Ex Vivo Radiation Leads to Opposing Neurite Growth in Whole Ganglia vs Dissociated Cultured Pelvic Neurons

In vitro high glucose increases apoptosis, decreases nerve outgrowth, and promotes survival of sympathetic pelvic neurons

Background

Diabetes mellitus (DM) is a common cause of erectile dysfunction (ED), yet the molecular basis of DM neurogenic ED remains unknown.

Aim

In this study we examined the impact of high glucose on survival and growth of primary cultured pelvic neurons in a rat model and assessed whether coculturing with healthy Schwann cells (SCs) can rescue pelvic neuron growth in patients with DM.

Methods

Major pelvic ganglia (MPGs) from adult male Sprague Dawley rats (n = 8) were dissociated and plated on coverslips. Neurons were exposed to high glucose (45 mM) for 24 or 48 hours and compared to time-matched controls (25 mM). Neurons were stained for neuron-specific beta-tubulin, neuronal nitric oxide synthase, vesicular acetylcholine transferase, tyrosine hydroxylase, and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling) assay. Schwann cells were dissociated from MPGs of healthy male Sprague Dawley rats (n = 4) and grown to confluence. Additional Sprague Dawley rats were made diabetic with streptozotocin (50 mg/kg, n = 4), and 5 weeks later MPGs were collected from these rats, dissociated, and cocultured on healthy SCs. Neurons and SCs were stained with beta-tubulin and S100.

Outcomes

Length, branching, and survival of nitrergic, parasympathetic, and sympathetic neurons was assessed in neurons exposed to normal or high glucose concentrations, and neuron length was measured in neuron-SC coculture.

Results

The total number of neurons and the length and number of branches were significantly decreased after 24 and 48 hours of high glucose (P < .05). The percentage of nitrergic neurons decreased 10% after 24 hours and 50% after 48 hours of high glucose (P < .05). After 24 hours of high glucose, cholinergic-positive neurons were unchanged; however, these neurons decreased 30% after 48 hours (P < .05). The proportion of sympathetic neurons increased 25% after 48 hours of high glucose (P < .05). At both timepoints, there was a 2-fold increase in the total apoptotic neurons with high glucose (P < .05). Neurite outgrowth recovered to control lengths after coculture of diabetic neurons with healthy SCs (P < .05).

Clinical Translation

Glucose can be used as a tool to investigate the direct effects of DM on neuritogenesis. Our data suggest that an effective treatment for DM ED protects and repairs the penile neuronal supply.

Strengths and Limitations

Exposing MPG neurons to high glucose offers a quick and, inexpensive proxy for DM-related conditions. A limitation of our study is that our model reflects type 1 DM, whereas clinically, most diabetic ED patients have type 2 DM.

Conclusion

Culturing pelvic neurons in high glucose can be used as a tool to elucidate how to protect proerectile neurons from cell death and may lead to new therapeutic strategies for diabetic men suffering from ED.

Immunohistochemical Investigation of Autonomic and Sensory Innervation of Anterior Vaginal Wall Female Periurethral Tissue: A Study of the Surgical Field of Mid-Urethral Sling Surgery Using Cadaveric Simulation

BACKGROUND

Female sexual dysfunction, including female orgasm disorder, has been reported following mid-urethral sling (MUS) surgery to treat bothersome stress urinary incontinence. Anterior vaginal wall-female periurethral tissue (AVW-FPT) likely contains autonomic and sensory innervation involved in the female sexual response, and injury to these nerves may result from MUS implantation.

AIM

To characterize, using fresh cadaveric tissue, autonomic and sensory nerves in AVW- FPT using immunohistochemistry (IHC), and to assess their proximity to an implanted MUS.

METHODS

AVW-FPT was excised following careful dissection from four fresh cadavers. Prior to dissection, one cadaver underwent simulation of the MUS procedure by a urogynegologist, using a fascial sling. All samples were paraffin embedded, sectioned, and stained with hematoxylin. Serial sectioning and IHC were performed to identify nerves. IHC markers were used to characterize the sensory and autonomic innervation.

OUTCOMES

IHC localization of autonomic and sensory nerve markers consistent with neural tissue within the region of MUS implantation.

RESULTS

IHC of AVW-FPT using protein gene product 9.5 (PGP9.5), a general nerve stain, revealed innervation throughout the region targeted by the MUS implantation. More specifically, immunoreactivity for both autonomic (tyrosine hydroxylase, TH) and sensory (Na_v1.8 and S100ß) nerves were found in close proximity (<1 mm) to the implanted MUS. In addition, a subset of S100ß positive nerves also showed immunoreactivity for calcitonin gene-related peptide (CGRP). Combining the IHC findings with the surgical simulation of the MUS implantation revealed the potential for damage to both autonomic and sensory nerves as a direct result of the MUS procedure.

CLINICAL TRANSLATION

The identified autonomic and sensory nerves of the AVW-FPT may contribute to the female sexual response, and yet are potentially negatively impacted by MUS procedures. Given that surgeries performed on male genital tissue, including the prostate, may cause sexual dysfunction secondary to nerve damage, and that urologists routinely provide informed consent regarding this possibility, urogynaecologists are encouraged to obtain appropriate informed consent from prospective patients undergoing the MUS procedure.

STRENGTHS & LIMITATIONS

This is the first study to characterize the sensory and autonomic innervation within the surgical field of MUS implantation and demonstrate its relationship to an implanted MUS. The small sample size is a limitation of this study.

CONCLUSION

The present study provides evidence of potential injury to autonomic and sensory innervation of AVW-FPT as a consequence of MUS implantation, which may help explain the underlying mechanisms involved in the reported post-operative female sexual dysfunction in some women. Giovannetti O, Tomalty D, Gaudet D, et al. Immunohistochemical Investigation of Autonomic and Sensory Innervation of Anterior Vaginal Wall Female Periurethral Tissue: A Study of the Surgical Field of Mid-Urethral Sling Surgery Using Cadaveric Simulation. J Sex Med 2021;18:1168-1180.