Stress urinary incontinence is the most common type of urinary incontinence. Actual standard therapeutic modalitie offer symptomatic relief without treating the underlying disorder. Therefore, we developed a novel technology to apply cells for recovery of the urethral sphincter by waterjet (WJ). Based on our previous study in cadaveric samples1, we investigated if a) porcine muscle−derived cells (pMDC) could be injected by WJ in living pig urethrae with high viability, b) the WJ inherits the risk of full tissue penetration of the urethra and thus loss of cells, and c) WJ grants improved precision of cell injection and distribution in tissues targeted.
The pMDC were produced from boars as described1, labeled by PKH26, injected in living female urethrae by WJ (Erbe) using either a moderate (E60−10; n = 18) or elevated pressure (E80−10; n = 6) protocol, and follow-up (f/u) of up to 7 days. Cell injections targeted the site of the maximum urethral closure pressure (Aquarius TT, Laborie Medical). After harvesting the whole bladder and urethra, cells were traced by In Vivo Imaging System (IVIS) and visualized by fluorescence microscopy of cryosections. Nuclei were stained by DAPI, muscular tissue by phalloidin-iFluor 488. The pSRY gene was detected by PCR. The distribution of injected pMDC was measured as X−depth, Y−width, Z−height and calculated areas in the XY-, YZ-, XZ- planes were analyzed. The injection depth of cells in the urethra was measured simultaneously.
We report that the success rates of WJ cell application in living animals were significantly higher (≥ 95%, n = 24) when compared to needle injections2. Only one out of six samples with full penetration was observed in the WJ E80−10group. pMDC kept intact appearing nuclei as stained by DAPI and cellular bodies co−localized as determined by phalloidin-iFluor 488 and PHK26 staining. Intact Y-chromosomes were confirmed by pSRY PCR. The analyses of the 3D distribution of cells after WJ injection documented that the Y−width of the WJ E80-10 group was statistically significant wider (P = 0.0479) than that of WJ E60-10 group. The same was recorded for cell distribution in Z-height (P < 0.0001). The YZ-plane of the WJ E80−10 group was statistically significant larger (P = 0.0005) than that of WJ E60-10group, as well as XZ-plane (P = 0.0204). The injection depth of WJ E80-10 compared to WJ E60-10 showed a statistically significant decrease in length (P < 0.0001). This indicated that WJ E80-10 injections transported cells closer to the targeted rhabdosphincter, but at a higher risk for full penetration.
We conclude that the novel WJ is a fast, precise, and easy-to-use innovative method to inject living cells in tissues with a significantly wider and diffuse distribution, with less disintegration of the tissue targeted, and at higher success rates. Future studies will investigate the feasibility of the WJ technology in a model of stress urinary incontinence3.
1 Geng et al. Proceedings of TERMIS 2021 abstract P_BF22 # 73, Maastricht.
2 Amend et al. Neurourol Urodyn. 36(7):1723-1733 (2017).
3 Kelp et al. World J Urol. 35:1977-1986 (2017).