The Rhesus Macaque Serves As a Model for Human Lateral Branch Nephrogenesis

Background Most nephrons are added in late gestation. Truncated extrauterine nephrogenesis in premature infants results in fewer nephrons and significantly increased risk for CKD in adulthood. To overcome the ethical and technical difficulties associated with studies of late-gestation human fetal kidney development, third-trimester rhesus macaques served as a model to understand lateral branch nephrogenesis (LBN) at the molecular level. Methods Immunostaining and 3D rendering assessed morphology. Single-cell (sc) and single-nucleus (sn) RNA-Seq were performed on four cortically enriched fetal rhesus kidneys of 129?131 days gestational age (GA). An integrative bioinformatics strategy was applied across single-cell modalities, species, and time. RNAScope validation studies were performed on human archival tissue. Results Third-trimester rhesus kidney undergoes human-like LBN. scRNA-Seq of 23,608 cells revealed 37 transcriptionally distinct cell populations, including na?ve nephron progenitor cells (NPCs), with the prior noted marker genes CITED1, MEOX1, and EYA1 (c25). These same populations and markers were reflected in snRNA-Seq of 5972 nuclei. Late-gestation rhesus NPC markers resembled late-gestation murine NPC, whereas early second-trimester human NPC markers aligned to midgestation murine NPCs. New, age-specific rhesus NPCs (SHISA8) and ureteric buds (POU3F4 and TWIST) predicted markers were verified in late-gestation human archival samples. Conclusions Rhesus macaque is the first model of bona fide LBN, enabling molecular studies of late gestation, human-like nephrogenesis. These molecular findings support the hypothesis that aging nephron progenitors have a distinct molecular signature and align to their earlier human counterparts, with unique markers highlighting LBN-specific progenitor maturation. Significance Statement Premature infants far fewer nephrons than newborns on average, and thus are at increased risk for CKD and ESKD in adulthood. Most nephrons are added during late gestation in a poorly understood process, lateral branch nephrogenesis. As direct study of human late gestation fetal kidney development is fraught with ethical and technical difficulties, the rhesus macaque was identified as a suitable model to bridge this knowledge gap. The rhesus kidney undergoes human-like lateral branch nephrogenesis. Initial molecular characterization, validated on human kidney archival samples, indicates the kidney progenitor cell transcriptome changes over time. A molecular study of lateral branch nephrogenesis could be leveraged to enhance nephrogenesis in preterm infants.