TABLE 1.

Some chemicals or bioactive factors in hydrogel promoting the viability of MSCs.

Factor	Type of hydrogels	MSC origin	Characteristic	Efficacy	References
Cellulose Nanocrystal	Collagen-Based Nanocomposite Hydrogel	BM-MSCs	fast shear thinning, self-healing and improved elastic modulus	high cell viability after extrusion in vitro, improved implant integrity and higher cell retention	Zhang et al. (2020a)
Reduced graphene oxide	Reduced graphene oxide	UC-MSCs	Anti-oxidant activity	higher cell viability and cardiac maturation	Choe et al. (2019)
ROS	Collagen biocomposite	BM-MSCs	Anti-oxidant activity	suppressed superoxide penetration into the hydrogel and cell membrane and stimulating MSC growth	Li et al. (2009)
Platelet-rich plasma	chitosan, batroxobin, thrombin, calcium chloride, or a combination of the latter two	BM-MSCs	promoting growth factor and inflammatory proteins release	the highest cell viability and DNA content found in PRP-gels with 1×106 platelets/mL	Jalowiec et al. (2016)
PDGF-BB	Aptamer-functionalized fibrin hydrogel	MSC spheroids	Inhibiting the apoptosis and promoting the proliferation	promoted the survival of MSC spheroids	Zhao et al. (2020)
Heparan sulfate mimetics	Si-HPMC hydrogel	AD-MSCs	Restore the extracellular matrix network and enhance the biological activity of growth factors	increased cell engraftment and cell survival, and improved the therapeutic benefit	Moussa et al. (2019)
miR-21	Collagen hydrogel	AD-MSCs	interfering the expressions of apoptotic related proteins	protect MSCs from ROS-induced cellular dysfunction	Zhang et al. (2017)

Adding some chemicals or bioactive factors to the hydrogel also promoted the viability of MSCs. Compared to chemical modification, bioactive factors appeared to have better biocompatibility. MSC: mesenchymal stem cell; ROS: reactive oxygen species; BM-MSCs: MSCs derived from bone marrow; UC-MSCs: MSCs derived from umbilical cord; AD-MSCs: MSCs derived from adipose.