Occurence of lipid bodies in canine type II pneumocytes during hypothermic lung ischemia

Abstract

Type II pneumocytes defend the pulmonary alveolus by synthesis and secretion of surfactant and by contributing to alveolar epithelial regeneration. Lipid bodies are regarded as intracellular domains for the synthesis of eicosanoid mediators that can be induced by inflammatory stimuli. The aim of the present study was to establish whether hypothermic ischemic lung storage without further preservation measures leads to an induction of lipid body formation in canine type II pneumocytes. The lungs of 18 dogs were fixed for transmission electron microscopy (TEM) immediately after cardiac arrest (six double lungs) and after ischemic storage in Tutofusin solution at 4°C for 20 min, 4 hr, 8 hr, and 12 hr (six single lungs, respectively). Type II pneumocytes were analyzed qualitatively by conventional TEM (CTEM) and quantitatively by stereology. The relative phosphorus content of surfactant containing lamellar bodies, lipid bodies, and intermediate forms was investigated by energyfiltering TEM (EFTEM). By CTEM, lipid bodies as well as forms intermediate between lipid bodies and lamellar bodies were already noted in the control group but were more pronounced in the ischemia groups. Beginning at 20 min of ischemic storage, a significant increase in the volume density of lipid bodies was noted in the ischemic groups as compared to the control group. By EFTEM, the highest intracellular phosphorus signals were recorded over lamellar bodies and lamellar areas of intermediate forms in all experimental groups, while lipid bodies and homogeneous areas of intermediate forms did not show a clear phosphorus signal. These results indicate that the formation of lipid bodies in canine type II pneumocytes is induced early during ischemic lung storage. Anat Rec Part A 277A: 287-297, 2004.

Categorization of lung mesenchymal cells in development and fibrosis

“…Traditionally, lipofibroblasts have been identified histologically by the presence of intracellular lipid droplets, markers of an adipose like phenotype, enzymatic properties, characteristic cytokines, and canonical marker genes like Plin2 , Lpl , and Fgf10 among others ( El Agha, et al., 2014 ; Rehan, et al., 2006 ). The reliance on lipid dyes, and/or associated genes like PLIN2, to distinguish and quantitate lipofibroblasts in the lung is not ideal given that lipid droplets, and associated genes, exist and are expressed by a variety of pulmonary cell types ( Ntokou, et al., 2017 ; Mochizuki, et al., 2011 ; Besnard, et al., 2009 ; Ochs, et al., 2004 ; Zhang and Chawla, 2004 ; Dvorak, et al., 1992 ). More recently, lineage tracing studies have demonstrated Tcf21 to be preferentially expressed in adult murine lung lipofibroblasts while previous reports suggested both Pdgfra + and Fgf10 + lineage lung stromal cell populations included lipofibroblasts ( Park, et al., 2019 ; Al Alam, et al., 2015 ; Barkauskas, et al., 2013 ; Chen, et al., 2012 ).…”

Pulmonary abnormalities due to ABCA1 deficiency in mice

“…To our knowledge, this is the first report of the cholesterol content of a cell type freshly isolated from the ABCA1Ϫ/Ϫ mouse, other than macrophages. One of the striking features of type II cells in intact lungs of ABCA1Ϫ/Ϫ mice was the presence of spherical, nonmembrane-bound cytoplasmic organelles containing amorphous material, typical in appearance to lipid bodies (48). In other cell types, lipid bodies represent a site for cholesteryl ester or lipid storage as is the case for smooth muscle cells (66) and macrophages (13) and may be the case for type II cells.…”

“…In other cell types, lipid bodies represent a site for cholesteryl ester or lipid storage as is the case for smooth muscle cells (66) and macrophages (13) and may be the case for type II cells. Few are present in pneumocytes under normal conditions but are induced in response to stress such as ischemia and are felt to be the site of eicosanoid mediator synthesis (48). The role of lipid bodies in the type II cells of the lungs from ABCA1Ϫ/Ϫ mice is unknown.…”

How common is the lipid body-containing interstitial cell in the mammalian lung?

“…Such organelles can be found regularly in several types of cell and appear to be inducible in nearly all cell types (33) and to be important for the synthesis of eicosanoids (61,62). Under normal conditions, in the alveolar region, they occur frequently in lipofibroblasts and rarely in other cell types, such as alveolar epithelial type II (AE2) cells (8,36). The latter are known to synthesize, store, secrete, and partly recycle pulmonary surfactant (10).…”