mTORC1 signaling facilitates differential stem cell differentiation to shape the developing murine lung and is associated with mitochondrial capacity.

Formation of branched organs requires sequential differentiation of stem cells. In this work, we find that the conducting airways derived from SOX2+ progenitors in the murine lungs fail to form without mTOR complex 1 (mTORC1) signaling and are replaced by lung cysts. Proximal-distal patterning through transitioning of distal SOX9+ progenitors to proximal SOX2+ cells is disrupted. Mitochondria number and ATP production are reduced. Compromised mitochondrial capacity results in a similar defect as that in mTORC1-deficient lungs. This suggests that mTORC1 promotes differentiation of SOX9+ progenitors to form the conducting airways by modulating mitochondrial capacity. Surprisingly, in all mutants, saccules are produced from lung cysts at the proper developmental time despite defective branching. SOX9+ progenitors also differentiate into alveolar epithelial type I and type II cells within saccules. These findings highlight selective utilization of energy and regulatory programs during stem cell differentiation to produce distinct structures of the mammalian lungs.

Wnt5a-Vangl1/2 signaling regulates the position and direction of lung branching through the cytoskeleton and focal adhesions.

Lung branching morphogenesis requires reciprocal interactions between the epithelium and mesenchyme. How the lung branches are generated at a defined location and projected toward a specific direction remains a major unresolved issue. In this study, we investigated the function of Wnt signaling in lung branching in mice. We discovered that Wnt5a in both the epithelium and the mesenchyme plays an essential role in controlling the position and direction of lung branching. The Wnt5a signal is mediated by Vangl1/2 to trigger a cascade of noncanonical or planar cell polarity (PCP) signaling. In response to noncanonical Wnt signaling, lung cells undergo cytoskeletal reorganization and change focal adhesions. Perturbed focal adhesions in lung explants are associated with defective branching. Moreover, we observed changes in the shape and orientation of the epithelial sheet and the underlying mesenchymal layer in regions of defective branching in the mutant lungs. Thus, PCP signaling helps define the position and orientation of the lung branches. We propose that mechanical force induced by noncanonical Wnt signaling mediates a coordinated alteration in the shape and orientation of a group of epithelial and mesenchymal cells. These results provide a new framework for understanding the molecular mechanisms by which a stereotypic branching pattern is generated.

A functional circuit formed by the autonomic nerves and myofibroblasts controls mammalian alveolar formation for gas exchange.

Alveolar formation increases the surface area for gas exchange. A molecular understanding of alveologenesis remains incomplete. Here, we show that the autonomic nerve and alveolar myofibroblast form a functional unit in mice. Myofibroblasts secrete neurotrophins to promote neurite extension/survival, whereas neurotransmitters released from autonomic terminals are necessary for myofibroblast proliferation and migration, a key step in alveologenesis. This establishes a functional link between autonomic innervation and alveolar formation. We also discover that planar cell polarity (PCP) signaling employs a Wnt-Fz/Ror-Vangl cascade to regulate the cytoskeleton and neurotransmitter trafficking/release from the terminals of autonomic nerves. This represents a new aspect of PCP signaling in conferring cellular properties. Together, these studies offer molecular insight into how autonomic activity controls alveolar formation. Our work also illustrates the fundamental principle of how two tissues (e.g., nerves and lungs) interact to build alveoli at the organismal level.

Acquisition of cellular properties during alveolar formation requires differential activity and distribution of mitochondria.

Alveolar formation requires coordinated movement and interaction between alveolar epithelial cells, mesenchymal myofibroblasts, and endothelial cells/pericytes to produce secondary septa. These processes rely on the acquisition of distinct cellular properties to enable ligand secretion for cell-cell signaling and initiate morphogenesis through cellular contraction, cell migration, and cell shape change. In this study, we showed that mitochondrial activity and distribution play a key role in bestowing cellular functions on both alveolar epithelial cells and mesenchymal myofibroblasts for generating secondary septa to form alveoli in mice. These results suggest that mitochondrial function is tightly regulated to empower cellular machineries in a spatially specific manner. Indeed, such regulation via mitochondria is required for secretion of ligands, such as platelet-derived growth factor, from alveolar epithelial cells to influence myofibroblast proliferation and contraction/migration. Moreover, mitochondrial function enables myofibroblast contraction/migration during alveolar formation. Together, these findings yield novel mechanistic insights into how mitochondria regulate pivotal steps of alveologenesis. They highlight selective utilization of energy in cells and diverse energy demands in different cellular processes during development. Our work serves as a paradigm for studying how mitochondria control tissue patterning.

The lungs display an intricate, tree-shaped structure which enables the complex gas exchanges required for life. The end of each tiny 'branch' hosts delicate air sacs, or alveoli, which are further divided by internal walls called septa. In mammals, this final structure is acquired during the last stage of lung development. Then, many different types of cells in the immature alveoli multiply and reach the right location to start constructing additional septa. While the structural changes underlining alveoli maturation are well-studied, the energy requirements for that process remain poorly understood. In particular, the exact role of the mitochondria, the cellular compartments that power most life processes, is still unclear. Zhang et al. therefore set out to map, in detail, the role of mitochondria in alveolar development. Microscope imaging revealed how mitochondria were unevenly distributed within the lung cells of newborn mice. Mitochondria accumulated around the machinery that controls protein secretion in the epithelial cells that line the air sacs, and around the contractile apparatus in the underlying cells (the 'myofibroblasts'). Genetically altering the mice to reduce mitochondrial activity or perturb mitochondrial location in these two cell types produced defective alveoli with fewer septa, but it had no effect on lung development before alveoli formation. This suggests that the formation of alveoli requires more energy than other steps of lung development. Disrupting mitochondrial activity or location also compromised how epithelial cells produced chemical signals necessary for the contraction or migration of the myofibroblasts. Together, these results highlight the importance of tightly regulating mitochondrial activity and location during lung patterning. In the future, this insight could lay the groundwork to determine how energy requirements in various tissues shape other biological processes in health and disease.

Hispanic parental perceptions about telemedicine: Potential targets for interventions to improve access to care.

INTRODUCTION: One benefit of the COVID-19 pandemic has been the growth and expansion of telemedicine capabilities with the potential to improve access to healthcare in the face of social isolation mandates. However, adoption of telemedicine has been suboptimal in the Hispanic community and data has been sparse regarding Hispanic experiences with and opinions regarding telemedicine. METHODS: To gather feedback regarding telemedicine and to identify potential barriers to telemedicine use in the Hispanic community, we performed semi-structured interviews about telemedicine experiences among both Hispanic and non-Hispanic parents who had performed both in-person and at least one telemedicine visit for their child at our institution. Mixed methods were utilized to analyze interview responses. RESULTS AND DISCUSSION: Overall, Hispanic parents overwhelmingly preferred in-person to telemedicine encounters as compared with non-Hispanic parents. Targets were identified to improve the use of telemedicine and to potentially improve access to healthcare in the Hispanic community.

Regulation of T helper cell responses during antigen presentation by norepinephrine-exposed endothelial cells.

Dermal blood vessels and regional lymph nodes are innervated by sympathetic nerves and, under stress, sympathetic nerves release norepinephrine (NE). Exposure of primary murine dermal microvascular endothelial cells (pDMECs) to NE followed by co-culture with Langerhans cells (LCs), responsive CD4+ T-cells and antigen resulted in modulation of CD4+ T-cell responses. NE-treatment of pDMECs induced increased production of interleukin (IL)-6 and IL-17A while down-regulating interferon (IFN)-γ and IL-22 release. This effect did not require contact between pDMECs and LCs or T-cells and depended upon pDMEC production of IL-6. The presence of NE-treated pDMECs increased the proportion of CD4+ T-cells expressing intracellular IL-17A and increased IL-17A mRNA while decreasing the proportion of IFN-γ- or IL-22-expressing CD4+ T-cells and mRNA levels for those cytokines. Retinoic acid receptor-related orphan receptor gamma (ROR-γt) mRNA was significantly increased in CD4+ T-cells while T-box transcription factor (T-bet) mRNA was decreased. Intradermal administration of NE prior to hapten immunization at the injection site produced a similar bias in draining lymph node CD4+ T-cells towards IL-17A and away from IFN-γ and IL-22 production. Under stress, release of NE may have significant regulatory effects on the outcome of antigen presentation through actions on ECs with enhancement of inflammatory skin disorders involving IL-17/T helper type 17 (Th17) cells.