Dwight E. Nelson

A Chronic, Conscious Large Animal Platform to Quantify Therapeutic Effects of Sacral Neuromodulation on Bladder Function

PURPOSE Sacral neuromodulation is a Food and Drug Administration approved therapy for urinary urge incontinence, urgency-frequency and fecal incontinence. Most preclinical studies have used anesthetized preparations in small animals. To expand the testing capabilities of sacral neuromodulation stimulation parameters and novel concepts we created a large animal model in fully conscious sheep. MATERIALS AND METHODS Six adult female sheep were tested weekly using 10 trials of single fill cystometry, similar to clinical urodynamics. Maximal bladder capacity was measured without (trials 1 to 5) and with (trials 6 to 10) sacral neuromodulation. A mixed effects regression model was used to analyze the effect of sacral neuromodulation on bladder capacity. RESULTS Acute sacral neuromodulation significantly increased bladder capacity in conscious female sheep from 75.2 to 118.7 ml, an almost 60% increase. This was not simply an effect of repeat cystometric trials since testing without sacral neuromodulation was not associated with an increase in bladder capacity. CONCLUSIONS These data demonstrate the effects of acute sacral neuromodulation on bladder capacity in the conscious sheep. This model represents a useful testing platform for novel sacral neuromodulation concepts such as alternate methods and parameters of therapy delivery.

Differentiation and interaction of tibial versus spinal nerve stimulation for micturition control in the rat.

To determine time course of the bladder inhibitory response to unilateral or bilateral stimulation of the tibial nerve (TN) and spinal nerve (SN) as well as the interaction of stimulation at these two sites.

Optimization of Neuromodulation for Bladder Control in a Rat Cystitis Model.

In a bladder overactivity model of cystitis induced by intravesical infusion of acetic acid (a.a.), several parameters of spinal nerve stimulation (SNS) were optimized using continuous infusion cystometry. The optimal stimulation was further characterized through measurements of urodynamic function using single‐fill cystometry.

AB291. SPR-18 Correlation of sacral nerve lead targeting and urological efficacy: motor mapping, electrode position, and stimulation amplitude

Objective Sacral neuromodulation (SNM) is a clinically used therapy for refractory urge frequency and incontinent patients. Using a recently developed sheep model, this preclinical study retrospectively evaluated the relationship between implanted sacral lead locations, motor threshold (MT) values, motor mapping, and acute urological efficacy to determine if acute location and physiological measurements are correlated. Methods Twelve female polypay sheep were implanted with bilateral InterStim® devices (Model 3058) connected to quadripolar leads (model 3889) placed in the S2-4 foramina with S3 as the ideal target. CT scans at post-op and ≥12 months later were used for 3D rendering using MedCAD points placed on the sacrum and lead contacts to compare coordinates across animals. Acute cystometry was performed to test responses to SNM (0.21 ms PW, 10 Hz) at maximum tolerable amplitude (MTA). MT values were obtained by visual identification of the first motor response and the motor reflex was mapped to an anatomical map. Results Sheep were categorized as responders (n=6; 50%) or non-responders (n=6; 50%) based on ≥50% increase in bladder capacity to acute SNM. There was a significant difference in motor mapping areas between responders (peri-anal contacts) and non-responders (activation of leg) (chi-square; P<0.05). Higher MTA values correlated with larger bladder capacity increases (Pearson correlation; P<0.05). Contact position correlated with urological response (ANOVA; P<0.05). A generalized Procrustes analysis on the 17 leads in S3 (remainder in S2 or S4) showed variability of distributions was higher in distal contacts (0 & 1, mean distance to center 7.3±1.8 mm, left & 6.8±1.3 mm, right) than proximal (2 & 3, mean distance to center 5.8±0.86 mm, left & 4.3±0.35 mm, right (ANOVA; alpha =0.05; F(3,64) =20.55; P<0.0001). Conclusions (I) Responder sheep showed motor responses in peri-anal areas significantly more often than non-responders; (II) MTA weakly correlated with increased bladder capacity; (III) activation of lead contacts proximal to the sacral foramen produced more reliable urological results than did activation of distal contacts. These results suggest well-positioned leads will elicit specific responses that could be essential to effective SNM therapy. Future work will characterize changes over time to provide a temporal correlation of this relationship. Funding Source(s) Medtronic

MP26-02 DIFFERENTIAL RESPONSIVENESS TO NEUROSTIMULATION ACROSS THE BLADDER FILLING CYCLE IN RODENTS

mRNA expression profiles associated with different states of BOOinduced LUTD in human patients. Animal models of experimentallyinduced partial BOO are widely used to study bladder wall remodeling. Here we determined the expression profiles of miRNAs and selected mRNAs in pBOO mice and compared the observed changes to human patients. METHODS: All experiments were performed using 10-to-12week-old male mice that underwent microsurgical creation of pBOO and sham-operated control animals. Bladders were harvested 2, 4, 6 and 8 weeks after pBOO and total RNA isolated. Muscle contractility was assessed in parallel cohorts at 1, 2, 4 and 6 weeks. Expression profiles of 598 miRNAs were established using NanoString nCounter Analysis System mouse miRNA assay kit. Levels of selected mouse mRNAs were determined by QPCR. Bladder dome biopsies were collected from controls and patients with urodynamically established BOO and miRNA and mRNA expression profiles determined by Next Generation Sequencing (NGS) analysis. RESULTS: Similar to human patients0 results, we observed a down-regulation of smooth muscle-associated miRNAs mmu-miR-1, mmu-miR-143, mmu-miR-145, mmu-miR-486 and mmu-miR-133a in pBOO mouse bladders. Pro-fibrotic mmu-miR-142-3p and mmumiR-21 were up-regulated, and anti-fibrotic mmu-miR-29c downregulated. Surprisingly, the expression levels of other miRNAs including miR-22, -26b, -10a and -342-3p, which were strongly regulated in human BOO patients, did not change in the mouse model. Pathway analysis in human BOO patients identified TNFalpha as the top upstream regulator, and revealed signalling molecules, including MYC, FOS, CTGF, PIK3R5, which were strongly induced in different urodynamic states of BOO. In pBOO mice there was evidence of hypertrophic changes (MYBL2, MYH11 and MYC up-regulation) at 2 weeks pBOO, and CTGF was significantly increased at 4 and 6 weeks post-obstruction. Contrary to human data, we observed no regulation of TNF-responsive genes in the mouse model. CONCLUSIONS: Experimentally-induced pBOO in mice led to significant gene expression changes, including alteration of pro-fibrotic mRNAs and miRNAs resembling human BOO patients. Lack of evidence of TNF-alpha-induced miRNA and mRNA regulation might indicate a different pathophysiological mechanism of organ remodelling in pBOO model compared to human disease.

Screening and Optimization of Nerve Targets and Parameters Reveals Inhibitory Effect of Pudendal Stimulation on Rat Bladder Hypersensitivity.

Background and Objectives Neuromodulation has been reported to reliably improve symptoms of bladder overactivity and sometimes pain. The effect of electrical stimulation of several nerve pathways demonstrated to alter cystometric responses to bladder distension was examined on nociceptive responses in models of bladder hypersensitivity. Methods Bladder hypersensitivity was produced by several published methods including neonatal inflammation, acute inflammation, and chronic stress. Effects of different sites of stimulation (L6 and T13 nerve roots, proximal and distal pudendal nerves [PNs]) on nociceptive reflex responses to urinary bladder distension in urethane-anesthetized female rats were assessed and a parametric analysis of parameters of stimulation was performed. Results Bilateral biphasic stimulation of the proximal PNs resulted in statistically significant inhibition of visceromotor and cardiovascular responses to bladder distension in rats made hypersensitive by neonatal bladder inflammation. We found a range of optimal stimulation frequencies (5–10 Hz) which produced robust inhibitory effects when using short pulse widths (100–240 &mgr;s). Onset of inhibition was within minutes and persisted for several minutes after the stimulus was discontinued. Use of bilateral PN stimulation in acute inflammation and stress-induced hypersensitivity models as well as unilateral stimulation, very distal PN cutaneous branch stimulation, and stimulation of the T13 and L6 nerve roots all proved ineffective with the parameters used. Conclusions This study suggests that inhibitory effects of bilateral PN stimulation can be evoked in a rodent hypersensitivity model at relatively low frequencies with short pulse widths. The onset of effect is rapid, which suggests the potential for treating episodic pain in painful bladder disorders.

Differentiation of Bilateral Neuromodulation for Bladder Control Using a Preclinical Model

Therapy,applies electrical stimulation unilaterally to the sacral spinal nerve(SN, S3) as an established clinical treatment modality forpatients with overactive bladder [1]. Scheepens and colleagues [2]reported that bilateral stimulation was superior to unilateral sacralneuromodulation in only 2 out of 25 patients. Retrospective stud-ies, however, have also suggested that patients receiving bilateralstimulation are more likely to show a significant symptomaticimprovement [3–5]. Preclinical testing is consistent with thisclinical finding. Bilateral stimulation results in a stronger bladderinhibition than unilateral stimulation when tested in cats [6,7] andpigs [8].In the present study we attempt to define and characterizeresponses to several forms of bilateral SN neuromodulation usingend-points related to bladder control. We characterize the effec-tiveness of three stimulation modalities: 1) bilateral stimulationwith phase-matched individual pulses, 2) bilateral stimulationwith phase-mismatched pulses, and 3) unilateral stimulation of asingle SN root sequentially with stimulation of the alternate side.For all testing stimulation was applied at a fixed frequency of10 Hz which has been shown to be optimal for inhibition of blad-der contractions in the rat using both low and high intensity stimu-lation [9].