Dynamics of caspase-3 activation and inhibition in embryonic micromasses evaluated by a photon-counting chemiluminescence approach.

Caspases are key enzymatic components of the intracellular apoptotic machinery, and their role in mammalian systems is often studied using fluoromethylketone (FMK) inhibitors. Despite many advantages of such approach, efficiency of the inhibitor and membrane permeability speed are often questioned. This work therefore focuses on an exact evaluation of caspase-3 FMK inhibition dynamics in camptothecin-induced mesenchymal micromasses. Two parameters of caspase-3 FMK inhibitor were investigated: first, the stability of the inhibitory potential in the time course of cultivation and, simultaneously, the dynamics of caspase-3 FMK inhibition after camptothecin-induced apoptosis peak. A photon-counting chemiluminescence approach was applied for quantification of active caspase-3. The sensitivity of the photon-counting method allowed for evaluation of active caspase-3 concentration in femtogram amounts per cell. The inhibitor penetrated the cells within the first minute after its application, and the peak of caspase-3 started to decline to the blank level after 30 min. The inhibitory effect of the FMK inhibitor was unchanged during the entire 48 h of cultivation.

Cell proliferation and apoptosis in the primary enamel knot measured by flow cytometry of laser microdissected samples.

Laser capture microdissection (LCM) uniquely allows the selection of specific cell populations from histological sections. These selected cells are then catapulted into a test tube without any contamination from surrounding tissues. During the last ten years, many significant results have been achieved, particularly at the level of DNA and RNA where amplification techniques are available. However, where amplification procedures are difficult, the benefits of LCM diminish. To overcome such difficulties, a novel approach, combining laser capture microdissection and flow cytometry, has been tested here for detection of apoptosis and proliferation in tissue bound cell populations without any amplification steps. The mouse cap stage molar tooth germ was used as a model. At the centre of the inner enamel epithelium, the primary enamel knot is a clearly defined apoptotic population with minimal proliferation, flanked by the highly proliferative cervical loops on each side. Thus within the tooth germ epithelium at this stage, two distinct populations of cells are found side by side. These populations were selected by laser capture microdissection and then analysed by flow cytometry for apoptosis and proliferation. Flow cytometric results correlated well with immunohistochemical findings, demonstrating the success and sensitivity of this combined procedure.