3. Preparation of taste bud organoids
Many applications of human cancer models including cancer cell lines and patient-derived tumor xenografts (PDX) had emerged[13,63]. In these models, the primary tumor tissues were transplanted into immunodeficient mice[64,65]. PDX can better retain the complexity and heterogeneity of parental tumors, but it is still difficult to establish because of the high cost of analysis and long construction cycle. In recent years, patient-derived organoid (PDO) have made significant progress. The formation process of organoids is divided into self-mode events and morphogenesis rearrangements, which involve different mechanisms[66]. Any disturbance of physical or chemical signals may affect the acquisition of organoids. The earliest successful cultivation of taste organoids was based on fluorescence-activated cell sorting (FASC)[67]. Transgenic mice were used to screen out Lgr5+ cells, then taste bud was obtained ex vivo . It is proved that the obtained taste organoids contain proliferation and mature taste cells. Furthermore, the author used circumvallate papilla tissue to establish taste bud organoids[68]. Therefore, different preparation approaches can obtain taste bud organoids, but it seems that the tissue-derived approach is simpler and time-saving.
3.1 Stem/progenitor cell-derived approach
Taste bud organoids derived from stem cells only select stem/progenitor cells of taste cells for culture, thereby obtaining a more unitary culture system. Meanwhile, the stem/progenitor cell-derived culture method requires the labeling of taste progenitor cells in advance (Figure 3a). These cells are then sorted using FACS and cultured individually (Figure 3b-c). Finally, taste bud organoids can be achieved (Figure 3d). Inoculating taste cells on the sensor to simulate the perception of complex tastes to construct an artificial tongue model is the first utilization of taste cells to cultivate a tongue organ modelin vitro . The system detects tastants through high-efficiency functional receptors and provides ideas for artificial taste devices for taste perception and taste information standardization[9]. Moreover, in terms of disease treatment, taste bud organoids are able to mimic the state of the body well and produce consistent responses[69]. By transcriptome sequencing of organoids derived from Lgr5+ cells, preferential taste cell generation was age-related [70] and regulated via multiple signaling pathways[71], [72]which also enriches the signal transduction network that regulates the production of taste cells and provides a theoretical basis for the study of the proliferation and differentiation of taste cells as well as the development mechanism of taste buds.