Urinary incontinence is a common disease affecting about 8% of worldwide population. Stress urinary incontinence (SUI), caused by intrinsic sphincter deficiency or hypermobility of the urethra, represents approximately 50% of the cases. Urinary incontinence, and especially SUI, have detrimental effects on women quality of life but also on sexual functions.  
Mid-urethral slings (MUS) is the standard treatment for women with SUI refractory to intensive pelvic floor muscle training. A majority of MUS are synthetic surgical mesh materials composed of polypropylene. Although clinical efficacy of MUS has long been demonstrated, recent warnings from scientific societies and regulatory agencies in various countries led to recall some mesh products used in pelvic organ prolapsus surgery. Infection, chronic pain and erosions are the main complications reported for MUS and are likely to be associated with the synthetic material used. 
In light of these findings, biological mesh materials have been proposed for SUI and pelvic prolapsus management in order to reduce these adverse events. Biological materials, such as autologous fascial slings, have been proven efficient and safe in the management of SUI. However, heterologous materials still lack high level clinical evidence especially for SUI surgical management. Moreover, the biomechanical properties of these materials have to be well understood in order to propose our patients the best care. 
The human umbilical vein has shown advantage of the longitudinal mechanical properties to use it as a scaffold material. Umbilical vessel slings (UVS), extracted from umbilical cord lining, could be promising biological meshes for the management of SUI related to urethral hypermobility.
In this study, we evaluate the efficiency and the safety of UVS placement in the management of induced SUI in female rats.

Twenty-four females were randomly divided into three groups, including a naive group (group 1, n=4), a group who underwent bilateral pelvic nerves injury (PNI) (group 2, n=10) and a group who underwent both PNI and UVS placement (group 3, n=10). UVS were extracted from human umbilical cord lining. After written consent, umbilical cord was obtained from women seronegative for hepatitis B virus, hepatitis C virus, syphilis, human T-lymphotropic virus and human immunodeficiency virus. The umbilical vessels were chemically viro-inactivated and flattened during the freeze-drying step. 
Micturition calendar was frequently recorded and leak pressure point (LPP) test was performed at day 28. After LPP test, rats were euthanized, and bladder/urethra were collected for histopathological analysis. 
All experiments were performed according to the European Community Council Directive 2010/63/UE and the French Ministry for Agriculture, Agrifood and Forestry (Decree 2013-118). Experimental protocols were reviewed by CEEA-122 Ethical Committee for Protection of Animals used for Scientific Purposes and approved by French Ministry for National Education, Higher Education and Research under the number APAFIS # 26650-2020072010588593 v3. All studies were performed according to local hygiene and risk prevention regulations.

Overall, 24 rats were included whom 10 had both PNI and UVS placement. Compared with group 2, group 3 had increased maximal LPP (respectively 21.8±2.1mmHg versus 28.4±4.1mmHg, p=0.2). Micturition frequencies were similar between the groups. Total voided volume was higher in the group 3 at the end of the study compared with group 2 (12.5±1.1mL versus 9.4±0.6mL respectively, p<0.05). Histopathological findings evidenced a good local tolerance and a moderate to high tissue integration of the UVS.

Biological sling derived from human umbilical vessel could be safely placed with a slight improvement of LPP in a population of rats who had bilateral PNI without major modification of micturition calendar. Moreover, there was no evidence of implant-induced inflammation or tissue damage in or around the urethra or the bladder. Only rare inflammatory cells were observed in a few sites and no fibrosis could be seen. Comparison of groups PNI and PNI/UVS suggested that the presence of the sling had no negative impact on the integrity of the urethra or urinary bladder regardless of the site.

UVS could be a promising biomaterial in the management of SUI in women. Clinical studies are needed.

Continence 2S2 (2022) 100202
DOI: 10.1016/j.cont.2022.100202