Proliferative Vitreoretinopathy After Combat Ocular Trauma in Operation Iraqi Freedom and Operation Enduring Freedom: 2001-2011

Ligand-independent activation of platelet-derived growth factor receptor β promotes vitreous-induced contraction of retinal pigment epithelial cells

BACKGROUND

Epiretinal membranes in patients with proliferative vitreoretinopathy (PVR) consist of extracellular matrix and a number of cell types including retinal pigment epithelial (RPE) cells and fibroblasts, whose contraction causes retinal detachment. In RPE cells depletion of platelet-derived growth factor (PDGF) receptor (PDGFR)β suppresses vitreous-induced Akt activation, whereas in fibroblasts Akt activation through indirect activation of PDGFRα by growth factors outside the PDGF family (non-PDGFs) plays an essential role in experimental PVR. Whether non-PDGFs in the vitreous, however, were also able to activate PDGFRβ in RPE cells remained elusive.

METHODS

The CRISPR/Cas9 technology was utilized to edit a genomic PDGFRB locus in RPE cells derived from an epiretinal membrane (RPEM) from a patient with PVR, and a retroviral vector was used to express a truncated PDGFRβ short of a PDGF-binding domain in the RPEM cells lacking PDGFRβ. Western blot was employed to analyze expression of PDGFRβ and α-smooth muscle actin, and signaling events (p-PDGFRβ and p-Akt). Cellular assays (proliferation, migration and contraction) were also applied in this study.

RESULTS

Expression of a truncated PDGFRβ lacking a PDGF-binding domain in the RPEM cells whose PDGFRB gene has been silent using the CRISPR/Cas9 technology restores vitreous-induced Akt activation as well as cell proliferation, epithelial-mesenchymal transition, migration and contraction. In addition, we show that scavenging reactive oxygen species (ROS) with N-acetyl-cysteine and inhibiting Src family kinases (SFKs) with their specific inhibitor SU6656 blunt the vitreous-induced activation of the truncated PDGFRβ and Akt as well as the cellular events related to the PVR pathogenesis. These discoveries suggest that in RPE cells PDGFRβ can be activated indirectly by non-PDGFs in the vitreous via an intracellular pathway of ROS/SFKs to facilitate the development of PVR, thereby providing novel opportunities for PVR therapeutics.

CONCLUSION

The data shown here will improve our understanding of the mechanism by which PDGFRβ can be activated by non-PDGFs in the vitreous via an intracellular route of ROS/SFKs and provide a conceptual foundation for preventing PVR by inhibiting PDGFRβ transactivation (ligand-independent activation).

Aerosolized, Gas-Phase, Intravitreal Methotrexate Reduces Proliferative Vitreoretinopathy in a Randomized Trial in a Porcine Model

Purpose

To determine the effectiveness of aerosol-delivered methotrexate (AD-MTx) in a large-animal (porcine) model of proliferative vitreoretinopathy (PVR).

Design

Prospective, randomized, interventional, double-masked, controlled, large-animal study with predetermined clinical and histopathologic outcome criteria.

Controls

Half of the pigs were randomly assigned to receive an identical volume of aerosol-delivered normal saline (AD-NS) using identical delivery systems and treatment intervals.

Methods

Proliferative vitreoretinopathy was surgically induced in 16 pigs (8 males and 8 females), randomly assigned to receive 2 doses (group A) or 3 doses (group B) of either AD-MTx (1.6 mg/0.4 ml) or normal saline (AD-NS). Group A pigs were euthanized at week 2 (n = 8), and group B pigs were euthanized at week 3 (n = 8). Masked clinical PVR scores (0-6) by a vitreoretinal surgeon and histopathology PVR scores (0-8) by a masked ophthalmic pathologist were used to determine outcomes.

Main Outcome Measures

The mean, combined clinical and histopathology scores (both anterior and posterior) were used to determine the overall treatment effect between the groups.

Results

The mean masked score (± standard deviation) when all grading end points (clinical + histopathology) were combined was a mean of 8.0 ± 2.3 in the AD-MTx group versus a higher 9.9 ± 2.0 in the AD-NS control group (P = 0.05). The clinical score was 3.88 ± 1.2 in the AD-MTx group versus 4.63 ± 1.6 in the AD-NS group (P = 0.16). The histopathology score for anterior PVR was 2.5 ± 0.8 in the AD-MTx group versus 2.5 ± 0.5 in the AD-NS group (P = 0.50), and the posterior PVR was 1.63 ± 1.6 in the AD-MTx group versus 2.75 ± 1.3 in the AD-NS group (P = 0.07). When the frequency of methotrexate dosing in group A (2 doses) was compared with that in group B (3 doses), the mean score was 8.75 versus 9.13 (P = 0.38), respectively, suggesting an insignificant difference.

Conclusions

After surgical induction of PVR in an aggressive, high-risk, large-animal model, AD-MTx reduced posterior PVR formation compared with AD-NS. Additional dosing at week 3 did not improve the outcomes. No difference in anterior PVR formation was noted with intervention. This novel drug delivery system has implications for PVR reduction and warrants further investigation.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Risk Factors for Failure of Final Anatomic Surgical Reattachment in Retinal Detachments From Combat Ocular Trauma

BACKGROUND AND OBJECTIVE

The goal of this study was to determine the anatomic outcome of traumatic retinal detachment (RD) from combat ocular trauma.

MATERIALS AND METHODS

Retrospective study of patients sustaining a traumatic RD in Operation Iraqi Freedom and Operation Enduring Freedom who were evacuated to Walter Reed Army Medical Center from 2001 to 2011. The Fisher exact test, Wilcoxon rank sum test, and Agresti and Coull methods were used for analyses.

RESULTS

There were 143 eyes of 134 patients in which a traumatic RD developed, of a total of 890 eyes of 652 patients in the Walter Reed Ocular Trauma Database. Based on our results, predictors for failure to reattach the retina include maculaoff status (P = .0002), open-globe injury (P = .03), proliferative vitreoretinopathy postoperatively (P = .002), and presence of hyphema (P = .02). Intraocular foreign body and time to initial retinal surgery did not increase risk for failure. Thirty-four percent (34%) of eyes failed to be reattached.

CONCLUSIONS

Traumatic RD due to injury sustained in a combat zone resulted in poor prognosis, with 82.09% of eyes with RD having a best-corrected visual acuity worse than 20/200. The anatomic success of RD repair was shown to be 65.71%, likely owing to the severity of the injuries, concomitant systemic injuries, and delayed surgical intervention. [Ophthalmic Surg Lasers Imaging Retina 2022;53:493-501.].