[Effects of different time of cryoablation on the proliferation of airway traumatic granuloma and its mechanism in rabbits].

Objective: To investigate the effect of different cryoablation time on tracheal traumatic granulation formation and its mechanism. Methods: A total of 32 rabbits were randomly assigned into four groups (A-D). Group A underwent tracheotomy alone. Group B, C and D received intra-tracheal brush rubbing to establish airway granulation model. Group C and D underwent 30 s and 2-minute cryoablation respectively. Tracheal specimens of all groups were collected to examine pathological changes using HE staining. Levels of transforming growth factor beta 1 (TGF-ß(1)) and CD34 in tracheal granulation were evaluated using immunohistochemistry (IHC) and real-time quantitative reverse transcription polymerase chain reaction (RT-qCR). Results: Tracheal lumens of group A were smooth without granulation. While the growth of granulation and luminal stenosis were most severe in Group B, followed by Group D and C. Submucosa thickness of Group B was largest as compared with other groups (0.20±0.07, 0.77±0.28, 0.44±0.13 and 0.55±0.18 mm for Group A to D, respectively. P<0.05). And the submucosa layer of Group C was thinner than Group D (P<0.05). The expression and transcription levels of TGF-ß(1) of trachea were highest in Group B as detected by IHC and RT-qPCR (P<0.05), followed by Group D and C (IHC: 0.48±0.01 vs 0.43±0.01, P<0.05; RT-qPCR: 12.61±2.14 vs 2.38±0.10, P<0.05). Both protein and mRNA levels of CD34 were highest in Group B as detected by IHC and RT-qPCR (P<0.05). Tracheal mRNA levels of CD34 were more abundant in Group D than Group C (4.92±0.90 vs 2.09±0.10, P<0.05), while no significant difference was found between groups regarding protein levels measured by IHC. Conclusions: Cryoablation could alleviate the hyperplasia of tracheal traumatic granulation, possibly due to the inhibition of TGF-ß(1) and CD34 expression. The effect of 30 s cryoablation for tracheal traumatic granulation is better.