Lei, Yuguo

Introduction Large-scale production of mammalian cells is pivotal for applications in biotechnology, regenerative medicine, and therapeutic manufacturing. However, current bioreactor technologies face significant technical and economic challenges, including excessive cell aggregation, shear stress-induced cell death, batch-to-batch inconsistencies, and limited scalability. We propose that engineering a cell-friendly microenvironment can enhance culture efficiency. Previously, we developed alginate hydrogel microtubes (AlgTubes) that significantly improved cell density and growth rates; however, AlgTubes lack adhesion sites essential for anchorage-dependent cells and frequently break, causing cell leakage and production inconsistencies. Methods To address these limitations, we reinforced AlgTubes with collagen nanofibers, creating collagen-alginate hybrid hydrogel microtubes (ColAlgTubes). Collagen was integrated to form a dense nanofiber network interwoven with the alginate mesh, with the dual aim of enhancing mechanical properties and providing cell adhesion sites. ColAlgTubes were fabricated to maintain cell mass within a 400 μm diameter to ensure efficient nutrient exchange and waste removal. Results ColAlgTubes successfully formed a reinforced hybrid hydrogel structure in which the collagen nanofiber network improved the mechanical integrity of the alginate matrix while supplying adhesion sites for anchorage-dependent cells. The optimized 400 μm diameter microenvironment supported high cell viability, rapid proliferation, and exceptional yields of 5 × 10 8 cells/mL. Discussion These results demonstrate that ColAlgTubes overcome the key limitations of AlgTubes by combining structural reinforcement with biological functionality. The improved mechanical properties reduce tube breakage and cell leakage, while collagen-derived adhesion sites broaden compatibility to anchorage-dependent cell types. With their scalability, cost-effectiveness, and high efficiency, ColAlgTubes represent a transformative solution for large-scale mammalian cell production across biotechnology, regenerative medicine, and therapeutic manufacturing.

Abstract Mesenchymal stem cells (MSCs) offer significant therapeutic potential, but traditional 2D culture on rigid substrates results in progressive cell enlargement and senescence, reducing proliferative capacity and therapeutic potency. This poses a major challenge for widespread clinical application. We explored a novel strategy for placenta-derived MSCs combining 2D expansion with 3D spheroid culture to address these limitations. Our research shows that culturing MSCs as 3D spheroids significantly reduces individual cell size and size distribution compared to 2D culture. Spheroid formation is feasible in chemically defined media with minimal cell death, and is enhanced by extracellular matrix protein supplementation. Although MSCs do not proliferate in 3D suspension, an alternating 2D/3D culture protocol, transitioning cells between 2D flasks and 3D spheroids after each passage, effectively slows MSC enlargement and senescence over long periods. This alternating method also preserves MSC immunomodulatory function, unlike continuous 2D culture which leads to its loss. For scalability, we developed an RGD-functionalized alginate hydrogel tube (AlgTube) system that mimics this alternating environment, supporting both adherent growth and chemically triggered spheroid formation. This alternating 2D/3D culture strategy and the scalable AlgTube platform provide a foundation for developing next-generation MSC manufacturing technologies to meet future clinical demands.