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Abstract: FR-PO377

CXCL12 and WNT5A Control Nephron Number in the Normal and Hypodysplastic Kidney

Session Information

Category: Development‚ Stem Cells‚ and Regenerative Medicine

  • 500 Development‚ Stem Cells‚ and Regenerative Medicine

Authors

  • D'Cruz, Robert, The Hospital for Sick Children, Toronto, Ontario, Canada
  • Jiang, Nan, The Hospital for Sick Children, Toronto, Ontario, Canada
  • Rosenblum, Norman D., The Hospital for Sick Children, Toronto, Ontario, Canada
Background

Renal hypodysplasia, defined by abnormally small kidneys with low nephron number and expanded stromal tissue, is the major cause of childhood renal failure. While molecular mechanisms controlling nephrogenesis have been elucidated, factors that control the number of nephrons is largely unknown and important as low nephron number is critical to kidney function in childhood and as an antecedent cause of adult-onset kidney and cardiovascular disease. Nephrons and stromal cells arise during embryonic development from Osr1-derived Six2+ and Foxd1+ progenitors, respectively. Previous work demonstrated that increased Hedgehog (Hh) signaling in Osr1+ kidney progenitor cells disrupts normal stromal patterning (Sheybani et al., 2018). Here, we investigate the functional contribution of the embryonic renal stroma in determining nephron number.

Methods

Constitutive active Hh signaling in Foxd1+ stromal cells was generated by deletion of Ptch1, a Hh cell surface receptor, in a Cre-dependent manner. Compound mutant mice with Foxd1Cre-dependent deficiency of Cxcl12 or Wnt5a together with Ptch1, and mice with Foxd1Cre-dependent deletion of Cxcl12, were generated. Kidney tissue was analyzed by histology, single-cell (sc) and bulk RNA sequencing.

Results

Stromal Ptch1-deficient kidneys exhibited renal hypodysplasia characterized by a 41% reduction in nephron number (P<0.01,n=4) and expansion of Foxd1-derived PDGFRB+ medullary stromal cells at E18.5. Complementary scRNA-seq and bulk RNA sequencing (n=3) identified increased expression of medullary stromal Cxcl12 (P<0.001) and Wnt5a (P<0.01) ligands. Foxd1Cre-dependent deficiency of Cxcl12 or Wnt5a together with Ptch1 rescued nephron number by 32% (P<0.001,n=4) or 31% (P<0.05,n=3), respectfully. Analysis of stromal Cxcl12-deficient kidneys demonstrated renal hypoplasia characterized by a 28% reduction in nephron number (P<0.01,n=4) at P4 due to impaired nephron epithelialization. Bulk RNA sequencing of stromal Cxcl12-deficient kidneys (n=3) showed dysregulation of genes associated with retinoic acid signaling, such as Crabp1/2 (P<0.01) and Aldh1a2 (P<0.05), and genes associated with Hippo signaling, such as Cdc42 (P<0.05) and Taz (P<0.05).

Conclusion

Increased stromal Cxcl12 and Wnt5a signal non-autonomously to drive low nephron number in renal hypodysplasia. Stromal Cxcl12 functions physiologically to regulate nephron number.

Funding

  • Government Support – Non-U.S.