今天下午Helmholtz-CentreGeesthacht的Regine Willument教授来我实验室做报告，讲解了她们最近在利用细胞模型更精确模拟体内骨环境的相关研究进展。

In vitro strategies to mimic in vivo events after osseous implantation

B.J.C. Luthringer¹, L. Wu^{1; 2},M. Costantino¹, A. Burmester¹, A.F. Schilling²,F. Feyerabend¹, R. Willumeit¹

¹Department for Structural Research on Macromolecules, Instituteof Materials Research,Helmholtz-Centre Geesthacht, Geesthacht, Germany

² Klinikund Poliklinik für Plastische Chirurgie und Handchirurgie, TechnischeUniversität München, Munich, Germany

INTRODUCTION: At leastthree important types of cells areinterplaying before and after implantation of osseous medical devices:macrophages, osteoblasts, and osteoclasts. Even if the canonical cascade ofevents is understood, the effects of degradation products from magnesium-basedimplants on this scene remain unclear. To unveil these mechanisms, different invitro models considering different aspects of interactions were developed.

METHODS: For osteoblasts,several cell lines (Saos-2, U2OS, and MG63) as well as primary cells (humanbone derived cells (HBDC) and human umbilical cord perivascular (HUCPV)) were investigated. The U937 cell line(pro-monocytes) and peripheral blood mononuclear cells (PBMC)were selected as macrophage and osteoclast models, respectively. The cellmodels were differentiated and the effect of magnesium (MgCl₂and magnesiumextracts) on this process was investigated.Model-specific markers were followed by biochemical means (e.g., real time PCR, Elisa tests, and microscopy).

RESULTS:Asosteoblast model only Saos-2 exhibit a similar protein and gene expressionprofile than primary cells, MG-63 the least comparable. A drastic effect ofmagnesium extract on bone specific markers (e.g.,osteocalcin) was measured on HBDC supplemented with factors promotingosteogenic differentiation. For osteoclasts and macrophages, the attainablenessof differentiated cells was another obstacle. To approbate the cell model,selection was performed on their ability to exhibit closed patterns to what hasbeen reported in vivoviai.e., specific osteoclasttartrate resistant acid phosphatase and cathepsin K or macrophage tumournecrosis alpha (TNFα) interleukin 6 & 1 alpha (IL6 & IL1α) activity/expression. Osteoclast (PBMC) and osteoclast / osteoblast models weresuccessfully established and effect of magnesium on cell differentiation wasobserved¹. While osteoclast activity was increasing withhigher MgCl₂ concentrations, magnesium extract had a two-phase effect: first inducedby low magnesium concentration and then reduced with higher concentrations.Similar results were obtained in co-culture model. Similarly, macrophages were obtained and characterised. The co-culture macrophage/ osteoblast remains under set-up and the effect of magnesium is currentlyinvestigated.

DISCUSSION & CONCLUSIONS: Morecomplex models were successfully established and characterised to investigatethe intricate in vivo processes(inflammation / repair / remodelling) which are taking place duringimplantation. Magnesium extracts show in general different results as comparedto Mg salt which isimplying that other compounds/mechanisms are interplaying during in vivo magnesium-based implantdegradation.