The study on the function and cell source of interleukin-6 in interstitial cystitis/bladder painful syndrome rat model

Objective: The elevated expression of interleukin-6 (IL-6) in patients with interstitial cystitis/bladder painful syndrome (IC/BPS) has been demonstrated, but the role of IL-6 in IC/BPS and its source remain to be explored. Methods: IC/BPS rat model was created in female rats by using long-term intermittent intravesical hyaluronidase (0.5 ml, 4 mg/ml). After modeling, IL-6 stimulation group, and anti-IL-6R group were treated with recombinant rat IL-6 and tocilizumab, respectively. Symptomatic changes were detected by Vonfrey pain score and urodynamics, and hematoxylin-eosin (HE) staining, mast cell staining and Masson staining were used to evaluate the changes of inflammation in the bladder tissue of rats. Cell sources of IL-6 was explored through enzyme linked immunosorbent assay (ELISA) test, reverse transcription polymerase chain reaction (RT-PCR), and western-blot test on the supernatant of coculturing rat bladder epithelial cells and rat macrophages. Results: The Vonfrey pain scores of the model group and IL-6 stimulation group were significantly higher than those of the control group, while the anti-IL-6R group were significantly lower (p < .05). Compared with the blank control group, urodynamic results showed that the urination interval of the model group and IL-6 stimulation group was significantly shortened, and the maximum bladder capacity was significantly reduced (p < .05), and anti-IL-6R treatment significantly alleviated the inflammatory response of bladder tissue. The results of HE, Mast cell staining, and Masson staining showed that the inflammatory response of bladder tissue after anti-IL-6R treatment was significantly reduced. Through cells coculture, the relative expression of IL-6 from model group was found significantly higher than blank control group by RT-PCR, ELISA, and western blot test (p < .05). Conclusions: IL-6 played an essential role in the development of IC/BPS rat model as a proinflammation cytokine. Further evidence from coculture proved that macrophages are the cell resource of IL-6 in IC/BPS.