Changes in Microbiome in Patients with Kidney Injury after Allogeneic Hematopoietic Stem Cell Transplantation

Key Points Changes in microbiome diversity index are common in patients with stem cell transplant. Changes in microbiome diversity do not explain the high incidence of AKI in patients with stem cell transplant. Background AKI is a common complication of allogeneic hematopoietic cell transplantation (allo-HCT) that increases the risk of mortality. By contrast, higher diversity of intestinal microbiota at the time of neutrophil engraftment has been associated with lower mortality. We aimed to better understand kidney outcomes in relation to changes in gut diversity in this patient population, hypothesizing that patients with lower microbiome diversity at baseline and at engraftment were at higher risk of developing kidney complications. Methods We performed a single-center retrospective study of 419 hematopoietic cell transplant recipients from 2014 to 2017 at our institution whose gut microbiota were analyzed. We defined AKI and CKD on the basis of Kidney Disease Improving Global Outcomes criteria and eGFR using the CKD Epidemiology Collaboration equation. We defined gut microbiome diversity using Shannon and Simpson reciprocal diversity indices, with higher levels indicating more diverse microbiota. Results Simpson reciprocal diversity index and Shannon diversity index were 21.8 (interquartile range [IQR], 13.7–35.2; range, 1.6–102.5) and 3.7 (IQR, 3.2–4.2; range, 0.7–5.2) in our cohort at baseline and 6.3 (IQR, 3.7–10.4) and 2.3 (IQR, 1.7–2.8) at periengraftment, respectively. Of the 419, 263 patients (63%) developed any grade AKI in 100 days after hematopoietic cell transplantation and 114 (27%) developed grade 2+ AKI. There were no significant differences in microbiome diversity at baseline or periengraftment in patients who developed post-transplant AKI or CKD, respectively, in comparison with those who did not develop kidney complications. Conclusions Our findings do not support the existence of a link between baseline or periengraftment gut diversity and the risk of development of AKI or CKD in patients undergoing allo-HCT. This study highlights the complex and multifactorial etiology of AKI in allo-HCT recipients and the need for additional prospective and mechanistic studies.