OBJECTIVETo establish an animal model of obliterative bronchiolitis (OB) after lung transplantation and investigate the pathogenesis preliminarily.

METHODSTracheal segments (5 cartilaginous rings each) were transplanted from SD rats to SD rats (Group I) or to Wistar rats (Group II and III). Grafts were implanted into an abdominal cavity and wrapped in the omentum. Animals in Group I and II did not receive CsA, animals in Group III received CsA daily by gastro-tube at 10 mg.kg(-1).d(-1) from beginning to end. Grafts were harvested on day 3, 14, 28 after transplantation as representative time points for 3 phases of injury in the evolution of allograft airway obliteration, then examined histological changes and gene expression of T-helper 1-and T-helper 2-type cytokines [Th1: interleukin-2 (IL-2), interferon-gamma (IFN-gamma); Th2: interleukin-4 (IL-4), interleukin-10 (IL-10)] in grafts. At the same time, effects of CsA were observed on the above-mentioned indices.

RESULTSThere was no significant difference in histological changes on day 3 after transplantation among 3 groups (P > 0.05). Tracheas in Group I approached to normal morphology on day 14 after transplantation. Airway epithelium of Group II and III almost lost completely on day 14 after transplantation. There was no significant difference between Group II and Group III (P > 0.05), but there were significant differences between Group I and Group II or Group III. The cross-sectional area of the tracheal lumen was narrowed by approximately (5.0 +/- 1.2)%, (28.5 +/- 5.0)% and (19.4 +/- 2.9)% respectively on day 14 after transplantation in Group I, II and III, there were significant differences among 3 groups. On day 14 after transplantation, tracheas in Group I revealed few lymphocytic infiltration, but it showed dense lymphocytic infiltration in Group II. Tracheas in Group III have much more lymphocyte infiltration than that in Group I, but much less than that in Group II. There were significant differences among 3 groups, too (P < 0.01). The tracheal lumen revealed almost total luminal obstruction (94.8 +/- 3.6)% on day 28 after transplantation in Group II. The cross-sectional area of the tracheal lumen was narrowed by approximately (3.7 +/- 0.8)% and (36.6 +/- 7.6)% respectively in Group I and III on day 28. There were significant differences among 3 groups (P < 0.01). Compared with that on day 14, lymphocytic infiltration had decreased gradually on day 28 in Group II and III. There were significant differences among 3 groups all the same (P < 0.01). In Group II, expression of IL-2, IFN-gamma, IL-4, and IL-10 were much higher than that in Group I. Expression of Th1 cytokines was increased to a greater extent than that of Th2 cytokines in Group II compared with Group I. Allografts in Group III expressed significantly less IL-2 gene transcripts than that in Group II over all the points. There was no significant difference between Group II and III in IFN-gamma, IL-4, and IL-10 gene expression.

CONCLUSIONSCompared with isografts, allografts have more obvious changes, such as epithelial damage, fibroproliferation and lymphocytic infiltration. Th1 and Th2 lymphocyte subtypes contribute to the development of obliterative bronchiolitis in heterotopic trachea transplant model of rat, and changes of their cytokines gene expression may be involved in the pathogenesis. CsA could reduce the development of fibroproliferation and lymphocyte infiltration markedly, but it could not protect airway epithelium. CsA inhibits IL-2 gene transcripts, so it can reduce development of the pathologic lesion of obliterative bronchiolitis to a certain degree.