Validation of Molecular and Genomic Biomarkers of Retinal Drug Efficacy: Use of Ocular Fluid Sampling to Evaluate VEGF

Vitreous Levels of Luteinizing Hormone and VEGF are Strongly Correlated in Healthy Mammalian Eyes

Purpose/Aim: Luteinizing hormone (LH) is known to function as a key regulator of vascular endothelial growth factor (VEGF) expression in reproductive organs. In recent years, LH has also been detected in human vitreous and LH receptors have been identified in human retina. This study was aimed to investigate a potential correlation between LH and VEGF levels in healthy mammalian eyes to provide supporting evidence of LH's potential involvement in intraocular VEGF regulation.

METHODS

18 bovine and 30 porcine eyes were procured from an abattoir and VEGF and LH levels were measured in the vitreous extracted from these eyes by commercially available bovine & porcine ELISA assay kits. Total protein of the vitreous was measured by using Micro BSA protein assay kit.

RESULTS

After total protein normalization, the Pearson Correlation Coefficients (PCC) showed a strong and significant correlation between LH and VEGF levels. (Bovine LH/VEGF PCC: 0.89, p < 0.001; Porcine LH/VEGF PCC: 0.80, p < 0.001). Linear regression analyses, adjusted for gender, showed significant linear relationships between LH and VEGF levels in both bovine and porcine vitreous. (Bovine: t-value = 7.69, p < 0.0001, adjusted r² = .79; Porcine: t-value = 6.71, p < 0.001, adjusted r² = .62) Conclusions: We show that VEGF and LH are strongly correlated in healthy, adult mammalian eyes. The robustness of the correlation is shown both by its strength of association and reproducibility in two species. Given that LH is well known to regulate VEGF levels in several tissue types, the LH/VEGF linear relationship in vitreous potentially implicates LH in homeostatic VEGF regulation of the eye. Because we also found that the correlation between LH and VEGF only became manifest when our targeted analytes were normalized by total amount of protein, preclinical and clinical investigators should consider normalizing analytes in vitreous by total protein when assessing potential correlations among them.

Angiofibrotic response to vascular endothelial growth factor inhibition in diabetic retinal detachment: report no. 1

OBJECTIVES To assess the effect of bevacizumab injection on connective tissue growth factor (CTGF) and vascular endothelial growth factor (VEGF) in the ocular fluids of patients with diabetic traction retinal detachment, and to determine whether intraoperative and postoperative complications are decreased in eyes given adjunctive preoperative bevacizumab injection. METHODS Twenty eyes of 19 patients were randomized to receive intravitreal bevacizumab or sham injection 3 to 7 days before vitrectomy for severe proliferative diabetic retinopathy. We collected aqueous samples before injection and at the time of vitrectomy and extracted undiluted vitreous samples. RESULTS Five eyes had decreased vascularization of membranes from preinjection to the time of vitrectomy (all in the bevacizumab treatment arm). Median visual acuities were 20/400 in control eyes at baseline and postoperative month 3 (POM3) and 8/200 in the bevacizumab-treated group at baseline and 20/100 at POM3 (P= .30 between control and bevacizumab-treated groups at POM3). All retinas were attached at POM3. Vitreous levels of VEGF were significantly lower in the bevacizumab group than in the control group (P= .03). Vitreous levels of CTGF were slightly lower in the bevacizumab group compared with the control group, but this difference was not statistically significant (P= .38). Levels of CTGF in the aqueous were strongly correlated with CTGF levels in the vitreous of controls (Spearman correlation coefficient, 0.95 [P< .001]). CONCLUSIONS Intravitreal bevacizumab injection reduces vitreous levels of VEGF and produces a clinically observable alteration in diabetic fibrovascular membranes. Ocular fluid levels of CTGF are not significantly affected within the week after VEGF inhibition. Retinal reattachment rates and visual acuity are not significantly altered by preoperative intravitreal bevacizumab injection at POM3. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01270542.