Presentation Authors: Amy D. Dobberfuhl*, Mason A. Briggs, Shannon L. Wallace, Yan Wen, Yingying Zhou, Edward E. Graves, Edward C. Diaz, Susan J. Knox, Bertha Chen, Stanford, CA
Introduction: Adverse effects of radiation include urothelial hemorrhage and bladder fibrosis. Mesenchymal stem cells are known to promote tissue repair and inhibit inflammation. Our aim was to investigate the effect of intradetrusor iPSC-derived human progenitor smooth muscle cells (pSMC) in a rat model of radiation cystitis.
Methods: Twenty-four female Rowett nude rat bladders were irradiated on day 0 [n=6 (0Gy); n=18 (20Gy)]. On day 53, randomized-blinded intradetrusor injection was performed [n=5 (20Gy-Vehicle); n=8 (20Gy-pSMC)]. Nocturnal void volume was measured using metabolic cages biweekly (day 0-81). 4-weeks after injection (day 81), bladders were assessed by cystometry, organ bath and histology. Data were analyzed in SAS.
Results: 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=-0.03, p=0.892), total urine production (r=0.01, p=0.96) and stool output (r=-0.15, p=0.53). On multivariate linear regression, after adjusting for covariates (water intake, total urine output, rat weight, stool output), there was a reduction in voided volume after vehicle injection (p < 0.05, ref 0Gy), and partial improvement after pSMC injection (p=0.19, ref 0Gy) [LS-means: 0.50mL (0Gy), 0.42mL (20Gy-Vehicle), 0.45mL (20Gy-pSMC)]. On cystometry, 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 (day 81), irradiation weakened carbachol response in all tissues. pSMC bladder strips demonstrated partial improvement in potassium-chloride response (100-200mM) and sustained increase in electrical field stimulation contractility at 64Hz [mean tension 1.21g (20Gy-pSMC) vs. 0.84g (0Gy), p=0.12]. On histology, human nuclei colocalized with smoothelin, a marker of smooth muscle.
Conclusions: Following pelvic irradiation, pSMC intradetrusor injection partially improved ambulatory mean voided volume, cystometric voiding efficiency, potassium-chloride response and electrical field stimulation contractility.
Source of Funding: California Institute of Regenerative Medicine