Developmental shift in the relative percentages of lung fibroblast subsets: role of apoptosis postseptation

Developmental shift in the relative percentages of lung fibroblast subsets: role of apoptosis... Abstract We have used the lipophilic, fluorescent dye Nile red and flow cytometry to identify and isolate two rat lung fibroblast subsets, lipid-containing interstitial cells (LICs) and non-LICs (NLICs) and to quantitate developmental changes in the relative percentages of these subsets. A significant decrease was observed in the percentage of LICs (from 79.0 ± 3.8% on postnatal day 4 to 28.6 ± 4.2% on day 30 ; P < 0.0001). To determine whether one or both subsets undergo apoptosis postseptation, fibroblasts from 16- to 18-day rats were treated with BODIPY-conjugated dUTP to label DNA strand breaks, which were then quantitated by flow cytometry. Apoptotic cells were judged to be predominantly LICs based on flow cytometric estimates of cell size and granularity and on light-microscopic colocalization of intracellular lipid and Hoechst-positive apoptotic bodies. Cell proliferation was compared in LICs and NLICs with both an in vitro 3 Hthymidine incorporation assay and cell cycle analysis of propidium iodide-stained cells. Results of both assays indicated that on days 4 – 5 , LICs proliferated more rapidly than NLICs. Tropoelastin and fibronectin mRNA expression, evaluated by RT-PCR, indicated that although tropoelastin mRNA levels did not differ, fibronectin mRNA levels were approximately ninefold greater in LICs. These results demonstrate the feasibility of a flow cytometric assay for the analysis of size, granularity, and intracellular lipid content of neonatal rat lung fibroblast subsets. Subsets differed substantially with respect to proliferative capacity, fibronectin mRNA expression, and incidence of apoptosis postseptation. Together with the observed changes in relative percentages of fibroblast subsets with age, these data suggest that the ratio of LICs to NLICs could be a critical determinant of fibroblast function during lung development. fibroblast heterogeneity flow cytometry Nile red lipid interstitial cell fibronectin Footnotes Address for reprint requests and other correspondence: M. Bruce, Dept. of Pediatrics, Neonatology Division, Univ. of Kentucky Medical School, 800 Rose St., Lexington, KY 40536 (E-mail: mbruce@pop.uky.edu ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 1999 the American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Lung Cellular and Molecular Physiology The American Physiological Society

Developmental shift in the relative percentages of lung fibroblast subsets: role of apoptosis postseptation

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Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
1040-0605
eISSN
1522-1504
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Abstract

Abstract We have used the lipophilic, fluorescent dye Nile red and flow cytometry to identify and isolate two rat lung fibroblast subsets, lipid-containing interstitial cells (LICs) and non-LICs (NLICs) and to quantitate developmental changes in the relative percentages of these subsets. A significant decrease was observed in the percentage of LICs (from 79.0 ± 3.8% on postnatal day 4 to 28.6 ± 4.2% on day 30 ; P < 0.0001). To determine whether one or both subsets undergo apoptosis postseptation, fibroblasts from 16- to 18-day rats were treated with BODIPY-conjugated dUTP to label DNA strand breaks, which were then quantitated by flow cytometry. Apoptotic cells were judged to be predominantly LICs based on flow cytometric estimates of cell size and granularity and on light-microscopic colocalization of intracellular lipid and Hoechst-positive apoptotic bodies. Cell proliferation was compared in LICs and NLICs with both an in vitro 3 Hthymidine incorporation assay and cell cycle analysis of propidium iodide-stained cells. Results of both assays indicated that on days 4 – 5 , LICs proliferated more rapidly than NLICs. Tropoelastin and fibronectin mRNA expression, evaluated by RT-PCR, indicated that although tropoelastin mRNA levels did not differ, fibronectin mRNA levels were approximately ninefold greater in LICs. These results demonstrate the feasibility of a flow cytometric assay for the analysis of size, granularity, and intracellular lipid content of neonatal rat lung fibroblast subsets. Subsets differed substantially with respect to proliferative capacity, fibronectin mRNA expression, and incidence of apoptosis postseptation. Together with the observed changes in relative percentages of fibroblast subsets with age, these data suggest that the ratio of LICs to NLICs could be a critical determinant of fibroblast function during lung development. fibroblast heterogeneity flow cytometry Nile red lipid interstitial cell fibronectin Footnotes Address for reprint requests and other correspondence: M. Bruce, Dept. of Pediatrics, Neonatology Division, Univ. of Kentucky Medical School, 800 Rose St., Lexington, KY 40536 (E-mail: mbruce@pop.uky.edu ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 1999 the American Physiological Society

Journal

AJP - Lung Cellular and Molecular PhysiologyThe American Physiological Society

Published: Oct 1, 1999

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