Detection of Infiltrating Fibroblasts by Single-Cell Transcriptomics in Human Kidney Allografts
Abstract We tested the hypothesis that single-cell RNA-sequencing (scRNA-seq) analysis of human kidney allograft biopsies will reveal distinct cell types and states and yield insights to decipher the complex heterogeneity of alloimmune rejection. We selected 3 kidney biopsies from 3 individuals for scRNA-seq and processed them fresh using an identical protocol on the 10x Chromium platform; (i) HK: native kidney biopsy from a living donor, (ii) AK1: allograft kidney with transplant glomerulopathy and tubulointerstitial fibrosis, and worsening graft function, and (iii) AK2: allograft kidney after successful treatment of active antibody-mediated rejection. We generated 7217 high-quality single cell transcriptomes. Taking advantage of the recipient-donor sex mismatches, we determined that in AK1 with fibrosis, more than half of the kidney allograft fibroblasts were—unexpectedly—recipient-derived and therefore likely migratory and graft infiltrative, whereas in the AK2 without fibrosis, all the fibroblasts were donor-derived. Furthermore, AK1 was enriched by tubular cells that overexpressed profibrotic extracellular matrix genes. AK2, eight months after successful treatment of rejection, contained endothelial cells that expressed T-cell chemoattractant cytokines. In addition to these key findings, our analysis revealed unique cell types and cell states. Altogether, single cell transcriptomics yielded novel mechanistic insights for individualizing the care of transplant recipients.