Engineering Multi‐Cellular Spheroids for Tissue Engineering and Regenerative Medicine

Abstract

Multi-cellular spheroids are formed as a 3D structure with dense cell-cell/cell-extracellular matrix interactions, and thus, have been widely utilized as implantable therapeutics and various ex vivo tissue models in tissue engineering. In principle, spheroid culture methods maximize cell-cell cohesion and induce spontaneous cellular assembly while minimizing cellular interactions with substrates by using physical forces such as gravitational or centrifugal forces, protein-repellant biomaterials, and micro-structured surfaces. In addition, biofunctional materials including magnetic nanoparticles, polymer microspheres, and nanofiber particles are combined with cells to harvest composite spheroids, to accelerate spheroid formation, to increase the mechanical properties and viability of spheroids, and to direct differentiation of stem cells into desirable cell types. Biocompatible hydrogels are developed to produce microgels for the fabrication of size-controlled spheroids with high efficiency. Recently, spheroids have been further engineered to fabricate structurally and functionally reliable in vitro artificial 3D tissues of the desired shape with enhanced specific biological functions. This paper reviews the overall characteristics of spheroids and general/advanced spheroid culture techniques. Significant roles of functional biomaterials in advanced spheroid engineering with emphasis on the use of spheroids in the reconstruction of artificial 3D tissue for tissue engineering are also thoroughly discussed.

Flow cytometric quantification of apoptotic and proliferating cells applying an improved method for dissociation of spheroids

“…Consequently, the 3D organization of endothelial cells might be an unphysiological situation for the cells, leading to a high number of apoptotic cells, which clearly increases with the age of the spheroids. In contrast, only very few NHDF were found to be positive for caspase‐3 and no increase over time could be seen making them promising candidates for long‐term experiments or tissue engineering approaches (Kim et al, 2020).…”

Preparation of Single, Heteromorphic Microspheres, and Their Progress for Medical Applications

“…As a result, it can induce the migration of host cells in the whole defect and microspheres, so as to promote the formation of new bone. [ 113,114 ] Jiang et al. fabricated microsphere by recombining collagen (COL) and bacterial cellulose (BC).…”

Discovery of Cell Aggregate-Inducing Peptides

“…Cells in a 3D environment behave fundamentally differently from cells in monolayer culture [1][2][3]. Aggregation can manipulate cell-cell interactions, resulting in enhanced cell proliferation [1][2][3][4]. Conventional cell culture is performed in 2D systems, which is very different from the local environment of cells in living tissues.…”

“…Conventional cell culture is performed in 2D systems, which is very different from the local environment of cells in living tissues. Therefore, 3D cell culture technologies have been developed [4,5]. Spheroids prepared from various cell types have also been used in ex vivo assays and drug screening tools in organoid and tumor research [6][7][8][9][10].…”

“…However, the larger the cell aggregate, the greater the difference in oxygen and nutrient supply and waste removal between the central part and the outer surface. In any case, no chemical method has been discovered yet, so a new method to solve these problems is needed [4,5].…”