Attempt to develop taste bud models in three-dimensional culture

The existence of cells exhibiting characteristics of both Type II and Type III cells in rat taste buds. An immunohistochemical and electron-microscopic study

Taste bud cells are classified into four types by their ultrastructural features. Immunohistochemical detection of taste-signaling molecules is used to distinguish cell types of taste bud cells; however, the characteristics of taste cell types such as the immunoreactivity for taste-signaling molecules have long remained unclear. We investigated the detailed characteristics of taste cells in rat vallate taste buds by electron microscopy and immunohistochemistry for gustducin, neural cell adhesion molecule (NCAM) and vesicle-associated membrane protein 2 (VAMP2), which are known as markers of Type II cells, Type III cells and both cell types, respectively. Triple immunostaining for these molecules discriminated seven kinds of cell, including the totally immunopositive cell. Electron microscopy revealed Type III cells with a typical synaptic structure and subsurface cisterna as a specialized contact between a nerve and a Type II cell. The present study clarified the existence of cells with features of both Type II and Type III cells as a subtype of taste bud cells in the rat taste bud.

Cocktail Formula and Application Prospects for Oral and Maxillofacial Organoids

Oral and maxillofacial organoids (OMOs), tiny tissues and organs derived from stem cells cultured through 3-d cell culture models, can fully summarize the cell tissue structure, physiological functions and biological characteristics of the source tissues in the body. OMOs are applied in areas such as disease modelling, developmental and regenerative medicine, drug screening, personalized treatment, etc. Although the construction of organoids in various parts of the oral and maxillofacial (OM) region has achieved considerable success, the existing cocktail formulae (construction strategies) are not widely applicable for tissues of various sources due to factors including the heterogeneity of the source tissues and the dependence on laboratory technology. Most of their formulae are based on growth factor niches containing expensive recombinant proteins with their efficiency remaining to be improved. In view of this, the cocktail formulae of various parts of the OM organs are reviewed with further discussion of the application and prospects for those OMOs to find some affordable cocktail formula with strong operability and high repeatability for various maxillofacial organs. The results may help improve the efficiency of organoid construction in the laboratory and accelerate the pace of the clinical use of organoid technology.

Nanoscale and Macroscale Scaffolds with Controlled-Release Polymeric Systems for Dental Craniomaxillofacial Tissue Engineering

Tremendous progress in stem cell biology has resulted in a major current focus on effective modalities to promote directed cellular behavior for clinical therapy. The fundamental principles of tissue engineering are aimed at providing soluble and insoluble biological cues to promote these directed biological responses. Better understanding of extracellular matrix functions is ensuring optimal adhesive substrates to promote cell mobility and a suitable physical niche to direct stem cell responses. Further, appreciation of the roles of matrix constituents as morphogen cues, termed matrikines or matricryptins, are also now being directly exploited in biomaterial design. These insoluble topological cues can be presented at both micro- and nanoscales with specific fabrication techniques. Progress in development and molecular biology has described key roles for a range of biological molecules, such as proteins, lipids, and nucleic acids, to serve as morphogens promoting directed behavior in stem cells. Controlled-release systems involving encapsulation of bioactive agents within polymeric carriers are enabling utilization of soluble cues. Using our efforts at dental craniofacial tissue engineering, this narrative review focuses on outlining specific biomaterial fabrication techniques, such as electrospinning, gas foaming, and 3D printing used in combination with polymeric nano- or microspheres. These avenues are providing unprecedented therapeutic opportunities for precision bioengineering for regenerative applications.

Human cell-based taste perception - a bittersweet job for industry

Covering: 2000 to 2016On the molecular level humans sense food by a variety of specialized tissues which express sensory receptors to handle nutritive value. In general, this means the interplay of gustatory, olfactory, trigeminal and haptic sensation is translated into perception and leads, in terms of taste, to descriptions like sweet, bitter, salty, sour and umami. Further perceptions include astringent, cool, hot, prickle, lingering, kokumi and fatty to name predominant characterizations. It is still not fully understood how this plethora of impressions can be perceived by quite a limited number of receptors obviously being the initial compilers to judge palatability. However, since the discovery of mammalian taste receptors (TASRs) almost 30 years ago the use of taste receptors in cell-based screening campaigns is advancing in industrial approaches. The article will highlight the impacts and the limits of cell-based guided identification of taste modulators for food applications with an emphasis on sweet, bitter and savory taste as well as implications emerging from natural products.

Regulator of G-protein signaling-21 (RGS21) is an inhibitor of bitter gustatory signaling found in lingual and airway epithelia

The gustatory system detects tastants and transmits signals to the brain regarding ingested substances and nutrients. Although tastant receptors and taste signaling pathways have been identified, little is known about their regulation. Because bitter, sweet, and umami taste receptors are G protein-coupled receptors (GPCRs), we hypothesized that regulators of G protein signaling (RGS) proteins may be involved. The recent cloning of RGS21 from taste bud cells has implicated this protein in the regulation of taste signaling; however, the exact role of RGS21 has not been precisely defined. Here, we sought to determine the role of RGS21 in tastant responsiveness. Biochemical analyses confirmed in silico predictions that RGS21 acts as a GTPase-accelerating protein (GAP) for multiple G protein α subunits, including adenylyl cyclase-inhibitory (Gα(i)) subunits and those thought to be involved in tastant signal transduction. Using a combination of in situ hybridization, RT-PCR, immunohistochemistry, and immunofluorescence, we demonstrate that RGS21 is not only endogenously expressed in mouse taste buds but also in lung airway epithelial cells, which have previously been shown to express components of the taste signaling cascade. Furthermore, as shown by reverse transcription-PCR, the immortalized human airway cell line 16HBE was found to express transcripts for tastant receptors, RGS21, and downstream taste signaling components. Over- and underexpression of RGS21 in 16HBE cells confirmed that RGS21 acts to oppose bitter tastant signaling to cAMP and calcium second messenger changes. Our data collectively suggests that RGS21 modulates bitter taste signal transduction.