"Race for the Surface" : Competition between Bacteria and Host Cells in Implant Colonization Process

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http://urn.fi/URN:ISBN:978-951-51-5257-2
Title: "Race for the Surface" : Competition between Bacteria and Host Cells in Implant Colonization Process
Author: Pérez Tanoira, Ramón
Other contributor: Helsingin yliopisto, lääketieteellinen tiedekunta
Helsingfors universitet, medicinska fakulteten
University of Helsinki, Faculty of Medicine, Department of Otorhinolaryngology - Head and Neck Surgery
Kliininen tohtoriohjelma
Doktorandprogrammet i klinisk forskning
Doctoral Program in Clinical Research
Publisher: Helsingin yliopisto
Date: 2019-06-07
Language: en
URI: http://urn.fi/URN:ISBN:978-951-51-5257-2
http://hdl.handle.net/10138/303925
Thesis level: Doctoral dissertation (article-based)
Abstract: Prosthetic infection represents a major problem in the outcome of patients after implantation of a foreign body. The presence of biomaterial in the body provides a substratum to host either tissue-cell integration or bacterial colonization. In obliteration of an infected bone, artificial bone substitutes and rigid fixation materials are usually necessary to fill bone cavity and to restore the properties of the bone respectively. This study attempted to discover the effect of bioactive glass bone substitute granules (BAG) S53P4 on bacterial and human-cell adhesion on other implant used simultaneously (I, II). During development of new infection-resistant biomaterials, adherence and colonization of either bacterial cells or tissue cells on biomaterials must be evaluated in parallel. A methodology allowing study of the simultaneous growth of bacteria and tissue cells on the same biomaterial surface was developed. This will allow discovery of the effect of various bacterial concentrations on host-cell viability and integration with an implant surface, and their relation to increasing reactive oxygen species (ROS) levels and cell apoptosis (III). Finally, considering our first results and that microorganisms frequently infect an implant surface during surgery and start to compete for the surface before tissue integration, it was hypothesized that incubation of implants with host cells before implantation may be one way to reduce the bacterial living space available and would prevent bacterial adhesion and consequently the infection of biomaterials (IV). Bacterial and human osteoblast-like osteosarcoma cells (SaOS-2) or primary osteoblast (hOB) cells were incubated for 4.5 hours, 2 days, or 4 days at 37°C. As substratum, titanium (Ti), polytetrafluoroethylene (PTFE), polydimethyl-siloxane (PDMS), or bioactive glass plates (IV) were used. The study was done separately (I, II), in competition with SaOS-2 or hOB (III), or in competition with SaOS-2 after 24-hour pre-incubation with SaOS-2 (IV). The effect of BAG S53P4 on bacteria (I) and cell (II) adhesion was studied in either a normal atmosphere or in hypoxia-simulating atmospheric conditions of the middle ear, mastoid cavity, or sinuses. Human osteoblast-like SaOS-2 cells or primary osteoblast (hOB) cells (III) (both, 1x105cells/mL), and collection strains of Staphylococcus aureus and Staphylococcus epidermidis (I) [108 colony forming units (CFU) (I) or (serial 1:10 dilutions of 108 CFU (III, IV)] were employed. The bacteria and cell proliferation, cytotoxicity (III, IV), and production of reactive oxygen species (ROS) (III) were evaluated by colorimetric (MTT, LDH, and crystal violet) (III, IV) as well as by fluorometric methods (fluorescent microscopy and flow cytometry) (III). Bacterial cell viability was studied by use of a drop-plate method after sonication. Effects of BAG S53P4 on cell adhesion were linked intimately with modifications of cellular attachment organs (vinculin containing focal adhesions), rearrangement of the actin cytoskeleton, and cellular spreading. The presence of bioglass under normoxic and hypoxic conditions prevented bacterial and biofilm adhesion for most of the materials and promoted integration of SaOS-2 cells with various biomaterial surfaces, especially under hypoxic conditions, in which S53P4 granules cause increased pH (I, II). In the competitive study, the presence of bacteria resulted in reduced adherence of human cells to the surface of the biomaterials, increased production of ROS, and increased apoptosis. The presence of either type of human cell was associated with a reduction in bacteria compared with that for the materials incubated with S. aureus only (III). Pretreatment with human cells was also associated with a reduction in bacterial colonization of the biomaterial compared with that of the non-pretreated materials, but the presence of bacteria produced a decrease in viable human cells for all materials (IV). In conclusion, the presence of S53P4 granules may both protect implants from bacterial colonization and promote their osteointegration. In the presence of bacteria and cells, colonization of the surface by one reduces colonization by the other. The bacteria produce cellular oxidative stress in human cells, which may be related to the cellular death. The preoperative incubation of prostheses with host cells could be a new way to prevent infection of biomaterials and lessen the risk for bacterial antibiotic resistance.
Subject: Medicine
Rights: Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.


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