The distribution of relaxin receptors in the anterior segment of primary open-angle glaucoma patients

Purpose: Relaxin is a polypeptide hormone produced by the corpus luteum and the decidua in females and by the prostate in males. It has vasodilatory and antifibrotic effects. In the past, it has been reported that injection of relaxin hormone has caused a reduction in the intraocular pressure although its mechanism has not yet been fully understood and the expression of relaxin receptors has not yet been evident in the human eye. Therefore, the purpose of this current study was to examine the presence of relaxin receptors in the human eye anterior segment. Methods: This is an interventional non-randomized study. Patients with primary open-angle glaucoma who underwent trabeculectomy were recruited. During the surgery, a punch biopsy (including the cornea, sclera, trabecular meshwork, and Schlemm's canal) was taken and stained with hematoxylin-eosin, and immunohistochemistry staining for relaxin/insulin-like family peptide receptor 1 (RXFP1). Results: A positive staining was noted for RXFP1 in the inner uveal, corneoscleral, and cribriform meshwork and Schlemm's canal's endothelium. Negative staining for RXFP1 was noted in the cornea and sclera. Conclusion: RXFP1 is present in the anterior segment drainage system of the human eye. Therefore, this receptor may have an active role in regulating the outflow facility and in the reduction of intraocular pressure.