On metabolic cage data analysis, there were 1,242 nocturnal voids (146 cage cycles, 7 time points). Volume per void was immediately reduced after irradiation. There was 28% (5/18) mortality from radiation proctitis (day 28-51). Following injection, survival of cells was confirmed by luciferase bioluminescence imaging. Nocturnal mean voided volume was partially improved in 20Gy-pSMC rats at 2-weeks after injection. After pSMC injection (day 51-81), there was normalization in number of voids (r=-0.032, p=0.892), total urine production (r=0.012, p=0.960) and stool output (r=-0.149, p=0.531). On multivariate linear regression (Table 1), after adjusting for covariates (water intake, total urine output, rat weight, stool output), there was a reduction in volume per void after vehicle injection (p<0.05, ref 0Gy), and partial improvement after pSMC injection (p=0.1864, ref 0Gy). Using a least squares (LS) estimate, mean voided volume was noted to partially normalize following pSMC treatment [LS-means: 0.50mL (0Gy), 0.42mL (20Gy-Vehicle), 0.45mL (20Gy-pSMC)].
On bladder cystometry data analysis, irradiation resulted in poor voiding efficiency (VE<15%) in 100% (4/4) of vehicle rats. The majority (67%, 4/6) of non-irradiated bladders had efficient voids (VE>20%). Improved voiding (VE>30%) was noted in 80% (4/5) of rats at 4-weeks after pSMC injection (day 81).
On organ bath myography analysis at day 81; there were 19 rats with 44 bladder strips (2-4 strips per rat), used to generate 660 maximum tension data points (total) as a result of 4 stimulation tests [electrical field stimulation (EFS) duration response (1 and 10 second), EFS frequency response (2, 8, 32 and 64 Hz), KCL dose response (100 and 200 mM), and carbachol dose response (0.01, 0.1, 1, 10, 20 µM]. On EFS of all rats, not excluding animals who died prior to day 81, the 1 and 10 second frequency response tension generated was increased at 32 and 64 Hz in pSMC treated animals (versus 0 Gy and 20Gy-Vehicle).
On organ bath myography analysis at 81+ days after radiation and 28+ days after injection, after excluding rats who did not survive to 81 days (3 pSMC rats died prior to 81 days due to radiation proctitis), our final group of rats subject to analysis were 0Gy (n=6), 20Gy-Vehicle (n=4), and 20Gy-pSMC (n=5). From this group, again an increase in tension generated (grams) is noted after pSMC treatment at 1 and 10 second EFS duration response. Sustained increase in contractility is noted at 64Hz [mean tension 1.21g (20Gy-pSMC) vs. 0.84g (0Gy), ANOVA p=0.12], however was not statistically significant as a result of the small number of animals per group and high morbidity as a result of radiation proctitis (Figure 1). Similarly pSMC partially improved potassium-chloride (KCL) response (100-200mM), however was not statistically significant. Radiotherapy weakened carbachol response in all tissues regardless of treatment, and anterior bladder contractility to carbachol was more impaired in 20Gy-Vehicle rats than pSMC rats.