Enhanced growth and myogenic differentiation of spheroid-derived C2C12 cells

Skeletal Muscle Spheroids as Building Blocks for Engineered Muscle Tissue

Spheroids exhibit enhanced cell-cell interactions that facilitate improved survival and mimic the physiological cellular environment in vivo. Cell spheroids have been successfully used as building blocks for engineered tissues, yet the viability of this approach with skeletal muscle spheroids is poorly understood, particularly when incorporated into three-dimensional (3D) constructs. Bioprinting is a promising strategy to recapitulate the hierarchical organization of native tissue that is fundamental to its function. However, the influence of bioprinting on skeletal muscle cell spheroids and their function are yet to be interrogated. Using C2C12 mouse myoblasts and primary bovine muscle stem cells (MuSCs), we characterized spheroid formation as a function of duration and cell seeding density. We then investigated the potential of skeletal muscle spheroids entrapped in alginate bioink as tissue building blocks for bioprinting myogenic tissue. Both C2C12 and primary bovine MuSCs formed spheroids of similar sizes and remained viable after bioprinting. Spheroids of both cell types fused into larger tissue clusters over time within alginate and exhibited tissue formation comparable to monodisperse cells. Compared to monodisperse cells in alginate gels, C2C12 spheroids exhibited greater MyHC expression after 2 weeks, while cells within bovine MuSC spheroids displayed increased cell spreading. Both monodisperse and MuSC spheroids exhibited increased expression of genes denoting mid- and late-stage myogenic differentiation. Together, these data suggest that skeletal muscle spheroids have the potential for generating myogenic tissue via 3D bioprinting and reveal areas of research that could enhance myogenesis and myogenic differentiation in future studies.

Auxenochlorella pyrenoidosa extract supplementation replacing fetal bovine serum for Carassius auratus muscle cell culture under low-serum conditions

Cultured meat production requires large-scale cell proliferation in vitro with the supplementation of necessary media especially serum. This study investigated the capacity of Auxenochlorella pyrenoidosa extract (APE) to replace fetal bovine serum (FBS) for cell culture under low-serum conditions using Carassius auratus muscle (CAM) cells. Supplementation with APE and 5% FBS in the culture media significantly promoted the proliferation of CAM cells and increased the expression of MyoD in cells compared to that with 5% FBS through cell counting kit-8 and immunofluorescence staining assay. In addition, CAM cells in the media containing 5% FBS and APE could be continually cultured for 4 passages, and the cell number was 1.58 times higher than the counterpart without APE in long-term culture. Moreover, supplementation with APE realized large-scale culture on microcarriers under low-serum conditions, and more adherent cells were observed on microcarriers in 2% FBS supplemented with APE, compared with those in 2% FBS and 10% FBS without APE. These findings highlighted a potentially promising application of APE in muscle cell culture under low-serum conditions for cultured meat production.