Development of epithelial cholinergic chemosensory cells of the urethra and trachea of mice

Tas1R3 Dependent and Independent Recognition of Sugars in the Urethra and the Role of Tuft Cells in this Process

Increased sugar concentrations on mucosal surfaces display risk factors for infections. This study aims to clarify sugar monitoring in the urethra. Urethral tuft cells (UTC) are known sentinels monitoring the urethral lumen for potentially harmful substances and initiating protective mechanisms. Next-generation sequencing (NGS), RT-PCR, and immunohistochemistry show expression of the taste receptor Tas1R3 in murine UTC, a crucial component of the classical sweet detection pathway. Isolated UTC respond to various sugars with an increase of intracellular [Ca2+]. The Tas1R3 inhibitor gurmarin and Tas1R3 deletion reduces these responses. Utilizing mice lacking UTC, glibenclamide, a K+-ATP channel antagonist, and phlorizin, a SGLT1 inhibitor, reveal an additional Tas1R3 independent sweet detection pathway. Inhibition of both pathways abrogates the sugar responses. Rat cystometry shows that intraurethral application of sucrose and glucose increases detrusor muscle activity Tas1R3 dependently. Sugar monitoring in the urethra occurs via two distinct pathways. A Tas1R3 dependent pathway, exclusive to UTC, and a Tas1R3 independent sweet detection pathway, which can be found both in UTC and in other urethral epithelial cells.

Tuft Cells: Context- and Tissue-Specific Programming for a Conserved Cell Lineage

Tuft cells are found in tissues with distinct stem cell compartments, tissue architecture, and luminal exposures but converge on a shared transcriptional program, including expression of taste transduction signaling pathways. Here, we summarize seminal and recent findings on tuft cells, focusing on major categories of function-instigation of type 2 cytokine responses, orchestration of antimicrobial responses, and emerging roles in tissue repair-and describe tuft cell-derived molecules used to affect these functional programs. We review what is known about the development of tuft cells from epithelial progenitors under homeostatic conditions and during disease. Finally, we discuss evidence that immature, or nascent, tuft cells with potential for diverse functions are driven toward dominant effector programs by tissue- or perturbation-specific contextual cues, which may result in heterogeneous mature tuft cell phenotypes both within and between tissues.

The effects and significance of gut microbiota and its metabolites on the regulation of osteoarthritis: Close coordination of gut-bone axis

Osteoarthritis (OA) is a common chronic degenerative disease of articular cartilage in middle-aged and older individuals, which can result in the joint pain and dysfunction, and even cause the joint deformity or disability. With the enhancing process of global aging, OA has gradually become a major public health problem worldwide. Explaining pathogenesis of OA is critical for the development of new preventive and therapeutic interventions. In recent years, gut microbiota (GM) has been generally regarded as a “multifunctional organ,” which is closely relevant with a variety of immune, metabolic and inflammatory functions. Meanwhile, more and more human and animal researches have indicated the existence of gut-bone axis and suggested that GM and its metabolites are closely involved in the pathogenic process of OA, which might become a potential and promising intervention target. Based on the close coordination of gut-bone axis, this review aims to summarize and discuss the mechanisms of GM and its metabolites influencing OA from the aspects of the intestinal mucosal barrier modulation, intestinal metabolites modulation, immune modulation and strategies for the prevention or treatment of OA based on perspectives of GM and its metabolites, thus providing a profound knowledge and recognition of it.

Tuft Cells Are Present in Submandibular Glands Across Species

Tuft cells are bottle-shaped, microvilli-projecting chemosensory cells located in the lining of a variety of epithelial tissues and, following their identification approximately 60 years ago, have been linked to immune system function in a variety of epithelia. Until recently, Tuft cells had not been convincingly demonstrated to be present in salivary glands with their detection by transmission electron microscopy only shown in a handful of earlier studies using rat salivary glands, and no follow-up work has been conducted to verify their presence in salivary glands of other species. Here, we demonstrate that Tuft cells are present in the submandibular glands of various species (i.e., mouse, pig and human) using transmission electron microscopy and confocal immunofluorescent analysis for the POU class 2 homeobox 3 (POU2F3), which is considered to be a master regulator of Tuft cell identity.

A Single-Cell Atlas of Large and Small Airways at Birth in a Porcine Model of Cystic Fibrosis

Lack of CFTR (cystic fibrosis transmembrane conductance regulator) affects the transcriptome, composition, and function of large and small airway epithelia in people with advanced cystic fibrosis (CF); however, whether lack of CFTR causes cell-intrinsic abnormalities present at birth versus inflammation-dependent abnormalities is unclear. We performed a single-cell RNA-sequencing census of microdissected small airways from newborn CF pigs, which recapitulate CF host defense defects and pathology over time. Lack of CFTR minimally affected the transcriptome of large and small airways at birth, suggesting that infection and inflammation drive transcriptomic abnormalities in advanced CF. Importantly, common small airway epithelial cell types expressed a markedly different transcriptome than corresponding large airway cell types. Quantitative immunohistochemistry and electrophysiology of small airway epithelia demonstrated basal cells that reach the apical surface and a water and ion transport advantage. This single cell atlas highlights the archetypal nature of airway epithelial cells with location-dependent gene expression and function.

Tuft Cells and Their Role in Intestinal Diseases

The interests in intestinal epithelial tuft cells, their basic physiology, involvement in immune responses and relevance for gut diseases, have increased dramatically over the last fifteen years. A key discovery in 2016 of their close connection to helminthic and protozoan infection has further spurred the exploration of these rare chemosensory epithelial cells. Although very sparse in number, tuft cells are now known as important sentinels in the gastrointestinal tract as they monitor intestinal content using succinate as well as sweet and bitter taste receptors. Upon stimulation, tuft cells secrete a broad palette of effector molecules, including interleukin-25, prostaglandin E2 and D2, cysteinyl leukotriene C4, acetylcholine, thymic stromal lymphopoietin, and β-endorphins, some of which with immunomodulatory functions. Tuft cells have proven indispensable in anti-helminthic and anti-protozoan immunity. Most studies on tuft cells are based on murine experiments using double cortin-like kinase 1 (DCLK1) as a marker, while human intestinal tuft cells can be identified by their expression of the cyclooxygenase-1 enzyme. So far, only few studies have examined tuft cells in humans and their relation to gut disease. Here, we present an updated view on intestinal epithelial tuft cells, their physiology, immunological hub function, and their involvement in human disease. We close with a discussion on how tuft cells may have potential therapeutic value in a clinical context.

Tuft cell integration of luminal states and interaction modules in tissues

Chemosensory processes are integral to the physiology of most organisms. This function is typically performed by specialized cells that are able to detect input signals and to convert them to an output dedicated to a particular group of target cells. Tuft cells are cholinergic chemosensory epithelial cells capable of producing immunologically relevant effector molecules. They are scattered throughout endoderm-derived hollow organs and function as sensors of luminal stimuli, which has been best studied in mucosal barrier epithelia. Given their epithelial origin and broad distribution, and based on their interplay with immune pathways, tuft cells can be considered a prototypical example of how complex multicellular organisms engage innate immune mechanisms to modulate and optimize organ physiology. In this review, I provide a concise overview of tuft cells and discuss how these cells influence organ adaptation to dynamic luminal conditions.