Determining the ideal osteotomy for stemless total shoulder replacement: a cadaveric study.

HYPOTHESIS: We sought to determine the angle of osteotomy that produces a circular humeral cut surface. METHODS: A total of 49 cadaveric shoulders, from 25 cadavers, underwent sequential humeral head osteotomy from 180° (vertical, in line with the humeral diaphyseal shaft), in 10° increments, until the rotator cuff insertion was encountered. At each stage, the anteroposterior (AP) and superoinferior (SI) distances were recorded. The data were analyzed for normality and then assessed to determine the optimum cut angle. RESULTS: The AP/SI ratio is an indication of roundness. Plotting values of 1 - AP/SI (ie, error) vs. cut angle allowed us to plot the likelihood of producing a circular cut surface using a third-order curve that created the best fit to the data set (R2 = 0.99). The results from this study suggest that the optimum osteotomy angle that produces a circular cut surface is 23° from the vertical. The cohort data illustrated that at this angle, the average roundness error was 1% with a 95% confidence limit of <1%. There was no significant difference (P > .05) between sexes. CONCLUSION: The humeral head shape changes from oval to circular and then to an oval cut surface as the osteotomy angle increases from the vertical toward the horizontal. The range of angles within which the cut surface is circular, within a 10% error margin, is 18°-27° from the vertical, which is much less than the traditional osteotomy angle of 45°.

Up-regulation of ACE2, the SARS-CoV-2 receptor, in asthmatics on maintenance inhaled corticosteroids.

BACKGROUND: The first step in SARS-CoV-2 infection is binding of the virus to angiotensin converting enzyme 2 (ACE2) on the airway epithelium. Asthma affects over 300 million people world-wide, many of whom may encounter SARS-CoV-2. Epidemiologic data suggests that asthmatics who get infected may be at increased risk of more severe disease. Our objective was to assess whether maintenance inhaled corticosteroids (ICS), a major treatment for asthma, is associated with airway ACE2 expression in asthmatics. METHODS: Large airway epithelium (LAE) of asthmatics treated with maintenance ICS (ICS+), asthmatics not treated with ICS (ICS-), and healthy controls (controls) was analyzed for expression of ACE2 and other coronavirus infection-related genes using microarrays. RESULTS: As a group, there was no difference in LAE ACE2 expression in all asthmatics vs controls. In contrast, subgroup analysis demonstrated that LAE ACE2 expression was higher in asthmatics ICS+ compared to ICS‾ and ACE2 expression was higher in male ICS+ compared to female ICS+ and ICS‾ of either sex. ACE2 expression did not correlate with serum IgE, absolute eosinophil level, or change in FEV1 in response to bronchodilators in either ICS- or ICS+. CONCLUSION: Airway ACE2 expression is increased in asthmatics on long-term treatment with ICS, an observation that should be taken into consideration when assessing the use of inhaled corticosteroids during the pandemic.

Expression of the SARS-CoV-2 ACE2 Receptor in the Human Airway Epithelium.

Rationale: Infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease (COVID-19), a predominantly respiratory illness. The first step in SARS-CoV-2 infection is binding of the virus to ACE2 (angiotensin-converting enzyme 2) on the airway epithelium.Objectives: The objective was to gain insight into the expression of ACE2 in the human airway epithelium.Methods: Airway epithelia sampled by fiberoptic bronchoscopy of trachea, large airway epithelia (LAE), and small airway epithelia (SAE) of nonsmokers and smokers were analyzed for expression of ACE2 and other coronavirus infection-related genes using microarray, RNA sequencing, and 10x single-cell transcriptome analysis, with associated examination of ACE2-related microRNA.Measurements and Main Results:1) ACE2 is expressed similarly in the trachea and LAE, with lower expression in the SAE; 2) in the SAE, ACE2 is expressed in basal, intermediate, club, mucus, and ciliated cells; 3) ACE2 is upregulated in the SAE by smoking, significantly in men; 4) levels of miR-1246 expression could play a role in ACE2 upregulation in the SAE of smokers; and 5) ACE2 is expressed in airway epithelium differentiated in vitro on air-liquid interface cultures from primary airway basal stem/progenitor cells; this can be replicated using LAE and SAE immortalized basal cell lines derived from healthy nonsmokers.Conclusions:ACE2, the gene encoding the receptor for SARS-CoV-2, is expressed in the human airway epithelium, with variations in expression relevant to the biology of initial steps in SARS-CoV-2 infection.

Cell-specific expression of lung disease risk-related genes in the human small airway epithelium.

BACKGROUND: The human small airway epithelium (SAE) plays a central role in the early events in the pathogenesis of most inherited and acquired lung disorders. Little is known about the molecular phenotypes of the specific cell populations comprising the SAE in humans, and the contribution of SAE specific cell populations to the risk for lung diseases. METHODS: Drop-seq single-cell RNA-sequencing was used to characterize the transcriptome of single cells from human SAE of nonsmokers and smokers by bronchoscopic brushing. RESULTS: Eleven distinct cell populations were identified, including major and rare epithelial cells, and immune/inflammatory cells. There was cell type-specific expression of genes relevant to the risk of the inherited pulmonary disorders, genes associated with risk of chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis and (non-mutated) driver genes for lung cancers. Cigarette smoking significantly altered the cell type-specific transcriptomes and disease risk-related genes. CONCLUSIONS: This data provides new insights into the possible contribution of specific lung cells to the pathogenesis of lung disorders.

Exaggerated BMP4 signalling alters human airway basal progenitor cell differentiation to cigarette smoking-related phenotypes.

Airway remodelling in chronic obstructive pulmonary disease (COPD) originates, in part, from smoking-induced changes in airway basal stem/progenitor cells (BCs). Based on the knowledge that bone morphogenetic protein 4 (BMP4) influences epithelial progenitor function in the developing and adult mouse lung, we hypothesised that BMP4 signalling may regulate the biology of adult human airway BCs relevant to COPD.BMP4 signalling components in human airway epithelium were analysed at the mRNA and protein levels, and the differentiation of BCs was assessed using the BC expansion and air-liquid interface models in the absence/presence of BMP4, BMP receptor inhibitor and/or small interfering RNAs against BMP receptors and downstream signalling.The data demonstrate that in cigarette smokers, BMP4 is upregulated in ciliated and intermediate undifferentiated cells, and expression of the BMP4 receptor BMPR1A is enriched in BCs. BMP4 induced BCs to acquire a smoking-related abnormal phenotype in vitro mediated by BMPR1A/Smad signalling, characterised by decreased capacity to differentiate into normal mucociliary epithelium, while generating squamous metaplasia.Exaggerated BMP4 signalling promotes cigarette smoking-relevant airway epithelial remodelling by inducing abnormal phenotypes in human airway BCs. Targeting of BMP4 signalling in airway BCs may represent a novel target to prevent/treat COPD-associated airway disease.

Role of KRAS in regulating normal human airway basal cell differentiation.

BACKGROUND: KRAS is a GTPase that activates pathways involved in cell growth, differentiation and survival. In normal cells, KRAS-activity is tightly controlled, but with specific mutations, the KRAS protein is persistently activated, giving cells a growth advantage resulting in cancer. While a great deal of attention has been focused on the role of mutated KRAS as a common driver mutation for lung adenocarcinoma, little is known about the role of KRAS in regulating normal human airway differentiation. METHODS: To assess the role of KRAS signaling in regulating differentiation of the human airway epithelium, primary human airway basal stem/progenitor cells (BC) from nonsmokers were cultured on air-liquid interface (ALI) cultures to mimic the airway epithelium in vitro. Modulation of KRAS signaling was achieved using siRNA-mediated knockdown of KRAS or lentivirus-mediated over-expression of wild-type KRAS or the constitutively active G12 V mutant. The impact on differentiation was quantified using TaqMan quantitative PCR, immunofluorescent and immunohistochemical staining analysis for cell type specific markers. Finally, the impact of cigarette smoke exposure on KRAS and RAS protein family activity in the airway epithelium was assessed in vitro and in vivo. RESULTS: siRNA-mediated knockdown of KRAS decreased differentiation of BC into secretory and ciliated cells with a corresponding shift toward squamous cell differentiation. Conversely, activation of KRAS signaling via lentivirus mediated over-expression of the constitutively active G12 V KRAS mutant had the opposite effect, resulting in increased secretory and ciliated cell differentiation and decreased squamous cell differentiation. Exposure of BC to cigarette smoke extract increased KRAS and RAS protein family activation in vitro. Consistent with these observations, airway epithelium brushed from healthy smokers had elevated RAS activation compared to nonsmokers. CONCLUSIONS: Together, these data suggest that KRAS-dependent signaling plays an important role in regulating the balance of secretory, ciliated and squamous cell differentiation of the human airway epithelium and that cigarette smoking-induced airway epithelial remodeling is mediated in part by abnormal activation of KRAS-dependent signaling mechanisms.

Association Between Diaphragmatic Paralysis and Ipsilateral Cervical Spondylosis on MRI.

PURPOSE: Diaphragmatic paralysis (DP) is an important cause of dyspnea with many underlying etiologies; however, frequently no cause is identified despite extensive investigation. We hypothesized that cervical spondylosis (CS), as manifest by cervical neuroforaminal stenosis on magnetic resonance imaging (MRI), is an underrecognized cause of unilateral DP. METHODS: A retrospective study was performed assessing cervical spine imaging utilization in the investigation of unilateral DP, and the contribution of CS to its pathogenesis. To assess the relationship between CS and DP, comparison was made between severity of ipsilateral and contralateral foraminal stenosis on cervical spine MRI in individuals with idiopathic DP, and to controls with DP of known etiology. RESULTS: Record searches identified 334 individuals with DP who were classified as idiopathic (n = 101) or DP of known etiology (n = 233). Of those with idiopathic DP, only 37% had undergone cervical spine imaging. Cervical spine MRIs, available for 32 individuals from the total cohort identified (n = 15 idiopathic DP, n = 17 DP of known etiology), were reviewed and severity of CS graded (0-2). In idiopathic DP, CS was significantly more severe (grade 2 stenosis) on the side of DP at C3-C4 (73% affected vs 13% unaffected side; p = 0.031) and C4-C5 (60% affected vs 20% unaffected side; p = 0.0039), while no difference was observed in DP of known etiology. Overall severity of CS across all cervical spine levels was significantly worse in idiopathic DP versus those with DP of known etiology. CONCLUSIONS: In unilateral idiopathic DP, severity of CS is associated with DP laterality and is an underrecognized cause of diaphragmatic dysfunction. We propose that evaluation of 'idiopathic' DP should routinely include cervical spine imaging, preferably by MRI.

Ambient Pollution-related Reprogramming of the Human Small Airway Epithelial Transcriptome.

RATIONALE: Epidemiologic studies have demonstrated that exposure to particulate matter ambient pollution has adverse effects on lung health, exacerbated by cigarette smoking. Particulate matter less than or equal to 2.5 µm in aerodynamic diameter (PM2.5) is among the most harmful urban pollutants and is closely linked to respiratory disease. OBJECTIVES: Based on the knowledge that the small airway epithelium (SAE) plays a central role in the pathogenesis of smoking-related lung disease, we hypothesized that elevated PM2.5 levels are associated with dysregulation of SAE gene expression, which may contribute to the development of respiratory disease. METHODS: From 2009 to 2012, healthy nonsmoker (n = 29) and smoker (n = 129) residents of New York City underwent bronchoscopy with SAE brushing (2.6 ± 1.3 samples/subject; total of 405 samples). SAE gene expression was assessed by Affymetrix HG-U133 Plus 2.0 microarray. New York City PM2.5 levels (Environmental Protection Agency data) were averaged for the 30 days before bronchoscopy. A linear mixed model was used to assess PM2.5-related gene dysregulation accounting for multiple clinical and methodologic variables. MEASUREMENTS AND MAIN RESULTS: Thirty-day mean PM2.5 levels varied from 6.2 to 18 µg/m3. In nonsmokers, there was no dysregulation of SAE gene expression associated with ambient PM2.5 levels. In marked contrast, n = 219 genes were significantly dysregulated in association with PM2.5 levels in the SAE of smokers. Many of these genes relate to cell growth and transcription regulation. Interestingly, 11% of genes were mitochondria associated. CONCLUSIONS: PM2.5 exposure contributes to significant dysregulation of the SAE transcriptome of smokers, linking pollution and airway epithelial biology in the risk of development of respiratory disease in susceptible individuals.

Ontogeny and Biology of Human Small Airway Epithelial Club Cells.

RATIONALE: Little is known about human club cells, dome-shaped cells with dense cytoplasmic granules and microvilli that represent the major secretory cells of the human small airways (at least sixth-generation bronchi). OBJECTIVES: To define the ontogeny and biology of the human small airway epithelium club cell. METHODS: The small airway epithelium was sampled from the normal human lung by bronchoscopy and brushing. Single-cell transcriptome analysis and air-liquid interface culture were used to assess club cell ontogeny and biology. MEASUREMENTS AND MAIN RESULTS: We identified the club cell population by unbiased clustering using single-cell transcriptome sequencing. Principal component gradient analysis uncovered an ontologic link between KRT5 (keratin 5)+ basal cells and SCGB1A1 (secretoglobin family 1A member 1)+ club cells, a hypothesis verified by demonstrating in vitro that a pure population of human KRT5+ SCGB1A1- small airway epithelial basal cells differentiate into SCGB1A1+KRT5- club cells on air-liquid interface culture. Using SCGB1A1 as the marker of club cells, the single-cell analysis identified novel roles for these cells in host defense, xenobiotic metabolism, antiprotease, physical barrier function, monogenic lung disorders, and receptors for human viruses. CONCLUSIONS: These observations provide novel insights into the molecular phenotype and biologic functions of the human club cell population and identify basal cells as the human progenitor cells for club cells.

Phenotypes of organ involvement in sarcoidosis.

Sarcoidosis is a highly variable, systemic granulomatous disease of hitherto unknown aetiology. The GenPhenReSa (Genotype-Phenotype Relationship in Sarcoidosis) project represents a European multicentre study to investigate the influence of genotype on disease phenotypes in sarcoidosis.The baseline phenotype module of GenPhenReSa comprised 2163 Caucasian patients with sarcoidosis who were phenotyped at 31 study centres according to a standardised protocol.From this module, we found that patients with acute onset were mainly female, young and of Scadding type I or II. Female patients showed a significantly higher frequency of eye and skin involvement, and complained more of fatigue. Based on multidimensional correspondence analysis and subsequent cluster analysis, patients could be clearly stratified into five distinct, yet undescribed, subgroups according to predominant organ involvement: 1) abdominal organ involvement, 2) ocular-cardiac-cutaneous-central nervous system disease involvement, 3) musculoskeletal-cutaneous involvement, 4) pulmonary and intrathoracic lymph node involvement, and 5) extrapulmonary involvement.These five new clinical phenotypes will be useful to recruit homogenous cohorts in future biomedical studies.

CXCL9 Regulates TGF-ß1-Induced Epithelial to Mesenchymal Transition in Human Alveolar Epithelial Cells.

Epithelial to mesenchymal cell transition (EMT), whereby fully differentiated epithelial cells transition to a mesenchymal phenotype, has been implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF). CXCR3 and its ligands are recognized to play a protective role in pulmonary fibrosis. In this study, we investigated the presence and extent of EMT and CXCR3 expression in human IPF surgical lung biopsies and assessed whether CXCR3 and its ligand CXCL9 modulate EMT in alveolar epithelial cells. Coexpression of the epithelial marker thyroid transcription factor-1 and the mesenchymal marker α-smooth muscle actin and CXCR3 expression was examined by immunohistochemical staining of IPF surgical lung biopsies. Epithelial and mesenchymal marker expression was examined by quantitative real-time PCR, Western blotting, and immunofluorescence in human alveolar epithelial (A549) cells treated with TGF-ß1 and CXCL9, with Smad2, Smad3, and Smad7 expression and cellular localization examined by Western blotting. We found that significantly more cells were undergoing EMT in fibrotic versus normal areas of lung in IPF surgical lung biopsy samples. CXCR3 was expressed by type II pneumocytes and fibroblasts in fibrotic areas in close proximity to cells undergoing EMT. In vitro, CXCL9 abrogated TGF-ß1-induced EMT. A decrease in TGF-ß1-induced phosphorylation of Smad2 and Smad3 occurred with CXCL9 treatment. This was associated with increased shuttling of Smad7 from the nucleus to the cytoplasm where it inhibits Smad phosphorylation. This suggests a role for EMT in the pathogenesis of IPF and provides a novel mechanism for the inhibitory effects of CXCL9 on TGF-ß1-induced EMT.

CXCR3 Requirement for the Interleukin-13-Mediated Up-Regulation of Interleukin-13Rα2 in Pulmonary Fibroblasts.

Idiopathic pulmonary fibrosis (IPF) is a progressive disease characterized by fibrosis and abnormal vascularity. IL-13, a profibrotic cytokine that plays a role in IPF, functions through the Jak/STAT pathway after binding to the IL-13 receptor α1 (IL-13Rα1)/IL-4Rα complex. IL-13 also binds to IL-13Rα2, which has been thought to function as a nonsignaling decoy receptor, although possible signaling roles of this receptor have been proposed. CXCR3 and its IFN-inducible ligands-CXCL9, CXCL10, and CXCL11-have been implicated in vascular remodeling and fibroblast motility during the development of IPF. In this study, CXCR3 expression was demonstrated in cultured pulmonary fibroblasts from wild-type BALB/c mice and was found to be necessary for the IL-13-mediated gene and protein up-regulation of IL-13Rα2. In fibroblasts from CXCR3-deficient mice, STAT6 activation was prolonged. This study is the first to demonstrate the expression of CXCR3 in fibroblasts and its association with the expression of IL-13Rα2. Taken together, the results from this study point strongly to a requirement for CXCR3 for IL-13-mediated IL-13Rα2 gene expression. Understanding the function of CXCR3 in IL-13-mediated lung injury may lead to novel approaches to combat the development of pulmonary fibrosis, whether by limiting the effects of IL-13 or by manipulation of angiostatic pathways. The elucidation of the complex relationship between these antifibrotic receptors and manipulation of the CXCR3-mediated regulation of IL-13Rα2 may represent a novel therapeutic modality in cases of acute lung injury or chronic inflammation that may progress to fibrosis.

Modulation of pulmonary fibrosis by IL-13Rα2.

Pulmonary fibrosis is a progressive and fatal disease that involves the remodeling of the distal airspace and the lung parenchyma, which results in compromised gas exchange. The median survival time once diagnosed is less than three years. Interleukin (IL)-13 has been shown to play a role in a number of inflammatory and fibrotic diseases. IL-13 modulates its effector functions via a complex receptor system that includes the IL-4 receptor (R) α, IL-13Rα1, and the IL-13Rα2. IL-13Rα1 binds IL-13 with low affinity, yet, when it forms a complex with IL-4α, it binds with much higher affinity, inducing the effector functions of IL-13. IL-13Rα2 binds IL-13 with high affinity but has a short cytoplasmic tail and has been shown to act as a nonsignaling decoy receptor. Transfection of fibroblasts and epithelial cells with IL-13Rα2 inhibited the IL-13 induction of soluble collagen, TGF-ß, and CCL17. Adenoviral overexpression of IL-13Rα2 in the lung reduced bleomycin-induced fibrosis. Our work shows that overexpression of IL-13Rα2 inhibits the IL-13 induction of fibrotic markers in vitro and inhibits bleomycin-induced pulmonary fibrosis. In summary our study highlights the antifibrotic nature of IL-13Ra2.

Role of SLMAP genetic variants in susceptibility of diabetes and diabetic retinopathy in Qatari population.

BACKGROUND: Overexpression of SLMAP gene has been associated with diabetes and endothelial dysfunction of macro- and micro-blood vessels. In this study our primary objective is to explore the role of SLMAP gene polymorphisms in the susceptibility of type 2 diabetes (T2DM) with or without diabetic retinopathy (DR) in the Qatari population. METHODS: A total of 342 Qatari subjects (non-diabetic controls and T2DM patients with or without DR) were genotyped for SLMAP gene polymorphisms (rs17058639 C > T; rs1043045 C > T and rs1057719 A > G) using Taqman SNP genotyping assay. RESULTS: SLMAP rs17058639 C > T polymorphism was associated with the presence of DR among Qataris with T2DM. One-way ANOVA and multiple logistic regression analysis showed SLMAP SNP rs17058639 C > T as an independent risk factor for DR development. SLMAP rs17058639 C > T polymorphism also had a predictive role for the severity of DR. Haplotype Crs17058639Trs1043045Ars1057719 was associated with the increased risk for DR among Qataris with T2DM. CONCLUSIONS: The data suggests the potential role of SLMAP SNPs as a risk factor for the susceptibility of DR among T2DM patients in the Qatari population.

Airflow rates and breathlessness recovery from submaximal exercise in healthy adults: prospective, randomised, cross-over study.

OBJECTIVES: Facial airflow from a hand-held fan may reduce breathlessness severity and hasten postexertion recovery. Data from randomised controlled trials are limited and the optimal airflow speed remains unknown. We aimed to determine the effect of different airflow speeds on recovery from exercise-induced breathlessness. METHODS: A prospective, randomised, cross-over design. Ten healthy participants (seven male; mean age 29±4 years; height 175±9 cm; body mass 76.9±14.1 kg) completed six bouts of 4 min of exercise. During the first 5 min of a 20 min recovery phase, participants received one of five airflow speeds by holding a fan ~15 cm from their face, or no fan control, administered in random order. Fan A had an internal blade, and fan B had an external blade. Breathlessness was measured using a numerical rating scale (NRS) at minute intervals for the first 10 min, and facial skin temperature was recorded using a thermal imaging camera (immediately postexertion and 5 min recovery). RESULTS: Nine participants completed the trial. A significant main effect for airflow speed (p=0.016, ηp2=0.285) and interaction effect for airflow speed over time (p=0.008, ηp2=0.167) suggest that the airflow speed modifies breathlessness during recovery from exercise. Fan speeds of 1.7 m/s or greater increased the speed of recovery from breathlessness compared with control (p<0.05) with the highest airflow speeds (2.5 m/s and 3.3 m/s) giving greatest facial cooling. CONCLUSION: Higher airflow rates (1.7 m/s or greater) reduced self-reported recovery times from exercise-induced breathlessness and reduced facial temperature .

Misalignment between Clinical Mold Antigen Extracts and Airborne Molds Found in Water-damaged Homes.

Rationale: Epidemiologic studies have demonstrated that exposure to molds and other fungi can play a role in a variety of allergic and pulmonary diseases in susceptible individuals. Species-specific mold antigen extracts are used in the clinical evaluation of suspected mold-related conditions; however, alignment between these extracts and the species of molds identified in the indoor environment of water-damaged homes has not been rigorously evaluated. Objectives: To identify the predominant genera and species of mold in the air of homes with water damage, mold growth, and/or occupants with respiratory complaints (complaint homes), and to assess their alignment with the mold antigen extracts used in clinical practice. Methods: The genera and species of molds identified in culture-type outdoor and indoor air samples collected from complaint homes throughout the United States and Canada from 2002 to 2017 were examined. Mold antigen extracts available and utilized for skin and serum testing in clinical practice were assessed, and alignment between these data were evaluated. Results: Culture data from 24,455 indoor air samples from 7,547 complaint homes and 29,493 outdoor samples were evaluated. Mean exposure values (colony-forming units [cfu]/m3) were calculated for each genus and species and indoor versus outdoor values were compared. Penicillium was the predominant genus identified in water-damaged homes, with a mean exposure (233.3 cfu/m3) 2.9 times higher than that of the Aspergillus genus (81.4 cfu/m3). Five Penicillium (P. aurantiogriseum, P. brevicompactum, P. citrinum, P. crustosum, and P. variabile) and three Aspergillus (A. versicolor, A. sydowii, and A. niger) species were identified as the predominant indoor water-damage-related fungi. However, none of these Penicillium species and only one of the Aspergillus species is currently available as an antigen extract for use in skin testing or serum testing panels. Conclusions: Significant misalignment exists between the currently available mold antigen extracts and the predominant species of molds found in water-damaged homes. Improving alignment has the potential to enhance diagnosis of mold-related diseases, including allergic asthma and hypersensitivity pneumonitis and to improve patient outcomes via interventions, including antigen avoidance through building remediation and occupant relocation, consistent with the findings of a recent American Thoracic Society Workshop Report.

Impaired differentiation of small airway basal stem/progenitor cells in people living with HIV.

With highly active anti-retroviral therapy (HAART), higher incidence of airway abnormalities is common in the HIV population consistent with the concept of accelerated lung "aging". Our previous findings demonstrated that HIV induces human airway basal cells (BC) into destructive and inflammatory phenotypes. Since BC function as stem/progenitor cells of the small airway epithelium (SAE), responsible for self-renewal and differentiation of SAE, we hypothesized that BC from people living with HIV (PLWH) may have altered differentiation capacity that contribute to premature aging. The data demonstrates that BC from PLWH have impaired capacity to differentiate in vitro and senescent phenotypes including shortened telomeres, increased expression of ß-galactosidase and cell cycle inhibitors, and mitochondrial dysfunction. In vitro studies demonstrated that BC senescence is partly due to adverse effects of HAART on BC. These findings provide an explanation for higher incidence of airway dysfunction and accelerated lung aging observed in PLWH.