Activation of mTOR signaling in adult lung microvascular progenitor cells accelerates lung aging
Emma C. Mason, … , Fabienne Gally, Susan M. Majka
Emma C. Mason, … , Fabienne Gally, Susan M. Majka
Published October 24, 2023
Citation Information: J Clin Invest. 2023;133(24):e171430. https://doi.org/10.1172/JCI171430.
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Research Article Vascular biology

Activation of mTOR signaling in adult lung microvascular progenitor cells accelerates lung aging

Abstract

Reactivation and dysregulation of the mTOR signaling pathway are a hallmark of aging and chronic lung disease; however, the impact on microvascular progenitor cells (MVPCs), capillary angiostasis, and tissue homeostasis is unknown. While the existence of an adult lung vascular progenitor has long been hypothesized, these studies show that Abcg2 enriches for a population of angiogenic tissue-resident MVPCs present in both adult mouse and human lungs using functional, lineage, and transcriptomic analyses. These studies link human and mouse MVPC-specific mTORC1 activation to decreased stemness, angiogenic potential, and disruption of p53 and Wnt pathways, with consequent loss of alveolar-capillary structure and function. Following mTOR activation, these MVPCs adapt a unique transcriptome signature and emerge as a venous subpopulation in the angiodiverse microvascular endothelial subclusters. Thus, our findings support a significant role for mTOR in the maintenance of MVPC function and microvascular niche homeostasis as well as a cell-based mechanism driving loss of tissue structure underlying lung aging and the development of emphysema.

Authors

Emma C. Mason, Swapna Menon, Benjamin R. Schneider, Christa F. Gaskill, Maggie M. Dawson, Camille M. Moore, Laura Craig Armstrong, Okyong Cho, Bradley W. Richmond, Jonathan A. Kropski, James D. West, Patrick Geraghty, Brigitte N. Gomperts, Kevin C. Ess, Fabienne Gally, Susan M. Majka

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Figure 1

mTOR-activated lung MVPCs negatively impact progenitor function and alveolar structure.

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mTOR-activated lung MVPCs negatively impact progenitor function and alve...
(A) Expression of p-S6 levels as an indication of mTOR signaling by Western blot analysis in isolated normal (3 independent patient primary cell lines) or LAM MVPCs (mTOR+; 1 patient, 3 independent cell lines, all female) normalized to total protein and β-actin. (B) Expression of p-S6, TSC2, and TSC1 normalized to total protein and β-actin relative to control MVPCs respectively by Western blot analysis in normal (3–4 independent patient primary cell lines, 2 female, 2 male, age 60–67), mTOR+ (1 patient, 3 independent cell lines, age 63), and fetal (human fetal lung [HFL]; 3 independent patient primary cell lines, 17–20 weeks of gestation, 2 male, 1 female) MVPCs. Data were analyzed by 1-way ANOVA followed by Tukey’s honestly significant difference (HSD) post hoc analysis and are presented as mean ± SEM. *P < 0.05, **P < 0.01. (C) Immunostaining to localize TSC2 (red) in control and mTOR+ MVPCs. Scale bars: 100 μm. (D) Representative images of colony-forming unit fibroblasts (CFU-F) on day 10. (E) Electric Cell-Substrate Impedance Sensing analysis of endothelial barrier function recovery following injury in the presence of control MVPC or two mTOR+ MVPC lines. ***P < 0.001. (F) To create humanized mice, we adoptively transferred 500,000 age-matched (age 60–66 years) female human MVPCs from a healthy control (n = 5 recipient mice), unaffected (non-cystic lung; 2 independent COPD patient cell lines, n = 3 recipient mice per line), mTOR+ (cystic lung; 3 independent cell lines, n = 5, 3, and 3 recipient mice), or HBSS vehicle control (n = 9 recipient mice) via tail vein of recipient female NSG mice (age 14 weeks). This study was repeated twice independently. Lung function and structure were analyzed at 2 months. (G–K) Airway physiology was measured using flexiVent analyses. (G) Area under the curve of pressure/volume (PV) loops. (H) Mean inspiratory capacity (IC). (I) Quasi-static compliance (Cst). (J) Respiratory system compliance (Crs). (K) Respiratory system elastance (Ers). (L) Aerated lung volume determined by micro-CT. (M) Representative H&E staining. Scale bars: 100 μm. (N) Mean linear intercept (MLI). (O) Collagen deposition quantified by trichrome stain and Fiji (NIH) analysis. Data were analyzed by 1-way ANOVA followed by Tukey’s HSD post hoc analysis and are presented as mean ± SEM. *P < 0.05, **P < 0.01. (P–S) Lung vascular lesions were identified at 2 months and trichrome stained to detect collagen (P) and immunostained to localize α-smooth muscle actin (SMA, red) and factor 8 (F8, green) (Q). (R) Enlarged image. (S) Costaining to detect human mitochondrial antigen (white). Scale bars: 100 μm.