Deciphering the Role of TGF-β1 in Altering Collagen I and Collagen III in the New Zealand Rabbit’s (Oryctolagus cuniculus) Urethral Wall in Urethral Stricture Development

Background: Presently, there's a lack of standardization in animal models used for studying urethral stricture. Transforming Growth Factor Beta 1 (TGF-β1) is known to regulate the deposition of extracellular matrix in both normal and pathological conditions. This factor holds promise as a potential model for simulating urethral stricture. Objective: This study aims to investigate the impact of Transforming Growth Factor Beta 1 (TGF-β1) on Collagen I and Collagen III within the urethral wall of New Zealand Rabbits (Oryctolagus cuniculus) in the context of developing urethral stricture in animal models. Methods: We conducted genuine laboratory experiments using Male New Zealand rabbits (Oryctolagus cuniculus), which were categorized into five groups: control, placebo, and three treatment groups (TGF-β1 injections of 1 µg, 2 µg, 4 µg). After a duration of 6 weeks, we conducted urethrography, histopathological analysis, and assessed the formation of collagen I and collagen III within the urethral wall. Results: Elevating the dosage of TGF-β1 led to a reduction in the average urethral lumen diameter of rabbits (29.3% in the 2µg group and 34% in the 4µg group) compared to the control group. In fact, three rabbits experienced a decrease of ≤ 50% in their urethral lumen diameter. As the doses of TGF-β1 increased, we observed significant increases in the density of collagen I, and collagen III in both the periluminal and peripheral regions of the urethral spongiosum. Additionally, there was a tendency for the collagen I/collagen III ratio to decrease in the periluminal region, with collagen III density surpassing that of collagen I. In the peripheral spongiosa area, notable mean differences were observed between the control group, 1T, and 2T groups, with collagen I density tending to be higher than that of collagen III. Furthermore, the percentage of urethral lumen diameter exhibited a robust negative correlation with periluminal collagen I density (r = -0.672, p = 0.001), peripheral spongiosa collagen I density (r = -0.603, p = 0.005), periluminal collagen III density (r = -0.717, p = 0.001), and an exceptionally strong negative correlation with collagen III density of peripheral spongiosa (r = -0.804, p = 0.000). Conclusion: TGF-β1 exerts an influence on altering the composition of collagen I and collagen III within the urethral wall of rabbits, leading to a reduction in the diameter of the urethral lumen. Further research is warranted to determine the optimal dose of TGF-β1 required to induce urethral stricture effectively.