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C. Mayo, M. A. Stepp, V. Trinkaus-Randall; The Role of the P2X7 Receptor in Corneal Wound Healing. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3476.
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P2X receptors are ligand gated ion channels implicated in both apoptosis and cell proliferation. The elongated C-terminus of the P2X7 receptor allows it to form a large non-specific pore as well as act as a cationic channel. This function allows for blebbing of the membrane and uptake of larger molecules by the cell. Corneal epithelial cells express P2X receptors 4, 5 and 7 and respond to BzATP, a P2X7 specific agonist. The purpose of this study is to determine the role of the P2X7 receptor in corneal epithelial cell migration and repair.
A transformed human corneal epithelial cell line (HCET) and P2X 7 knock out mice were used. In calcium studies, cells were stimulated with BzATP in the presence or absence of extracellular calcium and magnesium using a flow through apparatus and imaged on a Zeiss LSM510. Migration was monitored using Transwell migration chambers or a scratch wound assay. Apoptosis and cell viability was assessed after BzATP treatment. Wounding of P2X7-/- and WT mice corneas was performed using a 1.5 mm trephine and wound area was measured after 16 hours. The corneas were removed for analysis.
Treatment of HCETs with BzATP induced the mobilization of calcium which was inhibited by the removal of extracellular calcium and enhanced by the removal of extracellular magnesium. This behavior is indicative of the P2X7 receptor. Treatment of HCETs with BzATP caused increased migration compared to non-treated cells in both transwell and scratch wound migration studies. Neither apoptosis nor blebbing was observed following BzATP application. Measurements of wounded mice corneas showed that the average wild type wound area was 23% smaller than that of P2X7 knock out mice.
These results indicate that the P2X7 receptor plays a role in the wound healing process of corneal epithelial cells. The calcium results provide evidence that treatment with BzATP is specifically activating P2X7 receptors. Both migration assays and mice models show that the P2X7 receptor acts to increase cell migration and wound healing.
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