Acute Kidney Injury in Children after Hematopoietic Cell Transplantation Is Associated with Elevated Urine CXCL10 and CXCL9

Abstract

Acute kidney injury (AKI) is nearly universally associated with worse outcomes, especially among children after hematopoietic stem cell transplant (HCT). Our objective was to examine urinary immune biomarkers of AKI after HCT to provide insights into novel mechanisms of kidney injury in this population. Studying patients undergoing allogeneic HCT provides a unique opportunity to examine immune markers of AKI because the risk of AKI is high and the immune system newly develops after transplant. Children (>2 years old) and young adults undergoing their first allogeneic HCT and enrolled in a prospective, observational cohort study at 2 large children's hospitals had urine collected pre-HCT and monthly for the first 4 months after HCT. Urine samples at each monthly time point were assayed for 8 immune-related biomarkers. AKI was defined as a 1.5-fold increase in the monthly serum creatinine value, which was recorded ±1 day from when the research urine sample was obtained, as compared with the pre-HCT baseline. Generalized estimating equation regression analysis evaluated the association between the monthly repeated measures (urinary biomarkers and AKI). A total of 176 patients were included from 2 pediatric centers. Thirty-six patients from 1 center were analyzed as a discovery cohort and the remaining 140 patients from the second center were analyzed as a validation cohort. AKI rates were 18% to 35% depending on the monthly time point after HCT. Urine CXCL10 and CXCL9 concentrations were significantly higher among children who developed AKI compared with children who did not (P < .01) in both cohorts. In order to gain a better understanding of the cellular source for these biomarkers in the urine, we also analyzed in vitro expression of CXCL10 and CXCL9 in kidney cell lines after stimulation with interferon-γ and interferon-α. HEK293-epithelial kidney cells demonstrated interferon-induced expression of CXCL10 and CXCL9, suggesting a potential mechanism driving the key finding. CXCL10 and CXCL9 are associated with AKI after HCT and are therefore promising biomarkers to guide improved diagnostic and treatment strategies for AKI in this high-risk population.

Keywords: Acute kidney injury; Biomarkers; CXCL10; CXCL9; Pediatric hematopoietic stem cell transplantation.

Figure 1:. Cohort design.

Each participant had a pre-hematopoietic cell transplant (HCT) visit including urine sample collection and baseline serum creatinine and then monthly samples starting a month after HCT. Time 0 is the day of stem cell infusion.

Figure 2:. Acute kidney injury rates among discovery and validation cohort.

Acute kidney injury rates among the two cohorts at every time point (baseline, 1, 2, 3, and 4 months after hematopoietic cell transplant)

Figure 3:. Urinary CXCL10 and CXCL9 levels among the two cohorts at monthly intervals after hematopoietic cell transplant HCT.

Concentrations of urinary CXCL10 and CXCL9 at every monthly time point among both cohorts comparing patients who developed acute kidney injury to those who did not. Results presented as median and interquartile range.

Figures 4a, 4b, 4C:. CXCL10 and CXCL9 relative expression in HEK293 and HK2 cells. CXCL10 and CXCL9 expression using qPCR in HEK293 and HEK293 cells, respectively.

X-axis presents each stimulus and incubation time (hours) and Y-axis is normalized compared to control (no stimulus); bars represent standard error of the mean, summary of 3 replicates per each experiment *P <0.05