Cyclooxygenase‐2 expression in experimental post‐transplant obliterative bronchiolitis

Abstract

Epithelial cell injury, inflammation, progressive fibrosis, and airway obliteration are histological features of post-transplant obliterative bronchiolitis (OB). Cyclooxygenase (COX)-2 is expressed in acute and chronic inflammatory responses. Our aim was to elucidate the possible role of COX-2 in post-transplant OB by using a heterotopic bronchial porcine model. Bronchial allografts from non-related donors were transplanted subcutaneously into 24 random-bred domestic pigs, each weighing about 20 kg. Groups studied had grafts, non-treated allografts, allografts given cyclosporine A (CsA), methylprednisolone (MP), and azathioprine (Aza), and allografts given CsA, MP, and everolimus. Grafts were serially harvested during a follow-up period of 21 days for histology (H&E) and immunohistochemistry. Immunostaining was performed with monoclonal IgG against human COX-2 peptide, and histological alterations and immunohistochemical positivity were graded on a scale from 0 to 5. Epithelial COX-2 index was calculated by multiplying the percentage of positive cells by grade of epithelial COX-2 intensity. Ischaemic epithelial loss, evident in all implants, recovered rapidly in autografts, and bronchi remained patent. Epithelial loss in non-treated allografts preceded fibroblast proliferation, resulting in total luminal obliteration. In CsA-, MP-, and Aza-treated allografts epithelial destruction and luminal obliteration were delayed, and these were prevented in CsA-, MP-, and everolimus-treated allografts. COX-2 expression due to operative ischaemia was evident in all implants on day 2. Thereafter, the epithelial COX-2 index preceded epithelial injury and obliteration. During the inflammatory response and fibroblast proliferation, COX-2 expression occurred in macrophages and fibroblasts. In conclusion, in the early stage of OB development, COX-2 induction occurred in airway epithelial cells prior to luminal obliteration. In addition, the observation that COX-2 expression in macrophages and fibroblasts paralleled the onset of inflammation and fibroblast proliferation indicates a role in OB development, but the causal relationships need further study.

Local C-Reactive Protein Expression in Obliterative Lesions and the Bronchial Wall in Posttransplant Obliterative Bronchiolitis

“…Animals were anesthetized for surgical procedures as described previously [20] and euthanized with high-dose intravenous sodium pentobarbital at the end of the follow-up. The donor left caudal pulmonary lobe was removed for preparation of implants.…”

“…The percentages of CRP-positive cells in the epithelium and the obliterative plug were counted separately, and the staining intensity was graded on a scale from 0 to 3, where 0 = negative; 1 = positive cells showing weak staining; 2 = more intense and/or irregular staining; 3 = intense, uniform staining. The CRP index was calculated by multiplying the percentage of CRP-positive cells by the CRP staining intensity score, a method we previously used to assess cyclo-oxygenase expression [20]. CRP-positive cells in the bronchial wall were assessed on a scale from 0–3 based on the intensity of immunocytochemical staining and the number of positive cells.…”

Epithelial Tenascin Predicts Obliterative Airway Disease

“…22 In preparation for implantation, a left thoracotomy was performed, and the caudal lobe was removed. 21 To obtain a series of consecutive samples from the same recipient, 20 to 30 segments of terminal bronchi, 1.5 cm in length, were transplanted subcutaneously into the ventral side of each animal.…”

“…The tenascin index was calculated by multiplying the percentage of tenascinpositive cells by the grade of tenascin intensity, a method previously used to assess cyclooxygenase expression. 22 Tenascin-positive cells in the bronchial wall were assessed on a scale of 0 to 3, based on the intensity of immunocytochemical staining and the number of tenascin-positive cells.…”

Ingraft chimerism in lung transplantation - a study in a porcine model of obliterative bronchiolitis

“…20 kg. Animals were anesthetized for the surgical procedures as previously described [21]. Left thoracotomy was performed for removal of the caudal lobe.…”