Biology subjects

Carraro, G.

Publications and source records attributed to Carraro, G..

9 recordsLinked to original sources

bioRxiv2023

A potential acoustic role for CFTR ion channel in conductive hearing loss

Loss-of-function mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF). The middle ear and eustachian tube could be adversely affected in CF. In this study, we provide evidence of the role of CFTR function in conductive hearing. We developed an in-situ model to determine CFTR dependent fluid secretion in the middle ear using native mouse auditory capsule. A unique middle ear-on-a-chip was developed to address the functional and molecular basis of conductive hearing impairment. Using single-cell transcriptomics, middle ear cell composition and the associated transcriptomic signature were compared between CF and WT groups. A specialized subset of epithelial cells expressed CFTR with an overlapping signature with secretory epithelial cells. Genes related to ciliogenesis, hearing and ossification were significantly altered in CF mice middle ear. Our data suggest that CF middle ear may be at higher risk for conductive hearing loss.

cell biology↗

bioRxiv2022

Cell-surface PD-L1 expression identifies a sub-population of distal epithelial cells enriched in idiopathic pulmonary fibrosis

Idiopathic lung fibrosis (IPF) is a fatal lung disease characterized by chronic epithelial injury and exhausted repair capacity of the alveolar compartment, associated with the expansion of cells with intermediate alveolar epithelial cell (AT2) characteristics. Using SftpcCreERT2/+: tdTomatoflox/flox mice, we previously identified a lung population of quiescent injury activated alveolar epithelial progenitors (IAAPs) marked by low expression of the AT2 lineage trace marker tdTomato (Tomlow), and characterized by high levels of Pd-l1 (Cd274) expression. This led us to hypothesize that a population with similar properties exists in the human lung. To that end, we used flow cytometry to characterize the CD274 cell surface expression in lung epithelial cells isolated from donor and end-stage IPF lungs. The identity and functional behavior of these cells were further characterized by qPCR analysis, in vitro organoid formation, and ex vivo precision-cut lung slices (PCLS). Our analysis led to the identification of a population of CD274pos cells expressing intermediate levels of SFTPC, which was expanded in IPF lungs. While donor CD274pos cells initiated clone formation, they did not expand significantly in 3D organoids in AT2-supportive conditions. However, an increased number of CD274pos cells was found in cultured PCLS. In conclusion, we demonstrate that, similar to the IAAPs in the mouse lung, a population of CD274 expressing cells exists in the normal human lung and this population is expanded in the IPF lung and in an ex vivo PCLS assay, suggestive of progenitor cell behavior.

cell biology↗

bioRxiv2022

Fgfr2b signaling is essential for the maintenance of the alveolar epithelial type 2 lineage during lung homeostasis in mice

Fibroblast growth factor receptor 2b (Fgfr2b) signaling is essential throughout lung development to form the alveolar epithelial lineage. However, its role in alveolar epithelial type 2 cells (AT2s) homeostasis was recently considered dispensable. SftpcCreERT2; tdTomatoflox/flox mice were used to delete Fgfr2b expression in cells belonging to the AT2 lineage, which contains mature AT2s and a novel SftpcLow lineage-traced population called "injury activated alveolar progenitors" or IAAPs. Upon continuous tamoxifen exposure for either one or two weeks to delete Fgfr2b, a shrinking of the AT2s is observed. Mature AT2s exit the cell cycle, undergo apoptosis and fail to form alveolospheres in vitro. However, the lung morphometry appears normal, suggesting the involvement of compensatory mechanisms. In mutant lungs, IAAPs which escaped Fgfr2b deletion expand, display enhanced alveolosphere formation in vitro and increase drastically their AT2 signature suggesting differentiation towards mature AT2s. Interestingly, a significant increase in AT2s and decrease in IAPPs occurs after a one-week tamoxifen exposure followed by an eight-week chase period. While mature AT2s partially recover their alveolosphere formation capabilities, the IAAPs no longer display this property. Single-cell RNA seq analysis confirms that AT2s and IAAPs represent stable and distinct cell populations and recapitulate some of their characteristics observed in vivo. Our results underscore the essential role played by Fgfr2b signaling in the maintenance of the AT2 lineage in the adult lung and suggest that the IAAPs could represent a new population of AT2 progenitors.

developmental biology↗

bioRxiv2022

Characterization of alveolar epithelial lineage heterogeneity during the late pseudoglandular stage of mouse lung development

The specification, characterization, and fate of alveolar type 1 and type 2 (AT1 and 2) progenitors during embryonic lung development remains mostly elusive. In this paper, we build upon our previously published work on the regulation of airway epithelial progenitors by fibroblast growth factor receptor 2b (Fgfr2b) signalling during early (E12.5) and mid (E14.5) pseudoglandular lung development. Here, we looked at the regulation by Fgfr2b signalling on alveolar progenitors during late pseudoglandular/early canalicular (E14.5-E16.5) development. Using a dominant negative mouse model to conditionally inhibit Fgfr2b ligands at E16.5, we used gene array analyses to characterize a set of potential direct targets of Fgfr2b signalling. By mining published single-cell RNA sequence (scRNAseq) datasets, we showed that these Fgfr2b signature genes narrow on a discreet subset of AT2 cells at E17.5 and in adult lungs. Furthermore, we demonstrated that Fgfr2b signalling is lost in AT2 cells in their transition to AT1 cells during repair after injury. We also used CreERT2-based mouse models to conditionally knock-out the Fgfr2b gene in AT2 and in AT1 progenitors, as well as lineage label these cells. We found, using immunofluorescence, that in wildtype controls AT1 progenitors labeled at E14.5-E15.5 contribute a significant proportion to AT2 cells at E18.5; while AT2 progenitors labeled at the same time contribute significantly to the AT1 lineage. We show, using immunofluorescence and FACS-based analysis, that knocking out of Fgfr2b at E14.5-E15.5 in AT2 progenitors leads to an increase in lineage-labeled AT1 cells at E18.5; while the reverse is true in AT1 progenitors. Furthermore, we demonstrate that increased Fgfr signalling in AT2 progenitors reduces their contribution to the AT1 pool. Taken together, our results suggest that a significant proportion of AT2 and AT1 progenitors are cross-lineage committed during late pseudoglandular development, and that lineage commitment is regulated in part by Fgfr2b signalling. We have characterized a set of direct Fgfr2b targets at E16.5 which are likely involved in alveolar lineage formation. These signature genes concentrate on a subpopulation of AT2 cells later in development, and are downregulated in AT2 cells transitioning to the AT1 lineage during repair after injury in adults. Our findings highlight the extensive heterogeneity of alveolar cells by elucidating the role of Fgfr2b signalling in these cells during early alveolar lineage formation, as well as during repair after injury.

developmental biology↗

bioRxiv2021

Cryobanking of human distal lung epithelial cells for preservation of their phenotypic and functional characteristics.

The epithelium lining airspaces of the human lung is maintained by regional stem cells including basal cells of pseudostratified airways and alveolar type 2 pneumocytes (AT2) of the alveolar gas-exchange region. Despite effective methods for long-term preservation of airway basal cells, methods for efficient preservation of functional epithelial cell types of the distal gas-exchange region are lacking. Here we detail a method for cryobanking of epithelial cells from either mouse or human lung tissue for preservation of their phenotypic and functional characteristics. Flow cytometric profiling, epithelial organoid-forming efficiency, and single cell transcriptomic analysis, were used to compare cells recovered from cryopreserved tissue with those of freshly dissociated tissue. Alveolar type 2 cells within single cell suspensions of enzymatically digested cryobanked distal lung tissue retained expression of the pan-epithelial marker CD326 and the AT2 cell surface antigen recognized by monoclonal antibody HTII-280, allowing antibody-mediated enrichment and downstream analysis. Isolated AT2 cells from cryobanked tissue were comparable with those of freshly dissociated tissue both in their single cell transcriptome and their capacity for in vitro organoid formation in 3D cultures. We conclude that the cryobanking method described herein allows long-term preservation of distal human lung tissue for downstream analysis of lung cell function and molecular phenotype, and is ideally suited for creation of an easily accessible tissue resource for the research community.

cell biology↗

bioRxiv2021

Epithelial Plasticity and Innate Immune Activation Promote Lung Tissue Remodeling following Respiratory Viral Infection.

Epithelial plasticity has been suggested in lungs of mice following genetic depletion of stem cells but is of unknown physiological relevance. Viral infection and chronic lung disease share similar pathological features of stem cell loss in alveoli, basal cell (BC) hyperplasia in small airways, and innate immune activation, that contribute to epithelial remodeling and loss of lung function. We show that a novel subset of distal airway secretory cells, intralobar serous (IS) cells, are activated to assume BC fates following influenza virus infection. Injury-induced hyperplastic BC (hBC) differ from pre-existing BC by high expression of IL-22Ra1 and undergo IL-22-dependent expansion for colonization of injured alveoli. Resolution of virus-elicited inflammation resulted in BC>IS re-differentiation in repopulated alveoli, and increased local expression of antimicrobial factors, but failed to replace normal alveolar epithelium. Epithelial plasticity therefore protects against mortality from acute respiratory viral infection but results in distal lung remodeling and loss of lung function.

cell biology↗

bioRxiv2020

Single cell reconstruction of human basal cell diversity in normal and IPF lung.

RationaleDeclining lung function in patients with interstitial lung disease is accompanied by epithelial remodeling and progressive scarring of the gas-exchange region. There is a need to better understand the contribution of basal cell hyperplasia and associated mucosecretory dysfunction to the development of idiopathic pulmonary fibrosis (IPF). ObjectivesWe sought to decipher the transcriptome of freshly isolated epithelial cells from normal and IPF lung to discern disease-dependent changes within basal stem cells. MethodsSingle cell RNA sequencing was used to map epithelial cell types of the normal and IPF human airway. Organoid and ALI cultures were used to investigate functional properties of basal cell subtypes. Measurements and Main ResultsWe found that basal cells included multipotent and secretory primed subsets in control adult lung tissue. Secretory primed basal cells include an overlapping molecular signature with basal cells obtained from distal lung tissue of IPF lungs. We confirmed that NOTCH2 maintains undifferentiated basal cells and restrict basal-to-ciliated differentiation, and present evidence that NOTCH3 functions to restrain secretory differentiation. ConclusionsBasal cells are dynamically regulated in disease and are specifically biased towards expansion of the secretory primed basal cell subset in idiopathic pulmonary fibrosis. Modulation of basal cell plasticity may represent a relevant target for therapeutic intervention in IPF.

cell biology↗

bioRxiv2020

A molecular atlas of proximal airway identifies subsets of known airway cell types revealing details of the unique molecular pathogenesis of Cystic Fibrosis

Introduction/AbstractCystic fibrosis (CF) is a lethal autosomal recessive disorder that afflicts in excess of 70,000 people globally. People with CF experience multi-organ dysfunction resulting from aberrant electrolyte transport across polarized epithelia due to mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. CF-related lung disease is by far the most significant determinant of morbidity and mortality. In this study we report results from a multi-institute consortium in which single cell transcriptomics were applied to define disease-related changes to the proximal airway of CF donors (n=19) undergoing transplantation for end-stage lung disease compared to the proximal airway of previously healthy lung donors (n=19). We found that all major airway epithelial cell types were conserved between control and CF donors. Disease-dependent differences were observed, including an overabundance of epithelial cells transitioning to specialized ciliated and secretory cell subtypes coupled with an unexpected decrease in cycling basal cells. This study developed a molecular atlas of the proximal airway epithelium that will provide insights for the development of new targeted therapies for CF airway disease.

cell biology↗

bioRxiv2019

Senescence of alveolar stem cells drives progressive pulmonary fibrosis

Tissue fibrosis is a common pathological outcome of chronic disease that markedly impairs organ function leading to morbidity and mortality. In the lung, idiopathic pulmonary fibrosis (IPF) is an insidious and fatal interstitial lung disease associated with declining pulmonary function. Here, we show that alveolar type 2 (AT2) stem cells isolated from IPF lung tissue exhibit characteristic transcriptomic features of cellular senescence. We used conditional loss of Sin3a in adult mouse AT2 cells to initiate a program of p53-dependent cellular senescence, AT2 cell depletion, and spontaneous, progressive pulmonary fibrosis. We establish that senescence rather than loss of epithelial stem cells serves as a proximal driver of Tgf{beta} activation and progressive fibrosis and show that either genetic or pharmacologic interventions targeting p53 activation, senescence, or downstream Tgf{beta} activation, block fibrogenesis.

cell biology↗