Total Cell-Free DNA as a Noninvasive Biomarker of a Delayed Graft Function After Kidney Transplantation From Donors After Cardiac Death

BACKGROUND

Because of the organ shortage, donation after cardiac death (DCD) kidney transplantation (KTx) is an alternative way of achieving KTx using brain-dead donors (BDs). Although the prognosis of DCD-KTx is improving, the graft suffers from delayed graft function (DGF), the management of which is essential. With progress in understanding the characteristics of cell-free DNA (CF-DNA), we consider plasma total CF-DNA (tCF-DNA) to be a useful biomarker for predicting DGF in DCD-KTx.

STUDY DESIGN AND METHOD

Consecutive patients from living donors (LDs; n = 9), BDs (n = 8), or DCD donors (n = 13) were enrolled. Plasma samples were collected after KTx and on postoperative days 3 and 5. CF-DNA was isolated, and tCF-DNA was quantified using the TapeStation 2200 software program.

RESULTS

The tCF-DNA levels after BD-KTx and DCD-KTx were higher than those after LD-KTx (LD, 78 ± 27 (ng/mL); BD, 99 ± 20; DCD, 150 ± 23); the difference between DCD-KTx and LD-KTx was statistically significant (P < .05). The tCF-DNA levels declined at postoperative day 5 (LD, 45 ± 10; BD, 51 ± 11; DCD, 66 ± 13). tCF-DNA levels were significantly increased in patients with DGF after KTx (DGF, 139 ± 22; immediate function, 91 ± 18; P < .05). The tCF-DNA level was correlated with the duration of DGF (r = 0.5825, P < .05).

CONCLUSION

Although the mechanism underlying DNA release from transplanted grafts into the recipient circulation remains unclear, cell death by apoptosis or necrosis and the active secretion of the immune system may play important roles in DGF. These data suggest that monitoring tCF-DNA may help predict graft recovery after DCD-KTx.

Biomarkers as diagnostic tests for delayed graft function in kidney transplantation

Delayed graft function (DGF) after kidney transplantation is associated with inferior outcomes and higher healthcare costs. DGF is currently defined as the requirement for dialysis within seven days post-transplant; however, this definition is subjective and nonspecific. Novel biomarkers have potential to improve objectivity and enable earlier diagnosis of DGF. We reviewed the literature to describe the range of novel biomarkers previously studied to predict DGF. We identified marked heterogeneity and low reporting quality of published studies. Among the novel biomarkers, serum NGAL had the greatest potential as a biomarker to predict DGF, but requires further assessment and validation through larger scale studies of diagnostic test performance. Given inadequacies in the dialysis-based definition, coupled with the high incidence and impact of DGF, such studies should be pursued.

Hypoxia and Complement-and-Coagulation Pathways in the Deceased Organ Donor as the Major Target for Intervention to Improve Renal Allograft Outcome

BACKGROUND

In the last few decades, strategies to improve allograft survival after kidney transplantation have been directed to recipient-dependent mechanisms of renal injury. In contrast, no such efforts have been made to optimize organ quality in the donor. Optimizing deceased donor kidney quality opens new possibilities to improve renal allograft outcome.

METHODS

A total of 554 kidney biopsies were taken from donation after brain death (DBD) and donation after cardiac death (DCD) kidneys before donation, after cold ischemia and after reperfusion. Healthy living donor kidney biopsies served as controls. Transcriptomics was performed by whole genome microarray analyses followed by functional pathway analyses.

RESULTS

Before organ retrieval and before cessation of blood circulation, metabolic pathways related to hypoxia and complement-and-coagulation cascades were the major pathways enhanced in DBD donors. Similar pathways were also enriched in DCD donors after the first warm ischemia time. Shortly after reperfusion of DCD grafts, pathways related to prolonged and worsening deprivation of oxygen were associated with delayed graft function in the recipient.

CONCLUSION

In conclusion, this large deceased donor study shows enrichment of hypoxia and complement-and-coagulation pathways already in DBD donors before cessation of blood flow, before organ retrieval. Therefore, future intervention therapies should target hypoxia and complement-and-coagulation cascades in the donor to improve renal allograft outcome in the recipient.

Serum neutrophil gelatinase associated lipocalin during the early postoperative period predicts the recovery of graft function after kidney transplantation from donors after cardiac death

PURPOSE

Kidneys procured from donors after cardiac death hold great potential to expand the donor pool. However, they have not yet been fully used, in part due to the high incidence of delayed graft function. Although urine neutrophil gelatinase-associated lipocalin is a well-known early biomarker for renal injury after kidney transplantation, its usefulness is limited in cases with delayed graft function because of the unavailability of a urine sample. We evaluated serum neutrophil gelatinase-associated lipocalin as a potential biomarker to predict the functional recovery of kidneys transplanted from donors after cardiac death.

MATERIALS AND METHODS

Consecutive patients transplanted with a kidney from a living related (39), brain dead (1) or post-cardiac death (27) donor were retrospectively enrolled in the study. Serum samples were collected serially before and after kidney transplantation. Serum neutrophil gelatinase-associated lipocalin was measured using the ARCHITECT® assay.

RESULTS

Average serum neutrophil gelatinase-associated lipocalin was markedly high during the pre transplantation period. It decreased rapidly after transplantation. The slope of the decrease correlated well with the recovery period. By analyzing ROC curves we determined cutoffs to predict immediate, slow or delayed graft function requiring hemodialysis for longer than 1 week with high sensitivity and specificity.

CONCLUSIONS

These data suggest that serial monitoring of serum neutrophil gelatinase-associated lipocalin may allow us to predict graft recovery and the need for hemodialysis after kidney transplantation from a donor after cardiac death.

Serum tissue inhibitor of metalloproteinases 1 (TIMP-1) predicts organ recovery from delayed graft function after kidney transplantation from donors after cardiac death

Donors after cardiac death (DCD) have recently become an important source of renal transplants to alleviate the shortage of renal grafts in kidney transplantation (KTx), although DCD kidneys often have complications associated with a delayed graft function (DGF). A microarray-based approach using renal biopsy samples obtained at 1 h after KTx from DCD identified the tissue inhibitor of metalloproteinases 1 (TIMP-1) gene as a potential predictive marker for DGF. The current study measured serum TIMP-1 in patients undergoing KTx and analyzed the time course after KTx. The average serum TIMP-1 level before KTx was 240 ± 10 ng/ml (n = 34). In patients undergoing KTx from a living donor (n = 23), the serum TIMP-1 levels showed no increase after KTx (POD1: 226 ± 12, POD2: 211 ± 12, and POD3: 195 ± 10 ng/ml), but in one case, the only patient who required post-KTx HD due to DGF, the level on POD1 was the highest among subjects (361 ng/ml). In contrast, patients undergoing KTx from DCDs (n = 11), the serum TIMP-1 levels increased rapidly after a KTx (POD1: 418 ± 32, POD2: 385 ± 42, and POD3: 278 ± 25 ng/ml). However, two patients who avoided post-KTx HD due to the immediate function of the graft did not show increased levels (<370 ng/ml) on either POD1 or POD2. The peak serum TIMP-1 values appeared to correlate to the post-KTx dialysis period. Furthermore, the increment of serum TIMP-1 on the early POD was found to be predictive of immediate or delayed function of the grafts. These data suggest that monitoring of serum TIMP-1 levels allow the prediction of graft recovery and the need for HD after a KTx from a DCD.