Shigeo Tamiya

Myofibroblasts derived from retinal pigment epithelial (RPE) cells play a key role in the pathogenesis of retinal fibrotic conditions such as proliferative vitreoretinopathy (PVR). Upon exposure to growth factors and cytokines such as TNF-α and TGF-β (TNT), RPE cells undergo epithelial-mesenchymal transition and subsequent transdifferentiation to contractile myofibroblasts. In this study, the effects of JD5037, a peripherally restricted CB1 antagonist, on myofibroblast transdifferentiation of primary cultures of human RPE cells were assessed. JD5037 significantly reduced TNT-induced, RPE cell-mediated collagen gel contraction, an indicator of myofibroblast function, in a concentration-dependent manner. Western blot analysis showed that JD5037 attenuated TNT-induced expression of α-SMA and fibronectin, two molecular markers of myofibroblasts. Furthermore, siRNA knockdown of CB1 cannabinoid receptor partially inhibited TNT-induced myofibroblast transdifferentation of human RPE cells and eliminated the inhibitory effects of JD5037 on myofibroblast transdifferentiation. These data demonstrate, for the first time, that peripherally restricted antagonists, such as JD5037, targeting the CB1 cannabinoid receptor have therapeutic potential for PVR and other retinal fibrotic conditions.

Aberrant wound healing in the retina can manifest as proliferative vitreoretinopathy (PVR), which involves the myofibroblast transdifferentiation of retinal pigment epithelial (RPE) cells. In this study, experiments were conducted to examine the structure–activity relationships of endocannabinoid-like compounds, N-acyl dopamines, on the myofibroblast transdifferentiation of RPE cells. The collagen matrix contraction assay was used to assess myofibroblast function. Western blot analysis and immunocytochemistry techniques were used to evaluate myofibroblast markers. N-palmitoyl dopamine (PALDA), N-oleoyl dopamine (OLDA), and N-arachidonoyl dopamine (NADA), in a concentration-dependent manner, inhibited contraction of collagen matrices mediated by either primary porcine RPE cells treated with TGF-β2, or human RPE cells treated with TGF-β2 plus TNFα (TNT). The rank order of potency was PLDA = OLDA > NADA. In contrast, the substitution of dopamine with other polar head groups led to a complete loss of their ability to inhibit myofibroblast transdifferentiation. Western blot analysis demonstrated that PALDA, OLDA, and NADA down-regulated the myofibroblast markers fibronectin and α-SMA. Immunocytochemistry experiments showed that these N-acyl dopamines reduced the incorporation of α-SMA into F-actin stress fibers. Overall, these structure–activity relationship studies demonstrate that the dopamine head group is crucial for N-acyl dopamine to inhibit myofibroblast transdifferentiation of RPE cell, whereas the fatty acid side chain determines the potency of it. This study points to the potential of N-acyl dopamines as a novel class of therapeutic agents for treating retinal fibrotic conditions, such as PVR.

Purpose: Posterior ocular trauma and the subsequent fibrotic retinal complication termed proliferative vitreoretinopathy (PVR) are leading causes of blindness in children and young adults. A previous study suggested that changes occurring within the first month post-trauma can lead to development of PVR later. The aim of this study was to examine the effect of dasatinib, a tyrosine kinase inhibitor clinically used to treat chronic myeloid leukemia, on fibrotic changes occurring within the first month following ocular trauma. Methods: A previously established swine ocular trauma model that mimics both contusion and penetrating injuries was used. Dasatinib was administered on days 4 and 18 post-trauma via intravitreal injection of either bolus solution or suspension of a sustained release system incorporated in biodegradable poly (lactic-co-glycolic acid) (PLGA) nanoparticles. Animals were followed up to day 32, and the development of traction full-thickness fold in the posterior retina was assessed. Results: A full-thickness retinal fold extending from the wound site developed in 3 out of 4 control eyes injected with PLGA nanoparticles alone at 1 month. Administration of dasatinib solution had little preventative effect with 6 out of 7 eyes developing a fold. In contrast, dasatinib-incorporated PLGA nanoparticle injection significantly reduced the incidence of fold to 1 out of 10 eyes. Conclusions: Injection of dasatinib-incorporated PLGA significantly reduced early fibrotic retinal changes which eventually lead to PVR following posterior ocular trauma. Thus, our sustained dasatinib release system can potentially be used to both prevent and/or broaden the surgical treatment window for PVR.

The purpose of the present study was to evaluate the intraretinal migration of the retinal pigment epithelium (RPE) cells in age-related macular degeneration (AMD) using polarimetry. We evaluated 155 eyes at various AMD stages. Depolarized light images were computed using a polarization-sensitive scanning laser ophthalmoscope (PS-SLO), and the degree of polarization uniformity was calculated using polarization-sensitive optical coherence tomography (OCT). Each polarimetry image was compared with the corresponding autofluorescence (AF) images at 488 nm (SW-AF) and at 787 nm (NIR-AF). Intraretinal RPE migration was defined by the presence of depolarization at intraretinal hyperreflective foci on PS-SLO and PS-OCT images, and by the presence of hyper-AF on both NIR-AF and SW-AF images. RPE migration was detected in 52 of 155 eyes (33.5%) and was observed in drusenoid pigment epithelial detachment (PED) and serous PED with significantly higher frequencies than in other groups (P = 0.015). The volume of the migrated RPE cluster in serous PED was significantly correlated with the volume of the PED (R² = 0.26; P = 0.011). Overall, our results showed that intraretinal RPE migrations occurred in various AMD stages, and that they occurred more commonly in eyes with serous and drusenoid PED.

(2015). Risk factors and prevention of proliferative vitreoretinopathy. Expert Review of Ophthalmology: Vol. 10, No. 5, pp. 431-440. doi: 10.1586/17469899.2015.1090875