Cell–cell signaling in co-cultures of macrophages and fibroblasts

Abstract

The foreign body response (FBR) comprises a general, ubiquitous host tissue-based reaction to implanted materials. In vitro cell-based models are frequently employed to study FBR mechanisms involving cell signaling responses to materials. However, these models often study only one cell type, identify only limited signals, and cannot accurately represent the complexity of in vivo inflammatory signaling. To address this issue, a cell co-culture system involving two primary effector cells of the FBR, macrophages and fibroblasts, was employed. Cell-cell signaling systems were monitored between these cell types, including long-term 1) culture of one cell type in conditioned media from the other cell type, 2) non-contacting cell co-cultures (paracrine signaling), and 3) contact co-cultures (juxtacrine signaling) of primary-and secondary-derived cells. Cell culture media and cell images were collected on Days 1, 2, 3, 7, 14, and 21 and changes in soluble protein secretion, cellular behavior, and morphology were assessed. Primary-and secondary-derived cells responded uniquely during each signaling scenario and to one another. In general higher in vitro fidelity to FBRlike responses was found in primary cell co-cultures compared to their mono-cultures and all secondary cell cultures.

A macrophage/fibroblast co-culture system using a cell migration chamber to study inflammatory effects of biomaterials

“…This indicates that the IL-6 release was provoked by the effect of hydrophobicity of CH 3 SAM. The data also show that the IL-6 release from co-cultures on all surfaces after LPS treatment was much higher than the arithmetic sum of cytokine release on the corresponding macrophage and fibroblast mono-cultures, which indicates a cooperative action of both cell types in the co-cultures [11]. This is in line with previous reports, showing synergistic IL-6 and MCP-1 production in co-cultures of monocytes and vascular smooth muscle cells [65][66][67].…”

“…These data suggest that fibroblasts did not produce significant quantities of TNF-a, but reduced TNF-a production of macrophages in the co-culture. Also, in other studies such reduction of TNF-a release by macrophages was found in the presence of fibroblast-released cytokines [11,68].…”

“…Secretion of pro-inflammatory cytokines such as interleukin-6 (IL-6) and tumour necrosis factor-a (TNF-a) by macrophages and fibroblasts is immediately up-regulated in the presence of most foreign materials [8][9][10]. These soluble signals are recognized by the same cells in an autocrine manner and by neighboring cells in a paracrine manner [11]. Fibroblasts, affected by signals from macrophages can differentiate into myofibroblasts, which produce extracellular matrix (ECM), specifically collagens that finally can lead to implant encapsulation [12].…”

“…Furthermore, these THP-1-derived macrophages can be further differentiated in a proinflammatory M1 phenotype by lipopolysaccharide (LPS) stimulation [7]. Since experimental models applying only one cell type can only identify a limited set of pro-inflammatory signals [16,17], cell co-culture systems involving two or more types of cells have been employed to mimic more accurately the complexity of the in vivo inflammatory situation [11,18,19]. So far, different in vitro macrophage/fibroblast co-culture models have been used to study inflammatory reactions [18,20,21].…”

Podosomes in space

“…This results mostly in a choice between assays investigating random or directional migration in 2D vs. 3D environments, 102,103 either of single cell types or of co-cultures. 104,105 In particular, different kinds of 3D migration assays have been established for studies of macrophages and other cell types, 102 including ex vivo explants (such as dermal explants), 106 tumor cell spheroids, 6 and matrices polymerized in vitro (e.g., Matrigel TM , fibrillar/gelled type I collagen, or native basement membrane). 17,55,58,59,107 However, each type of assay presents intrinsic disadvantages, for example, limited access for imaging processes in the case of thick 3D matrices.…”