Abstract
Purpose :
Normal corneal epithelial homeostasis is maintained by limbal epithelial stem cells (LSCs). We previously reported that pigment epithelial derived factor (PEDF) accelerates self-renewal of LSCs and limbal regeneration in rabbit partial limbal deficiency. This study was conducted to investigate the mechanism of PEDF-mediated limbal regeneration.
Methods :
3-5-month-old BALB/c mice were used in this study. Inferior 120 degree limbal epithelia was surgically removed using a metal burr. PEDF short peptide 44-mer was subconjunctivally injected at the end of surgery, and DMSO was used as control. The repair of inferior limbus was assessed by immunofluorescence staining with antibodies for △Np63α and Lrig1 at 2 weeks, 1 and 3 months. Corneal epithelial wounding was performed to evaluate the function of limbus. LSCs were isolated from New Zealand white rabbits and used for cell-suspension culture, colony-forming efficiency assay and BrdU labeling assay. Inhibitors for Sonic Hedgehog, STAT3 and ATGL were applied to investigate the role of these signaling pathways in PEDF-mediated LSC expansion and limbal regeneration.
Results :
In vivo, the expressions of △Np63α-positive cells and Lrig1-positive cells within the inferior limbal wound were observed at 2 weeks after operation in PEDF group, but not in control group. The number of △Np63α-positive cells and Lrig1-positive cells in PEDF group was also higher than those in control at 1 and 3 months. Maintenance of corneal transparency without neovascularization and normal wound healing substantiated the restoration of limbal function by PEDF. Inhibitors for Sonic Hedgehog (SHH), STAT3 and ATGL significantly suppressed the PEDF effect on △Np63α and Lrig1 expression at 2 weeks. Result from organ culture and cell study showed that PEDF upregulated SHH activity accompanied with nuclear translocation of Gli1 and active form full-length Gli3, and the effect was blocked by the inhibitor for STAT3 or ATGL in vitro. Furthermore, inhibitor of ATGL suppressed phosphorylation of STAT3 at Tyr705 in response to PEDF in LSCs.
Conclusions :
PEDF-mediated limbal regeneration was dependent on the SHH-Gli pathway activity through ATGL/STAT3 signaling. The novel murine partial limbal deficiency is a useful model for limbal regeneration research.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.