A novel in vitro tubular model to recapitulate features of distal airways: The bronchioid.

BACKGROUND: Airflow limitation is the hallmark of obstructive pulmonary diseases, with the distal airways representing a major site of obstruction. Although numerous in vitro models of bronchi already exist, there is currently no culture system for obstructive diseases that reproduces the architecture and function of small airways. Here, we aimed to engineer a model of distal airways to overcome the limitations of current culture systems. METHODS: We developed a so-called bronchioid model by encapsulating human bronchial adult stem cells derived from clinical samples in a tubular scaffold made of alginate gel. RESULTS: This template drives the spontaneous self-organisation of epithelial cells into a tubular structure. Fine control of the level of contraction is required to establish a model of the bronchiole, which has a physiologically relevant shape and size. 3D imaging, gene expression and single-cell RNA-seq analysis of bronchioids made of bronchial epithelial cells revealed tubular organisation, epithelial junction formation and differentiation into ciliated and goblet cells. Ciliary beating is observed, at a decreased frequency in bronchioids made of cells from COPD patients. The bronchioid can be infected by rhinovirus. An air-liquid interface is introduced that modulates gene expression. CONCLUSION: Here, we provide a proof of concept of a perfusable bronchioid with proper mucociliary and contractile functions. The key advantages of our approach, such as the air‒liquid interface, lumen accessibility, recapitulation of pathological features and possible assessment of clinically relevant endpoints, will make our pulmonary organoid-like model a powerful tool for preclinical studies.

Identification of Nucleoside Analogs as Inducers of Neuronal Differentiation in a Human Reporter Cell Line and Adult Stem Cells.

Nucleoside analogs (NSAs) were among the first chemotherapeutic agents and could also be useful for the manipulation of cell fate. To investigate the potential of NSAs for the induction of neuronal differentiation, we developed a novel phenotypic assay based on a human neuron-committed teratocarcinoma cell line (NT2) as a model for neuronal progenitors and constructed a NT2-based reporter cell line that expressed eGFP under the control of a neuron-specific promoter. We tested 38 structurally related NSAs and determined their activity to induce neuronal differentiation by immunocytochemistry of neuronal marker proteins, live cell imaging, fluorometric detection and immunoblot analysis. We identified twelve NSAs, which induced neuronal differentiation to different extents. NSAs with highest activity carried a halogen substituent at their pyrimidine nucleobase and an unmodified or 2'-O-methyl substituted 2-deoxy-ß-D-ribofuranosyl residue as glyconic moiety. Cladribine, a purine nucleoside with similar structural features and in use to treat leukemia and multiple sclerosis, induced also differentiation of adult human neural crest-derived stem cells. Our results suggest that NSAs could be useful for the manipulation of neuronal cell fate in cell replacement therapy or treatment of neurodegenerative disorders. The data on the structure and function relationship will help to design compounds with increased activity and low toxicity.

Interaction of 2-oxoglutarate dehydrogenase OdhA with its inhibitor OdhI in Corynebacterium glutamicum: Mutants and a model.

Pyruvate dehydrogenase and oxoglutarate dehydrogenase catalyze key reactions in central metabolism. In Corynebacterium glutamicum and related bacteria like Mycobacterium tuberculosis both activities reside in a novel protein supercomplex with the fusion protein OdhA catalyzing the conversion of oxoglutarate to succinyl-coenzyme A. This activity is inhibited by the forkhead-associated (FHA) domain of the small autoinhibitory protein OdhI. Here we used a biological screen which enabled us to isolate suppressor mutants that are influenced in OdhA-OdhI interaction. Five mutants carrying an OdhI mutation were isolated and one with an OdhA mutation. The OdhA mutein OdhA-C704E and three additional C704 variants were constructed. They exhibited unaltered or even slightly enhanced OdhA activity but showed reduced inhibition and interaction with OdhI. The FHA domain of OdhI was crystallized and its structure found in full agreement with previously determined NMR structures. Based on further structural studies, OdhA-OdhI crosslinking experiments, and modeling we discuss the experimental data generated on OdhA-OdhI interaction, with the latter protein representing a rare example of an FHA domain also recognizing a non-phosphorylated interaction partner.

The E2 domain of OdhA of Corynebacterium glutamicum has succinyltransferase activity dependent on lipoyl residues of the acetyltransferase AceF.

Oxoglutarate dehydrogenase (ODH) and pyruvate dehydrogenase (PDH) complexes catalyze key reactions in central metabolism, and in Corynebacterium glutamicum there is indication of an unusual supercomplex consisting of AceE (E1), AceF (E2), and Lpd (E3) together with OdhA. OdhA is a fusion protein of additional E1 and E2 domains, and odhA orthologs are present in all Corynebacterineae, including, for instance, Mycobacterium tuberculosis. Here we show that deletion of any of the individual domains of OdhA in C. glutamicum resulted in loss of ODH activity, whereas PDH was still functional. On the other hand, deletion of AceF disabled both PDH activity and ODH activity as well, although isolated AceF protein had solely transacetylase activity and no transsuccinylase activity. Surprisingly, the isolated OdhA protein was inactive with 2-oxoglutarate as the substrate, but it gained transsuccinylase activity upon addition of dihydrolipoamide. Further enzymatic analysis of mutant proteins and mutant cells revealed that OdhA specifically catalyzes the E1 and E2 reaction to convert 2-oxoglutarate to succinyl-coenzyme A (CoA) but fully relies on the lipoyl residues provided by AceF involved in the reactions to convert pyruvate to acetyl-CoA. It therefore appears that in the putative supercomplex in C. glutamicum, in addition to dihydrolipoyl dehydrogenase E3, lipoyl domains are also shared, thus confirming the unique evolutionary position of bacteria such as C. glutamicum and M. tuberculosis.

The FHA domain of OdhI interacts with the carboxyterminal 2-oxoglutarate dehydrogenase domain of OdhA in Corynebacterium glutamicum.

In Corynebacterium glutamicum, the unphosphorylated 15-kDa OdhI protein inhibits the activity of the 2-oxoglutarate dehydrogenase complex (ODHc) by binding to OdhA, which in corynebacteria and mycobacteria is a large fusion protein with two major domains exhibiting structural features of E1o and E2 proteins. Using copurification and surface plasmon resonance experiments with different OdhI and OdhA length variants it was shown that the entire forkhead-associated (FHA) domain of OdhI and the C-terminal dehydrogenase domain of OdhA are required for interaction. The FHA domain was also sufficient for inhibition of ODHc activity. Phosphorylated OdhI was binding-incompetent and did not inhibit ODHc activity.