Viability assay | EPFL Graph Search

A viability assay is an assay that is created to determine the ability of organs, cells or tissues to maintain or recover a state of survival. Viability can be distinguished from the all-or-nothing states of life and death by the use of a quantifiable index that ranges between the integers of 0 and 1 or, if more easily understood, the range of 0% and 100%. Viability can be observed through the physical properties of cells, tissues, and organs. Some of these include mechanical activity, motility, such as with spermatozoa and granulocytes, the contraction of muscle tissue or cells, mitotic activity in cellular functions, and more. Viability assays provide a more precise basis for measurement of an organism's level of vitality. Viability assays can lead to more findings than the difference of living versus nonliving. These techniques can be used to assess the success of cell culture techniques, cryopreservation techniques, the toxicity of substances, or the effectivenes

Characterization of bone progenitor cells after GFP lentivirus transfection

Tanja Cloé Hausherr, Axelle Deirdre Eve Justafré

Several treatments have been developed for treating bone fractures as they are very common events. Amongst other new strategies, synthetic bone substitutes present a very high potential therapy because they lower the risk of infection and rejection. Moreover, bone progenitor cells have been added to these bone graft substitutes, allowing them to gain the property of osteogenesis. Surprisingly, it has been observed that bone formation was less efficient in the case of bone substitutes seeded with bone progenitor cells compared to cell-free bone substitutes. This result raised questions about the evolution of these cells inside the implant. In order to investigate this shortcoming, osteoprogenitor cells have been transfected using a GFP lentivirus. Using a viability assay and Alizarin and ALP stainings, the characterization of GFP-transfected bone progenitor cells demonstrated a phenotype unaltered after transfection with a lentivirus.

2015

Viability Assay and Osteogenic Induction of Bone Progenitor Cells

Florence Gavin, Tanja Cloé Hausherr

Tissue engineering scaffolds are the new approach to replace common bone grafts. The first aim of this project was to investigate whether bone progenitor cells used in previous studies can undergo osteogenic differentiation. In osteogenic staining experiments we demonstrated that the cells indeed undergo osteogenic induction. Further cell viability tests showed regular cell growth in the scaffold in the timespan of 0-14 days. For the second aim of the project, we investigated into the influence of the volume of interest when deducing bone parameters from microCT images. The microCT images were acquired in a previous study to deduce the effect of loading and cell seeding on the bone growth within the scaffold. Using a modified volume of interest, similar conclusions regarding the effect of loading were made, as when using the original volume of interest.

2014

Study of Cell Adhesion and Tracking Methods for in Vivo Cell Localisation in a Tissue-Engineering Scaffold

Thaïs Cléa Laura Séverine Clouet, Tanja Cloé Hausherr

Bone fracture healing problems, because of the loss of tissue regeneration, can affect many old or multi-pathologic patients around the world. Among the therapeutic strategies, bone substitutes, such as poly-(L-lactitve acid) with 5% wt. % ß-tricalcium phosphate (PLA/5%ß-TCP) scaffolds, are promising as a clinical solution. One strategy to tune their osteoinductive properties is the addition of bone progenitor cells. Therefore, cell- free and cell-seeded PLA/5% ß-TCP scaffolds were implanted into femoral condyles of rats to promote bone regeneration. The in vivo study showed that the bone growth inside a cell-seeded scaffold with human bone progenitor cells was delayed compared to cell-free scaffold. What happened to the cells? Did they trigger an immune response, migrate or die? Therefore, the goals of this project are to evaluate the cell adhesion in vitro to the scaffold and to propose a reliable cell labeling method to track them in future in vivo studies. In the first aim, the adhesion of the cells was qualitatively assessed by the cell morphology and the presence of fibronectin using fluorescence imaging. To quantify their adherence, seeded scaffolds were washed up to 3 times with a 0.9 % NaCl solution. The luminescence of the scaffolds and the washing solutions was measured using a cell viability assay. These experiments demonstrated that after 72h of culture, the measured adherent bone progenitor cells on the scaffolds decreased after 3 washes down to 50 % while it stayed stable after 14 days of culture. In the second aim, we focused on methods to label the cells either once implanted or prior to implantation. The first method was to translate the in situ hybridization protocol with the human specific Alu sequence from paraffin embedded samples to resin embedded ones. The obtained results were so far inconclusive. Concerning the labeling of the cells before implantation, the transmembrane label PKH26 was investigated. Its staining efficacy was high just after labeling, while it decreased drastically over time due to cell division.

2015

Study of Cell Adhesion and Tracking Methods for in Vivo Cell Localisation in a Tissue-Engineering Scaffold

Thaïs Cléa Laura Séverine Clouet, Tanja Cloé Hausherr

2015