Autonomous osteogenic differentiation of hASCs encapsulated in methacrylated gellan-gum hydrogels

Methacrylated gellan-gum (GG-MA) alone and combined with collagen type I (Coll) is suggested here for the first time as a cell-laden injectable biomaterial for bone regeneration. On-chip high-throughput studies allowed rapidly assessing the suitability of 15 biomaterials/media combinations for the osteodifferentiation of human adipose stem cells (hASCs). Hydrogels composed solely of GG-MA (GG100:0Coll) led hASCs from three different donors into the osteogenic lineage after 21Â days of cell culture, in the absence of any osteogenic or osteoconductive factors. Hydrogels containing more than 30% of Coll promoted increased cellular proliferation and led hASCs into osteogenic differentiation under basal conditions. Studies using isolated individual hydrogels â excluding eventual on-chip crosstalk â and standard biochemical assays corroborated such findings. The formation of focal adhesions of hASCs on GG100:0Coll hydrogels was verified. We hypothesize that the hydrogels osteogenic effect could be guided by mechanotransduction phenomena. Indeed, the hydrogels showed elastic modulus in ranges previously reported as osteoinductive and the inhibition of the actin-myosin contractility pathway impaired hASCsâ osteodifferentiation. GG-MA hydrogels also did not promote hASCsâ adipogenesis while used in basal conditions. Overall, GG-MA showed promising properties as an innovative and off-the shelf self-inducing osteogenic injectable biomaterial.This work was supported by European Research Council grant agreement ERC-2012-ADG 20120216-321266 for project ComplexiTE, the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no REGPOT-CT2012-316331-POLARIS, and the ON.2 SR&TD Integrated Program (N-01-01-01-24-01-07) Research Line 2 (Ref.: NORTE-01-0124-FEDER-000018). The authors acknowledge Dr. Andreia Carvalho and Dr. Sara Oliveira for kindly providing isolated hASCs, and Clara Correia for the qPCR training.