Apoptosis is an organized process that signals cells to self-destruct for cell renewal or to control aberrant cell growth. As cells become damaged or are no longer needed, they undergo apoptosis or programmed cell death, a normal physiological process that occurs during embryonic development and tissue homeostasis. Apoptosis controls the orderly death of damaged cells, whereas necrosis occurs as a result of tissue damage, causing the loss of both damaged and surrounding cells.
Apoptotic process
The apoptotic process is characterized by certain morphological features. These include changes in the plasma membrane (such as loss of membrane symmetry and attachment), a condensation of the cytoplasm and nucleus, protein cleavage, and internucleosomal cleavage of DNA. In the final stages of the process, dying cells become fragmented into apoptotic bodies and consequently are eliminated by phagocytic cells without significant inflammatory damage to surrounding cells.
However, some cell types do not display characteristic features of apoptosis. In those cases, multiple aspects of apoptosis might need to be analyzed to confirm the mechanism of cell death.
To support this spectrum of requirements, BD Biosciences offers a full range of apoptosis detection tools and technologies for measuring indicators at different stages across the apoptotic process. BD Biosciences tools use multiple methodologies including flow cytometry, bioimaging and microscopy (for live and fixed cell analysis) as well as ELISA, IHC, western blot and spectrofluorometry.
Methods for detecting apoptosis or dead cells (viability) by cell preparation type.
Methods for detecting apoptosis in different cell or tissue types
Annexin V—a key protein in apoptosis signaling
Changes in the plasma membrane are one of the characteristics of the apoptotic process detected in living cells. Apoptosis can be detected by the presence of phosphatidylserine (PS), which is normally located on the cytoplasmic face of the plasma membrane. During apoptosis, PS translocates to the outer leaflet of the plasma membrane and can be detected by flow cytometry and cell imaging through binding to fluorochrome-labeled annexin V when calcium is present.
BD Biosciences offers annexin V in several common formats such as FITC, PE, BD Horizon™ BV421 for the violet laser, and BD Horizon™ BUV395 for the ultraviolet laser. With the addition of these new formats, more complex assays can be developed to look at apoptosis within heterogeneous cell subsets.
Since intracellular annexin V is also exposed if the plasma membrane is compromised, a membrane-impermeant dye such as 7-AAD is commonly used to distinguish between apoptotic and dead cells to exclude the dead cells. The populations of cells that are stained with annexin V only represent the apoptotic cell populations.
Radio-frequency dose-dependent apoptosis, necrosis and cell death monitored by annexin V-BD Horizon™ V450. Radio-frequency dose-dependent apoptosis, necrosis and cell death monitored by annexin V-BD Horizon™ V450 in pancreatic carcinoma cell lines treated with a low dose of cetuximab targeted gold nanoparticles. As the RF field power increases, the temperature increases, and a shift from apoptosis (lower right quadrant) to frank necrosis (upper left quadrant) is seen.
