David Han | PubMed Health

PubMed2025

Hypoxia-inducible factor 2 regulates alveolar regeneration after repetitive injury in three-dimensional cellular and in vivo models.

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease in which repetitive epithelial injury and incomplete alveolar repair result in accumulation of profibrotic intermediate/transitional "aberrant" epithelial cell states. The mechanisms leading to the emergence and persistence of aberrant epithelial populations in the distal lung remain incompletely understood. By interrogating single-cell RNA sequencing (scRNA-seq) data from patients with IPF and a mouse model of repeated lung epithelial injury, we identified persistent activation of hypoxia-inducible factor (HIF) signaling in these aberrant epithelial cells. Using mouse genetic lineage-tracing strategies together with scRNA-seq, we found that these disease-emergent aberrant epithelial cells predominantly arose from airway-derived (Scgb1a1-CreER-traced) progenitors and exhibited transcriptional programs of Hif2a activation. In mice treated with repetitive intratracheal bleomycin, deletion of Epas1 (Hif2a) but not Hif1a, from airway-derived progenitors, or administration of the small-molecule HIF2 inhibitor PT-2385, using both prevention and rescue approaches, attenuated experimental lung fibrosis, reduced the appearance of aberrant epithelial cells, and promoted alveolar repair. In mouse alveolar organoids, genetic or pharmacologic inhibition of Hif2 promoted alveolar differentiation of airway-derived epithelial progenitors. In addition, treatment of human distal lung organoids with PT-2385 increased colony-forming efficiency, enhanced protein and transcriptional markers of alveolar type 2 epithelial cell maturation, and prevented the emergence of aberrant epithelial cells. Together, these studies showed that HIF2 activation drives the emergence of aberrant epithelial populations after repetitive injury and that targeted HIF2 inhibition may represent an effective therapeutic strategy to promote functional alveolar repair in IPF and other interstitial lung diseases.

Animals↗

PubMed2007

Conversion locked-in syndrome after implantation of a spinal cord stimulator.

BACKGROUND: The locked-in syndrome is defined as quadriplegia and anarthria (loss of articulate speech) with the preservation of consciousness. It is typically caused by a lesion to the ventral pons. Conversion disorder is the deficit of voluntary motor or sensory function requiring an extensive work-up to exclude any organic cause. METHODS AND RESULTS: After surgery for an implantation of a spinal cord stimulator, a 42-year-old woman presented with quadriplegia and lower facial diplegia, but was able to open and blink her eyes. We found no organic causes to explain her condition after appropriate radiological studies looking for intracranial or intraspinal causes, and reversal drugs were administered with no immediate effect. Over the course of several hours, the patient gradually recovered and was discharged the following day. A psychology consultation was obtained during her stay and she was found to meet the criteria for a conversion disorder to explain her condition. CONCLUSIONS: Before considering a psychological cause, all organic factors should be excluded with proper tests and consultations, as conversion disorder is a diagnosis of exclusion. We report a patient who, after implantation of a spinal cord stimulator, manifested locked-in syndrome resulting from a conversion disorder.

Adult↗

PubMed2005

Developing the young academic surgeon.

In the past, the process of developing the young academic surgeon was arguably less strategic, one that was often not deliberately managed and monitored, leading in some cases to academic drift and disillusionment. Once upon a time it was assumed that greatness was genetic and that the next triple threat would emerge when a pre-programmed set of genes was turned on. Today, as the complexities and vicissitudes of our work increase, it is practically impossible for even the most gifted young person to be successful without careful attention to career development. Faculty development must be deliberate and strategic--every junior faculty member is unique and will require a customized career development plan that is well thought out, linked to measurable goals, monitored routinely and buttressed by effective mentoring. This approach will require time and commitment--precious commodities that are in short supply as the demands on our time are only escalating. By recruiting the right people (those who fit with the organization's values and goals) and providing the right environment, we can optimize the growth and satisfaction of our young faculty and, in so doing, create departments that are leaders in carrying out our missions of research, education and patient care. We cannot afford to have our young people fail--it is simply too costly, both from a financial and a human perspective.

Academic Medical Centers↗

PubMed2004

Systematic comparison of a two-dimensional ion trap and a three-dimensional ion trap mass spectrometer in proteomics.

The utility and advantages of the recently introduced two-dimensional quadrupole ion trap mass spectrometer in proteomics over the traditional three-dimensional ion trap mass spectrometer have not been systematically characterized. Here we rigorously compared the performance of these two platforms by using over 100,000 tandem mass spectra acquired with identical complex peptide mixtures and acquisition parameters. Specifically we compared four factors that are critical for a successful proteomic study: 1) the number of proteins identified, 2) sequence coverage or the number of peptides identified for every protein, 3) the data base matching SEQUEST X(corr) and S(p) score, and 4) the quality of the fragment ion series of peptides. We found a 4-6-fold increase in the number of peptides and proteins identified on the two-dimensional ion trap mass spectrometer as a direct result of improvement in all the other parameters examined. Interestingly more than 70% of the doubly and triply charged peptides, but not the singly charged peptides, showed better quality of fragmentation spectra on the two-dimensional ion trap. These results highlight specific advantages of the two-dimensional ion trap over the conventional three-dimensional ion traps for protein identification in proteomic experiments.

Computational Biology↗

PubMed2004

A systematic characterization of mitochondrial proteome from human T leukemia cells.

Global understanding of tissue-specific differences in mitochondrial signal transduction requires comprehensive mitochondrial protein identification from multiple cell and tissue types. Here, we explore the feasibility and efficiency of protein identification using the one-dimensional gel electrophoresis in combination with the nano liquid-chromatography tandem mass spectrometry (GeLC-MS/MS). The use of only 40 mug of purified mitochondrial proteins and data analysis using stringent scoring criteria and the molecular mass validation of the gel slices enables the identification of 227 known mitochondrial proteins (membrane and soluble) and 453 additional proteins likely to be associated with mitochondria. Replicate analyses of 60 mug of mitochondrial proteins on the faster scanning LTQ mass spectrometer validate all the previously identified proteins and most of the single hit proteins except the 81 single hit proteins. Among the identified proteins, 466 proteins are known to functionally participate in various processes such as respiration, tricarboxylic acid cycle (TCA cycle), amino acid and nucleotide metabolism, glycolysis, protection against oxidative stress, mitochondrial assembly, molecular transport, protein biosynthesis, cell cycle control, and many known cellular processes. The distribution of identified proteins in terms of size, pI, and hydrophobicity reveal that the present analytical strategy is largely unbiased and very efficient. Thus, we conclude that this approach is suitable for characterizing subcellular proteomes form multiple cells and tissues.

Amino Acid Sequence↗

PubMed2004

Developing the young academic surgeon.

In the past, the process of developing the young academic surgeon was arguably less strategic, one that was often not deliberately managed and monitored, leading in some cases to academic drift and disillusionment. Once upon a time it was assumed that greatness was genetic and that the next triple threat would emerge when a pre-programmed set of genes was turned on. Today, as the complexities and vicissitudes of our work increase, it is practically impossible for even the most gifted young person to be successful without careful attention to career development. Faculty development must be deliberate and strategic--every junior faculty member is unique and will require a customized career development plan that is well thought out, linked to measurable goals, monitored routinely and buttressed by effective mentoring. This approach will require time and commitment--precious commodities that are in short supply as the demands on our time are only escalating. By recruiting the right people (those who fit with the organization's values and goals) and providing the right environment, we can optimize the growth and satisfaction of our young faculty and, in so doing, create departments that are leaders in carrying out our missions of research, education and patient care. We cannot afford to have our young people fail--it is simply too costly, both from a financial and a human perspective.

Academic Medical Centers↗

PubMed2004

Interaction of the CDK2-associated protein-1, p12(DOC-1/CDK2AP1), with its homolog, p14(DOC-1R).

Human DOC-1/CDK2AP1 gene encodes a growth suppressor protein of 12kDa (p12(DOC-1/CDK2AP1)). Recently, p12(DOC-1/CDK2AP1) has been shown to associate with cell cycle proteins including CDK2 and DNA polymerase alpha/primase. It negatively regulates CDK2 activities and suppresses DNA replication. Therefore, identification of other p12(DOC-1/CDK2AP1) interacting proteins might clarify its role in the cell cycle regulation and carcinogenesis. The purpose of this study was to identify additional p12(DOC-1/CDK2AP1) interacting proteins using the yeast two-hybrid system. Using human p12(DOC-1/CDK2AP1) as a bait in a liver cDNA library screening, cDNA clones identical to human DOC-1R transcript were identified. The interaction between p12(DOC-1/CDK2AP1) and p14(DOC-1R) was verified in vitro and in cells. GST pull-down assay and immunoprecipitation experiments confirmed the interaction between the two proteins. The critical region for p12(DOC-1/CDK2AP1)'s interaction with p14(DOC-1R) was defined to amino acids 20-25 by using a series of deletion mutants as baits in the yeast two-hybrid system. Our data indicated that p12(DOC-1/CDK2AP1) could associate with its homologous protein, p14(DOC-1R).

Amino Acid Sequence↗