Prognostic significance of early pulmonary function changes after onset of chronic lung allograft dysfunction.

BACKGROUND: Chronic lung allograft dysfunction (CLAD), including the phenotypes of bronchiolitis obliterans syndrome (BOS) and restrictive CLAD (R-CLAD), represents the leading cause of late death after lung transplantation. Little is known, however, regarding the natural history or prognostic significance of pulmonary function changes after the onset of these conditions. We examined changes in forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) over the first 18 months after CLAD. We also sought to determine whether lung function changes occurring early after CLAD impact longer term outcomes. METHODS: We performed a retrospective analysis of 216 bilateral lung recipients with CLAD, which included those with R-CLAD (n = 65) or BOS (n = 151). The course of FEV1 and FVC after CLAD was described. Cox proportional hazards models were used to evaluate the impact of a ≥10% decline in FEV1 or FVC within the first 6 months of CLAD on graft loss after that time. RESULTS: Lung recipients with CLAD, whether BOS or R-CLAD, had the largest decreases in FEV1 and FVC within the first 6 months after onset. Moreover, a decline in FEV1 or FVC of ≥10% within the first 6 months after CLAD was associated with a significantly increased hazard for graft loss after that time (hazard ratio [HR] = 3.17, 95% confidence interval [CI] 1.56 to 6.42, p = 0.001, and HR = 2.80, 95% CI 1.66 to 4.70, p ≤ 0.001, respectively), an effect observed in both BOS and R-CLAD patients. CONCLUSIONS: Early physiologic changes after CLAD were independently associated with graft loss. This suggests lung function changes after CLAD, specifically a ≥10% decline in FEV1 or FVC, could be a surrogate measure of graft survival.

Epithelial clara cell injury occurs in bronchiolitis obliterans syndrome after human lung transplantation.

Bronchiolitis obliterans syndrome (BOS) is a condition of progressive airflow obstruction that affects a majority of lung transplant recipients and limits long-term posttransplant survival. Although epithelial injury appears central to the development of BOS, little is known regarding the specific epithelial cell types that are affected in this condition. We hypothesized that BOS would involve preferential injury to the secretory Clara cells that function in innate defense and epithelial repair. To test this hypothesis, we assessed tissue transcript, tissue protein and lung fluid protein expression of Clara cell secretory protein (CCSP), a marker for Clara cells, in lung transplant recipients with BOS, BOS-free patients and in donor controls. Our results demonstrate that CCSP tissue transcript and protein expression are significantly reduced in lung transplant recipients with BOS compared to BOS-free or donor controls. In addition, we demonstrate that CCSP protein levels are significantly reduced in the lung fluid of patients with BOS compared to BOS-free controls, in cross-sectional and longitudinal analysis. Collectively, these complementary results illustrate that BOS involves a selective alteration in the distribution and function of bronchiolar Clara cells.

Spirometrically significant acute rejection increases the risk for BOS and death after lung transplantation.

Acute rejection (AR) is a common complication following lung transplantation and is an established risk factor for bronchiolitis obliterans syndrome (BOS). AR clinical presentation varies considerably and is sometimes associated with an acute decrease in forced expiratory volume in 1 s (FEV1). We hypothesized that lung transplant recipients who experience such spirometrically significant AR (SSAR), as defined by a ≥10% decline in FEV1 relative to the prior pulmonary function test, are subsequently at increased risk for BOS and worse overall survival. In a large single center cohort (n = 339), SSAR occurred in 79 subjects (23%) and significantly increased the risk for BOS (p < 0.0001, HR = 3.2, 95% CI 2.3-4.6) and death (p = 0.0001, HR = 2.3, 95% CI 1.5-3.5). These effects persisted after multivariate adjustment for pre-BOS AR and lymphocytic bronchiolitis burden. An analysis of the subset of patients who experienced severe SSAR (≥20% decline in FEV1) resulted in even greater hazards for BOS and death. Thus, we demonstrate a novel physiological measure that allows discrimination of patients at increased risk for worse posttransplant outcomes. Further studies are needed to determine mechanisms of airflow impairment and whether aggressive clinical interventions could improve post-SSAR outcomes.