Screening of factors inducing alveolar type 1 epithelial cells using human pluripotent stem cells

Alveolar type 2 (AT2) epithelial cells are tissue stem cells capable of differentiating into alveolar type 1 (AT1) cells for injury repair and maintenance of lung homeostasis. However, the factors involved in human AT2-to-AT1 cell differentiation are not fully understood. Here, we established SFTPCGFP and AGERmCherry-HiBiT dual-reporter induced pluripotent stem cells (iPSCs), which detected AT2-to-AT1 cell differentiation with high sensitivity and identified factors inducing AT1 cell differentiation from AT2 and their progenitor cells. We also established an "on-gel" alveolar epithelial spheroid culture suitable for medium-throughput screening. Among the 274 chemical compounds, several single compounds, including LATS-IN-1, converted AT1 cells from AT2 and their progenitor cells. Moreover, YAP/TAZ signaling activation and AKT signaling suppression synergistically recapitulated the induction of transcriptomic, morphological, and functionally mature AT1 cells. Our findings provide novel insights into human lung development and lung regenerative medicine.

Past and Future of Alveolar Organoids for Lung Regenerative Medicine

The lung is regarded as having limited regenerative capacity, and there are few treatment options for refractory lung diseases, such as interstitial pneumonia. Lung transplantation is the final option available in some scenarios. Research in this area has been slow owing to the complex structure of the lung for efficient gas exchange between the alveolar spaces and capillaries as well as the difficulty in obtaining specimens from patients with progressive lung disease. However, basic research over the past decade in the field of mouse and human embryology using genetic lineage tracing techniques and stem cell biology using primary and pluripotent stem cell-derived alveolar organoids has begun to clarify the tissue response in various intractable lung diseases and the mechanisms underlying remodeling. Advancement in this area may expand potential therapeutic targets for alveolar regeneration, providing alternatives to lung transplantation, and contribute to the development of effective therapeutic methods that activate or repopulate stem cells in the lung. In this review, we cover research focused on alveolar epithelial cells and discuss methods expected to regenerate lungs that are damaged by diseases.

ACE2 knockout hinders SARS-CoV-2 propagation in iPS cell-derived airway and alveolar epithelial cells

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, continues to spread around the world with serious cases and deaths. It has also been suggested that different genetic variants in the human genome affect both the susceptibility to infection and severity of disease in COVID-19 patients. Angiotensin-converting enzyme 2 (ACE2) has been identified as a cell surface receptor for SARS-CoV and SARS-CoV-2 entry into cells. The construction of an experimental model system using human iPS cells would enable further studies of the association between viral characteristics and genetic variants. Airway and alveolar epithelial cells are cell types of the lung that express high levels of ACE2 and are suitable for in vitro infection experiments. Here, we show that human iPS cell-derived airway and alveolar epithelial cells are highly susceptible to viral infection of SARS-CoV-2. Using gene knockout with CRISPR-Cas9 in human iPS cells we demonstrate that ACE2 plays an essential role in the airway and alveolar epithelial cell entry of SARS-CoV-2 in vitro. Replication of SARS-CoV-2 was strongly suppressed in ACE2 knockout (KO) lung cells. Our model system based on human iPS cell-derived lung cells may be applied to understand the molecular biology regulating viral respiratory infection leading to potential therapeutic developments for COVID-19 and the prevention of future pandemics.

Cryptotanshinone is a candidate therapeutic agent for interstitial lung disease associated with a BRICHOS-domain mutation of SFTPC

Interstitial lung disease (ILD) represents a large group of diseases characterized by chronic inflammation and fibrosis of the lungs, for which therapeutic options are limited. Among several causative genes of familial ILD with autosomal dominant inheritance, the mutations in the BRICHOS domain of SFTPC cause protein accumulation and endoplasmic reticulum stress by misfolding its proprotein. Through a screening system using these two phenotypes in HEK293 cells and evaluation using alveolar epithelial type 2 (AT2) cells differentiated from patient-derived induced pluripotent stem cells (iPSCs), we identified Cryptotanshinone (CPT) as a potential therapeutic agent for ILD. CPT decreased cell death induced by mutant SFTPC overexpression in A549 and HEK293 cells and ameliorated the bleomycin-induced contraction of the matrix in fibroblast-dependent alveolar organoids derived from iPSCs with SFTPC mutation. CPT and this screening strategy can apply to abnormal protein-folding-associated ILD and other protein-misfolding diseases.

Protocol for assessing senescence-associated lung pathologies in mice

Cellular senescence underlies tissue aging and aging-associated pathologies, as well as lung pathology. We and others have shown that elimination of senescent cells alleviates pulmonary diseases such as fibrosis and emphysema in animal models. We herein describe a protocol for assessing senescence-dependent lung phenotypes in mice. This protocol describes the use of ARF-DTR mice for semi-genetic elimination of lung senescent cells, followed by a pulmonary function test and the combination with pulmonary disease models to study lung pathologies.

For complete details on the use and execution of this protocol, please refer to Hashimoto et al. (2016), Kawaguchi et al. (2021), and Mikawa et al. (2018).

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Cellular senescence promotes lung aging and diseases

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Detection and elimination of senescent lung cells in ARF-DTR mice

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Assessment of senescence-associated phenotypes in lung tissue

Senolytic vaccination improves normal and pathological age-related phenotypes and increases lifespan in progeroid mice

Elimination of senescent cells (senolysis) was recently reported to improve normal and pathological changes associated with aging in mice^1,2. However, most senolytic agents inhibit antiapoptotic pathways³, raising the possibility of off-target effects in normal tissues. Identification of alternative senolytic approaches is therefore warranted. Here we identify glycoprotein nonmetastatic melanoma protein B (GPNMB) as a molecular target for senolytic therapy. Analysis of transcriptome data from senescent vascular endothelial cells revealed that GPNMB was a molecule with a transmembrane domain that was enriched in senescent cells (seno-antigen). GPNMB expression was upregulated in vascular endothelial cells and/or leukocytes of patients and mice with atherosclerosis. Genetic ablation of Gpnmb-positive cells attenuated senescence in adipose tissue and improved systemic metabolic abnormalities in mice fed a high-fat diet, and reduced atherosclerotic burden in apolipoprotein E knockout mice on a high-fat diet. We then immunized mice against Gpnmb and found a reduction in Gpnmb-positive cells. Senolytic vaccination also improved normal and pathological phenotypes associated with aging, and extended the male lifespan of progeroid mice. Our results suggest that vaccination targeting seno-antigens could be a potential strategy for new senolytic therapies.

Disease modeling of pulmonary fibrosis using human pluripotent stem cell-derived alveolar organoids

Although alveolar epithelial cells play a critical role in the pathogenesis of pulmonary fibrosis, few practical in vitro models exist to study them. Here, we established a novel in vitro pulmonary fibrosis model using alveolar organoids consisting of human pluripotent stem cell-derived alveolar epithelial cells and primary human lung fibroblasts. In this human model, bleomycin treatment induced phenotypes such as epithelial cell-mediated fibroblast activation, cellular senescence, and presence of alveolar epithelial cells in abnormal differentiation states. Chemical screening performed to target these abnormalities showed that inhibition of ALK5 or blocking of integrin αVβ6 ameliorated the fibrogenic changes in the alveolar organoids. Furthermore, organoid contraction and extracellular matrix accumulation in the model recapitulated the pathological changes observed in pulmonary fibrosis. This human model may therefore accelerate the development of highly effective therapeutic agents for otherwise incurable pulmonary fibrosis by targeting alveolar epithelial cells and epithelial-mesenchymal interactions.

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Human pluripotent stem cell-based in vitro pulmonary fibrosis model was established

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Bleomycin-treated alveolar organoids showed epithelium-dependent contraction

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Abnormal differentiation state and cellular senescence in AT2 cells were mimicked

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Inhibition of TGFβ signaling ameliorated the fibrogenic changes of the disease model

Cellular senescence promotes cancer metastasis by enhancing soluble E-cadherin production

Cellular senescence acts as a potent tumor-suppression mechanism in mammals; however, it also promotes tumor progression in a non-cell-autonomous manner. We provided insights into the mechanism underlying senescence-dependent metastatic cancer development. The elimination of senescent cells suppressed the lung metastasis of melanoma cells. Using an antibody array screening of humoral factor(s) that depend on cellular senescence, we identified soluble E-cadherin (seCad) as a potential mediator of the senescence-induced melanoma metastasis. seCad enhanced the invasive activity of melanoma cells both in vitro and in vivo, and gene expression profiling revealed that seCad induced genes associated with poor prognosis in patients with melanoma. An analysis of sera from patients revealed that serum seCad is associated with distant metastasis. Our data suggest that senescent cells promote metastatic lung cancer through seCad, and that seCad may be a potential diagnostic marker as well as a therapeutic target for metastatic lung cancer.

p19Arf Exacerbates Cigarette Smoke-Induced Pulmonary Dysfunction

Senescent cells accumulate in tissues during aging or pathological settings. The semi-genetic or pharmacological targeting of senescent cells revealed that cellular senescence underlies many aspects of the aging-associated phenotype and diseases. We previously reported that cellular senescence contributes to aging- and disease-associated pulmonary dysfunction. We herein report that the elimination of Arf-expressing cells ameliorates cigarette smoke-induced lung pathologies in mice. Cigarette smoke induced the expression of Ink4a and Arf in lung tissue with concomitant increases in lung tissue compliance and alveolar airspace. The elimination of Arf-expressing cells prior to cigarette smoke exposure protected against these changes. Furthermore, the administration of cigarette smoke extract lead to pulmonary dysfunction, which was ameliorated by subsequent senescent cell elimination. Collectively, these results suggest that senescent cells are a potential therapeutic target for cigarette smoking-associated lung disease.

5219A novel senolytic drug, seno-7284 ameliorates age-related cardiometabolic diseases

Background

Senescence at cellular level develops with various genotoxic stresses and it plays a pivotal role in aging and age-related disorders. Recently, it was shown that elimination of senescent cells, so called “senolysis” has potential to become a next generation therapy for age-related disorders including cardiovascular diseases, pulmonary emphysema, Alzheimer's diseases, etc. However, currently there is no senolytic agent available in clinical settings.

Purpose

Present study was aimed to identify a novel senolytic agent effective for cardiometabolic diseases in compounds already available in clinical settings. Here we demonstrate a compound called “seno-7284” exhibits senolytic effect in murine models of type 2 diabetes, atherosclerosis and progeroid.

Methods

We generated 1) diet-induced obase and diabetic model by imposing a high fat diet for two months, 2) atherosclerosis mice model by imposing western diet to ApoE homozygous knockout mice (ApoE-KO mice) for three months, and 3) Zmpste24 homozygous knockout mice (Zmpste24-KO mice) as a progeroid mice model. We administrated seno-7284 by mixing it into the diet (0.03% w/w). In one, two or four weeks after the administration of seno-7284 to each mice model, we collected tissue samples for further analyses.

Results

Seno-7284 reduced the accumulation of senescent cells in visceral adipose tissue of dietary obese mice as senescence-associated beta-galactosidase (SA-beta-gal) staining exhibits (Figure a). This effect was associated with the suppression in systemic glucose intolerance (Figure b), and adipose tissue inflammation in four weeks after the administration of seno-7284. Administrating seno-7284 for two weeks also reduced accumulation of senescent cells in atherosclerotic lesion in aorta of ApoE-KO mice (Figure c), and inhibited the progression of atherosclerosis (Figure d). Surprisingly, this drug significantly improved the lifespan of Zmpste24-KO mice by administering it from 12 weeks old. Further analysis including RNA-seq or metabolomic analysis suggested that seno-7284 stimulates endogenous senolytic function of NK cells and CD8+ T cells.

Conclusion

Our results indicate that seno-7284 mediates its biological effects by inducing senolysis in some murine aging models. Seno-7284 would become a promising therapeutic agent for age-related cardiometabolic diseases.

Partial Identification of Amyloid-β Degrading Activity in Human Serum

The major hallmarks of Alzheimer’s disease (AD) are the extracellular accumulation of pathological amyloid beta (Aβ) in the brain parenchyma and Aβ deposition in cerebral blood walls (cerebral amyloid angiopathy; CAA). Although CAA occurs in more than 80% of AD patients, the mechanisms of Aβ deposition and clearance around the vessel walls are unknown. We found Aβ-degrading activity in human serum during analysis of the regulatory mechanism of Aβ production in human endothelial cells. To elucidate the metabolic dynamics of Aβ surrounding the brain microvessels, we identified Aβ-degrading activity in human serum (blood Aβ-degrading activity: BADA) by column chromatography and LC/MS. BADA exhibited characteristics of an acidic protein, pI 4.3, which had two different protein surface charges (low and high affinity cations). Both BADA fractions had a relative molecular mass of greater than 400 kDa. Furthermore, BADA in the low affinity cation fraction was inhibited by the serine protease inhibitor 4-(2-Aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF). We clarified alpha-2-macroglobulin (a2M) and several serine proteases from this BADA by LC-MS. Moreover, we demonstrated that BADA is increased by approximately 5000-fold in human serum by column chromatography. Therefore, BADA may play an important role in the circulation and metabolism of Aβ in human brain microvessels.

Elimination of p19ARF -expressing cells protects against pulmonary emphysema in mice

Senescent cells accumulate in tissues during aging and are considered to underlie several aging‐associated phenotypes and diseases. We recently reported that the elimination of p19^ARF‐expressing senescent cells from lung tissue restored tissue function and gene expression in middle‐aged (12‐month‐old) mice. The aging of lung tissue increases the risk of pulmonary diseases such as emphysema, and cellular senescence is accelerated in emphysema patients. However, there is currently no direct evidence to show that cellular senescence promotes the pathology of emphysema, and the involvement of senescence in the development of this disease has yet to be clarified. We herein demonstrated that p19^ARF facilitated the development of pulmonary emphysema in mice. The elimination of p19^ARF‐expressing cells prevented lung tissue from elastase‐induced lung dysfunction. These effects appeared to depend on reduced pulmonary inflammation, which is enhanced after elastase stimulation. Furthermore, the administration of a senolytic drug that selectively kills senescent cells attenuated emphysema‐associated pathologies. These results strongly suggest the potential of senescent cells as therapeutic/preventive targets for pulmonary emphysema.

Elimination of p19ARF-expressing cells enhances pulmonary function in mice

Senescent cells accumulate in many tissues as animals age and are considered to underlie several aging-associated pathologies. The tumor suppressors p19^ARF and p16^INK4a, both of which are encoded in the CDKN2A locus, play critical roles in inducing and maintaining permanent cell cycle arrest during cellular senescence. Although the elimination of p16^INK4a-expressing cells extends the life span of the mouse, it is unclear whether tissue function is restored by the elimination of senescent cells in aged animals and whether and how p19^ARF contributes to tissue aging. The aging-associated decline in lung function is characterized by an increase in compliance as well as pathogenic susceptibility to pulmonary diseases. We herein demonstrated that pulmonary function in 12-month-old mice was reversibly restored by the elimination of p19^ARF-expressing cells. The ablation of p19^ARF-expressing cells using a toxin receptor-mediated cell knockout system ameliorated aging-associated lung hypofunction. Furthermore, the aging-associated gene expression profile was reversed after the elimination of p19^ARF. Our results indicate that the aging-associated decline in lung function was, at least partly, attributed to p19^ARF and was recovered by eliminating p19^ARF-expressing cells.

Affinity imaging mass spectrometry (AIMS): high-throughput screening for specific small molecule interactions with frozen tissue sections

A novel screening system, called affinity imaging mass spectrometry (AIMS), identifies candidate small molecules with specific affinity for nanoscale structures, including proteins, in unfixed human tissue sections.

Lipidomic analysis of brain tissues and plasma in a mouse model expressing mutated human amyloid precursor protein/tau for Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD), the most common cause of dementia among neurodegenerative diseases, afflicts millions of elderly people worldwide. In addition to amyloid-beta (Aβ) peptide and phosphorylated tau, lipid dysregulation is suggested to participate in AD pathogenesis. However, alterations in individual lipid species and their role in AD disease progression remain unclear.

METHODS

We performed a lipidomic analysis using brain tissues and plasma obtained from mice expressing mutated human amyloid precursor protein (APP) and tau protein (Tg2576×JNPL3) (APP/tau mice) at 4 (pre-symptomatic phase), 10 (early symptomatic) and 15 months (late symptomatic).

RESULTS

Levels of docosahexaenoyl (22:6) cholesterol ester (ChE) were markedly increased in APP/tau mice compared to controls at all stages examined. Several species of ethanolamine plasmalogens (pPEs) and sphingomyelins (SMs) showed different levels between brains from APP/tau and control mice at various stages of AD. Increased levels of 12-hydroxyeicosatetraenoic acid (12-HETE) during the early symptomatic phase were consistent with previous reports using human AD brain tissue. In addition, 19,20-dihydroxy-docosapentaenoic acid (19,20-diHDoPE) and 17,18-dihydroxy-eicosatetraenoic acid (17,18-diHETE), which are produced from docosahexaenoic acid and eicosapentaenoic acid via 19,20-epoxy-docosapentaenoic acid (19,20-EpDPE) and 17,18-epoxy-eicosatetraenoic acid (17,18-EpETE), respectively, were significantly increased in APP/tau brains during the pre-symptomatic phase, and concomitant increases occurred in plasma. Several arachidonic acid metabolites such as prostaglandin D2 (PGD2) and 15-hydroxyeicosatetraenoic acid (15-HETE), which have potential deteriorating and protective actions, respectively, were decreased in the early symptomatic phase of APP/tau mice. Significant decreases in phosphatidylcholines and PEs with polyunsaturated fatty acids were also detected in the late symptomatic phase, indicating a perturbation of membrane properties.

CONCLUSION

Our results provide fundamental information on lipid dysregulation during various stages of human AD.

Biosynthesis of cytochrome P-450 on membrane-bound ribosomes and its subsequent incorporation into rough and smooth microsomes in rat hepatocytes

Intracellular sites of synthesis of cytochrome P-450 and the subsequent incorporation of it into membrane structures of the endoplasmic reticulum (ER) in rat hepatocytes have been studied using an antibody monospecific for phenobarbital-inducible cytochrome P-450. The cytochrome is synthesized mainly on the "tightly bound" type of membrane-bound ribosomes whose release from the membrane requires treatment with puromycin in a high salt buffer (500 mM KCI, 5mM MgCl2, and 50 mM Tris-HCL [pH 7.5]). Subsequently the cytochrome is incorporated directly into the rough ER membranes with its major part exposed to the outer surface to the membrane and accessible to proteolytic enzymes added externally. The newly synthesized molecules, which appeared first in the rough membrane, are translocated to the smooth membrane, and are then distributed evenly between the two types of microsomeal membranes in approximately 1 h. Administration of cycloheximide, an inhibitor of protein biosynthesis, did not significantly inhibit the transfer of the enzyme from the rough to the smooth ER. It is suggested, therefore, that the translocation of the newly synthesized cythochrome P-450 between the rough and smooth microsomes is mainly due to the lateral movement of the molecules in the plane of the membranes rather than to the attachment and detachment of the ribosomes on the microsomal membranes after the ribosomal cycle for protein synthesis.