Scheme of the hair follicle structures during the hair cycle. The hair follicle goes through cycles of telogen (resting), anagen (growth), catagen (regression). HFSCs (light green) are found in the bulge and hair germ in telogen hair follicle. The sebaceous gland is located above the bulge and the dermal papilla (blue) is below the hair germ. In anagen hair follicle, the matrix is produced by the proliferation of the hair germ.

Definition of organoid. An organoid is in vitro miniaturized and simplified three-dimensional (3D) structure having multiple organ-specific cell types constituting the organ. For example, intestinal organoids are composed of enterocytes, Paneth ells, goblet cells, enteroendocrine cells and stem cells (Lgr5+ crypt base columnar cells), which constitute the actual intestinal epithelium. In addition, organoid have organ-like structures (e.g., crypt and villus structures in intestinal organoids) and mimic their specific functions (e.g., secretory and absorptive functions in intestinal organoids).

Generation and applications of patient-derived tumor organoid (PDTO) from kidney or prostate cancer tissues. Kidney or prostate cancer tissues of patients are isolated, mechanically minced and then enzymatically digested. The dissociated cell suspension is strained to remove clumpy tissues, washed and embedded within matrigel to form organoids. To compare the diversity and similarity between in vivo tissues and organoids or to analyze a distinct inter-/intratumoral-heterogeneity at the genomic level, genomic/or transcriptomic analysis assessed a degree of variance or similarity of organoids corresponding parental tissues from cancer patients. Genome editing by using CRISPR Cas9 is employed in organoids. Prostate cancer or kidney cancer organoids can be used for preclinical models, such as anti-cancer drug screening, or biobanks.

Cell components and engineering platforms for the development of cardiac tissue models. Several types of cardiac tissue models have been developed, to include various cardiac cells, using engineering platforms such as microwells, microfluidic devices, functional hydrogel, and bioprinting. This figure was created with BioRender.com.