The pulmonary vessel adventitia role in pathology of

The pulmonary vessel adventitia: role in pathology of fat embolism Susamita Kesh, Agostino Molteni, Todd M. Stevens, Betty Herndon UMKC School of Medicine Introduction v The pulmonary arterial wall consists of 3 layers, intima, media, adventitia v Smooth muscle cells & endothelial cells make up the first 2 layers, the adventitia is the most complex v Adventitia contains fibroblasts, blood and lymphatics, adrenergic nerves, progenitor and immune cells v It is the major injury-sensing tissue of the vessel wall v Adventitia is activated by hormones, inflammation, hypoxia, foreign substances in blood and responds by upregulating cytokines and chemokines that regulate the vessel wall v Adventitia becomes, when blood pressure↑, the most important part of the blood vessel due to its stiffening, secretion, and the presence of inflammatory cells. v Hypothesis: The pulmonary adventitia is crucial to the lung pathology induced by fat embolism. intima media Results Lung Adventitia v. The adventitia consists of an extracellular scaffold containing fibroblasts, blood and lymphatic vessels, nerves, progenitor and immune cells v. This makes the adventitia the most complex compartment of the blood vessel wall v. Recent published data shows that the adventitia is a center for storage, integration and release of the key components of blood vessel function: v. Adventitial cells are often the first vascular wall cells to be activated v. They are early in cell proliferation v. They express many important proteins (adhesion, extracellular matrix) v. Adventitia secretes chemokines, cytokines, angiogenic proteins that effect other cell walls v. In summary, the adventitia regulates vascular structure and function adventitia Sub-endothelial zone Adventitia stem & progenitor cells Fat embolism model and adventitia v. In humans fat embolism (FE: from marrow lipids reaching the lung secondary to long bone fracture) is seen early post injury as respiratory insufficiency which clears without intervention v. It is commonly believed that there are no long term pulmonary sequelae after FE—although human studies have shown decreased PFTs in groups with healed long bone fractures compared to controls v. To further evaluate responses of pulmonary vessel components to FE, this study attempts to evaluate changes in pulmonary vessel adventitia following a model of long bone fracture: fat embolism complicated by a “second hit” v 36 rats were administered fat embolism model (triolein i. v. ) or saline, followed at 6 weeks by LPS i. p. or saline, with lung study at 24 hr Bronchoalveolar lavages Methods Groups: 18 saline i. v. or 18 triolein i. v. (fat embolism and controls) Each of these groups were further divided into saline or LPS i. p. treated animals at 6 weeks. Necropsy was performed 48 hours later. v 4 -5 digital photos at 400 x were taken of each lung section v Lumen, media and adventitia diameters were measured for each lung v Lumen-media ratio and media-adventitia ratios were calculated v The vessel ratios were compared by group using Statistica parametric comparison v Adventitia diameters were statistically analyzed separately • • %PMN in BAL Saline + 6 wk + saline @ 24 hr 3. 5% Triolein + 6 wk + saline @ 24 hr 5. 5% Saline + 6 wk + LPS @ 24 hr 11. 1% Triolein + 6 wk + LPS @ 24 hr 14. 4% • ~ 15% elevation in BAL PMN by triolein 6 weeks earlier and ~ threefold elevation by LPS , 24 hr before BAL counts • Macrophages and lymphocytes were not significantly different by treatment group LPS at 6 wk (right) increases inflammation but does not change the vessel. control artery with adventitia H&E 400 x Triolein (fat embolism model) stimulates vessel adventitia; added LPS shows similar effect trichrome 400 x Summary /Conclusion vadventitial change in a model of fat embolism was measured vboth initial insult (fat embolism) and a second hit (LPS at 6 weeks) produce effects on pulmonary vasculature and the adventitia in particular v. This and previous work suggest an effect of the renin-angiotensin system on lung vessels in this model of fat embolism References 1. Majesky MW et al. Nature Biotechnology 30: 152 -4, 2012 2. Grudzinska MK et al. Arterioscler Thromb Vasc Biol 33: 1271 -9, 2013 3. Tilki D, et al, Trends in Molecular Med 15 L 501 -8, 2009 4. Majesky MW et al, Cells, Tissues, Organs 195: 7381, 2012