Telomere shortening and karyotypic alterations in hepatocytes in long-term transplanted human liver allografts

Impact of donor age on recipient morbidity and mortality after living donor liver transplantation

BACKGROUND

Evidence for use of graft from older donors in living donor liver transplantation (LDLT) has been conflicting. This study aims to clarify the impact of donor age on recipient morbidity and mortality after adult LDLT.

METHODS

A total of 90 live liver donors and recipients who underwent primary adult-to-adult LDLT were divided into three groups according to donor age: donors in 20s (D-20s) group, donors in 30s and 40s (D-30s and 40s) group and donors in 50s & 60s (D-50s and 60s) group. Multivariate analyses were conducted to look for independent risk/prognostic factors. Donor age was analysed as a continuous variable to determine an optimal cut off.

RESULTS

Overall donor morbidity was 4/90 (4.44%), major donor morbidity was 1/90 (1.11%) and there was no donor mortality. Recipients in the D-20s group had better 1-, 3- and 5-year recipient survival than recipients in the D-50s and 60s group (96%, 91%, 91% versus 73%, 58%, 58%, respectively) (P = 0.020). Donor age was identified to be an independently significant risk factor for increased major complications (P = 0.007) and prognostic factor for reduced overall survival (P = 0.014). The optimal donor age cut off was determined to be 46.5 years old.

CONCLUSION

Older donors are associated with poorer recipient outcomes after adult-to-adult LDLT. Usage of liver grafts from older donors should be carefully considered when choosing liver grafts for patients undergoing LDLT.

Understanding the Unique Microenvironment in the Aging Liver

In the past decades, many studies have focused on aging because of our pursuit of longevity. With lifespans extended, the regenerative capacity of the liver gradually declines due to the existence of aging. This is partially due to the unique microenvironment in the aged liver, which affects a series of physiological processes. In this review, we summarize the related researches in the last decade and try to highlight the aging-related alterations in the aged liver.

Sinusoidal and pericellular fibrosis in adult post-transplant liver biopsies: association with hepatic stellate cell activation and patient outcome

Post-transplant sinusoidal fibrosis (SF) and pericellular fibrosis (PCF) have not been extensively investigated in adults. Fifty-two post-transplant liver biopsies from 28 consented patients (12 men, mean age 49, range 33–67 years) were studied. Tissue morphology, including an arbitrary summative fibrosis score was assessed in detail. Collagen proportionate area (CPA) and alpha-smooth muscle actin (α-SMA) immunostain were evaluated by digital image analysis (DIA). Anti-keratin 7, anti-C4d and anti-sonic hedgehog (Shh) immunostains were scored semi-quantitatively. SF was observed in 36/52 (69.2%) biopsies and most of these (20/36, 55.6%) had centrilobular fibrosis (CLF). PCF was seen in 7/52 (13.5%) biopsies exclusively in cases with CLF. CPA was significantly correlated with time since liver transplantation (p = 0.043), summative fibrosis score and its main components but not with α-SMA. α-SMA-positive area significantly correlated with the Banff rejection score (p = 0.022) and centrilobular inflammatory changes were more severe in cases with CLF (p = 0.003). Hepatocyte ballooning of cholestatic type was associated with PCF (p = 0.016) and Shh expression (p < 0.001). Sinusoidal fibrosis is a frequent occurrence in post-transplant adult livers, with predilection toward centrilobular areas. Graft age and oxidative stress may contribute to SF development, while hepatocyte ballooning may be implicated in PCF development. Hepatic stellate cell (HSC) activation is likely affected by centrilobular inflammation.

Recipient Outcomes with Younger Donors Undergoing Living Donor Liver Transplantation

Introduction

The impact of donor age on liver transplantation is well known. Data on an appropriate donor age cut-off for living donor liver transplantation (LDLT) with a background of hepatitis C (HCV) is generally limited. The objective of this study was to determine whether limiting donor age to less than 35 years improved outcomes in patients with HCV-related end-stage liver disease (ESLD).

Methods

This was a retrospective review of 169 patients who underwent LDLT for HCV-related ESLD. The patients were divided into two groups based on whether they received grafts from donors ≤ 35 (Group 1) or > 35 (Group 2) years of age. Kaplan Meier curves were used to determine survival. Uni and multivariate analysis were performed to determine independent predictors of mortality.

Results

Mean donor age was 25.1 ± 5.2 and 40.1 ± 3.4 years (P < 0.0001). Early allograft dysfunction (EAD) was seen in 11.7% patients in Group 1 versus 29.6% in Group 2 (P = 0.02). A significant difference in mortality was present between the two groups, i.e., 33.3% versus 15.8% (P = 0.04). The estimated four-year overall survival (OS) was 78% and 64% (P = 0.03). Upon doing univariate analysis, the donor age (P = 0.04) and EAD (P = 0.006) were found to be significant variables for mortality. On multivariate analysis, EAD was the only independent predictor of mortality (Hazard ratio: 2.6; confidence interval: 1.1 - 5.8; P = 0.01).

Conclusion

Opting for younger donors (≤ 35 years) for HCV-related ESLD patients lowers the risk of EAD and improves overall survival.

Telomere Length Assessment for Prediction of Organ Transplantation Outcome. Future or Failure: A Review of the Literature

Telomeres are located at each end of eukaryotic chromosomes. Their functional role is genomic stability maintenance. The protective role of telomeres depends on various factors, including number of nucleotides repeats, telomere-binding proteins, and telomerase activity. Organ transplantation is the preferred replacement therapy in the case of chronic kidney disease and the only possibility of sustaining recipients’ life in the case of advanced liver failure. While the prevalence of acute rejection is constantly decreasing, prevention of transplanted organ long-term function loss is still challenging. It has been demonstrated that post-transplant stressors accelerate aging of the allografts manifested through telomere shortening.

The aim of this paper was to evaluate the importance of telomere length assessment for prediction of organ transplantation outcome. Literature review included the 10 most important studies regarding linkage between allograft function and telomere erosion, including 2 of our own reports.

Telomere length assessment is useful to predict organ transplantation outcome. The importance of telomere length as a prediction marker depends on the analyzed material. To obtain reliable results, both graft cells (donor material) and lymphocytes (recipient material) should be examined. In the case of kidney transplantation, assessment of telomere length in the early post-transplant period allows prediction of the long-term function of the transplanted organ. To increase the accuracy of transplantation outcome prediction, telomere length assessment should be combined with evaluation of other aging biomarkers, like CDKN2A (p16). Large-scale clinical studies regarding telomere length measurement, including genome wide association analysis introducing relevant genetic factors, are needed for the future.

Association of Donor and Recipient Telomere Length with Clinical Outcomes following Lung Transplantation

Background

Patients with short telomere syndromes and pulmonary fibrosis have increased complications after lung transplant. However, the more general impact of donor and recipient telomere length in lung transplant has not been well characterized.

Methods

This was an observational cohort study of patients who received lung transplant at a single center between January 1^st 2012 and January 31^st 2015. Relative donor lymphocyte telomere length was measured and classified into long (third tertile) and short (other tertiles). Relative recipient lung telomere length was measured and classified into short (first tertile) and long (other tertiles). Outcome data included survival, need for modification of immunosuppression, liver or kidney injury, cytomegalovirus reactivation, and acute rejection.

Results

Recipient lung tissue telomere lengths were measured for 54 of the 79 patients (68.3%) who underwent transplant during the study period. Donor lymphocyte telomeres were measured for 45 (83.3%) of these recipients. Neither long donor telomere length (hazard ratio [HR] = 0.58, 95% confidence interval [CI], 0.12–2.85, p = 0.50) nor short recipient telomere length (HR = 1.01, 95% CI = 0.50–2.05, p = 0.96) were associated with adjusted survival following lung transplant. Recipients with short telomeres were less likely to have acute cellular rejection (23.5% vs. 58.8%, p = 0.02) but were not more likely to have other organ dysfunction.

Conclusions

In this small cohort, neither long donor lymphocyte telomeres nor short recipient lung tissue telomeres were associated with adjusted survival after lung transplantation. Larger studies are needed to confirm these findings.

How important is donor age in liver transplantation?

The age of liver donors has been increasing in the past several years because of a donor shortage. In the United States, 33% of donors are age 50 years or older, as are more than 50% in some European countries. The impact of donor age on liver transplantation (LT) has been analyzed in several studies with contradictory conclusions. Nevertheless, recent analyses of the largest databases demonstrate that having an older donor is a risk factor for graft failure. Donor age is included as a risk factor in the more relevant graft survival scores, such as the Donor Risk Index, donor age and Model for End-stage Liver Disease, Survival Outcomes Following Liver Transplantation, and the Balance of Risk. The use of old donors is related to an increased rate of biliary complications and hepatitis C virus-related graft failure. Although liver function does not seem to be significantly affected by age, the incidence of several liver diseases increases with age, and the capacity of the liver to manage or overcome liver diseases or external injuries decreases. In this paper, the importance of age in LT outcomes, the role of donor age as a risk factor, and the influence of aging on liver regeneration are reviewed.

STAT5A Modulates Chemokine Receptor CCR6 Expression and Enhances Pre-B Cell Growth in a CCL20-Dependent Manner

Signal transducer and activator of transcription 5A (STAT5A) contributes to B-cell responses to cytokines through suppressor of cytokine signaling (Socs) genes in innate immunity. However, its direct roles in B-cell responses to chemokines are poorly understood. In this study, we examined the role of STAT5A in the innate immune response. We found that STAT5A upregulated the transcription of C-C motif receptor 6 (Ccr6) to induce responses to its ligand, CCL20. STAT5A transcriptional activity proceeded through binding to the interferon-γ activation site (GAS) element in the CCR6 promoter in the genome of pre-B cells. High levels of STAT5A and CCR6 increased CCL20-dependent colony growth of pre-B cells. In human B-lymphoblastic lymphoma with inflammation, STAT5A phosphorylation was correlated with CCR6 expression (P > 0.05 compared with that in cases without inflammation). In conclusion, our data supported our hypothesis that STAT5A enhanced the response of pre-B cells to CCL20 to promote their growth.   J. Cell. Biochem. 117: 2630-2642, 2016. © 2016 Wiley Periodicals, Inc.

What determines ageing of the transplanted liver?

BACKGROUND

Liver transplantation is used to treat patients with irreversible liver failure from a variety of causes. Long-term survival has been reported, particularly in the paediatric population, with graft survival longer than 20 years now possible. The goal for paediatric liver transplantation is to increase the longevity of grafts to match the normal life expectancy of the child. This paper reviews the literature on the current understanding of ageing of the liver and biomarkers that may predict long-term survival or aid in utilization of organs.

METHODS

Scientific papers published from 1950 to 2013 were sought and extracted from the MEDLINE, PubMed and University of Melbourne databases.

RESULTS

Hepatocytes appear resistant to the ageing process, but are affected by both replicative senescence and stress-related senescence. These processes may be exacerbated by the act of transplantation. The most studied biomarkers are telomeres and SMP-30.

CONCLUSION

There are many factors that play a role in the ageing of the liver. Further studies into biomarkers of ageing and their relationship to the chronological age of the liver are required to aid in predicting long-term graft survival and utilization of organs.

Association between donor leukocyte telomere length and survival after unrelated allogeneic hematopoietic cell transplantation for severe aplastic anemia

IMPORTANCE

Telomeres protect chromosome ends and are markers of cellular aging and replicative capacity.

OBJECTIVE

To evaluate the association between recipient and donor pretransplant leukocyte telomere length with outcomes after unrelated donor allogeneic hematopoietic cell transplantation (HCT) for patients with severe aplastic anemia.

DESIGN, PARTICIPANTS, AND SETTING

The study included 330 patients (235 acquired, 85 Fanconi anemia, and 10 Diamond-Blackfan anemia) and their unrelated donors who had pre-HCT blood samples and clinical and outcome data available at the Center for International Blood and Marrow Transplant Research. Patients underwent HCT between 1989 and 2007 in 84 centers and were followed-up to March 2013.

EXPOSURES

Recipient and donor pre-HCT leukocyte telomere length classified into long (third tertile) and short (first and second tertiles combined) based on donor telomere length distribution.

MAIN OUTCOMES AND MEASURES

Overall survival, neutrophil recovery, and acute and chronic graft-vs-host disease, as ascertained by transplant centers through regular patient follow-up.

RESULTS

Longer donor leukocyte telomere length was associated with higher survival probability (5-year overall survival, 56%; number at risk, 57; cumulative deaths, 50) than shorter donor leukocyte telomere length (5-year overall survival, 40%; number at risk, 71; cumulative deaths, 128; P = .009). The association remained statistically significant after adjusting for donor age, disease subtype, Karnofsky performance score, graft type, HLA matching, prior aplastic anemia therapy, race/ethnicity, and calendar year of transplant (hazard ratio [HR], 0.61; 95% CI, 0.44-0.86). Similar results were noted in analyses stratified on severe aplastic anemia subtype, recipient age, HLA matching, calendar year of transplant, and conditioning regimen. There was no association between donor telomere length and neutrophil engraftment at 28 days (cumulative incidence, 86% vs 85%; HR, 0.94; 95% CI, 0.73-1.22), acute graft-vs-host disease grades III-IV at 100 days (cumulative incidence, 22% vs 28%; HR, 0.77; 95% CI, 0.48-1.23), or chronic graft-vs-host disease at 1-year (cumulative incidence, 28% vs 30%; HR, 0.81; 95% CI, 0.53-1.24) for long vs short, respectively. Pretransplant leukocyte telomere length in the recipients was not associated with posttransplant survival (HR, 0.91; 95% CI, 0.64-1.30).

CONCLUSIONS AND RELEVANCE

Longer donor leukocyte telomere length was associated with increased 5-year survival in patients who received HCT for severe aplastic anemia. Patient leukocyte telomere length was not associated with survival. The results of this observational study suggest that donor leukocyte telomere length may have a role in long-term posttransplant survival.

Q-FISH measurement of hepatocyte telomere lengths in donor liver and graft after pediatric living-donor liver transplantation: donor age affects telomere length sustainability

Along with the increasing need for living-donor liver transplantation (LDLT), the issue of organ shortage has become a serious problem. Therefore, the use of organs from elderly donors has been increasing. While the short-term results of LDLT have greatly improved, problems affecting the long-term outcome of transplant patients remain unsolved. Furthermore, since contradictory data have been reported with regard to the relationship between donor age and LT/LDLT outcome, the question of whether the use of elderly donors influences the long-term outcome of a graft after LT/LDLT remains unsettled. To address whether hepatocyte telomere length reflects the outcome of LDLT, we analyzed the telomere lengths of hepatocytes in informative biopsy samples from 12 paired donors and recipients (grafts) of pediatric LDLT more than 5 years after adult-to-child LDLT because of primary biliary atresia, using quantitative fluorescence in situ hybridization (Q-FISH). The telomere lengths in the paired samples showed a robust relationship between the donor and grafted hepatocytes (r = 0.765, p = 0.0038), demonstrating the feasibility of our Q-FISH method for cell-specific evaluation. While 8 pairs showed no significant difference between the telomere lengths for the donor and the recipient, the other 4 pairs showed significantly shorter telomeres in the recipient than in the donor. Multiple regression analysis revealed that the donors in the latter group were older than those in the former (p = 0.001). Despite the small number of subjects, this pilot study indicates that donor age is a crucial factor affecting telomere length sustainability in hepatocytes after pediatric LDLT, and that the telomeres in grafted livers may be elongated somewhat longer when the grafts are immunologically well controlled.

Telomere length of recipients and living kidney donors and chronic graft dysfunction in kidney transplants

BACKGROUND

A biological marker that would allow clinicians to determine the length of time an allograft will remain functional after transplantation would greatly aid the ability to stratify donors by risk and to use biologically "young" allografts in young recipients, maximizing the use of this rare resource. Telomere length (TL) has been proposed to be such a marker to determine the biological age of a tissue.

METHODS

We genotyped DNA from 1805 recipients and 1038 living kidney donors for TL to determine the association of TL with acute rejection (AR), chronic graft dysfunction (CGD), and graft failure of kidney allografts. DNA was isolated from peripheral blood white blood cells and TL was measured in DNA using the multiplexed monochrome quantitative polymerase chain reaction assay.

RESULTS

As has been previously shown, we found a significant association between log-transformed TL and donor age (P=3.8×10) and recipient age (P=5.6×10). Univariate and multivariate analysis did not show any significant associations between log-transformed TL in donor or recipient DNA with AR, CGD, or graft failure, although we did observe an association between donor chronological age and CGD (P=0.018).

CONCLUSION

Although older allografts have been shown to be at greater risk for AR and CGD, this does not appear to be associated with shorter TL. Different markers will need to be identified to determine how biological age impacts transplant outcome, such as age-related fibrosis or tubular atrophy and tubular loss.

"Plasma cell hepatitis" in liver allografts: identification and characterization of an IgG4-rich cohort

Plasma cell hepatitis (PCH), also known as "de novo autoimmune" hepatitis, is an increasingly recognized, but suboptimally named and poorly understood, category of late allograft dysfunction strongly resembling autoimmune hepatitis (AIH): They share plasma-cell-rich necro-inflammatory activity on biopsy, autoantibodies and steroid responsiveness, but overlap with rejection is problematic. A retrospective study of clinical, serological, histopathological and IgG4 immunohistological features of PCH (n = 20) in liver allograft recipients, native liver AIH (n = 19) and plasma-cell-rich renal allograft rejection (n = 20) showed: (1) high frequency (44%) of HLA-DR15; (2) less female predominance (p = 0.03) and (3) n = 9/20 PCH recipients showed >25 IgG4+ plasma cells/high-power field (IgG4+ PCH) versus AIH (n = 1/19, p = 0.008) or plasma-cell-rich kidney rejection (n = 2/20, p = 0.03). The IgG4+ PCH (n = 9) subgroup showed lower alanine transaminase (ALT) (p < 0.01) and aspartate transaminase (AST) (p < 0.05) at index biopsy but (a) higher plasma cell number/percentage, (b) more aggressive-appearing portal/periportal and perivenular necro-inflammatory activity and (c) more severe portal/periportal fibrosis than IgG4- PCH (n = 11). Significant demographic, histopathologic and plasma cell phenotype differences between PCH and AIH suggest distinct pathogenic mechanisms for at least the IgG4+ PCH subgroup likely representing an overlap between allo- and auto-immunity. IgG4+ PCH was associated with fibrosis, but also highly responsive to increased immunosuppression.

Aneuploidy, polyploidy and ploidy reversal in the liver

Polyploidy has been described in the liver for over 100 years. The frequency of polyploid hepatocytes varies by age and species, but up to 90% of mouse hepatocytes and approximately 50% of human hepatocytes are polyploid. In addition to alterations in the entire complement of chromosomes, variations in chromosome copy number have been recently described. Aneuploidy in the liver is pervasive, affecting 60% of hepatocytes in mice and 30-90% of hepatocytes in humans. Polyploidy and aneuploidy in the liver are closely linked, and the ploidy conveyor model describes this relationship. Diploid hepatocytes undergo failed cytokinesis to generate polyploid cells. Proliferating polyploid hepatocytes, which form multipolar spindles during cell division, generate reduced ploidy progeny (e.g., diploid hepatocytes from tetraploids or octaploids) and/or aneuploid daughters. New evidence suggests that random hepatic aneuploidy can promote adaptation to liver injury. For instance, in response to chronic liver damage, subsets of aneuploid hepatocytes that are differentially resistant to the injury remain healthy, regenerate the liver and restore function. Future work is required to elucidate the mechanisms regulating dynamic chromosome changes in the liver and to understand how these processes impact normal and abnormal liver function.

Frequent hepatocyte chimerism in long-term human liver allografts independent of graft outcome

Microchimerism after liver transplantation is considered to promote graft tolerance or tissue repair, but its significance is controversial. By using multiplex polymerase chain reaction (PCR) of short tandem repeat (STR) loci after laser capture microdissection of hepatocyte nuclei, we compared the proportions of recipient-derived hepatocytes in long-term stable liver allografts and late dysfunctional allografts caused by chronic rejection or idiopathic post-transplantation hepatitis. Through fluorescence in situ hybridization (FISH), we also analyzed the presence of recipient-derived Y-positive hepatocytes in the biopsies of livers transplanted from female donors to male recipients. The study population comprised 24 pediatric liver transplant recipients who survived with the initial graft, whose 10-year protocol biopsy records were available, and who had normal liver function (stable graft, SG; n=13) or a late dysfunctional graft (LDG; n=11) with similar follow-up periods (mean 10.8years in the SG group and 11.2years in the LDG group). STR analysis revealed that hepatocyte chimerism occurred in 7 of 13 (54%) SGs and 5 of 11 (45%) LDGs (p=0.68). The proportion of hepatocyte chimerism was low, with a mean of 3% seen in 2 of 3 female-to-male transplanted livers (one each of SG and LDG). In conclusion, hepatocyte chimerism was a constant event. The extent of engraftment of recipient-derived hepatocytes does not seem to correlate with the degree of hepatic injury in long-term liver allografts.