Peptide Amphiphile Nanofiber Delivery of Sonic Hedgehog Protein to Reduce Smooth Muscle Apoptosis in the Penis after Cavernous Nerve Resection

Abstract

Erectile dysfunction (ED) is a serious medical condition that affects 16-82% of prostate cancer patients treated by radical prostatectomy and current treatments are ineffective in 50-60% of prostatectomy patients. The reduced efficacy of treatments makes novel therapeutic approaches to treat ED essential. The secreted protein Sonic hedgehog (SHH) is a critical regulator of penile smooth muscle and apoptosis that is decreased in cavernous nerve (CN) injury and diabetic ED models. Past studies using Affi-Gel beads have shown SHH protein to be effective in suppressing apoptosis caused by CN injury. We hypothesize that SHH protein delivered via novel peptide amphiphile (PA) nanofibers will be effective in suppressing CN injury-induced apoptosis. Adult Sprague Dawley rats (n=50) were used to optimize PA injection in vivo. PA with SHH protein (n=16) or bovine serum albumin (BSA) (control, n=14) was injected into adult rats that underwent bilateral CN cut. Rats were sacrificed at 2, 4, and 7 days. Alexa Fluor-labeled SHH protein was used to determine the target of SHH signaling (n=3). Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and semiquantitative immunohistochemical analysis for SHH protein and cluster differentiation protein three (CD3) were performed. SHH-PA caused a 25% and 16% reduction in apoptosis at 4 and 7 days after CN injury and a 9.3% and 19% increase in SHH protein at 4 and 7 days after CN injury. CD3 protein was not observed in SHH-PA-treated penis. In vitro, 73% of SHH protein diffused from PA within 6 days. Labeled SHH was observed in smooth muscle. PA technology is effective in delivering SHH protein to the penis and SHH is effective in suppressing CN injury-induced apoptosis. These results suggest substantial translational potential of this methodology and show that only a short duration of SHH treatment is required to impact the apoptotic index.