Thaddeus S. Brink

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.

Real-Time Changes in Brain Activity during Sacral Neuromodulation for Overactive Bladder

Purpose: We performed functional magnetic resonance imaging to identify changes in brain activity during sacral neuromodulation in women with overactive bladder who were responsive to therapy. Materials and Methods: Women recruited into the study had nonneurogenic refractory overactive bladder, responded to sacral neuromodulation and had had a stable program for at least 3 months with no subsequent overactive bladder treatment. Enrolled patients completed validated symptom and quality of life instruments before functional magnetic resonance imaging. Stimulus settings were recorded, devices were switched off for a 5‐day washout and instruments were repeated. Three functional magnetic resonance imaging scans with simultaneous sacral neuromodulation stimulation were performed below, at and above stimulus sensory threshold using a block design. This yielded brain activity maps represented by changes in blood oxygenation level dependence. A total of 5 stimulator off and 4 stimulator on cycles of 42 seconds each were imaged. Group analysis was done using a single voxel p value of 0.05 with a false‐positive error of 0.05 on cluster analysis. Results: Six of the 13 patients enrolled completed functional magnetic resonance imaging. Median age was 52 years (range 36 to 64). Urinary symptoms and voiding diary data worsened with washout. Overall brain activation generally progressed with increasing stimulation amplitude. However, activation of the right inferior frontal gyrus remained stable while deactivation of the pons and the periacqueductal gray matter only occurred with subsensory stimulation. Sensory stimulation activated the insula but deactivated the medial and superior parietal lobes. Suprasensory stimulation activated multiple structures and the expected S3 somatosensory region. All devices had normal impedance after functional magnetic resonance imaging. Conclusions: Functional magnetic resonance imaging confirmed that sacral neuromodulation influences brain activity in women with overactive bladder who responded to therapy. These changes varied with stimulus intensity.

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.