Electrical conditioning of adipose-derived stem cells in a multi-chamber culture platform.

In tissue engineering, several factors play key roles in providing adequate stimuli for cells differentiation, in particular biochemical and physical stimuli, which try to mimic the physiological microenvironments. Since electrical stimuli are important in the developing heart, we have developed an easy-to-use, cost-effective cell culture platform, able to provide controlled electrical stimulation aimed at investigating the influence of the electric field in the stem cell differentiation process. This bioreactor consists of an electrical stimulator and 12 independent, petri-like culture chambers and a 3-D computational model was used to characterize the distribution and the intensity of the electric field generated in the cell culture volume. We explored the effects of monophasic and biphasic square wave pulse stimulation on a mouse adipose-derived stem cell line (m17.ASC) comparing cell viability, proliferation, protein, and gene expression. Both monophasic (8 V, 2 ms, 1 Hz) and biphasic (+4 V, 1 ms and -4 V, 1 ms; 1 Hz) stimulation were compatible with cell survival and proliferation. Biphasic stimulation induced the expression of Connexin 43, which was found to localize also at the cell membrane, which is its recognized functional mediating intercellular electrical coupling. Electrically stimulated cells showed an induced transcriptional profile more closely related to that of neonatal cadiomyocytes, particularly for biphasic stimulation. The developed platform thus allowed to set-up precise conditions to drive adult stem cells toward a myocardial phenotype solely by physical stimuli, in the absence of exogenously added expensive bioactive molecules, and can thus represent a valuable tool for translational applications for heart tissue engineering and regeneration.

The assessment of airborne bacterial contamination in three composting plants revealed site-related biological hazard and seasonal variations.

AIMS: The purpose of this study was to evaluate the degree of bacterial contamination generated by three Italian composting plants (1, 2 and 3) in two different seasons and to assess the health risk for the employees. METHODS AND RESULTS: Aerosols samples were collected with an agar impact sampler. Several plant sites and external upwind and downwind controls were examined. Total colony-forming counts of mesophilic and thermophilic bacteria, actinomycetes and streptomycetes, Gram-negatives, coliforms and sulfite-reducers were determined. Selective media were used in order to isolate pathogenic bacteria. The levels of total mesophilic and thermophilic micro-organisms ranged between 33 and >40,000 CFU m(-3) in plant 1, 39 and 18,700 CFU m(-3) in plant 2 and 261 and 6278 CFU m(-3) in plant 3. Strains of Escherichia coli, Staphylococcus aureus and Clostridium perfringens were also found. CONCLUSIONS: The plants monitored in this study have proved to be sources of aerosolized bacteria. The activities involving mechanical movement of the composting mass and the indoor activities were of greatest potential risk. In all the studied plants, a statistically significant dependence was found between the bacterial contamination and the season for some or almost all the analysed parameters, but a clear seasonal trend could not be observed. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides broad evidence of bacterial aerosol dispersion and site-related biological hazards that may be useful to the regional government to implement regulations on worker safety in composting plants.

Influence of biotic and abiotic factors on human pathogens in a finished compost.

The role of indigenous microflora of a finished compost, defined NK12, on the growth suppression of pathogens under different moisture and temperature storages was investigated. Total count of mesophilic and thermophilic bacteria was evaluated by the most probable number method and growth of seeded Salmonella arizonae 3924 serogroup B and enteropathogenic Escherichia coli 84 M in NK12 at different moisture temperature conditions was monitored. Results on sterile and non-sterile NK12 were compared. In all tested experimental conditions, the NK12 indigenous microflora was stable and biologically active. S. arizonae 3924 and E. coli 84 M grew rapidly in sterilized NK12 at different moistures and storage temperatures, and their growth was suppressed in non-sterilized NK12. Pathogens inactivation was lower when compost was stored at 40% and 80% humidity and at 37 degrees C. Our results show that the major role in the pathogens suppression was played by the indigenous microflora of the finished compost, although physical factors too influenced the growth phenomenon.