Transcription factor and microRNA interactions in lung cells: an inhibitory link between NK2 homeobox 1, miR-200c and the developmental and oncogenic factors Nfib and Myb

Differential microRNA expression patterns between TallyHo/JngJ mice and non-diabetic Swiss Webster Random/Jackson mice

Type 2 diabetes mellitus (T2DM) increases the susceptibility of bone fragility. The underlying mechanisms have, however, remained largely unknown. MicroRNAs (miRNAs) are short single-stranded non-coding RNA molecules with utility as biomarkers due to their easy accessibility and stability in bodily fluids. Here, we aimed to use an unbiased approach to identify miRNAs dysregulated in a polygenic mouse model of T2DM. Genome-wide analysis of miRNAs in serum, BM, and bone from the polygenic TallyHo/JngJ (TH) mice, which recapitulate T2DM in humans, was performed. This analysis was compared to the recommended control Swiss Webster Random/Jackson (SWR/J) and a strain-matched non-diabetic control (TH-ND). When comparing TH mice with TH-ND using an adjusted p-value false discovery rate (FDR) cut-off of 0.2 to identify differentially expressed miRNAs, mmu-miR-466i-5p and mmu-miR-1195 were found to be up-regulated in both serum and in BM. Dysregulated miRNAs were not found in bone tissue. When comparing TH-ND mice with SWR/J using the same FDR cut-off, mmu-miR-351-5p, and mmu-miR-322-3p were upregulated in both BM and serum, while mmu-miR-449a-5p and mmu-miR-6240 were downregulated in BM and serum. Dysregulated miRNAs in BM or cortical bone compared to serum between TH-ND mice and SWR/J were investigated for their cell-type enrichment to identify putative donor cells and their gene target networks. Gene target network analysis revealed genes involved in diabetes-related signaling pathways as well as in diabetic bone disease. Cell-type enrichment analysis identified hsa-miR-449a enriched in immune cells, hsa-miR-592 in hepatocytes and endothelial cells, while hsa-miR-424-3p, hsa-miR-1-3p, and hsa-miR-196b-5p were enriched in mesenchymal stem cells and their derived tissues. In conclusion, our comparative miRNA profiling sheds light on differential expression patterns between SWR/J and both subgroups of TH. No differences were observed between TH and TH-ND, suggesting the genetic background of SWR/J may be responsible for the change of dysregulated miRNA.

Construction of hub transcription factor-microRNAs-messenger RNA regulatory network in recurrent implantation failure

PURPOSE

Recurrent implantation failure (RIF) affects up to 10% of in vitro fertilization (IVF) patients worldwide. However, the pathogenesis of RIF remains unclear. This study was aimed at identifying hub transcription factors (TFs) of RIF in bioinformatics approaches.

METHODS

The GSE111974 (mRNA), GSE71332 (miRNA), and GSE103465 (mRNA) datasets were downloaded from the Gene Expression Omnibus database from human endometrial tissue using R version 4.2.1 and used to identify differentially expressed TFs (DETFs), differentially expressed miRNAs, and differentially expressed genes for RIF, respectively. DETFs were subjected to functional enrichment analysis and the protein-protein interaction network analysis using the Search Tool for the Retrieval of Interacting Genes (version 11.5) database. Hub TFs were identified using the cytoHubb plug-in, after which a hub TF-miRNA-mRNA network was constructed using Cytoscape v3.8.2.

RESULTS

Fifty-seven DETFs were identified, in which Gene Ontology analysis revealed to be mainly involved in the regulation of transcription. Kyoto Encyclopedia of Genes and Genomes pathway analysis suggested that DETFs were enriched in transcriptional misregulation in cancer, aldosterone synthesis and secretion, AMPK signaling pathway, and cGMP-PKG signaling pathway. EOMES, NKX2-1, and POU5F1 were identified as hub TFs, and a hub TF-miRNA-mRNA regulatory network was constructed using these three hub TFs, four miRNAs, and four genes.

CONCLUSION

Collectively, we identified three promising molecular biomarkers for the diagnosis of RIF, which may further be potential therapeutic targets. This study provides novel insights into the molecular mechanisms underlying RIF. However, further experiments are required to verify these results.

Characterization of the microRNA transcriptomes and proteomics of cochlear tissue-derived small extracellular vesicles from mice of different ages after birth

The cochlea is an important sensory organ for both balance and sound perception, and the formation of the cochlea is a complex developmental process. The development of the mouse cochlea begins on embryonic day (E)9 and continues until postnatal day (P)21 when the hearing system is considered mature. Small extracellular vesicles (sEVs), with a diameter ranging from 30 to 200 nm, have been considered a significant medium for information communication in both physiological and pathological processes. However, there are no studies exploring the role of sEVs in the development of the cochlea. Here, we isolated tissue-derived sEVs from the cochleae of FVB mice at P3, P7, P14, and P21 by ultracentrifugation. These sEVs were first characterized by transmission electron microscopy, nanoparticle tracking analysis, and western blotting. Next, we used small RNA-seq and mass spectrometry to characterize the microRNA transcriptomes and proteomes of cochlear sEVs from mice at different ages. Many microRNAs and proteins were discovered to be related to inner ear development, anatomical structure development, and auditory nervous system development. These results all suggest that sEVs exist in the cochlea and are likely to be essential for the normal development of the auditory system. Our findings provide many sEV microRNA and protein targets for future studies of the roles of cochlear sEVs.

Gallic Acid Improves Diabetic Steatosis by Downregulating MicroRNA-34a-5p through Targeting NFE2L2 Expression in High-Fat Diet-Fed db/db Mice

Type 2 diabetes mellitus (T2DM) has become epidemic worldwide and is strongly associated with nonalcoholic fatty liver disease (NAFLD). The molecular mechanisms of microRNAs in NAFLD and T2DM development and the corresponding therapies remain unclear. We performed microRNA microarray validation to determine whether hepatic miR-34a-5p was significantly upregulated in db/db mice fed with a high-fat diet (HFD), a mouse model of T2DM with steatohepatitis. The potential role of miR-34a-5p and gallic acid (GA) in regulating hepatic lipid metabolism and diabetic steatosis was explored. GA improved the activities of antioxidant enzymes and suppressed lipid accumulation in the HFD-induced steatotic liver of db/db mice. In vitro, the silencing of miR-34a-5p in hepatocyte HepG2 cells ameliorated high glucose + oleic acid/palmitic acid mixture–induced accumulation of cellular triglycerides. We identified nuclear factor erythroid-derived 2-like 2 (NFE2L2) as a direct target of miR-34a-5p. Reduction in intracellular triglyceride and the expression levels of sterol regulatory element-binding protein 1 and fatty acid synthase by GA were mediated by the inhibition of miR-34a-5p expression in HepG2 cells. The findings suggest that GA improves hepatic lipogenesis by downregulating miR-34a-5p by suppressing NFE2L2 expression, indicating the potential therapeutic role of GA or an NFE2L2-activating agent in diabetic fatty liver disease.

LSD1 enzyme inhibitor TAK-418 unlocks aberrant epigenetic machinery and improves autism symptoms in neurodevelopmental disorder models

Persistent epigenetic dysregulation may underlie the pathophysiology of neurodevelopmental disorders, such as autism spectrum disorder (ASD). Here, we show that the inhibition of lysine-specific demethylase 1 (LSD1) enzyme activity normalizes aberrant epigenetic control of gene expression in neurodevelopmental disorders. Maternal exposure to valproate or poly I:C caused sustained dysregulation of gene expression in the brain and ASD-like social and cognitive deficits after birth in rodents. Unexpectedly, a specific inhibitor of LSD1 enzyme activity, 5-((1R,2R)-2-((cyclopropylmethyl)amino)cyclopropyl)-N-(tetrahydro-2H-pyran-4-yl)thiophene-3-carboxamide hydrochloride (TAK-418), almost completely normalized the dysregulated gene expression in the brain and ameliorated some ASD-like behaviors in these models. The genes modulated by TAK-418 were almost completely different across the models and their ages. These results suggest that LSD1 enzyme activity may stabilize the aberrant epigenetic machinery in neurodevelopmental disorders, and the inhibition of LSD1 enzyme activity may be the master key to recover gene expression homeostasis. TAK-418 may benefit patients with neurodevelopmental disorders.

A Novel mRNA-miRNA Regulatory Sub-Network Associated With Prognosis of Metastatic Clear Cell Renal Cell Carcinoma

Background

Clear cell renal cell carcinoma (ccRCC) is a urinary disease with high incidence. The high incidence of metastasis is the leading cause of death in patients with ccRCC. This study was aimed to identify the gene signatures during the metastasis of ccRCC.

Methods

Two datasets, including one gene expression profile dataset and one microRNA (miRNA) expression profile dataset, were downloaded from Gene Expression Omnibus (GEO) database. The integrated bioinformatics analysis was performed using the (limma) R package, miRWalk, DAVID, STRING, Kaplan-Meier plotter databases. Quantitative real-time polymerase chain reaction (qPCR) was conducted to validate the expression of differentially expressed genes (DEGs) and DE-miRNAs.

Results

In total, 84 DEGs (68 up-regulated and 16 down-regulated) and 41 DE-miRNAs (24 up-regulated and 17 down-regulated) were screened from GSE22541 and GSE37989 datasets, respectively. Furthermore, 11 hub genes and 3 key miRNAs were identified from the PPI network, including FBLN1, THBS2, SCGB1A1, NKX2-1, COL11A1, DCN, LUM, COL1A1, COL6A3, SFTPC, SFTPB, miR-328, miR-502, and miR-504. The qPCR data showed that most of the selected genes and miRNAs were consistent with that in our integrated analysis. A novel mRNA-miRNA network, SFTPB-miR-328-miR-502-miR-504-NKX2-1 was found in metastatic ccRCC after the combination of data from expression, survival analysis, and experiment validation.

Conclusion

In conclusion, key candidate genes and miRNAs were identified and a novel mRNA-miRNA network was constructed in ccRCC metastasis using integrated bioinformatics analysis and qPCR validation, which might be utilized as diagnostic biomarkers and molecular targets of metastatic ccRCC.

Predicting the likelihood of bronchopulmonary dysplasia in premature neonates

Introduction: Bronchopulmonary dysplasia (BPD) is the most common serious pulmonary morbidity in premature infants. Despite ongoing advances in neonatal care, the incidence of BPD has not improved. A potential explanation for this phenomenon is the limited ability for accurate early prediction of the risk of BPD. BPD continues to represent a therapeutic challenge and no single effective therapy exists for this condition. Areas covered: Here, we review risk factors of BPD derived from clinical data, biological fluid biomarkers, respiratory management data, and scientific advancements using 'omics' technologies, and their ability to predict the pathogenesis of BPD in preterm neonates. Risk factors and biomarkers were identified via literature search with a focus on the last 5 years of data. Expert opinion: The most accurate predictive tools utilize risk factors that encompass a variety of categories. Numerous predictive models have been proposed but suffer from a lack of adequate validation. An ideal model should include multiple, easily measurable variables validated across a heterogeneous population. In addition to evaluating recent BPD prediction models, we suggest approaches to enhance future models.

CDX2/mir-145-5p/SENP1 Pathways Affect LNCaP Cells Invasion and Migration

Background/Aims: Recently, rapidly accumulating evidence has shown that microRNAs (miRNAs) are involved in human tumorigenesis, and the dysregulation of miRNAs has been observed in many cancers, including prostate cancer. miR-145-5p, an miRNA with reduced expression in prostate cancer cells, has been shown to have a tumor suppressive role in a variety of tumors. However, its underlying mechanism requires further elucidation.

Methods: A lentiviral expression vector for miR-145-5p was constructed and used to establish a stable cell line (LNCaP) expressing miR-145-5p. The cells were cultured normally and divided into the control group (control), negative control group (negative control), and test group (miR-145-5p). Inhibition of proliferation was measured by a WST-8 assay. The early apoptosis rate of cells was detected by flow cytometry. Clone formation ability was detected by a clone formation inhibition test. Cell invasion and migration capacity was detected by a Transwell assay. The relative expression levels of proteins were detected by western blotting. We constructed a nude mouse model of prostate cancer to observe the effect of miR-145-5p on the growth of transplanted tumors. TargetScan bioinformatics software was used to predict target genes regulated by miR-14-5p. ChIPBase was used to predict transcription factors with binding sites in the upstream promoter region of miR-145-5p. Quantitative reverse transcription PCR was used to detect the relative expression level of genes. A bifluorescence-reporter gene vector was constructed to confirm the regulation of target genes by miR-145-5p. We used 5′ rapid amplification of cDNA ends to confirm the transcription start site of miR-145-5p.Chromatin immunoprecipitation technology was used to detect the effect of transcription factors binding to miR-145-5p.

Results: The overexpression of miR-145-5p not only inhibited the proliferation, invasion, and migration of LNCaP cells but also promoted their early apoptosis. After overexpressing miR-145-5p, the expression of small ubiquitin-like modifier protein-specific protease 1 (SENP1), and caudal-related homeobox 2 (CDX2) protein was decreased in LNCaP cells. The transcription factor CDX2 bound to the miR-145-5p promoter region and inhibited its transcription. The transcription start site of miR-145-5p was located at a guanine residue 1,408 bp upstream of the stem-loop sequence. Upon overexpression, miR-145-5p could bind to the 3′-untranslated region of SENP1 to inhibit its translation.

Conclusion: These results suggested that CDX2 inhibits the expression of miR-145-5p, thereby relieving the inhibitory effect of miR-145-5p on the translation of SENP1 and affecting the invasion and migration of prostate cancer cells.

Analysis of the promoter region of the human miR-32 gene in colorectal cancer

The pathogenesis of colorectal cancer (CRC) is poorly understood. MicroRNA (miR)-32 upregulation in CRC tissues was previously reported, where it increased the proliferation, migration and invasion, and reduced apoptosis of CRC cells by inhibiting the expression of phosphatase and tensin homolog (PTEN). However, the mechanism underlying miR-32 upregulation remains unknown. miR-32 is an intronic miRNA located within intron 14 of the transmembrane protein 245 gene (TMEM245). The present study aimed to elucidate the biological pathways underlying miR-32 regulation in CRC. A truncated promoter containing the 5′-flanking region of TMEM245/miR-32 gene was constructed. The promoter region was analyzed by dual luciferase reporter assay in CRC cells. DNA pull-down assay and mass spectrometry (MS) were used to identify proteins binding to the core promoter. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and transcription factor (TF) analyses were used to identify the binding proteins. The −320 to −1 bp fragment of the 5′-flanking region exhibited the highest luciferase activity. The regions spanning −606 to −320 bp exhibited a significant decrease in luciferase activity, compared with the −320 to −1 bp fragment. DNA pull-down assay and MS revealed 403 potential miR-32 promoter binding proteins. GO and KEGG pathway analysis indicated that these proteins were involved in numerous physiological and biochemical processes, including ‘structural molecule activity’, ‘RNA binding’, ‘small molecule metabolic process’ and ‘biogenesis’. Furthermore, TF analysis revealed 10 potential interacting TFs, including SMAD family member 1 (SMAD1), signal transducer and activator of transcription 1 (STAT1) and forkhead box K1 (Foxk1). These results suggested that the core promoter region may be located within-320 to −1 bp of the 5′-flanking region of TMEM245/miR-32 gene, while the region from −606 to −320 bp may harbor repressive regulatory elements. The TFs SMAD1, STAT1 and Foxk1 may be involved in the transcriptional regulation of miR-32.

Encapsulated miR-200c and Nkx2.1 in a nuclear/mitochondria transcriptional regulatory network of non-metastatic and metastatic lung cancer cells

BACKGROUND

MicroRNAs are noncoding RNA molecules of ~ 22 nucleotides with diagnostic and therapeutic action [Curr Drug Targets, 2015. 16(12): p. 1381-403], affecting the expression of mRNAs involved in invasion, migration, and development [Oncotarget, 2015. 6(9): p. 6472-98, Cancer Manag Res, 2014. 6: p. 205-16]. miR-200c is part of the miR-200c/141 cluster on chromosome 12p13. Its mechanism of action when encapsulated is critical in lung cancer when patients express changes in miRNAs. miR-200c be a potential biomarkers for various lung diseases. As a potential therapy, miR-200c can impacts lives as target lung cancer is a leading cause of death with about 234,000 cases annually, high heterogeneity, complex screening, and a 5-year survival rate of 16% [CA Cancer J Clin, 2016.66(1): p. 7-30]. Encapsulated miR-200c efficiently enhances bioavailability, pharmacokinetics of therapeutics and targeting to cells, improves efficacy and provides potential cure.

METHODS

The functions of miR-200c were determined in non-metastatic KW-634 and metastatic 821-T4 and 821-LN mouse lung cancer cell lines after various Nano vehicle treatments. Viability and cytotoxicity were determined by cell cycle and quantitative real-time PCR analyses were used to quantify levels of miR-200c and its target genes. In situ hybridization was used to visualize patterns of expression of miR-200c and others in the lung and many organs. Next-generation sequencing accession number GSE125000, invasion and migration assays using transwell chambers, and ActivSignal were used to elucidate the activation and inhibition profiles and perform direct expression measurements and modification of cellular components.

RESULTS

Due to their effectiveness as intracellular vesicles transporting miR-200c into, out, and between parts of the cells, miR-200c is encapsulated with cholesterol, an integral part of the biological membranes with very important physical properties of the vehicle. Nano miR-200c showed efficient cellular uptake in KW-634, 821-T4, and 821-LN cells with important changes in gene expression and new isoforms. In KW-634, when treated with encapsulated miR-200c and compare to the non-encapsulated control; miR-29b increased by 5261-fold, and in 821-T4/LN, miR-1247 increased by 150-fold. Conversely, miR-1247 and miR-675 decreased by 348 and 1029.5-fold, respectively. miR-189 decreased by 34-fold in treated 821-T4 cells. A reduction of growth was observed only after 48 h of treatment with Nano miR-200c. Moreover, labeling the vehicle with carboxy-fluorescein showed that the encapsulated particles enter the nucleus and mitochondria. Encapsulated miR-200c by entering the cells, the nucleus and mitochondria, trigger changes in cell cycle phases with 4 up to 12 fold percentage in G2 and S phase respectively compare to miR-200c. Endogenous expression of Nkx2.1, miR-200c, and their targets Myb, Nfib, Six4 and Six1 showed an inverse correlation, as observed in development.

CONCLUSIONS

Little is known about miR-200c involvement in regulatory processes. Nano miR-200c affects invasion and migration mechanisms. The expression of encapsulated miR-200c contributes to the inhibition/activation of Kras, EMT, Hippo, regulatory pathways and blockers of metastasis. Delivery of miR-200c increases the expression of miR-29b, an EMY regulator, and miR-1247, an inhibitor of cancer genes, both tumor suppressors involved in lung metastasis. Encapsulated miR-200c act on different proteins that regulates cell cycle pathways. These findings represent a part of a regulatory network providing new insights towards improvement of therapy.

Transcription Factor and lncRNA Regulatory Networks Identify Key Elements in Lung Adenocarcinoma

Lung cancer is the second most commonly diagnosed carcinoma and is the leading cause of cancer death. Although significant progress has been made towards its understanding and treatment, unraveling the complexities of lung cancer is still hampered by a lack of comprehensive knowledge on the mechanisms underlying the disease. High-throughput and multidimensional genomic data have shed new light on cancer biology. In this study, we developed a network-based approach integrating somatic mutations, the transcriptome, DNA methylation, and protein-DNA interactions to reveal the key regulators in lung adenocarcinoma (LUAD). By combining Bayesian network analysis with tissue-specific transcription factor (TF) and targeted gene interactions, we inferred 15 disease-related core regulatory networks in co-expression gene modules associated with LUAD. Through target gene set enrichment analysis, we identified a set of key TFs, including known cancer genes that potentially regulate the disease networks. These TFs were significantly enriched in multiple cancer-related pathways. Specifically, our results suggest that hepatitis viruses may contribute to lung carcinogenesis, highlighting the need for further investigations into the roles that viruses play in treating lung cancer. Additionally, 13 putative regulatory long non-coding RNAs (lncRNAs), including three that are known to be associated with lung cancer, and nine novel lncRNAs were revealed by our study. These lncRNAs and their target genes exhibited high interaction potentials and demonstrated significant expression correlations between normal lung and LUAD tissues. We further extended our study to include 16 solid-tissue tumor types and determined that the majority of these lncRNAs have putative regulatory roles in multiple cancers, with a few showing lung-cancer specific regulations. Our study provides a comprehensive investigation of transcription factor and lncRNA regulation in the context of LUAD regulatory networks and yields new insights into the regulatory mechanisms underlying LUAD. The novel key regulatory elements discovered by our research offer new targets for rational drug design and accompanying therapeutic strategies.

Intercellular transfer of small RNAs from astrocytes to lung tumor cells induces resistance to chemotherapy

Brain metastases are resistant to chemotherapy and carry a poor prognosis. Studies have shown that tumor cells are surrounded by activated astrocytes, whose cytoprotective properties they exploit for protection from chemotherapy-induced apoptosis. The mechanism of such astrocytic protection is poorly understood. A non-mutational mechanism of resistance to chemotherapy that is receiving increased attention is the regulation of gene translation mediated by small noncoding RNAs (sRNAs), and particularly microRNAs (miRNAs). With the aim of examining the role of astrocytic sRNAs in promoting resistance of human lung tumor PC14 cells to chemotherapy-induced apoptosis, here we used a miRNA microarray to compare sRNA profiles of human lung tumor cells cultured with and without astrocytes. We found that sRNAs are transferred from astrocytes to PC14 cells in a contact-dependent manner. Transfer was rapid, reaching a plateau after only 6 hours in culture. The sRNA transfer was inhibited by the broad-spectrum gap-junction antagonist carbenoxolone, indicating that transfer occurs via gap junctions. Among the transferred sRNAs were several that are implicated in survival pathways. Enforced expression of these sRNAs in PC14 cells increased their resistance to the chemotherapeutic agent paclitaxel. These novel findings might be of clinical relevance for the treatment of patients with brain metastases.

Recent advances in our understanding of the mechanisms of late lung development and bronchopulmonary dysplasia

The objective of lung development is to generate an organ of gas exchange that provides both a thin gas diffusion barrier and a large gas diffusion surface area, which concomitantly generates a steep gas diffusion concentration gradient. As such, the lung is perfectly structured to undertake the function of gas exchange: a large number of small alveoli provide extensive surface area within the limited volume of the lung, and a delicate alveolo-capillary barrier brings circulating blood into close proximity to the inspired air. Efficient movement of inspired air and circulating blood through the conducting airways and conducting vessels, respectively, generates steep oxygen and carbon dioxide concentration gradients across the alveolo-capillary barrier, providing ideal conditions for effective diffusion of both gases during breathing. The development of the gas exchange apparatus of the lung occurs during the second phase of lung development-namely, late lung development-which includes the canalicular, saccular, and alveolar stages of lung development. It is during these stages of lung development that preterm-born infants are delivered, when the lung is not yet competent for effective gas exchange. These infants may develop bronchopulmonary dysplasia (BPD), a syndrome complicated by disturbances to the development of the alveoli and the pulmonary vasculature. It is the objective of this review to update the reader about recent developments that further our understanding of the mechanisms of lung alveolarization and vascularization and the pathogenesis of BPD and other neonatal lung diseases that feature lung hypoplasia.

MicroRNAs Regulate Thymic Epithelium in Age-Related Thymic Involution via Down- or Upregulation of Transcription Factors

Age-related thymic involution is primarily induced by defects in nonhematopoietic thymic epithelial cells (TECs). It is characterized by dysfunction of multiple transcription factors (TFs), such as p63 and FoxN1, and also involves other TEC-associated regulators, such as Aire. These TFs and regulators are controlled by complicated regulatory networks, in which microRNAs (miRNAs) act as a key player. miRNAs can either directly target the 3'-UTRs (untranslated regions) of the TFs to suppress TF expression or target TF inhibitors to reduce or increase TF inhibitor expression and thereby indirectly enhance or inhibit TF expression. Here, we review the current understanding and recent studies about how miRNAs are involved in age-related thymic involution via regulation of TEC-autonomous TFs. We also discuss potential strategies for targeting miRNAs to rejuvenate age-related declined thymic function.

MicroRNA in late lung development and bronchopulmonary dysplasia: the need to demonstrate causality

MicroRNA are emerging as powerful regulators of cell differentiation and tissue and organ development. Several microRNA have been described to play a role in branching morphogenesis, a key step in early lung development. However, considerably less attention has been paid to microRNA as regulators of the process of secondary septation, which drives lung alveolarization during late lung development. Secondary septation is severely perturbed in bronchopulmonary dysplasia (BPD), a common complication of preterm birth characterized by blunted alveolarization. A number of studies to date have reported microRNA microarray screens in animal models of BPD; however, only two studies have attempted to demonstrate causality. Although the expression of miR-150 was altered in experimental BPD, a miR-150^−/− knockout mouse did not exhibit appreciable protection in a BPD animal model. Similarly, while the expression of miR-489 in the lung was reduced in clinical and experimental BPD, antagomiR and over-expression approaches could not validate a role for miR-489 in the impaired alveolarization associated with experimental BPD. This mini-review aims to highlight microRNA that have been revealed by multiple microarray studies to be potential causal players in normal and pathological alveolarization. Additionally, the challenges faced in attempting to demonstrate a causal role for microRNA in lung alveolarization are discussed. These include the tremendous variability in the animal models employed, and the limitations and advantages offered by the available tools, including antagomiRs and approaches for the validation of a specific microRNA-mRNA interaction during lung alveolarization.