Interaction of Cutibacterium acnes with human bone marrow derived mesenchymal stem cells: a step toward understanding bone implant- associated infection development.

Crosstalk between mesenchymal stem cells (MSCs) and bacteria plays an important role in regulating the regenerative capacities of MSCs, fighting infections, modulating immune responses and maintaining tissue homeostasis. Commensal Cutibacterium acnes (C. acnes) bacterium becomes an opportunistic pathogen causing implant-associated infections. Herein, we examined MSCs/C. acnes interaction and analysed the subsequent bacteria and MSCs behaviours following infection. Human bone marrow derived MSCs were infected by two clinical and one laboratory C. acnes strains. Following 3h of interaction, all bacterial strains were able to invade MSCs. Viable intracellular bacteria acquired virulence factors by increasing biofilm formation and/or by affecting macrophage phagocytosis. Although the direct and indirect (through neutrophil stimulation) antibacterial effects of the MSCs secretome were not enhanced following C. acnes infection, ELISA analysis revealed that C. acnes clinical strains are able to license MSCs to become immunosuppressive cell-like by increasing the secretion of IL-6, IL-8, PGE-2, VEGF, TGF-ß and HGF. Overall, these results showed a direct impact of C. acnes on bone marrow derived MSCs, providing new insights into the development of C. acnes during implant-associated infections. STATEMENT OF SIGNIFICANCE: The originality of this work relies on the study of relationship between human bone marrow derived mesenchymal stem cells (MSCs) phenotype and C. acnes clinical strains virulence following cell infection. Our major results showed that C. acnes are able to invade MSCs, inducing a transition of commensal to an opportunistic pathogen behaviour. Although the direct and indirect antibacterial effects were not enhanced following C. acnes infection, secretome analysis revealed that C. acnes clinical strains were able to license MSCs to become immunosuppressive and anti-fibrotic cell-like. These results showed a direct impact of C. acnes on bone marrow derived MSCs, providing new insights into the development of C. acnes during associated implant infections.

Bioinspired Nanofeatured Substrates: Suitable Environment for Bone Regeneration.

Bone mimicking coatings provide a complex microenvironment in which material, through its inherent properties (such as nanostructure and composition), affects the commitment of stem cells into bone lineage and the production of bone tissue regulating factors required for bone healing and regeneration. Herein, a bioactive mineral/biopolymer composite made of calcium phosphate/chitosan and hyaluronic acid (CaP-CHI-HA) was elaborated using a versatile simultaneous spray coating of interacting species. The resulting CaP-CHI-HA coating was mainly constituted of bioactive, carbonated and crystalline hydroxyapatite with 277 ± 98 nm of roughness, 1 µm of thickness, and 2.3 ± 1 GPa of stiffness. After five days of culture, CaP-CHI-HA suggested a synergistic effect of intrinsic biophysical features and biopolymers on stem cell mechanobiology and nuclear organization, leading to the expression of an early osteoblast-like phenotype and the production of bone tissue regulating factors such as osteoprotegerin and vascular endothelial growth factor. More interestingly, amalgamation with biopolymers conferred to the mineral a bacterial antiadhesive property. These significant data shed light on the potential regenerative application of CaP-CHI-HA bioinspired coating in providing a suitable environment for stem cell bone regeneration and an ideal strategy to prevent implant-associated infections.

Reversing charges or how to improve Wharton's jelly mesenchymal stem cells culture on polyelectrolyte multilayer films.

BACKGROUND: Polyelectrolyte multilayer (PEMs) films made of poly(allylamine hydrochloride) (PAH) as polycation and poly(styrene sulfonate) (PSS) as polyanion, with a PAH ending layer, can be used as a coating in order to improve the anti-thrombogenicity and patency of vascular grafts in vascular engineering field. They induce strong adhesion of mature endothelial cells on glass, expanded polytetrafluoroethylene and cryopreserved arteries. Despite their outstanding effect on mature and progenitor endothelial cells, PEMs ending with PAH showed a poor outcome on Wharton's jelly mesenchymal stem cells (WJ-MSCs) culture. OBJECTIVE: The aim of this work was to examine the influence of the ending charge of PEMs on WJ-MSCs behavior. METHODS: WJ-MSCs amplified until the 3rd passage were seeded and cultured on (PAH-PSS)3-PAH and on (PAH-PSS)4 coated glass for 10 days. Stem cell phenotype was checked by flow cytometry and cell morphology was followed by bright field microscopy. RESULTS: Flow cytometry analysis showed that WJ-MSCs were positive for MSC's markers CD73, CD90 and CD105 and negative for hematopoietic markers CD34 and CD45. Light microscopy showed development of nodule-like structures after 10 days of culture on (PAH-PSS)3-PAH, which resulted in a disturbance of cell monolayer. Whereas WJ-MSCs cultured on (PAH-PSS)4 ending with PSS showed a normal cell growth like on collagen and reached confluence after 10 days. CONCLUSION: The culture surface seems to have a determining role in WJ-MSC's "spatial" behavior, which could be considered in the field of tissue engineering.

[Computer-assisted surgery in total knee replacement. Preliminary results: report of 60 cases]. / Prothèse totale du genou assistée par ordinateur Résultats préliminaires: à propos de 60 cas.

PURPOSE OF THE STUDY: Conventional techniques proposed for total knee arthroplasty (TKA), necessarily require an acceptable alignment of the lower limb. Computer-assisted surgery is becoming increasingly popular in order to improve the precision of the component alignment, an essential element for good long-term results. The purpose of this prospective study was to present our preliminary results with computer-assisted implantation of TKA. MATERIAL AND METHODS: This was a prospective study of 55 patients (60 knees) included at random for computer-assisted TKA between April 2004 and September 2005. Mean age was 70.5 years. The preoperative assessment noted genu varum in 56 knees and genu valgum in four knees. Three knees with unilateral degenerative disease presented a post traumatic tibia malunion. The same surgeon performed all of the operations using the same prosthesis and navigation system (P.F.C. Sigma). Lower limb alignment and orientation of the prosthetic implants were assessed with standard pre- and postoperative gonometry. Sagittal alignment was measured on the standard X-rays (lateral and anteroposterior view). RESULTS: Knee alignment improved from 8.1+/-4.5 degrees varus (10 degrees valgus to 18 degrees varus) preoperatively, to 0.4+/-0.6 degrees varus (1 degrees valgus to 2 degrees varus) postoperatively. In the frontal plane, the mean angle of the femoral component on the anteroposterior (ap) view was 89.7+/-0.7 degrees (88-91 degrees). The mean angle of the tibial component on the ap view was 89.9+/-0.7 degrees (88.5-91 degrees). The femorotibial mechanical axis was within +/-2 degrees for all prostheses. In the sagittal plane, the mean angle of the femoral component on the lateral view was 4.8 degrees (3-6.5 degrees). The mean tibial slope was 2.7 degrees (1-4 degrees) for the prostheses with a fixed tibial plateau and 0.2 degrees (-1 degrees to +1 degrees) for those with a rotating plateau. The mean operative time was 135 min (110-180 min) and was inversely proportional to experience. There was one conversion to conventional surgery due to software dysfunction. There were no complications related to the operative technique. DISCUSSION: The best outcome, particularly in terms of aseptic loosening, is reported for knees with a valgus or varus angle within 3 degrees . The improved accuracy of computer-assisted implantation has enabled better orientation of the components in the frontal, sagittal and horizontal planes with implantations well within this range.