Burdzinska and associates (2018) noted that cell therapy constitutes an attractive alternative to treat SUI. Although promising results have been demonstrated in this field, the procedure requires further optimization. The most commonly proposed cell types for intra-urethral injections are muscle derived cells (MDCs) and mesenchymal stem/stromal cell (MSCs). These investigators evaluated the effects of MDC-MSC co-transplantation into the urethra. Autologous transplantation of labeled MDCs, bone marrow MSCs or co-transplantation of MDC-MSC were performed in aged multi-parous female goats (n = 6 in each group). The mean number of cells injected per animal was 29.6 × 106(± 4.3 × 106); phosphate-buffered saline (PBS)-injected animals constituted the control group (n = 5). Each animal underwent urethral pressure profile (UPP) measurements before and after the injection procedure. The maximal urethral closure pressure (MUCP) and functional area (FA) of UPPs were calculated. The urethras were collected at the 28th or the 84th day after transplantation. The marker fluorochrome (DID) was visualized and quantified using in-vivo imaging system in whole explants. Myogenic differentiation of the graft was immunohistochemically evaluated. The grafted cells were identified in all urethras collected at day 28 regardless of injected cell type. At this time-point the strongest DID-derived signal (normalized to the number of injected cells) was noted in the co-transplanted group. There was a distinct decline in signal intensity between day 28 and day 84 in all types of transplantation. Both MSCs and MDCs contributed to striated muscle formation if transplanted directly to the external urethral sphincter. In the MSC group those events were rare. If cells were injected into the submucosal region they remained undifferentiated usually packed in clearly distinguishable depots. The mean increase in MUCP after transplantation in comparison to the pre-transplantation state in the MDC, MSC and MDC-MSC groups was 12.3 % (± 11.2 %, not significant (ns)), 8.2 % (± 9.6 %, ns) and 24.1 % (± 3.1 %, p = 0.02), respectively. The mean increase in FA after transplantation in the MDC, MSC and MDC-MSC groups amounted to 17.8 % (± 15.4 %, ns), 15.2 % (± 12.9 %, ns) and 17.8 % (± 2.5%, p = 0.04), respectively. The authors concluded that the findings of this study suggested that MDC-MSC co-transplantation provided a greater chance of improvement in urethral closure than transplantation of each population alone.