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Cell–cell interactions between fibroblasts and immune cells, like macrophages, are influenced by interaction with the surrounding extracellular matrix during wound healing. In vitro hydrogel models that mimic and modulate these interactions, especially of soluble mediators like cytokines, may allow for a more detailed investigation of immunomodulatory processes. In the present study, a biomimetic extracellular matrix model based on fibrillar 3D collagen I networks with a functionalization with heparin or 6-ON-desulfated heparin, as mimics of naturally occurring heparan sulfate, was developed to modulate cytokine binding effects with the hydrogel matrix. The constitution and microstructure of the collagen I network were found to be stable throughout the 7-day culture period. A coculture study of primary human fibroblasts/myofibroblasts and M-CSF-stimulated macrophages was used to show its applicability to simulate processes of progressed wound healing. The quantification of secreted cytokines (IL-8, IL-10, IL-6, FGF-2) in the cell culture supernatant demonstrated the differential impact of glycosaminoglycan functionalization of the collagen I network. Most prominently, IL-6 and FGF-2 were shown to be regulated by the cell culture condition and network constitution, indicating changes in paracrine and autocrine cell–cell communication of the fibroblast–macrophage coculture. From this perspective, we consider our newly established in vitro hydrogel model suitable for mechanistic coculture analyses of primary human cells to unravel the role of extracellular matrix factors in key events of tissue regeneration and beyond. [ABSTRACT FROM AUTHOR]

Synthetically sulfated hyaluronan derivatives were shown to facilitate osteogenic differentiation of human bone marrow stromal cells (hBMSC) by application in solution or incorporated in thin collagen-based coatings. In the presented study, using a biomimetic three-dimensional (3D) cell culture model based on fibrillary collagen I (3D Col matrix), we asked on the impact of binding mode of low sulfated hyaluronan (sHA) in terms of adsorptive and covalent binding on osteogenic differentiation of hBMSC. Both binding modes of sHA induced osteogenic differentiation. Although for adsorptive binding of sHA a strong intracellular uptake of sHA was observed, implicating an intracellular mode of action, covalent binding of sHA to the 3D matrix induced also intense osteoinductive effects pointing towards an extracellular mode of action of sHA in osteogenic differentiation. In summary, the results emphasize the relevance of fibrillary 3D Col matrices as a model to study hBMSC differentiation in vitro in a physiological-like environment and that sHA can display dose-dependent osteoinductive effects in dependence on presentation mode in cell culture scaffolds. [ABSTRACT FROM AUTHOR]

Controlled wound healing requires a temporal and spatial coordination of cellular activities within the surrounding extracellular matrix (ECM). Disruption of cell–cell and cell–matrix communication results in defective repair, like chronic or fibrotic wounds. Activities of macrophages and fibroblasts crucially contribute to the fate of closing wounds. To investigate the influence of the ECM as an active part controlling cellular behavior, coculture models based on fibrillar 3D biopolymers such as collagen have already been successfully used. With well-defined biochemical and biophysical properties such 3D scaffolds enable in vitro studies on cellular processes including infiltration and differentiation in an in vivo like microenvironment. Further, paracrine and autocrine signaling as well as modulation of soluble mediator transport inside the ECM can be modeled using fibrillar 3D scaffolds. Herein, we review the usage of these scaffolds in in vitro coculture models allowing in-depth studies on the crosstalk between macrophages and fibroblasts during different stages of cutaneous wound healing. A more accurate mimicry of the various processes of cellular crosstalk at the different stages of wound healing will contribute to a better understanding of the impact of biochemical and biophysical environmental parameters and help to develop further strategies against diseases such as fibrosis. [ABSTRACT FROM AUTHOR]

Neurodegenerative disorders are characterised by the activation of brain‐resident microglia cells and by the infiltration of peripheral T cells. However, their interplay in disease has not been clarified yet. It is difficult to investigate complex cellular dynamics in living animals, and simple two‐dimensional (2D) cell culture models do not resemble the soft 3D structure of brain tissue. Therefore, we developed a biomimetic 3D in vitro culture system for co‐cultivation of microglia and T cells. As the activation and/or migration of immune cells in the brain might be affected by components of the extracellular matrix, defined 3D fibrillar collagen I‐based matrices were constructed and modified with hyaluronan and/or chondroitin sulphate, resembling aspects of brain extracellular matrix. Murine microglia and spleen‐derived T cells were cultured alone or in co‐culture on the constructed matrices. Microglia exhibited in vivo‐like morphology and T cells showed enhanced survival when co‐cultured with microglia or to a minor degree in the presence of glia‐conditioned medium. The open and porous fibrillar structure of the matrix allowed for cell invasion and direct cell‐cell interaction, with stronger invasion of T cells. Both cell types showed no dependence on the matrix modifications. Microglia could be activated on the matrices by lipopolysaccharide resulting in interleukin‐6 and tumour necrosis factor‐α secretion. The findings herein indicate that biomimetic 3D matrices allow for co‐cultivation and activation of primary microglia and T cells and provide useful tools to study their interaction in vitro. [ABSTRACT FROM AUTHOR]

Persistent inflammation and impaired repair in dermal wound healing are frequently associated with cell–cell and cell–matrix miscommunication. A direct coculture model of primary human myofibroblasts (MyoFB) and M‐CSF‐differentiated macrophages (M‐Mɸ) in fibrillar three‐dimensional Collagen I (Coll I) matrices is developed to study intercellular interactions. The coculture experiments reveal the number of M‐Mɸ regulated MyoFB dedifferentiation in a dose‐dependent manner. The amount of MyoFB decreases in dependence of the number of cocultured M‐Mɸ, even in the presence of MyoFB‐inducing transforming growth factor β1 (TGF‐β1). Gene expression analysis of matrix proteins (collagen I, collagen III, ED‐A‐fibronectin) confirms the results of an altered MyoFB phenotype. Additionally, M‐Mɸ is shown to be the main source of secreted cytokine interleukin‐10 (IL‐10), which is suggested to affect MyoFB dedifferentiation. These findings indicate a paracrine impact of IL‐10 secretion by M‐Mɸ on the MyoFB differentiation status counteracting the TGF‐β1‐driven MyoFB activation. Hence, the in vitro coculture model simulates physiological situations during wound resolution and underlines the importance of paracrine IL‐10 signals by M‐Mɸ. In sum, the 3D Coll I‐based matrices with a MyoFB–M‐Mɸ coculture form a highly relevant biomimetic model of late stages of wound healing. [ABSTRACT FROM AUTHOR]