Duration 5min, Q&A 3min
In Vivo Evaluation of Intravitreally Delivered Connexin43 Mimetic Peptide in Reducing Retinal Ganglion Cell Loss and Vessel Leak after Retinal Ischemia
Recent research has shown that transient block of connexin43 (Cx43) hemichannels by mimetic peptides (MP) after retinal ischemia may inhibit uncontrolled hemichannel opening that causes blood-brain barrier permeability and endothelial cell loss, and may provide improved retinal ganglion cell (RGC) survival. However, the highly hydrophilic character and poor stability of these molecules can limit efficient delivery in a clinical setting. The present study investigated the ability of intravitreally applied modified Cx43 MP and Cx43 MP containing slow-release PLGA micro- (Mps) and nanoparticles (Nps) to promote RGC survival in a retinal ischemia-reperfusion rat model.
Chemically modified Cx43 MP were synthesized by BOC chemistry and PLGA Mps and Nps were prepared using the double emulsion solvent evaporation method. For in vivo efficacy studies, a total of 121 adult male Wistar rats weighing 200 to 300 g were obtained from the Vernon Jenson Unit at the University of Auckland.
Retinal ischemia was created in the left eye (120 mmHg for 60 min) and Cx43 MP formulations were injected intravitreally immediately after reperfusion. Evan's blue dye was injected intraperitoneally 4 h after reperfusion to visualize vessel leak using confocal microscopy. Retinal whole mounts were collected at predetermined time points and Cx43 and RGC densities were quantified. All procedures were compliant with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research.
Results and Conclusion
Intravitreally injected native and modified Cx43 MP appeared to effectively minimize vessel leak, reduce upregulation of Cx43 expression and hence rescue RGC after the ischemic injury. The modified Cx43 MP showed the most promising results in reducing Cx43 expression down to control levels and sparing 93% of RGC due to increased lipophilicity and vitreous stability. This effect lasted at least four weeks, suggesting that this technique may be a clinically relevant neuroprotective tool in the treatment of glaucomatous optic neuropathy. Cx43 MP loaded Nps and Mps displayed a delayed effect on Cx43 regulation and RGC preservation. A combination of both immediate and sustained delivery of Cx43 MP may thus be ideal to achieve optimal RGC survival after an ischemic insult.
[ Keyword ]
connexin43 / mimetic peptide / retinal ischemia / micro-/nanoparticles
[ Conflict of Interest ]