Dr.Ramandeep Singh, S10100, Dr. Mangat R Dogra, Dr. Mohit Dogra
Polypoidal choroidal vasculopathy shares many similarities with exudative age-related macular degeneration (ARMD), including the presentation of serosanguineous maculopathy. How ever, the natural course of the PCV, its diverse features, its angiographic features and prognosis to treatment, are different form AMD. Its cause, pathogenesis, and relationship with AMD ares till not fully understood. It remains controversial as to whether PCV represents a subtype of neovascular age-related macular degeneration.
PCV is more common in non-white populations (including blacks, Hispanics, and Asians). The incidence of PCV in Chinese and Japanese patients in exudative AMD has been reported to be much higher than in Caucasians.
The presence of ocular angiogenesis is believed to be balance of factors that stimulate or inhibit new vessel formation. Vascular endothelial growth factor (VEGF) has been considered an important stimulus for choroidal neovascular membrane (CNVM) formation and persistence It has been found that VEGF levels are high in PCV eyes but they are certainly less than the eyes with CNV due to AMD, signifying different pathogenesis processes between these two entities. Pigment epithelium – derived factor was also found less in PCV eyes as compared to AMD-CNV eyes.
There are several other cytokines related to AMD pathogenesis including Platelet derived growth factors (PDGF), Placental growth factor (PIGF), Fibroblast growth factor (FGF), Endostatin, Angiogenic angigenin and Antiangiogenic thrombospondin 2 (THBS-2). PDGF is a potent chemo attractant and mitogen for both fibroblasts and retinal pigment epithelial cells. It has been shown to be diminished in AMD associated CNV, while PIGF as well as FGF, which contribute to an alternate pathway of neovascularization, were elevated in neovascular membranes. The antiangiogenic cytokine endostatin has been up regulated in CNV, whereas endostatin treatment inhibited CNV development. Potential roles of angiogenic angiogenin and THBS-2 remain unclear. The role of all above cytokines except VEGF is not known in the pathogenesis of PCV.
This study was done to analyze cytokine concentration of aqueous humor samples in PCV and AMD related CNV, and possibly to look for any role of these cytokines other than VEGF in the pathogenesis of PCV.
Methodology
It was a propective, comparative control study done in the retina clinic of department of Ophthalmology, PGIMER, Chandigarh. Diagnosis of all patients of PCV and AMD associated CNV was confirmed using ancillary investigation like fundus fluorescein angiography (FFA), Indocyanine angiography (ICG) and Optical coherence tomography (OCT). Informed consent was obtained from all participants after through discussion and full understanding on the benefits and risks of treatment and use of aqueous sample for analysis. Aqueous samples from senile cataract patients undergoing cataract surgery was collected as controls. The control group was age–matched with PCV and AMD group. Patients with other ocular disease such as glaucoma, high myopia, ocular ischemic syndrome and retinal diseases, or with systemic disease like diabetes mellitus were excluded.
We investigated aqueous levels of VEGF, Platelet derived growth factors (PDGF), Placental growth factor (PIGF), Fibroblast growth factor (FGF), Endostatin, Angiogenic angigenin and Antiangiogenic thrombospondin 2 (THBS-2) for all the consecutive patients with AMD associated CNV and PCV. Undiluted Aqueous samples was collected from the eyes of patients undergoing intravitreal injection of bevacizumab for above etiologies and it was At the beginning of intravitreal injection or cataract surgery, undiluted aqueous samples of 0.05 ml will be collected in sterile tubes, placed in liquid nitrogen and stored at -80 degree C until use. Aqueous or Vitreous sample will be analyzed for VEGF and other cytokines using commercial kits by flow cytometery.
Demographic characteristics of the patients were summarized by descriptive statistics by SPSS for windows version 10.1.0 (SPSS Inc, Chicao, Illinios, USA). Comparisons of mean cytokine concentrations were calculated using Student’s t-test.
Results:
At the end of 2 years, we enrolled 7 patients of idiopathic polypoidal choroidal vasculopathy (IPCV), 13 patients of choroidal neovascular membrane (CNVM) i.e in age-related macular degeneration (ARMD) and 15 control subjects in this pilot study. Results of the intraocular growth factors and cytokine analysis in aqueous fluid are given below:
CNVM involves higher levels of Angiopoeitin-2 as compared to IPCV:- We assessed the levels of angiopoietin-2 in aqueous humor of 7 subjects with IPCV, 13 subjects with CNVM and 15 control subjects using angiopoeitin-2 ELISA kit. The levels of angiopoeitin-2 were found to be statistically different among three groups (p=0.01). The levels were significantly higher in subjects with CNVM (68.79±9.73 pg/ml) as compared to control (42.71 ± 3.825 pg/ml) (p=0.03), whereas no significant difference was observed among IPCV as compared to control and CNVM as compared to IPCV group.
Higher levels of PDGF-AA in subjects with IPCV as compared to CNVM:– The levels of PDGF-AA were assessed in subject groups using ELISA and analysed for statistical difference as discussed earlier. A statistically significant difference was observed in levels of PDGF-AA among subject groups (p=0.036). The levels of PDGF-AA were found to be significantly higher in subjects with IPCV (152.3 ± 39.41 pg/ml, N=7) as compared to CNVM (85.38 ± 7.930 pg/ml, N=13) (p=0.04). We found the levels of PDGF-AA to be apparently lower in CNVM as compared to control subjects (p=0.051), whereas no significant difference was observed in levels of PDGF-AA among IPCV and control subject groups.
Lower levels of PDGF-BB in subjects with IPCV as compared to CNVM:– The ;;levels of PDGF-BB were found to be statistically different among subject groups(p=0.006). The levels were significantly lower in IPCV (20.05 ± 3.922 pg/ml, N=7) as compared to CNVM subject groups (49.99 ± 7.736 pg/ml, N=13) (p=0.014) and IPCV (20.05 ± 3.922 pg/ml, N=7) as compared to control subjects (39.63 ± 2.156 pg/ml, N=15) (p=0.0001). There was no significant difference in levels of PDGF-BB between CNVM and control subjects (p=0.18).
Lower levels of VEGF in subjects with IPCV as compared to CNVM:- The levels of VEGF were found to be significantly different among subject groups (p=0.0001). The levels of VEGF were significantly lower in subjects with IPCV (59.88 ± 11.86 pg/ml, N=7) as compared to CNVM (151.0 ± 21.74 pg/ml, N=13) (p=0.009). The levels were also significantly lower in IPCV (59.88 ± 11.86 pg/ml, N=7) as compared to control subjects (247.2 ± 26.27 pg/ml, N=15) (p=0.0001). Additionally the levels of VEGF were significantly lower in CNVM as compared to control subjects (p=0.01).
Lower levels of FGF in subjects with IPCV as compared to CNVM:- The levels of FGF were significantly different among subject groups (p=0.0069).The levels of FGF were found to be significantly lower in subjects with IPCV (66.18 ± 16.18 pg/ml, N=7) as compared to CNVM (168.4 ± 22.48 pg/ml, N=13) (p=0.006). Further the levels of FGF were significantly lower in IPCV (66.18 ± 16.18 pg/ml, N=7) as compared to control group (137.9 ± 15.40 N=15) (), but there was no significant difference in FGF levels among CNVM and control subjects.
Discussion and conclusions:
Lower levels of VEGF, FGF and angiopoeitin-2 was seen in subjects with IPCV as compared to AMD related CNVM, where as higher level of PDGF-AA and PDGF-BB was seen in IPCV as compared to AMD related CNVM. The different levels of factors in eyes of IPCV and ARMD associated CNVM might suggest distinct entities or different angiogenesis course between the two. Anti- VEGF treatment for IPCV may not be as effective for IPCV as for ARMD related CNVM.