hMSC-encapsulation in hydrogels of tunable stiffness for regenerative medicine

Abstract

Many individuals suffer from damaged or diseased tissue, which requires tissue replacements to resolve. However, most current treatments have complications, which include limited supply, and immuno-rejections. The use of stem cell therapies to regenerate such tissues can be alternative strategy that can help alleviate the problems faced. The main challenge of this therapy is in effectively directing the differentiation of stem cells while ensuring their viability. Cell encapsulation in a suitable material to maintain the viability of the cells while simultaneously directing their differentiation effectively seems like the most appropriate strategy. Gelatin methacrylate (GelMA) emerged as the potential encapsulating material due to its excellent biocompatibility, tailorable mechanical properties and low immune response. However, limited research has been performed in investigating the directing of stem cell differentiation towards a specific lineage by tuning the mechanical stiffness of its encapsulat ion material. In this study, we will be tuning the mechanical stiffness of GelMA by using GelMA of different degrees of substitution. Rheology tests were conducted to study the storage moduli of these GelMA samples and the results obtained indicated that their storage moduli and thus stiffness were affected by the degree of substitution and concentration of the GelMA. Moreover, live/dead viability tests conducted for cells encapsulated in 10% w/v GelMA indicated that GelMA with higher degrees of substitution (DS) were associated with lower encapsulated cell viabilit ies. Furthermore, tests conducted with different culturing media helped to further indicate the effectiveness and limitations matrix stiffness had in directing differentiation of the encapsulated stem cells towards a chondrogenic lineage. The variation in matrix stiffness by using different DS GelMA did not cause a distinct variation in differentiation of cells when immersed in DMEM. However, there was a distinct difference observed when encapsulated cells were immersed in MesencultTM ACF Chondrogenic Differentiation Basal Medium. The DS75 GelMA scaffolds appeared to be the optimum encapsulation material in directing stem cell differentiation towards a chondrogenic lineage. In essence, the matrix stiffness of the encapsulation material does play a role in directing stem cell differentiation, though it is not solely responsible and other factors such as culture media are as significant.