP at our center and the prognostic value of MP (Pump) time.

METHODS

We retrospectively analyzed 339 adult, primary deceased donor kidney transplant recipients who were pooled across three prospective, randomized immunosuppression trials (since 2000) at our center. In addition to providing overall results for delayed graft function (DGF) (requirement for dialysis in the first week), slow graft function (SGF), first biopsy-proven acute rejection (BPAR), and graft failure, stepwise logistic and Cox regression analyses were used to determine the prognostic value of pump time, particularly after controlling for other significant prognosticators.

RESULTS

Mean cold storage and pump times were 6.6 and 26.7 hr, consistent across immunosuppression protocols. Overall DGF and SGF rates were 4.4% (15/339) and 12.1% (41/339). DGF was equally low for pump time less than 24 vs. more than or equal to 24 hr, 5.2% (6/116) vs. 4.0% (9/223) (P=0.63), with similar results after adjusting for known DGF predictors. A significantly lower first BPAR rate was observed for longer pump time (as a continuous variable) among more immunologically active recipients (those having more risk factors: DGF, age <50 yr, and non-white) (univariable P=0.005; multivariable P=0.009), with an estimated hazard ratio of 0.43 (P=0.006) favoring pump time more than or equal to 24 hr among those with more than or equal to two risk factors. CONCLUSIONS.: In this single-center, observational study, MP with prolonged pump times was associated with low DGF/SGF and first BPAR rates, supporting continued use of MP.

The combination of donor and recipient age is critical in determining host immunoresponsiveness and renal transplant outcome

OBJECTIVE

To evaluate the interaction of donor and recipient age on transplant outcome and immune response.

SUMMARY BACKGROUND DATA

The age of donor and recipient is becoming increasingly important in organ transplantation. We tested the relevance and consequences of recipient and donor age on immunoresponsiveness and transplant outcome in a uni- and multilateral cohort analysis.

METHODS

We obtained and analyzed data from 108,188 recipients of deceased donor kidneys of the United Network for Organ Sharing database transplanted between 1995 and 2008. Univariate analysis of allograft and patient survival was calculated by Kaplan Meyer. Multivariate analyses were performed using the Cox Proportional Hazards method. Data were assessed and compared by decades of increasing donor and recipient age with and without censoring transplant loss for death with a functioning graft. This approach allowed a detailed analysis of interacting factors.

RESULTS

Transplant survival was lowest in elderly recipients. However, when the analysis was censored for patient's death with a functioning kidney transplant, survival improved incrementally with each decade of increasing recipient age. This was even more surprising as older recipients had received less well-matched organs of poorer quality. The frequency of acute rejection decreased dramatically with increasing age, emphasizing the effect of age on the vigor of the recipient's immune responses. In contrast, increasing donor age was associated with more frequent acute rejection rates. The effects of donor and recipient age in combination demonstrated that grafts of older donors fared significantly better in older recipients.

CONCLUSIONS

Our results show that increasing recipient age is associated with an improved transplant survival, lower rates of rejection, and superior outcome of older donor organs. Physiological and/or immunologic aspects of organ and recipient age seem to determine, at least in part, the success of renal transplantation.

Immunological risk in recipients of kidney transplants from extended criteria donors

BACKGROUND

Determining if a kidney from a marginal donor is likely to elicit a strong and specific immune response, leading to an increased risk of acute rejection, is of importance in renal transplantation.

METHODS

In this study, we analysed the effect of extended criteria donor (ECD) on the incidence of biopsy-proven acute rejection (BPAR) and the effect of immunological risk factors on graft outcome in a large cohort of kidney transplant recipients (n = 2121 patients) grafted with ECD (n = 656 patients) or optimal donor (OD) (n = 1465 patients).

RESULTS

The incidence of BPAR was not statistically different between the ECD group recipients (105/656, 16%) and the OD group recipients (251/1465, 17%) (P = 0.52). These values remained similar after adjustment for immunological risk [defined as retransplantation and/or panel-reactive antibody (PRA) level >20%] (P = 0.92 for patients with immunological risk and P = 0.47 for patients without immunological risk). We next analysed the death-censored graft survival data for OD and ECD groups, as a function of immunological status, and found that the immunological risk factor did not affect graft survival in ECD transplant recipients (P = 0.64).

CONCLUSION

Although our groups were not homogenous, our study did not reveal an increased risk of acute rejection in recipients of ECD allograft.

Telomere shortening reduces regenerative capacity after acute kidney injury

Telomeres of most somatic cells progressively shorten, compromising the regenerative capacity of human tissues during aging and chronic diseases and after acute injury. Whether telomere shortening reduces renal regeneration after acute injury is unknown. Here, renal ischemia-reperfusion injury led to greater impairment of renal function and increased acute and chronic histopathologic damage in fourth-generation telomerase-deficient mice compared with both wild-type and first-generation telomerase-deficient mice. Critically short telomeres, increased expression of the cell-cycle inhibitor p21, and more apoptotic renal cells accompanied the pronounced damage in fourth-generation telomerase-deficient mice. These mice also demonstrated significantly reduced proliferative capacity in tubular, glomerular, and interstitial cells. These data suggest that critical telomere shortening in the kidney leads to increased senescence and apoptosis, thereby limiting regenerative capacity in response to injury.

Single kidney transplantation from young pediatric donors in the United States

Kidney transplantation (KTX) from small pediatric donors is performed as single or en bloc. Criteria to determine when to split pediatric donor kidneys and transplant as singles are not well established. Data reported to the Scientific Registry of Transplant Recipient for donors <10 yrs from 1995 to 2007 were reviewed (n = 5079). Donors were categorized by weight group by 5 kg increments and solitary (n = 3503) versus en bloc (n = 1576). The primary outcome was overall graft survival. Results were compared as adjusted hazard ratios (aHR) relative to ideal standard criteria donors (SCDs) (defined as age 18-39 without other risk factors), non-ideal SCDs (all other SCDs) and expanded criteria donors (age 50-59 with other risk factors or age >or=60). Single KTX from donors >or= 35 kg conferred a similar risk of graft survival as ideal SCDs. Of donors 10-34 kg, risks of en bloc KTX were similar to ideal and risks of single KTX to non-ideal SCDs; single and en bloc KTXs had 7.9 and 5.2 graft losses per 100 follow-up years, respectively. Single KTX from donors >35 kg are similar to ideal SCDs. Single KTX from donors 10-35 kg are similar to non-ideal SCDs. From a resource perspective, pediatric donors 10-35 kg used as singles offer more cumulative graft years than when used en bloc.

Ageing mouse kidney--not always the SAME old story

BACKGROUND

As interest in the ageing kidney grows rapidly, more experimental ageing studies are conducted in the field. One of the main obstacles that researchers have to face is that studies in old animals are often less reproducible than in young animals. We have observed that the aged animal's provenance can be an overlooked factor accounting for such experimental heterogeneity.

METHODS

Male C57BL/6J mice aged 19-22 months were purchased from four different suppliers. Baseline renal parameters were evaluated by measuring serum urea, serum creatinine and proteinuria. Renal morphology was analysed by quantifying glomerulosclerosis, interstitial fibrosis and amyloid deposits on paraffin sections stained with PAS, Masson trichrome, Sirius red and Congo red.

RESULTS

We found normal renal ageing in mice from three sources, but an unexpected renal pathology in mice from one major European supplier. Mice from this supplier had significantly elevated serum urea, creatinine values and an increased urinary protein excretion. Corresponding kidneys displayed massive glomerulosclerosis with evidence of amyloid deposits and increased interstitial fibrosis.

CONCLUSIONS

Supplier-dependent differences, such as observed here, can explain irreproducibility of experimental results in renal ageing research. This can be avoided by careful baseline analysis prior to in vivo experiments.