Symptomatic improvement versus objective urethral functional recovery following stem cell-based therapy for stress urinary incontinence: a systematic review

Background: Stem cell-based urethral injection has been proposed as a regenerative treatment for stress urinary incontinence (SUI), and symptom relief does not necessarily establish recovery of urethral sphincter function. Objective: To compare patient-centred symptomatic improvement with direct assessment of urethral functional recovery after cell-based treatment for female SUI. Method: PubMed/MEDLINE, Scopus, Web of Science Core Collection, and the Cochrane Library were searched from inception through 2026-05-31. Human interventional studies of adult women with SUI treated with a stem cell, muscle precursor cell, adipose-derived stem-cell, stromal vascular fraction, or related autologous regenerative cell product were eligible. Retracted reports were excluded. Two reviewers independently screened records, extracted study-level data, linked reports from the same cohort, and synthesized the findings narratively. Symptom outcomes included leakage episodes, pad tests, cough stress testing, validated questionnaires, and quality of life. Direct functional recovery required urethral pressure or length measurements, sphincter contractility, or structural imaging interpreted alongside function. Results: Twenty-two original reports were identified. Symptom measures improved, including pad weight, cough stress test, incontinence episodes, and questionnaire scores. Direct urethral measurements were sparse and heterogeneous. One phase I study documented increased functional urethral length and external sphincter diameter alongside improved ICIQ-UI-SF scores, whereas a 38-participant study reported persistent symptom benefit without overall improvement in urodynamic urethral properties. In the largest blinded trial, the primary symptom endpoint did not differ from placebo. An electrical-stimulation plus cell-implantation trial favored cellular arms against placebo on symptom endpoints without direct physiologic confirmation. Conclusion: Current findings support a short-term symptom signal and acceptable procedural tolerability; they do not establish consistent objective urethral functional regeneration. Future trials require standardized cell-product reporting, blinded comparison, direct pressure-based and imaging outcomes, and durable follow-up.