Cationic Hydrogels Modulate Neural Stem and Progenitor Cell Proliferation and Differentiation Behavior in Dependence of Cationic Moiety Concentration in 2D Cell Culture.

The central nervous system (CNS) has a limited regenerative capacity because a hostile environment prevents tissue regeneration after damage or injury. Neural stem/progenitor cells (NSPCs) are considered a potential resource for CNS repair, which raises the issue of adequate cultivation and expansion procedures. Cationic charge supports the survival and adhesion of NSPCs. Typically, tissue culture plates with cationic coatings, such as poly-l-ornithine (PLO), have been used to culture these cell types (NSPCs). Yet presently, little is known about the impact of cationic charge concentration on the viability, proliferation, and differentiation capacity of NSPCs. Therefore, we have recently developed well-defined, fully synthetic hydrogel systems G1 (gel 1) to G6 (gel 6) that allow for the precise control of the concentration of the cationic trimethylaminoethyl acrylate (TMAEA) molecule associated with the polymer in a range from 0.06 to 0.91 µmol/mg. When murine NSPCs were cultured on these gels under differentiation conditions, we observed a strong correlation of cationic charge concentration with NSPC survival. In particular, neurons were preferentially formed on gels with a higher cationic charge concentration, whereas astrocytes and oligodendrocytes favored weakly charged or even neutral gel surfaces. To test the properties of the gels under proliferative conditions, the NSPCs were cultivated in the presence of fibroblast growth factor 2 (FGF2). The cytokine significantly increased the number of NSPCs but delayed the differentiation toward neurons and glia cells. Thus, the hydrogels are compatible with the survival, expansion, and differentiation of NSPCs and may be useful to create supportive environments in transplantation approaches.

CLSM-Guided Imaging for Quantifying Endodontic Disinfection.

Elimination of microbes in the root canal system is crucial for achieving long-term success in endodontic treatment. Further efforts in study design and standardization are needed in order to improve the validity and comparability of in vitro results on endodontic disinfection procedures, in turn improving clinical outcomes. This study optimizes two models at all steps: tooth selection, pretreatment, inoculation method (by growth or centrifugation), and confocal laser scanning microscopy (CLSM)-guided imaging of LIVE/DEAD-stained specimens. Individual anatomical conditions lead to substantial differences in penetration depth. Sclerosis grading (SCG), a classification system introduced in this study, provides information about the sclerosis status of the dentine and is helpful for careful, specific, and comparable tooth selection in in vitro studies. Sonically activated EDTA for the pretreatment of roots, inoculation of Enterococcus faecalis in an overflow model, 3-4 weeks of incubation, as well as polishing of dentine slices before staining, led to advances in the visualization of bacterial penetration and irrigation depths. In contrast, NaOCl pretreatment negatively affected performance reproducibility and should be avoided in any pretreatment. Nonsclerotized teeth (SCG0) can be used for microbial semilunar-shaped inoculation by centrifugation as a "quick-and-dirty" model for initial orientation. In conclusion, CLSM-guided imaging for quantifying endodontic infection/disinfection is a very powerful method after the fine-tuning of materials and methods.

Effect of Vancomycin, Gentamicin and Clindamycin on Cartilage Cells In Vitro.

BACKGROUND: The treatment of grafts with vancomycin for ligament reconstruction in knee surgery is the current standard. However, high antibiotic concentrations have chondrotoxic effects. PURPOSE: To test the chondrotoxicity of clindamycin, gentamicin and vancomycin in comparable concentrations. In vitro and in vivo effective concentrations hugely vary from drug to drug. To allow for comparisons between these three commonly used antibiotics, the concentration ranges frequently used in orthopedic surgical settings were tested. STUDY DESIGN: Controlled laboratory study. METHODS: Human cartilage from 10 specimens was used to isolate chondrocytes. The chondrocytes were treated with clindamycin (1 mg/mL and 0.5 mg/mL), gentamicin (10 mg/mL and 5 mg/mL) or vancomycin (10 mg/mL and 5 mg/mL), at concentrations used for preoperative infection prophylaxis in ligament surgery. Observations were taken over a period of 7 days. A control of untreated chondrocytes was included. To test the chondrotoxicity, a lactate dehydrogenase (LDH) test and a water-soluble tetrazolium salt (WST-1) assay were performed on days 1, 3 and 7. In addition, microscopic examinations were performed after fluorescence staining of the cells at the same time intervals. RESULTS: All samples showed a reasonable vitality of the cartilage cells after 72 h. However, clindamycin and gentamicin both showed higher chondrotoxicity in all investigations compared to vancomycin. After a period of 7 days, only chondrocytes treated with vancomycin showed reasonable vitality. CONCLUSIONS: The preoperative treatment of ligament grafts with vancomycin is the most reasonable method for infection prophylaxis, in accordance with the current study results regarding chondrotoxicity; however, clindamycin and gentamicin cover a wider anti-bacterial spectrum. CLINICAL RELEVANCE: The prophylactic antibiotic treatment of ligament grafts at concentrations of 5 mg/mL or 10 mg/mL vancomycin is justifiable and reasonable. In specific cases, even the use of gentamicin and clindamycin is appropriate.