Programs and cores

Project 1 : Dynamic Effects of Chemokines on Systemic Inflammation

Project 2: Macrophage Activation /Deactivation in ALI

Project 3: Alveolar Mesenchymal Cells in Acute Lung Injury

Project 4: A Randomized Trial of GM-CSF in Patients with ALI

Core A: Clinical Core

Administrative Core

Alveolar Mesenchymal Cells in Acute Lung Injury; Victor J. Thannickal, PI.

Fibroproliferation is a common response to lung injury. While a fibroproliferative response is required for adequate repair of the injured alveolar-capillary membrane, this response must be appropriately controlled and is often dysregulated in the setting of ALI/ARDS. Events that promote exuberant fibroproliferation in ALI/ARDS have been incompletely defined, but are almost certainly linked to alterations in the phenotype of fibroblasts and other structural cells of the lung. Preliminary studies have identified cells in the alveolus of ALI/ARDS patients that express fibroblast differentiation markers. Furthermore, the phenotype of these cells is altered in patients with fibroproliferative ARDS, and the presence and/or phenotype of these alveolar mesenchymal cells may be predictive of dysregulated lung repair. These observations served to formulate the hypothesis that fibroblast progenitor cells are present in the alveolus of patients with ALI, and the phenotype of these cells is controlled by both genetic and microenvironmental factors. Furthermore, the presence and/or phenotype of alveolar mesenchymal cells are predictive of acute and long-term outcomes in patients with ALI/ARDS. Initial studies will be performed to determine the contribution of TGF- b to mesenchymal cell activation, differentiation, and apoptotic responses. Additional studies will be performed to determine the influence of environmental factors (oxidant stress) and genetic factors (gain in function TGF- b polymorphisms) on these responses. Finally, studies are ongoing to determine if the number and/or phenotype of alveolar mesenchymal cells present within the airspace of ALI/ARDS patients is predictive of persistent ARDS and other adverse clinical outcomes. Collectively, these studies are especially exciting because it is the first time that the biology and clinical implications of fibroblasts isolated from the airspace of patients with ARDS can be addressed.

PROJECT ABSTRACTS

Resolution of acute lung injury (ALI) is dependent on temporally and spatially regulated elimination of both inflammatory cells and mesenchymal cells from the alveolar space. The origin of mesenchymal cells and their mechanisms of activation and clearance in ALI/ARDS are unclear. We have isolated CD45(-) alveolar mesenchymal cells (AMCs) expressing fibroblast/myofibroblast markers (collagen I, prolyl-4-hydroxylase, a -smooth muscle actin) from bronchoalveolar lavage (BAL) of patients with ALI . AMCs proliferate in vitro and possess distinct, yet stable cellular phenotypes. AMCs from patients with fibroproliferative ALI vs resolving ALI are "intrinsically" resistant to apoptosis with constitutive activation of the pro-survival PI3K-Akt pathway. This activated AMC phenotype may be mediated by an autocrine TGF- b 1/thrombospondin-1 activation loop. Hyperoxia may further promote the anti-apoptotic phenotype by activating the PI3K-Akt pathway in AMCs, in contrast to primarily pro-apoptotic signaling in alveolar epithelial cells. Thus, "extrinsic" alveolar microenvironmental factors and "intrinsic" factors modulate AMC phenotype and contribute to dysregulated lung repair by promoting the activation and accumulation of AMCs within alveolar spaces.

HYPOTHESIS : Intra-alveolar accumulation of AMCs with an activated, apoptosis-resistant phenotype is predictive of dysregulated lung repair and persistent ALI. Both "intrinsic" and "extrinsic" (alveolar microenvironment) factors regulate this AMC phenotype.

SPECIFIC AIMS are to: (1) determine whether an "intrinsically" autocrine TGF- b 1/TSP-1 activation loop regulates the anti-apoptotic AMC phenotype in patients with persistent ALI/ARDS, (2) determine if elevated levels of activated TGF- b 1 and hyperoxia (alveolar microenvironmenta factors) promote an anti-apoptotic phenotype of AMCs, (3) prospectively determine whether the number of AMCs (CD45-/PH+/ a -SMA+ cells recovered by BAL), their phenotype (apoptosis, proliferation, oxidative burst activity), and/or activated TGF- b 1 in the alveolar microenvironment is predictive of persistent ALI and clinical outcomes in a cohort of ALI patients and (4) determine if the presence of TGF- b 1 gene polymorphisms (at codon 10 and/or 25) is predictive of persistent/fibroproliferative ALI.