Interactions between monocytes, mesenchymal stem cells, and implants evaluated using flow cytometry and gene expression

Abstract

Monocytes and mesenchymal stem cells (MSC) are evident at the implants during early healing. However, when coexisting, their interactions at different implants have not been determined. This study uses an in vitro system, consisting of monoculture and direct co-cultures of monocytes and MSC on screw-shaped machined and oxidized titanium implants in combination with scanning electron microscopy, enzyme-linked immunosorbent assay, flow cytometry, cell sorting, and quantitative polymerase chain reaction. The cell-specific adhesion and gene expression of monocytes and MSC was determined. After 24 hr, the coexistence of monocytes and MSC in co-culture led to equal proportions of adherent monocytes and MSC, irrespective of the implant type. In contrast, higher number of adherent monocytes than MSC was found on the oxidized implant in monoculture. Quantitative polymerase chain reaction analysis of fluorescent activated cell sorting-sorted cells revealed up-regulation of interleukin-1beta, in monocytes, and interleukin-1beta and C-X-C chemokine receptor type 4, in MSC, when the cell types coexisted compared with monocultures. Further, in co-culture, the expression of bone morphogenetic protein-2, stromal cell-derived factor 1, and integrin-β1 was enhanced in the implant-adherent MSC, but not monocytes. It is concluded that during the first 24 hr in an in vitro static condition, the effect of co-culture of monocytes and MSC was more prominent than the effect of the implant surface properties. The results indicate that the coexistence of monocytes and MSC on an implant alters the adhesion and expression of some genes compared with when each cell type existed alone. Further, the results show that the gene expression of major growth and recruitment factors is mainly enhanced in the implant-adherent MSC in contrast to implant-adherent monocytes in co-culture.

Influence of Hydroxyapatite Surface Functionalization on Thermal and Biological Properties of Poly(l-Lactide)- and Poly(l-Lactide-co-Glycolide)-Based Composites

“…These opposing findings on the role of monocyte activation in bone regeneration might be explained by monocyte polarization into proinflammatory (M1) or proregenerative (M2) phenotype. The monocyte polarization process depends on the type of bone fraction, type of biocomposite, host immune defense mechanisms, cytokine microenvironment, as well as the presence of bacteria and their antigens [37,40,41]. More importantly, the lack of composite-mediated activation of monocytes provides information on the amount of endotoxin contaminants, which, according to the Food and Drug Agency Guidance as well as the European Medicines Agency, cannot be present in biomaterials that have contact with human blood/tissues, in amounts higher than 0.25 EU.…”

“…These opposing findings on the role of monocyte activation in bone regeneration might be explained by monocyte polarization into proinflammatory (M1) or proregenerative (M2) phenotype. The monocyte polarization process depends on the type of bone fraction, type of biocomposite, host immune defense mechanisms, cytokine microenvironment, as well as the presence of bacteria and their antigens [37,40,41]. based hydrogel that enhanced cell adhesion due to lysine residues.…”

High shear stress amplitude in combination with prolonged stimulus duration determine induction of osteoclast formation by hematopoietic progenitor cells

“…In addition to macrophages, monocytes play a crucial role in the osseointegration of bone implants. Monocytes support the recruitment and attachment of mesenchymal stromal cells onto the implant surface, which promotes osseointegration . However, a disturbing mechanical environment due to micromotions by the loosening implant at the periprosthetic interface might interfere with the attachment of mesenchymal stromal cells, further advancing the loosening process.…”

Monocytes and pyrophosphate promote mesenchymal stem cell viability and early osteogenic differentiation

“…Attempts have been made to mimic the 3-dimensional in vivo healing environment around implants, using, for instance, explanted [30] or tissue-engineered [31] bone in combination with regenerative stem cells. Moreover, conditioned media (CM) transfer [10,32] and co-culture [33,34] in vitro studies have provided mechanistic insight into the role of cell-cell communication in the cellular response to the material properties. Soluble factors and signals conveyed by inflammatory cells to stem cells are of particular interest.…”