scholarly journals Alveoli form directly by budding led by a single epithelial cell

2021 ◽  
Author(s):  
Astrid Gillich ◽  
Krystal R. St. Julien ◽  
Douglas G. Brownfield ◽  
Kyle J. Travaglini ◽  
Ross J. Metzger ◽  
...  

Oxygen passes along the ramifying branches of the lung's bronchial tree and enters the blood through millions of tiny, thin-walled gas exchange sacs called alveoli. Classical histological studies have suggested that alveoli arise late in development by a septation process that subdivides large air sacs into smaller compartments. Although a critical role has been proposed for contractile myofibroblasts, the mechanism of alveolar patterning and morphogenesis is not well understood. Here we present the three-dimensional cellular structure of alveoli, and show using single-cell labeling and deep imaging that an alveolus in the mouse lung is composed of just 2 epithelial cells and a total of a dozen cells of 7 different types, each with a remarkable, distinctive structure. By mapping alveolar development at cellular resolution at a specific position in the branch lineage, we find that alveoli form surprisingly early by direct budding of epithelial cells out from the airway stalk between enwrapping smooth muscle cells that rearrange into a ring of 3-5 myofibroblasts at the alveolar base. These alveolar entrance myofibroblasts are anatomically and developmentally distinct from myofibroblasts that form the thin fiber partitions of alveolar complexes ('partitioning' myofibroblasts). The nascent alveolar bud is led by a single alveolar type 2 (AT2) cell following selection from epithelial progenitors; a lateral inhibitory signal transduced by Notch ensures selection of only one cell so its trailing neighbor acquires AT1 fate and flattens into the cup-shaped wall of the alveolus. Our analysis suggests an elegant new model of alveolar patterning and formation that provides the foundation for understanding the cellular and molecular basis of alveolar diseases and regeneration.

2002 ◽  
Vol 282 (5) ◽  
pp. L1004-L1011 ◽  
Author(s):  
Nguyet M. Nguyen ◽  
Yushi Bai ◽  
Katsumi Mochitate ◽  
Robert M. Senior

Basement membranes have a critical role in alveolar structure and function. Alveolar type II cells make basement membrane constituents, including laminin, but relatively little is known about the production of basement membrane proteins by murine alveolar type II cells and a convenient system is not available to study basement membrane production by murine alveolar type II cells. To facilitate study of basement membrane production, with particular focus on laminin chains, we examined transformed murine distal respiratory epithelial cells (MLE-15), which have many structural and biochemical features of alveolar type II cells. We found that MLE-15 cells produce laminin-α5, a trace amount of laminin-α3, laminins-β1 and -γ1, type IV collagen, and perlecan. Transforming growth factor-β1 significantly induces expression of laminin-α1. When grown on a fibroblast-embedded collagen gel, MLE-15 cells assemble a basement membrane-like layer containing laminin-α5. These findings indicate that MLE-15 cells will be useful in modeling basement membrane production and assembly by alveolar type II cells.


Author(s):  
Victor K. Lin ◽  
Shih-Ya Wang ◽  
Lanxiao Wu ◽  
Smitha M. Rao ◽  
J. C. Chiao ◽  
...  

Epithelial to mesenchymal transition (EMT) has been believed to play a critical role in cancer metastasis. TGFβ has been described as an inducer of EMT in normal mammary epithelial cells by signaling through receptor serine/threonine kinase pathways to regulate epithelial cell plasticity and invasion. In this study, we investigated the EMT cellular responses, including morphologic changes, phenotype switches, invasiveness enhancement, and cellular contraction alteration, in TGFβ stimulated human prostate normal epithelial cells (PZ-HPV-7). Migration of TGFβ treated PZ-HPV-7 cells across matrigel was measured in invasion chambers (8 μm pore size). The cells were treated with or without TGFβ (2 ng/ml) in PrEGM media for 3 days. Immunoblot assay was conducted and it was demonstrated that the induction of vimentin when stimulated by TGFβ was accompanied by a downregulation of E-cadherin, though p-cadherin level was not altered. It was also observed that there was a decrease in cytokaretin 5/6 expression associated with the downregulation of E-cadherin during the induction of EMT. In order to study the cell contraction, three-dimensional collage lattice assay was performed. It was demonstrated that TGFβ-stimulated PZ-HPV-7 cells gained contractility. Our results showed that TGFβ stimulation induced PZ-HPV-7 cells to undergo epithelial to mesenchymal transition. EMT characteristics such as acquisition of mesenchymal markers and loss of epithelial markers were evident in the induction of vimentin and downregulation of E-cadherin and cytokeratins, as well as phenotypic alterations including increased contraction and enhanced mobility were detected.


2000 ◽  
Vol 279 (6) ◽  
pp. L1066-L1074 ◽  
Author(s):  
Angela Naltner ◽  
Susan Wert ◽  
Jeffrey A. Whitsett ◽  
Cong Yan

Our laboratory has previously demonstrated that retinoic acid nuclear receptor, thyroid transcription factor-1 (TTF-1), and nuclear receptor coactivators such as cAMP response element binding protein (CREB) binding protein (CBP)/p300 and steroid receptor coactivator-1 (SRC-1) form an enhanceosome on the 5′-enhancer region of the human surfactant protein B gene. Immunohistochemistry was used to identify cells that coexpressed CBP/p300, SRC-1, retinoid X receptor, and TTF-1 in the developing and mature lung. CBP/p300 and SRC-1 were expressed in the adult mouse lung, CBP and p300 being present in both alveolar type I and type II epithelial cells and SRC-1 and TTF-1 being restricted to type II epithelial cells. CBP/p300, SRC-1, and TTF-1 were readily detected in the nuclei of developing respiratory epithelial tubules in fetal mice from embryonic days 10 to 18.CBP/p300 and SRC-1 were also detected in developing mesenchymal cells. These coactivators were coexpressed with TTF-1 and SP-B in human pulmonary adenocarcinoma cells (H441 cells) in vitro. Interaction assays with a two-hybrid reporter analysis demonstrated direct interactions among TTF-1, SRC-1, and CBP/p300 in H441 cells. These findings support a role for retinoic acid receptor and nuclear receptor coactivators in the regulation of SP-B gene expression in the respiratory epithelium.


PLoS ONE ◽  
2020 ◽  
Vol 15 (10) ◽  
pp. e0240333
Author(s):  
Munenori Habuta ◽  
Akihiro Yasue ◽  
Ken-ichi T. Suzuki ◽  
Hirofumi Fujita ◽  
Keita Sato ◽  
...  

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245558
Author(s):  
Sena Fujii ◽  
Taiga Muranaka ◽  
Jun Matsubayashi ◽  
Shigehito Yamada ◽  
Akio Yoneyama ◽  
...  

Some human organs are composed of bifurcated structures. Two simple branching modes—monopodial and dipodial—have been proposed. With monopodial branching, child branches extend from the sidewall of the parent branch. With dipodial branching, the tip of the bronchus bifurcates. However, the branching modes of the human bronchial tree have not been elucidated precisely. A total of 48 samples between Carnegie stage (CS) 15 and CS23 belonging to the Kyoto Collection were used to acquire imaging data with phase-contrast X-ray computed tomography. Bronchial trees of all samples were three-dimensionally reconstructed from the image data. We analyzed the lobar bronchus, segmental bronchus, and subsegmental bronchus. After calculating each bronchus length, we categorized the branching mode of the analyzed bronchi based on whether the parent bronchus was divided after generation of the analyzed bronchi. All lobar bronchi were formed with monopodial branching. Twenty-five bifurcations were analyzed to categorize the branching mode of the segmental and subsegmental bronchi; 22 bifurcations were categorized as monopodial branching, two bifurcations were not categorized as any branching pattern, and the only lingular bronchus that bifurcated from the left superior lobar bronchus was categorized as dipodial branching. The left superior lobar bronchus did not shorten during the period from CS17 or CS18, when the child branch was generated, to CS23. All analyzed bronchi that could be categorized, except for one, were categorized as monopodial branching. The branching modes of the lobar bronchus and segmental bronchus were similar in the mouse lung and human lung; however, the modes of the subsegmental bronchi were different. Furthermore, remodeling, such as shrinkage of the bronchus, was not observed during the analysis period. Our three-dimensional reconstructions allowed precise calculation of the bronchus length, thereby improving the knowledge of branching morphogenesis in the human embryonic lung.


Author(s):  
Julian P. Heath ◽  
Buford L. Nichols ◽  
László G. Kömüves

The newborn pig intestine is adapted for the rapid and efficient absorption of nutrients from colostrum. In enterocytes, colostral proteins are taken up into an apical endocytotic complex of channels that transports them to target organelles or to the basal surface for release into the circulation. The apical endocytotic complex of tubules and vesicles clearly is a major intersection in the routes taken by vesicles trafficking to and from the Golgi, lysosomes, and the apical and basolateral cell surfaces.Jejunal tissues were taken from piglets suckled for up to 6 hours and prepared for electron microscopy and immunocytochemistry as previously described.


2007 ◽  
Vol 177 (4S) ◽  
pp. 93-93
Author(s):  
Toshiyuki Tsunoda ◽  
Junichi Inocuchi ◽  
Darren Tyson ◽  
Seiji Naito ◽  
David K. Ornstein

2001 ◽  
Vol 7 (S2) ◽  
pp. 580-581
Author(s):  
CA Witz ◽  
S Cho ◽  
VE Centonze ◽  
IA Montoya-Rodriguez ◽  
RS Schenken

Using human peritoneal explants, we have previously demonstrated that endometrial stromal cells (ESCs) and endometrial epithelial cells (EECs) attach to intact mesothelium. Attachment occurs within one hour and mesothelial invasion occurs within 18 hours (Figure 1). We have also demonstrated that, in vivo, the mesothelium overlies a continuous layer of collagen IV (Col IV).More recently we have used CLSM, to study the mechanism and time course of ESC and EEC attachment and invasion through mesothelial monolayers. in these studies, CellTracker® dyes were used to label cells. Mesothelial cells were labeled with chloromethylbenzoylaminotetramethylrhodamine (CellTracker Orange). Mesothelial cells were then plated on human collagen IV coated, laser etched coverslips. Mesothelial cells were cultured to subconfluence. ESCs and EECs, labeled with chloromethylfluorscein diacetate (CellTracker Green) were plated on the mesothelial monolayers. Cultures were examined at 1, 6, 12 and 24 hours with simultaneous differential interference contrast and CLSM.


Author(s):  
Georgia Colleluori ◽  
Jessica Perugini ◽  
Giorgio Barbatelli ◽  
Saverio Cinti

AbstractThe mammary gland (MG) is an exocrine gland present in female mammals responsible for the production and secretion of milk during the process of lactation. It is mainly composed by epithelial cells and adipocytes. Among the features that make the MG unique there are 1) its highly plastic properties displayed during pregnancy, lactation and involution (all steps belonging to the lactation cycle) and 2) its requirement to grow in close association with adipocytes which are absolutely necessary to ensure MG’s proper development at puberty and remodeling during the lactation cycle. Although MG adipocytes play such a critical role for the gland development, most of the studies have focused on its epithelial component only, leaving the role of the neighboring adipocytes largely unexplored. In this review we aim to describe evidences regarding MG’s adipocytes role and properties in physiologic conditions (gland development and lactation cycle), obesity and breast cancer, emphasizing the existing gaps in the literature which deserve further investigation.


Sign in / Sign up

Export Citation Format

Share Document