Table 2.

Summary of representative studies that report the 3D in vitro cell behaviors altered by matrix properties, mainly the dynamically-changing matrix mechanics.

Matrix properties	Cells	Engineered matrix	Findings/comments	Refs
Rigidity (with adhesion ligand)	Mouse and human mesenchymal stem cell	Alginate hydrogel, PEG dimethacrylate gel	Differentiation of MSCs is regulated by substrate rigidity in 3D environment. However, unlike in 2D, adhesion ligand rather than cell morphology seems more critical in lineage commitment	Huebsch et al. [42]
Stress relaxation	3T3 fibroblast, D1 cell	Alginate hydrogel	Stress relaxation is a key mechanical parameter that influences cell spreading, differentiation, and proliferation in 3D environment	Chaudhuri et al. [46]
Stress relaxation	Bovine chondrocyte	Alginate hydrogel	Fast stress relaxation induces pro-chondrogenesis pathway for chondrocytes whereas slow stress relaxation leads to cartilage degradation and cell death	Lee et al. [49]
Stress relaxation	Adenocarcinoma cell line (MDA-MB-231)	Alginate hydrogel	Cancer cells in the fast-relaxing deform the surrounding matrix effectively to allow mitotic elongation and cell division, whereas those in slow-relaxing gels fail to complete mitosis	Nam et al. [50]
Stress relaxation (with adhesion ligand)	Human induced pluripotent stem cell	Alginate hydrogel	RGD density and stress relaxation are crucial factors in stem cell morphogenesis	Indana et al. [51]
Fiber elasticity, anisotropy	Fibroblast	Dextran methacrylated form (DexMa)	Cells dynamically interact with flexible fibers. Cell mechano-responses to 3D fibrillar anisotropic environment are different from those to isotropic gel matrix	Baker et al. [54]
Degradability	Human mesenchymal stem cell	Methacrylated hyaluronic acid (MeHA)	Degradation-mediated cellular traction regulates stem cell differentiation	Khetan et al. [55]
Elasticity change (due to void formation)	Mouse mesenchymal stem cell	High guluronic acid (GA)-content alginate hydrogel	Manipulation of elasticity by void-forming hydrogels results in enhanced in vitro osteogenesis	Huebsch et al. [56]
Plasticity	Adenocarcinoma cell line (MDA-MB-231)	Interpenetrating network of alginate and basement membrane matrix	Cells physically widen pores of matrices with protrusion of invadopodia to make space for squeeze-through migration, a mechanism that is protease-independent	Wisdom et al. [43]
Plasticity	human mesenchymal stem cell	PEG-coupled/free alginate hydrogel	Intermediate level of plasticity induces most dynamic cell-spreading, with activation of mechanotransductory molecules	Grolman et al. [52]
Plasticity	Primary rat cardiac, lung fibroblast	collagen type 1 hydrogel	When matrix plasticity decreases, cytoskeletal tension and YAP nuclear translocation increase, leading to enhanced fibroblast activation and spreading	Jia et al. [53]
Matrix deposition	Human mesenchymal stem cell	Norbornene hyaluronic acid hydrogel (NorHA), PEG-diacrylate, agarose and alginate hydrogel, guest-host double-network hyaluronic acid hydrogel	Locally deposited nascent proteins alter cell behavior in different types of hydrogels by masking the effect of synthetic substrates and interacting with the cells themselves	Loebel et al. [44]