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

ABSTRACT

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.

KEYWORDS:

• Vitreous VEGF
• intraocular VEGF
• luteinizing hormone
• vascular endothelial growth factor
• VEGF eye

Conflicts of Interest

Zietchick Research Institute (ZRI) is a private, (for-profit) research institute and Dr Tammy Movsas (Founder and Director of ZRI) has a pending patent application for the use of gonadotropin antagonists for the treatment of ocular diseases. Other than being a fulltime employee (ocular biochemist) at ZRI, Dr A Muthusamy has no other financial conflicts to report. Dr Robert Sigler is the Director of Unit Laboratory of Animal Medicine at University of Michigan and has no financial or other potential conflicts to report.

Additional information

Funding

This study was funded by NIH/NEI Grant No. R43EY026281-01 National Eye Institute [Grant No. R43EY026281-01].