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Juan Ding, David A Sullivan; Human Growth Hormone Promotes Corneal Wound Healing in Vitro. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4611.
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Corneal epithelial wound healing involves the migration and proliferation of epithelial cells, and cross talk between the epithelial cells and fibroblasts. Human growth hormone (HGH) has been shown to improve corneal wound healing in a rabbit debridement model, but the mechanism is not known. We hypothesize that HGH promotes corneal wound healing by activating the signaling pathway JAK2/STAT5 and promoting cell migration and/or proliferation in corneal epithelial cells and fibroblasts.
To test this hypothesis, we developed a cell culture system using immortalized human corneal epithelial cells (HCECs) and primary human corneal fibroblasts (HCFs). HGH activation (i.e. phosphorylation [p]) was assessed by treating both cell types for 15 minutes and examining the relative levels of p-JAK2 and p-STAT5 by Western blots. Cell proliferation was evaluated by manual counting with a hemocytometer after 2 days of HGH treatment in HCECs. Cell migration was determined with a scratch test in HCECs cultured alone or together with HCFs in three ways: in transwell plates where the two cell types exchanged media but had no physical contact, HCEC on top of HCF feeder layer, or mixed in the same well.
We discovered that HGH stimulates the dose-dependent accumulation of p-JAK2 and p-STAT5 in both HCECs and HCFs. Further, HGH promoted migration of HCECs when they were co-cultured with HCFs in transwell plates (no physical contact), or as two layers, or mixed together. In contrast, HGH did not have a consistent effect on proliferation or migration of HCECs when these cells were cultured alone or treated with conditioned media of HCFs.
HGH activates the JAK2/STAT5 signaling pathways in HCECs and HCFs, and promotes HCEC migration when epithelial cells and fibroblasts are allowed to communicate with each other, but not when they are isolated. These results may explain why HGH promotes corneal wound healing in rabbits and indicates that HGH may be of therapeutic value in corneal wound healing.
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