Monocyte-derived macrophage immune interactions with gellan gum-based hydrogel formulations

Gellan gum (GG) hydrogels have been widely used for tissue engineering and regenerative medicine approaches with minimal biocompatibility issues [1]. Biofunctionalization of GG with cell adhesive sites has shown improved in vitro cell response [2], but how it affects the immune response remains to be elucidated. Therefore, in this work, we intended to evaluate the impact of the absence/presence of cell adhesive sites on human monocyte-derived macrophages (MDM) response. MDM, differentiated from primary monocytes sorted from peripheral blood mononuclear cells, were encapsulated in GG hydrogels with or without the cell adhesive site RGD [2]. Cells showed a round-shape morphology in non-adhesive hydrogels and a spread adhesive-like morphology in RGD-containing hydrogels, while cell viability up to 12 days of encapsulation was not affected. A strong release of both proinflammatory (IL-1β, IL-6, IL-12p40, TNF-a) and antiinflammatory (IL-1RA, IL-10, CCL22) associated cytokines was observed 1 day after MDM encapsulation, independently of the hydrogel formulation. This release on day 3 was strongly reduced for most cytokines to undetectable levels for TNF-a. Conversely, CCL17, which was undetectable on day 1, was detected on day 3 even if at very low levels, and CCL22 release slightly increased.  A dependence on the hydrogel formulation was observed, as higher amounts of proinflammatory cytokines (IL-1β and IL-12p40) were detected from MDM within soft hydrogels lacking RGD, whereas a higher release of antiinflammatory cytokines (IL-1RA, IL-10, CCL17, and CCL22) was detected from MDM within RGD-containing hydrogels. Overall, this work reveals that MDM present an immediate but transient response to GG hydrogels, which is affected by its mechanical properties and the presence of a cell-adhesive site.

Acknowledgments: ERC consolidator grant ECM_INK (ERC-2016-COG-d726061), FCT grant (2020.01541.CEECIND/CP1600/CT0024), Project grant PTDC/BTM-ORG/31564/2017.

References:

[1] L. R. Stevens et al. (2016). Biomater. Sci., 2016, 4, 1276.

[2] L. P. da Silva, et al. (2018). Advance Healthcare Materials, 7(5).