In recent conflicts, explosions have been the most common cause of open- and closed-globe eye injury, particularly from improvised explosive devices. These injuries cause damage to the corneal endothelium, a non-proliferative monolayer of cells on the posterior layer of the cornea that regulates corneal clarity. The injury may not initially affect vision because the corneal endothelium has a “reserve” capacity to withstand 80% damage yet still retain function. However, the initial corneal endothelial cell (CEnC) loss can become significant later in life, when additional CEnCs are lost during cataract (high energy ultrasound phacoemulsification) and glaucoma surgery, conditions associated with both age and prior trauma with a high prevalence in the Veteran population. Corneal opacification due to CEnC loss can only be corrected with corneal transplantation and is a significant problem for both Veterans and civilians. This amplifies the need to identify sources of CEnC loss and to minimize cell loss in these circumstances. There is minimal data on how trauma causes CEnC loss. Preliminary data with post mortem human eyes show that CEnC injury from acoustic blast overpressure exposure is not from immediate disruption of cell membranes, but from subsequent cellular and metabolic injury. This provides a window of opportunity to intervene and rescue the injured cells. The objectives of this study are to determine the signature of corneal endothelial damage from blast exposure in comparison to iatrogenic CEnC loss and to determine if available pharmacologic therapeutics being studied for corneal endothelial cell loss can be used to mitigate the damage to corneal endothelium suffered from blast injury. The overall hypothesis tested in this study is that the mechanisms of corneal endothelial trauma from blast exposure are similar to that from iatrogenic trauma from phacoemulsification and similar therapeutics will prove to be beneficial for both conditions. This hypothesis is tested in three specific aims. All studies are performed in fresh paired human post-mortem eyes where one eye serves as control and the other is exposed to the experimental intervention. Aim 1 is to decipher the extent and mechanisms of corneal endothelial injury following blast exposure. Eyes will be subject to blast injury from a shock tube device to generate acoustic blast overpressure exposure. The corneal endothelium will be assessed immediately following trauma and at 3 days and 3 weeks following organ culture of the corneas to study the injury and healing response. Samples will be analyzed for cell damage, death, proliferation, oxidative damage, and metabolism. Aim 2 is to compare the mechanisms of corneal endothelial injury following blast exposure with corneal endothelial injury following cataract and glaucoma surgical procedures. For these assays, eyes will be subject to phacoemulsification damage or tube shunt insertion. Corneas will be analyzed with the same assays as specific aim 1 for comparison to the effects from blast exposure. Aim 3 is to determine the effectiveness of pharmacologic treatment for corneal endothelial injury following blast exposure and phacoemulsification injury with rho kinase inhibitors (to enhance corneal endothelial wound healing), N-acetylcysteine (to reduce oxidative damage), and ubiquinol (to support mitochondrial metabolism). In these studies, both eyes of a pair will be subject to trauma by blast exposure or phacoemulsification. One eye will receive pharmacologic intervention and both eyes will be compared for healing response focusing on the primary outcome of endothelial cell density. Successful completion of the proposed studies will provide knowledge on the cellular and molecular signature of blast overpressure injury on the human corneal endothelium, how it relates to common iatrogenic corneal endothelial injuries, and the therapeutic response to drugs. These data will have significant implications for the acute phase treatment of the corneal endothelium following blast or phacoemulsification injury. In addition to benefiting military personnel who suffer blast trauma, these findings will benefit many Veterans undergoing complex phacoemulsification cataract surgery by reducing the burden of blindness from CEnC loss.
