(061) Analysis of BMP4 and GREM1 as Targets of SHH Signaling and Downstream Regulators of the Collagen Axis in the Penis

Abstract

Abstract Introduction Cavernous nerve (CN) injury caused by prostatectomy and diabetes, initiates a remodeling process (smooth muscle apoptosis and increased collagen) in the corpora cavernosa of the penis of patients and animal models that is an underlying cause of erectile dysfunction (ED). The Sonic hedgehog (SHH) pathway plays an essential role in the response of the penis to denervation, as collagen increases with SHH inhibition and decreases with SHH treatment. Part of the mechanism of how SHH impacts collagen may involve bone morphogenetic protein four (BMP4) and GREMLIN (GREM1). Microarray analysis identified increased GREM1 (BMP4 antagonist) in corpora cavernosa of ED patients and SHH is a regulator of GREM1 in the limb bud. Objective We will examine the relationship between SHH, BMP4, GREM1 and collagen in penis of ED patients and rat models of CN injury, SHH inhibition, and SHH, BMP4 and GREM1 treatment. Methods Corpora cavernosa of Peyronie’s (control), prostatectomy and diabetic ED patients was obtained (n=26). Adult Sprague Dawley rats (n=90) underwent either: 1. CN crush (1-7 days) or sham control, 2. CN injury and BMP4, GREM1 or MSA (control) protein treatment via Affi-Gel beads or peptide amphiphile (PA) for 14 days, 3. 5E1 SHH inhibitor, IgG and PBS (controls), or SHH protein treatment for 2-4 days. Immunohistochemical and western analysis for BMP-4 and GREM1, and collagen analysis by hydroxyproline and trichrome stain were performed. Results BMP4 and GREM1 proteins were identified in corpora cavernosal smooth muscle of prostatectomy, diabetic and Peyronie’s patients, and in rat penis, sympathetic nerve fibers, perineurium, blood vessels, and urethra. Collagen decreased 25.4% in rats with CN injury and BMP4 PA treatment (p=0.02) and increased 61.3% with CN injury and GREM1 treatment (p=0.005). Trichrome showed increased collagen in rats treated with GREM1. BMP4 increased smooth muscle. Western identified increased BMP4 and GREM1 in corpora cavernosa of prostatectomy and diabetic patients, and after CN injury (1-2 days) in our rat model. Localization of BMP4 and GREM1 changed with SHH inhibition. SHH treatment increased BMP4 and GREM1. Aging did not impact BMP4 and GREM1 localization. Conclusions BMP4 and GREM1 are downstream targets of SHH that impact collagen and may be useful in collaboration with SHH to prevent penile remodeling and ED. Better understanding of penile remodeling and how fibrosis occurs is essential for development of novel therapies for ED. Disclosure No.