Hypothesis / aims of study
Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic debilitating condition with limited efficacy of standard therapies (30–50% response). Platelet-rich plasma (PRP) contains high concentrations of growth factors and may exert regenerative and immunomodulatory effects. We hypothesised that a course of intravesical PRP instillations in women with refractory IC/BPS is superior to placebo in reducing symptoms and pain, and that this improvement is associated with a shift of the local urinary cytokine profile from pro-inflammatory towards regenerative.
Study design, materials and methods
After ethical approval and written informed consent, 76 women (18–65 years) with moderate‑to‑severe IC/BPS (ICSI ≥10, ≥8 voids/day, failure of ≥1 prior therapy line) were randomised 1:1 to PRP (n=38) or placebo (n=38). Sample size calculation (80% power, α=0.05, anticipated 30% vs 10% ICSI reduction, 15% dropout) required 38 per group. PRP was prepared from 40 mL autologous venous blood by two‑step centrifugation (300g/5min, then 700g/17min, 12°C) to reach a platelet concentration of 1.0–1.5×10⁹/mL. Four intravesical instillations of 10–12 mL activated PRP (37°C, 15 min) or placebo (saline) were given at 2‑week intervals. Primary outcomes at 12 weeks: change in O’Leary-Sant Interstitial Cystitis Symptom Index (ICSI) and Visual Analog Scale (VAS) pain score. Secondary outcomes: changes in urinary cytokines (IL‑6, MCP‑1, calprotectin, IL‑10), voiding frequency, ICIQ-SF, and safety. Intention‑to‑treat analysis; Mann‑Whitney U test, χ², logistic regression (p<0.05).
Results
Baseline characteristics were similar between groups (p>0.05). At 12 weeks, the PRP group showed a significantly greater reduction in ICSI (median Δ –6.0 [IQR –8.0 to –4.0] vs –1.5 [–3.0 to 0.0], p<0.001) and VAS pain (Δ –3.2 cm [–4.5 to –2.0] vs –0.8 cm [–2.0 to 0.5], p<0.01). A clinically meaningful improvement (ΔICSI ≥4) was achieved in 65.8% (25/38) of PRP patients vs 21.1% (8/38) of placebo patients (p<0.001).
Table 1. Primary outcomes at 12 weeks
Outcome PRP (n=38) Placebo (n=38) p-value
ICSI, median Δ [IQR] –6.0 [–8.0; –4.0] –1.5 [–3.0; 0.0] <0.001
VAS pain, median Δ [IQR] –3.2 [–4.5; –2.0] –0.8 [–2.0; 0.5] <0.01
ΔICSI ≥4, n (%) 25 (65.8%) 8 (21.1%) <0.001
Urinary MCP 1 decreased by 41% (p<0.01), calprotectin by 45% (p<0.01), IL 6 by 43% (p<0.05), and IL 10 increased by 32% (p<0.05) in the PRP group, with no significant changes in the placebo group. Voiding frequency reduced from 14.0±3.0 to 8.8±2.5/day (p<0.01). ICIQ SF improved from 18.0±3.5 to 10.2±3.0 points (p<0.01).
Table 2. Urinary cytokine changes at 12 weeks (% change from baseline)
Cytokine PRP (n=38) Placebo (n=38)
MCP 1 –41%* –6%
Calprotectin –45%* –5%
IL 6 –43%** –8%
IL 10 +32%** +6%
*p<0.01; **p<0.05 vs placebo (Mann-Whitney U)
Transient dysuria (Grade 1) occurred in 15.8% (6/38) of PRP and 10.5% (4/38) of placebo patients (p=0.49). No serious adverse events were recorded.
Interpretation of results
Intravesical PRP significantly reduced symptom scores and pain compared to placebo, with a number needed to treat of approximately 2.2 for a clinically meaningful response (ΔICSI ≥4). The parallel reduction of pro‑inflammatory markers (MCP‑1, calprotectin, IL‑6) and elevation of IL‑10 in urine suggests that PRP exerts a local immunomodulatory effect, shifting the bladder environment from inflammation towards repair. The safety profile was favourable and similar to placebo.