A novel co-culture model of murine K12 osteosarcoma cells andS. aureuson common orthopedic implant materials: ‘the race to the surface’ studiedin vitro

Abstract

Infection is a major cause of orthopedic implant failure. There are few studies assessing both tissue cell and bacterial adherence on common orthopedic implant materials in a co-culture environment. An in vitro co-culture model was created using K12 osteosarcoma cells and Staphylococcus aureus in a medium incubated over metal disks for 48 h. The results showed that, in the presence of S. aureus, there were fewer osteosarcoma cells attached to the disks for all substrata tested. There were significantly more osteosarcoma cells adhering to the cobalt chrome than the stainless steel and titanium disks. Overall, in the presence of osteosarcoma cells, there were more bacteria adhering to the disks for all the substrata tested, with significantly more bacteria adhering to the stainless steel disks compared to cobalt chrome and titanium disks. Scanning electron microscopy verified that osteosarcoma cells and bacteria were adherent to the metal disks after incubation for 48 h. Furthermore, the observation that more bacteria were in the co-culture than in the control sample suggests that the osteosarcoma cells serve as a nutrient source for the bacteria. Future models assessing the interaction of osteogenic cells with bacteria on a substratum would be improved if the model accounted for the role of the immune system in secondary bone healing.

Competitive Surface Colonization of Antibacterial and Bioactive Materials Doped with Strontium and/or Silver Ions

“…Finally, a third protocol here named "competition" was designed following the hypothesis of the "race" (competition) for the surface, as postulated in 1987 by Gristina [25], where it is supposed that the fate of a biomaterial surface depends on the competition between the tissue and bacteria for the implant surface. Following this hypothesis, some works are reported in the literature involving the bone-dedicated materials and combining, for example, the human osteosarcoma (U2OS or K12) cells and Staphylococcus epidermidis or Staphylococcus aureus [37], the mouse embryonic pre-fibroblasts (MC3T3-E1), and Staphylococcus epidermidis [38], but the results are not easy to interpret. In fact, most of the results coming from the present literature suggest that the outcome of the study depends mainly by the bacterial inoculum concentration used at the start of the competition [37,[39][40][41]; in fact, considering a concentration range from 1 × 10 2 to 1 × 10 5 bacteria/specimen, only the lower inoculum led to significant results between antibacterial and control surfaces.…”

Successful bony integration of a porous tantalum implant despite longlasting and ongoing infection: Histologic workup of an explanted shoulder prosthesis

“…So far, the implant material is considered to have minimal influence on the development of infection, if any at all, compared to the surface characteristics of the material and the infecting microorganism . However, tantalum might have biological characteristics sufficiently different from other standard implant materials, which might be considered for, and investigated in co‐culture models …”

“…tantalum might have biological characteristics sufficiently different from other standard implant materials, which might be considered for, and investigated in co-culture models. [7][8][9]15,17,25…”

“…Despite standard perioperative precautions, infection rates are estimated to be 1–2% for elective major joint replacements, around 4% for internal fixation of closed fractures, and can be up to 10 times higher for specific patient subgroups, particularly in case of traumatic contamination in open fractures . The perioperative period is considered crucial in the development of infection, and is conceptualized as a “race for the surface” between microorganisms and host cells . Should bacteria win this race, integration of the implant with the surrounding tissues is affected due to host cell death at the implant surface .…”

“…5 The perioperative period is considered crucial in the development of infection, and is conceptualized as a "race for the surface" between microorganisms and host cells. [6][7][8] Should bacteria win this race, integration of the implant with the surrounding tissues is affected due to host cell death at the implant surface. 9 Microorganisms that adhere to the surface of the implant also become more resistant to antibiotic therapy and host defense mechanisms due to biofilm formation, 1,6,10 or the development of certain phenotypical bacterial variants such as small colony variants 11,12 and intracellular persistence.…”