%0 doctoral thesis
%@ 
%A Behr, S.

%D 2020
%J 
%N 
%P  

%T Impact of magnesium based degradable alloys on a coculture model of osteoblast and osteoclast
%U 
 
%X The currently available non-degradable implant materials may cause side effects like a stress shielding effect or an allergic reaction of patients to foreign implant materials. Finally, some of the non-degradable materials cannot remain in the body and must be removed via a second surgery. In order to counteract these undesired side effects, the degradable implant materials have already proven their effectiveness in the past. However, before new alloy materials can be tested and applied in vivo, a thorough in vitro investigation of these alloys is necessary. In order to create physiological osseous in vitro conditions as close as possible to in vivo (bone), a coculture of primary cells was established and applied in this study. The coculture consisted of  peripheral  blood  mononuclear  cells  (PBMC)  and  human  umbilical  cord  perivascular  cells  (HUCPV). The investigation of different experimental conditions has shown that at a ratio of 1:100  (HUCPV:PBMC),  was  optimal  to  obtain  a  differentiated  coculture  of  osteoblasts  and  osteoclasts within 28 days. Based on this coculture, the aim of the study was to investigate the effects of different magnesium-based alloys. The reaction of the coculture to these alloys was investigated by different cellular, enzymatic and molecular assays. In addition, the function of osteoblasts was monitored by the formation of hydroxyapatite and the function of osteoclasts was demonstrated by a resorption assay. For a more comprehensive investigation, the alloys were examined in 3 different ways. Firstly (i), the reaction of the coculture to the corresponding ions  (magnesium  chloride,  silver  nitrate  and  gadolinium  chloride)  was  investigated.  Thus,  it  could be shown that the gadolinium ions increase the formation of hydroxyapatite. In addition, (ii)  the  different  alloys  were  degraded  in  cell  culture  medium  to  prepare  extract  and  the  behaviour of the coculture was monitored in the presence of these extracts. The investigation of  the  Mg-8Ag  alloy  has  shown  that  silver  in  high  concentrations  had  a  toxic  effect  on  the  coculture.  Finally  (iii),  the  coculture  was  applied  directly  to  the  materials  (Mg-Pure,  Mg-2Ag and  Mg-10Gd)  and  incubated  to  determine,  whether  the  cells  could  settle  on  these  alloys  despite degradation stress, grow, and whether direct contact with the material influenced the behaviour of the cells. The enhancing effect of gadolinium, both as a salt and as an extract, on mineralisation,  is  assumed  to  be  mediated  via the  calcium  sensing  receptor  found  on  both  osteoblasts  and  osteoclasts.  Calcium  sensing  receptor  provides  an  affinity  to  positively  charged ions and is an important component of bone homeostasis. By using a phospholipase C inhibitor, an important component of the calcium sensing receptor dependent pathway was inhibited  and  the  influence  of  gadolinium  on  the  formation  of  the  calcium  sensing  receptor  dependent pathways demonstrated by reducing hydroxyapatite formation.,IV In addition, Mg-Pure and magnesium-silver alloys have also been shown to interact with the calcium  sensing  receptor.  This  interaction  led  to  an  inhibition  of  the  receptor  signal.  Nevertheless, a positive effect on bone formation of both magnesium and silver ions remained, indicating  other  implicated  pathways.  Indeed,  magnesium  positively  influenced  bone  growth  via the  transient  receptor  potential  cation  channel  7  /  phosphoinositide  3-kinase  pathway.  Furthermore, silver via the increased formation of reactive oxygen species supported alkaline phosphatase expression. Finally, a combination of the three materials magnesium, silver and gadolinium could be useful to combine their positive properties.