Stem Cell Factor/Kit Signal Insufficiency Contributes to Hypoxia-Induced Intestinal Motility Dysfunctions in Neonatal Mice.

BACKGROUND

Gastrointestinal (GI) motility disorders represent a group of problems that more constantly encountered in preterm infants. However, whether hypoxia exposure contributes to the GI dysfunctions is still unclear.

METHODS

Newborn mice were exposed to hypoxia (10%) from P1 to P7. Intestinal motilities were examined by a strain gauge transducer. The proliferation of ICCs was detected by using immunostaining for BrdU, Ki67, Kit, Ano1, and insulin-like growth factor 1 receptor (IGF-1R+). Smooth muscle cells and enteric neurons were revealed by immunostaining for α-SMA and NF200, respectively. Apoptosis was assessed by TUNEL assay. Kit signal pathway was examined by western blot and qPCR.

RESULTS

Intestinal motilities were found weakened significantly in the hypoxic small intestines as compared to controls on P8. Kit+ or Ano1+ interstitial cells of Cajal (ICCs) were found obviously decreased in the myenteric ICCs (ICC-MY) of neonatal mice after exposed to hypoxia. A large number of ICC progenitors (IGF-1R+) were found highly mitotic (BrdU+ Ki67+) to populate ICC during early postnatal development in the normoxic mice. We found the ICC proliferation was significantly inhibited upon hypoxia exposure, without increasing apoptosis (TUNEL+). We next identified that Kit phosphorylation was inhibited 3 days after hypoxia exposure. The inhibition of Kit signaling was largely due to decreased the expression of the ligand of Kit receptor, stem cell factor (SCF), in the intestinal walls. Exposure to imatinib, a Kit receptor inhibitor, for 3 days from P4 phenocopied the effect of hypoxia on the neonatal pups that resulted in inhibited intestinal motilities and decreased Kit+ ICC numbers.

CONCLUSION

All together, our findings indicate the SCF/Kit signaling insufficiency may contribute to the underdevelopment of ICCs and intestinal motility dysfunction upon hypoxia exposure. The decease in ICC density is likely due to the cell cycle arrest of ICC progenitor cells.