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A5786 - FOXF1 Expression Represents a Unique Resident Mesenchymal Stromal Cell Population in the Adult Lung
Author Block: R. Braeuer1, N. M. Walker2, D. Wheeler1, K. Misumi1, P. Cao3, Y. Aoki3, V. N. Lama4; 1Internal Medicine/Pulmonary Critical Care, University of Michigan, Ann Arbor, MI, United States, 2Pulmonary/Critical Care, University of Michigan, Ann Arbor, MI, United States, 3Pulmonary, University of Michigan, Ann Arbor, MI, United States, 4Univ of Michigan, Ann Arbor, MI, United States.
Introduction: Resident mesenchymal progenitor cells in an adult lung are very poorly understood and remain a “black box” of lung regenerative responses. Here we have sought out to understand the FoxF1 expressing mesenchymal cell population, their underlying niche, and unique gene expression pattern in normal adult lungs. Materials and Methods: Bacterial artificial chromosome (BAC) transgenic mice were generated with the FoxF1 promoter in front of the red fluorescent protein Td tomato (FoxF1-RFP). Crossed with Collagen 1α1-GFP (Col-GFP), we generated FoxF1-RFP/Col-GFP transgenic animals. By utilizing flow cytometry, CD45 negative cells were sorted into Col-GFP+/FoxF1-RFP+, Col-GFP+/FoxF1-RFP-, and Col-GFP-/FoxF1-RFP+ populations and subjected to RNA seq. To identify FoxF1 localization within the mouse lung, immunohistochemical co-staining of anti-FoxF1 was performed with anti-GFP in both Collagen 1a1-GFP and PDGFRα-GFP transgenic mice. Results: Hierarchal clustering of the RNA seq found three distinct gene expression patterns from our sorted cell populations. The Col-GFP-/FoxF1+ cell population was enriched for endothelial genes as expected. Although both Col-GFP populations expressed high levels of Collagen 1α1 mRNA, a subset of genes was identified that were unique to the Col-GFP+FoxF1-RFP+ population as compared to Col-GFP+/FoxF1-RFP- cells. Moreover, the gene expression pattern of the CD45-/Col-GFP+/FoxF1+ population sorted directly from mouse lungs was compared to FoxF1-RFP+ cells grown in vitro. We identified a completely unique gene expression pattern when grown in vitro, highlighting the challenges associated with studying a mesenchymal stromal cell population removed from its in vivo niche. Immunohistochemical co-staining of FoxF1 in either Col-GFP or PDGFRα-GFP transgenic mice found FoxF1 to co-stain with GFP in peribronchial mesenchymal stromal cells. However, in the alveolar interstitium, FoxF1 expression is located in endothelial cells but is absent in mesenchymal stromal cells. Conclusion: FoxF1 expression marks a sub-population of collagen positive cells in an adult lung. This population has a unique gene expression pattern compared to FoxF1-RFP negative mesenchymal stromal cells. Peribronchial mesenchymal stromal cells have high levels of FoxF1 protein expression. Crosstalk with the bronchial epithelial cells could provide an essential microenvironment for maintaining FoxF1 expression and its transcriptional activity in peribronchial residential mesenchymal stromal cells.