Bioreducible polymer-delivered siRNA targeting MMP-9: suppression of granulation tissue formation after bare metallic stent placement in a rat urethral model.
OBJECTIVE
To evaluate the effectiveness of small interfering RNA (siRNA) targeting matrix metalloproteinase 9 (MMP-9) in suppressing granulation tissue formation caused by bare metallic stent placement in a rat urethral model.


METHODS
All experiments were approved by the committee of animal research. In 20 Sprague-Dawley male rats (weight range, 300-350 g), a self-expanding metallic bare stent was inserted in the urethra with fluoroscopic guidance. One group of 10 rats (group A) was treated with MMP-9 siRNA/bioreducible branched polyethylenimine-disulfide cross-linked-indocyanine green (bioreducible BPEI-SS-ICG), while the other group of 10 rats (group B) received control siRNA/bioreducible BPEI-SS-ICG treatment. All rats were sacrificed at 4 weeks. The therapeutic effectiveness of the MMP-9 siRNA/bioreducible BPEI-SS-ICG complex was assessed by comparing the two results of retrograde urethrography, histologic examination, and quantification of MMP-9 by using zymography and Western blot analysis between the two groups. The Mann-Whitney U test was used to evaluate differences.


RESULTS
Stent placement was successful in all rats without a single case of migration at follow-up. Retrograde urethrography performed 4 weeks after stent placement demonstrated significantly larger luminal diameters of the urethra within the stents in group A compared with those in group B (P = .011). Histologic analysis revealed that the mean percentage of granulation tissue area (P < .001), mean number of epithelial layers (P < .001), and mean thickness of submucosal fibrosis (P < .001) were significantly decreased in group A compared with group B. Meanwhile, the mean density of inflammatory cell infiltration did not significantly differ between the two groups (P = .184). Quantitative analysis disclosed MMP-9 levels to be lower in group A relative to group B, indicating positive inhibition of MMP-9 by MMP-9 siRNA/bioreducible BPEI-SS-ICG.


CONCLUSIONS
MMP-9 siRNA/bioreducible BPEI-SS-ICG is effective for inhibiting granulation tissue formation after bare metallic stent placement in a rat urethral model.
From the Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Asanbyeongwon-gil, 388-1 Pungnap-dong, Songpa-gu, Seoul 138-736, Korea (J.H.P., J.H.K., H.Y.S., J.P., S.K.); Medical Device Development Center, Osong Medical Innovation Foundation, Chungbuk, Korea (E.Y.K.); Department of Radiology, Hanyang University Guri Hospital, Guri, Korea (J.K.); and Center for Self-assembly and Complexity, Institute for Basic Science, and Department of Chemistry, Pohang University of Science and Technology, Pohang, Korea (W.J.K., D.L.).
Jung-Hoon
JH
Park
Jin Hyoung
JH
Kim
Eun-Young
EY
Kim
Jinoo
J
Kim
Ho-Young
HY
Song
Won Jong
WJ
Kim
Duhwan
D
Lee
Jihong
J
Park
Soohwan
S
Kim
D000818:Animals; D015153:Blotting, Western; D003287:Contrast Media; D005471:Fluoroscopy; D006097:Granulation Tissue / Q000473:pathology*; D007472:Iohexol; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000494:pharmacology*; D008670:Metals; D011108:Polymers / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D015607:Stents; D014521:Urethra / Q000473:pathology*
D003287:Contrast Media; D008670:Metals; D011108:Polymers; D034741:RNA, Small Interfering; D007472:Iohexol; D020780:Matrix Metalloproteinase 9