A closer look into the cellular and molecular biology of myoepithelial cells across various exocrine glands.

Myoepithelial cells (MECs) are a unique subset of epithelial cells that possess several smooth muscle cell characteristics, such as a high number of actin-myosin filaments and the ability to contract. These cells are primarily located around the secretory cells of exocrine glands, including the salivary, mammary, lacrimal, and sweat glands. Their primary functions involve the construction of the basement membrane and help with secretion of gland products through contraction.

TNF is a critical cytokine in age-related dry eye disease.

Aging is a complex biological process that is characterized by low-grade inflammation, called inflammaging. Aging affects multiple organs including eye and lacrimal gland. Tumor necrosis factor (TNF) is a pleiotropic cytokine that participates in inflammation, activation of proteases such as cathepsin S, and formation of ectopic lymphoid organs.

The First Transcriptomic Atlas of the Adult Lacrimal Gland Reveals Epithelial Complexity and Identifies Novel Progenitor Cells in Mice.

The lacrimal gland (LG) secretes aqueous tears. Previous studies have provided insights into the cell lineage relationships during tissue morphogenesis. However, little is known about the cell types composing the adult LG and their progenitors.

Lacrimal Gland Epithelial Cells Shape Immune Responses through the Modulation of Inflammasomes and Lipid Metabolism.

Lacrimal gland inflammation triggers dry eye disease through impaired tear secretion by the epithelium. As aberrant inflammasome activation occurs in autoimmune disorders including Sjögren's syndrome, we analyzed the inflammasome pathway during acute and chronic inflammation and investigated its potential regulators. Bacterial infection was mimicked by the intraglandular injection of lipopolysaccharide (LPS) and nigericin, known to activate the NLRP3 inflammasome.

Ectopic lymphoid structures in the aged lacrimal glands.

Aging is a complex biological process in which many organs are pathologically affected. We previously reported that aged C57BL/6J had increased lacrimal gland (LG) lymphoid infiltrates that suggest ectopic lymphoid structures. However, these ectopic lymphoid structures have not been fully investigated.

Role of FGF10/FGFR2b Signaling in Homeostasis and Regeneration of Adult Lacrimal Gland and Corneal Epithelium Proliferation.

Purpose: Fibroblast growth factor 10 (FGF10) is involved in eye, meibomian, and lacrimal gland (LG) development, but its function in adult eye structures remains unknown. This study aimed to characterize the role of FGF10 in homeostasis and regeneration of adult LG and corneal epithelium proliferation.

Methods: Quantitative reverse transcription PCR was used for analysis of FGF10 expression in both early postnatal and adult mouse LG, and RNA sequencing was used to analyze gene expression during LG inflammation.

Spatial transcriptomics of the lacrimal gland features macrophage activity and epithelium metabolism as key alterations during chronic inflammation.

The lacrimal gland (LG) is an exocrine gland that produces the watery part of the tear film that lubricates the ocular surface. Chronic inflammation, such as Sjögren's syndrome (SS), is one of the leading causes of aqueous-deficiency dry eye (ADDE) disease worldwide. In this study we analyzed the chronic inflammation in the LGs of the NOD.

A mesenchymal to epithelial switch in Fgf10 expression specifies an evolutionary-conserved population of ionocytes in salivary glands.

Fibroblast growth factor 10 (FGF10) is well established as a mesenchyme-derived growth factor and a critical regulator of fetal organ development in mice and humans. Using a single-cell RNA sequencing (RNA-seq) atlas of salivary gland (SG) and a tamoxifen inducible Fgf10:R26-tdTomato mouse, we show that FGF10 cells are exclusively mesenchymal until postnatal day 5 (P5) but, after P7, there is a switch in expression and only epithelial FGF10 cells are observed after P15. Further RNA-seq analysis of sorted mesenchymal and epithelial FGF10 cells shows that the epithelial FGF10 population express the hallmarks of ancient ionocyte signature Forkhead box i1 and 2 (Foxi1, Foxi2), Achaete-scute homolog 3 (Ascl3), and the cystic fibrosis transmembrane conductance regulator (Cftr).

Pannexin 1 Regulates Skeletal Muscle Regeneration by Promoting Bleb-Based Myoblast Migration and Fusion Through a Novel Lipid Based Signaling Mechanism.

Adult skeletal muscle has robust regenerative capabilities due to the presence of a resident stem cell population called satellite cells. Muscle injury leads to these normally quiescent cells becoming molecularly and metabolically activated and embarking on a program of proliferation, migration, differentiation, and fusion culminating in the repair of damaged tissue. These processes are highly coordinated by paracrine signaling events that drive cytoskeletal rearrangement and cell-cell communication.

Innate Immunity and Biological Therapies for the Treatment of Sjögren's Syndrome.

Sjögren's syndrome (SS) is a systemic autoimmune disorder affecting approximately 3% of the population in the United States. This disease has a female predilection and affects exocrine glands, including lacrimal and salivary glands. Dry eyes and dry mouths are the most common symptoms due to the loss of salivary and lacrimal gland function.

THC Regulates Tearing via Cannabinoid CB1 Receptors.

Purpose: Aqueous deficiency dry eye (ADDE) is a chronic condition affecting millions, with symptoms ranging from a dry itchiness to blurred vision and accompanied by an increased risk of eye infections. ADDE typically arises from disorders of the lacrimal gland that produces tears necessary for eye lubrication. Cannabis users frequently report dry eye, but the basis for this is unknown.

Lacrimal Gland Myoepithelial Cells Are Altered in a Mouse Model of Dry Eye Disease.

The purpose of this study was to determine the pathogenic changes that occur in myoepithelial cells (MECs) from lacrimal glands of a mouse model of Sjögren syndrome. MECs were cultured from lacrimal glands of C57BL/6J [wild type (WT)] and thrombospondin 1 null (TSP1, alias Thbs1) mice and from mice expressing α-smooth muscle actin-green fluorescent protein that labels MECs. MECs were stimulated with cholinergic and α-adrenergic agonists, vasoactive intestinal peptide (VIP), and the purinergic agonists ATP and UTP.

Origin and Lineage Plasticity of Endogenous Lacrimal Gland Epithelial Stem/Progenitor Cells.

The lacrimal gland (LG) is an exocrine organ responsible for the secretion of aqueous tear film. Regenerative and stem cell therapies that target LG repair are coming to the fore, although our understanding of LG cell lineage hierarchy is still incomplete. We utilize the analysis of label-retaining cells (LRCs) and genetic lineage tracing to define LG cell lineage hierarchy.

Isolation of Myoepithelial Cells from Adult Murine Lacrimal and Submandibular Glands.

The lacrimal gland (LG) is an exocrine tubuloacinar gland that secretes an aqueous layer of tear film. The LG epithelial tree is comprised of acinar, ductal epithelial, and myoepithelial cells (MECs). MECs express alpha smooth muscle actin (αSMA) and have a contractile function.

FGF Gradient Controls Boundary Position Between Proliferating and Differentiating Cells and Regulates Lacrimal Gland Growth Dynamics.

Fibroblast growth factor (FGF) signaling plays an important role in controlling cell proliferation, survival, and cell movements during branching morphogenesis of many organs. In mammals branching morphogenesis is primarily regulated by members of the FGF7-subfamily (FGF7 and FGF10), which are expressed in the mesenchyme, and signal to the epithelial cells through the "b" isoform of fibroblast growth factor receptor-2 (FGFR2). Our previous work demonstrated that FGF7 and FGF10 form different gradients in the extracellular matrix (ECM) and induce distinct cellular responses and gene expression profiles in the lacrimal and submandibular glands.

Isolation and Propagation of Lacrimal Gland Putative Epithelial Progenitor Cells.

We present a protocol for isolation of putative epithelial progenitor cells from mouse lacrimal gland (LG) by fluorescence-activated cell sorting (FACS). Isolated LG epithelial progenitor cells can be cultured as 3D reaggregates within extracellular matrix gel or plated as a monolayer. 3D cultures could be maintained for several days and then dissociated with trypsin and plated as monolayer cultures, processed for analysis (e.

β-Catenin is essential for differentiation of primary myoblasts via cooperation with MyoD and α-catenin.

Canonical Wnts promote myoblast differentiation; however, the role of β-catenin in adult myogenesis has been contentious, and its mechanism(s) unclear. Using CRISPR-generated β-catenin-null primary adult mouse myoblasts, we found that β-catenin was essential for morphological differentiation and timely deployment of the myogenic gene program. Alignment, elongation and fusion were grossly impaired in null cells, and myogenic gene expression was not coordinated with cytoskeletal and membrane remodeling events.

Myoepithelial cell-driven acini contraction in response to oxytocin receptor stimulation is impaired in lacrimal glands of Sjögren's syndrome animal models.

The purpose of the present studies was to investigate the impact of chronic inflammation of the lacrimal gland, as occurs in Sjögren's syndrome, on the morphology and function of myoepithelial cells (MECs). In spite of the importance of MECs for lacrimal gland function, the effect of inflammation on MECs has not been well defined. We studied changes in MEC structure and function in two animal models of aqueous deficient dry eye, NOD and MRL/lpr mice.

The two faces of pannexins: new roles in inflammation and repair.

Pannexins belong to a family of ATP-release channels expressed in almost all cell types. An increasing body of literature on pannexins suggests that these channels play dual and sometimes contradictory roles, contributing to normal cell function, as well as to the pathological progression of disease. In this review, we summarize our understanding of pannexin "protective" and "harmful" functions in inflammation, regeneration and mechanical signaling.

Alteration in nerves and neurotransmitter stimulation of lacrimal gland secretion in the TSP-1 mouse model of aqueous deficiency dry eye.

The purpose of this study is to determine neural, vascular, protein secretion, and cellular signaling changes with disease progression in lacrimal glands of the thrombospondin-1 (TSP-1) mouse model of dry eye compared to C57BL/6 wild-type (WT) mice. Neural innervation was reduced in TSP-1 lacrimal glands compared to WT controls, whereas the number of blood vessels was increased. Intracellular Ca stores and the amount of lysosomes, mitochondria, and secretory granules, but not the endoplasmic reticulum, were reduced in TSP-1 compared to WT acini at 12 weeks of age.

Pannexin 1 Modulates Axonal Growth in Mouse Peripheral Nerves.

The pannexin family of channels consists of three members-pannexin-1 (Panx1), pannexin-2 (Panx2), and pannexin-3 (Panx3) that enable the exchange of metabolites and signaling molecules between intracellular and extracellular compartments. Pannexin-mediated release of intracellular ATP into the extracellular space has been tied to a number of cellular activities, primarily through the activity of type P2 purinergic receptors. Previous work indicates that the opening of Panx1 channels and activation of purinergic receptors by extracellular ATP may cause inflammation and apoptosis.

Manipulation of Panx1 Activity Increases the Engraftment of Transplanted Lacrimal Gland Epithelial Progenitor Cells.

Purpose: Sjögren's syndrome is a systemic chronic autoimmune inflammatory disease that primarily targets the salivary and lacrimal glands (LGs). Currently there is no cure; therefore, cell-based regenerative therapy may be a viable option. LG inflammation is facilitated by extracellular ATP and mediated by the Pannexin-1 (Panx1) membrane channel glycoprotein.

Nerve degeneration and regeneration in the cephalopod mollusc Octopus vulgaris: the case of the pallial nerve.

Regeneration is a process that restores structure and function of tissues damaged by injury or disease. In mammals complete regeneration is often unsuccessful, while most of the low phyla animals can re-grow many parts of their body after amputation. Cephalopod molluscs, and in particular Octopus vulgaris, are well known for their capacity to regenerate their arms and other body parts, including central and peripheral nervous system.