We thank Rev. Dr. Ralph Bohlmann and Rev. Dr. James Voelz for suggesting the word &#8220;anastasis&#8221; to describe reversal of apoptosis; Douglas R. Green for HeLa cells stably expressing cytochrome c-GFP; Charles M. Rudin and Eric E. Gardner for H446 cells; Heather Lamb for assistance in cartoon drawing at the video; Yee Hui Yeo for valuable discussion of this manuscript. This work was supported by a Sir Edward Youde Memorial Fellowship (H.L.T.), the Dr. Walter Szeto Memorial Scholarship (H.L.T.), Fulbright grant 007-2009 (H.L.T.), Life Science Research Foundation fellowship (H.L.T.), NIH grants NS037402 (J.M.H.) and NS083373 (J.M.H.), and University Grants Committee of the Hong Kong AoE/B-07/99 (M.C.F.). Ho Lam Tang is a Shurl and Kay Curci Foundation Fellow of the Life Sciences Research Foundation.

The authors have nothing to disclose.

Anastasis refers to the phenomenon where cells that have activated cell death pathway subsequently reverse the dying process and survive. Here, we have demonstrated that live cell imaging can be used to confirm that the same individual cells in fact can reverse apoptotic cell death process at a late stage, and then continue surviving and reproducing. Our protocols describe several optimized cell type-specific treatment conditions to induce apoptosis and allow a large proportion of the cells to undergo the reversal of apo...

Apoptosis (Greek for &#8220;falling to death&#8221;) is generally assumed to be a one-way process ending in cell suicide1-7. Genetic disruption of pro-death genes results in the survival of extra cells that would otherwise die in whole animals, including cells that have already initiated the apoptosis pathway8,9. Similarly, genetic manipulations&#160;allow&#160;healthy mammalian cells that artificially display &#8220;eat me&#8221; signals or that lose adhesiveness to their extracellular matrix to escape death by whole cell phagocytosis or entosis, respectively10,11. However,&#160;we and others have shown that without genetic manipulation normal healthy mammalian cells and cell lines can also recover from the early stages of apoptosis12-15. Using tools to track individual cells, we have further demonstrated recovery from late stages of apoptosis12,13, after cells have passed important checkpoints that typically mark the &#8220;point of no return&#8221;2-6. These checkpoints of late stage apoptosis&#160;include mitochondrial release of cytochrome c, activation of caspases, nuclear fragmentation, and formation of apoptotic bodies. We adopted a Greek compound word &#8220;anastasis&#8221;, which means &#8220;rising to life&#8221;, to describe this reversal of apoptosis at the brink of cell death2-6.
Unless the entire dying-recovery process is observed by live cell imaging, it is challenging to distinguish cells that have undergone anastasis from cells that never experienced apoptotic events. Decades of work have revealed that the morphological features of cell suicide by apoptosis are driven by evolutionarily conserved biochemical and molecular events16-19. These events promote self-destruction of cells to regulate developmental and homoeostatic processes in unicellular and multicellular organisms by eliminating damaged or dangerous cells16-19. While apoptotic cells can be readily distinguished by standardized morphological, biochemical and molecular manifestations of apoptosis1,5,6,16,20, currently there is no known marker specific to anastasis12,13. Importantly, cells that have undergone anastasis appear to be normal healthy cells, and cells that just start reversing apoptosis appear as apoptotic dying cells12,13. Thus, new tools are needed to conclude with certainty that a given surviving cell had previously experienced active apoptotic processes.
Apoptosis is generally assumed as an irreversible cascade because it is a rapid and massive destruction process. While it could take minutes to days for some cells to initiate apoptosis, once mitochondria have released apoptogenic factors such as cytochrome c into the cytosol 21,22, caspases can be activated within 5 minutes23,24, followed by cytoplasmic and nuclear condensation within 10 min25-27, and cell death shortly thereafter25-27. Activated caspases&#160;orchestrate apoptosis by cleaving and inactivating key structural and functional components for the purpose of cellular demolition2,28, such as the endonuclease inhibitor DFF45/ICAD29,30. Caspases also activate pro-apoptotic factors, such as BCL-2 family member BID, which translocates to mitochondria to promote mitochondrial release of cytochrome c31,32. Caspase activity also results in cell surface exposure of phosphatidylserine as an &#8220;eat me&#8221; signal for promoting engulfment of dying cells by macrophages or neighbor cells through phagocytosis33. Furthermore, apoptotic events render mitochondria dysfunctional, disrupting cellular bioenergetics and metabolism34,35,36. Thus, recovery from such destruction seems intuitively unlikely.
Contrary to original expectations, cells can reverse the apoptotic cell death process even at a late stage. By continuously monitoring the fate of dying cells in culture, we observed the reversibility of late stage apoptosis in a range of primary cells and cell lines12,13. Removal of the death stimulus allowed recovery from the overt features of apoptosis, such as mitochondrial fragmentation, chromatin condensation, DNA damage, plasma membrane blebbing, cell surface exposure of phosphatidylserine, release of mitochondrial cytochrome c, caspase activation, nuclear fragmentation, cell shrinkage, and formation of apoptotic bodies. These observations raise unanswered questions regarding the functions, consequences, and mechanisms of anastasis. To address these questions, a prerequisite is to reliably identify cells that have undergone anastasis. Here, we describe live microscopy&#160;methods and a caspase biosensor for&#160;detecting cells that have previously reversed late stage apoptosis and then survived.

<table><tbody><tr><td>LSM780 confocal microscopy</td><td>Carl Zeiss</td><td></td><td></td></tr><tr><td>Glass bottom culture dish</td><td>MatTek Corporation</td><td>P35G-0-14-C</td><td></td></tr><tr><td>Transparent CultFoi</td><td>Carl Zeiss</td><td>000000-1116-084</td><td></td></tr><tr><td>CO&lt;sub&gt;2&lt;/sub&gt; independent medium</td><td>Life Technologies</td><td>18045-088</td><td></td></tr><tr><td>CellTracker</td><td>Life Technologies</td><td>C34552</td><td></td></tr><tr><td>Mitotracker Red CMXRos</td><td>Life Technologies</td><td>M-7512</td><td></td></tr><tr><td>Hoechst 33342</td><td>Life Technologies</td><td>H1399</td><td></td></tr><tr><td>Fluorescently labeled annexin V</td><td>Biovision</td><td>K201</td><td></td></tr></tbody></table>

strategies for tracking anastasis, a cell survival phenomenon that reverses apoptosis

Anastasis (Greek for &#8220;rising to life&#8221;) refers to the recovery of dying cells. Before these cells recover, they have passed through important checkpoints of apoptosis, including mitochondrial fragmentation, release of mitochondrial cytochrome c into the cytosol, activation of caspases, chromatin condensation, DNA damage, nuclear fragmentation, plasma membrane blebbing, cell shrinkage, cell surface exposure of phosphatidylserine, and formation of apoptotic bodies. Anastasis can occur when apoptotic stimuli are removed prior to death, thereby allowing dying cells to reverse apoptosis and potentially other death mechanisms. Therefore, anastasis appears to involve physiological healing processes that could also sustain damaged cells inappropriately. The functions and mechanisms of anastasis are still unclear, hampered in part by the limited tools for detecting past events after the recovery of apparently healthy cells. Strategies to detect anastasis will enable studies of the physiological mechanisms, the hazards of undead cells in disease pathology, and potential therapeutics to modulate anastasis. Here, we describe effective strategies using live cell microscopy and a mammalian caspase biosensor&#160;for identifying and tracking anastasis in mammalian cells.

To study the reversal of apoptosis, tissue culture cells are first exposed to a death stimulus to trigger apoptosis. When the cells display hallmarks of apoptosis, fresh culture medium is then applied to wash away the stimulus&#160;and then incubate the dying cells to allow recovery (Figure 1A). Here, the key question being addressed is how far individual dying cultured cells can progress towards apoptosis and still undergo anastasis. This question can be definitively answered by continuous monitoring wi...

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Strategies for Tracking Anastasis, A Cell Survival Phenomenon that Reverses Apoptosis

The term anastasis refers to the phenomenon in which dying cells reverse a cell suicide process at a late stage, repair themselves, and ultimately survive. Here we demonstrate protocols for detecting and tracking cells that undergo anastasis.

Anastasis (Greek for &#8220;rising to life&#8221;) refers to the recovery of dying cells. Before these cells recover, they have passed through important ...

strategies-for-tracking-anastasis-cell-survival-phenomenon-that

Research

JoVE Journal

Biology

17.9K Views.  Johns Hopkins University Bloomberg School of Public Health. The term anastasis refers to the phenomenon in which dying cells reverse a cell suicide process at a late stage, repair themselves, and ultimately survive. Here we demonstrate protocols for detecting and tracking cells that undergo anastasis. 

Video: Strategies for Tracking Anastasis, A Cell Survival Phenomenon that Reverses Apoptosis

Long-term Live-cell Imaging to Assess Cell Fate in Response to Paclitaxel

Live-cell imaging is a powerful technique that can be used to directly visualize biological phenomena in single cells over extended periods of time. Over the past decade, new and innovative technologies have greatly enhanced the practicality of live-cell imaging. Cells can now be kept in focus and continuously imaged over several days while maintained under 37 &#176;C and 5% CO2 cell culture conditions. Moreover, multiple fields of view representing different experimental conditions can be acquired simultaneously, thus providing high-throughput experimental data. Live-cell imaging provides a significant advantage over fixed-cell imaging by allowing for the direct visualization and temporal quantitation of dynamic cellular events. Live-cell imaging can also identify variation in the behavior of single cells that would otherwise have been missed using population-based assays. Here, we describe live-cell imaging protocols to assess cell fate decisions following treatment with the anti-mitotic drug paclitaxel. We demonstrate methods to visualize whether mitotically arrested cells die directly from mitosis or slip back into interphase. We also describe how the fluorescent ubiquitination-based cell cycle indicator (FUCCI) system can be used to assess the fraction of interphase cells born from mitotic slippage that are capable of re-entering the cell cycle. Finally, we describe a live-cell imaging method to identify nuclear envelope rupture events.

Live-cell imaging provides a wealth of information on single cells or whole populations that is unattainable by fixed cell imaging alone. Here, live-cell imaging protocols to assess cell fate decisions following treatment with the anti-mitotic drug paclitaxel are described.

Live-cell imaging is a powerful technique that can be used to directly visualize biological phenomena in single cells over extended periods of time. Over ...

Cancer Research

Flow Cytometric Detection of Newly-formed Breast Cancer Stem Cell-like Cells After Apoptosis Reversal

Cancer recurrence has long been studied by oncologists while the underlying mechanisms remain unclear. Recently, we and others found that a phenomenon named apoptosis reversal leads to increased tumorigenicity in various cell models under different stimuli. Previous studies have been focused on tracking this process in vitro and in vivo; however, the isolation of real reversed cells has yet to be achieved, which limits our understanding on the consequences of apoptosis reversal. Here, we take advantage of a Caspase-3/7 Green Detection dye to label cells with activated caspases after apoptotic induction. Cells with positive signals are further sorted out by fluorescence-activated cell sorting (FACS) for recovery. Morphological examination under confocal microscopy helps confirm the apoptotic status before FACS. An increase in tumorigenicity can often be attributed to the elevation in the percentage of cancer stem cell (CSC)-like cells. Also, given the heterogeneity of breast cancer, identifying the origin of these CSC-like cells would be critical to cancer treatment. Thus, we prepare breast non-stem cancer cells before triggering apoptosis, isolating caspase-activated cells and performing the apoptosis reversal procedure. Flow cytometry analysis reveals that breast CSC-like cells re-appear in the reversed group, indicating breast CSC-like cells are transited from breast non-stem cancer cells during apoptosis reversal. In summary, this protocol includes the isolation of apoptotic breast cancer cells and detection of changes in CSC percentage in reversed cells by flow cytometry.

Here, we present a protocol to isolate apoptotic breast cancer cells by fluorescence-activated cell sorting and further detect the transition of breast non-stem cancer cells to breast cancer stem cell-like cells after apoptosis reversal by flow cytometry.

Cancer recurrence has long been studied by oncologists while the underlying mechanisms remain unclear. Recently, we and others found that a phenomenon ...

Cell Cycle-specific Measurement of &#947;H2AX and Apoptosis After Genotoxic Stress by Flow Cytometry

The presented method or slightly modified versions have been devised to study specific treatment responses and side effects of various anti-cancer treatments as used in clinical oncology. It enables a quantitative and longitudinal analysis of the DNA damage response after genotoxic stress, as induced by radiotherapy and a multitude of anti-cancer drugs. The method covers all stages of the DNA damage response, providing endpoints for induction and repair of DNA double-strand breaks (DSBs), cell cycle arrest and cell death by apoptosis in case of repair failure. Combining these measurements provides information about cell cycle-dependent treatment effects and thus allows an in-depth study of the interplay between cellular proliferation and coping mechanisms against DNA damage. As the effect of many cancer therapeutics including chemotherapeutic agents and ionizing radiation is limited to or strongly varies according to specific cell cycle phases, correlative analyses rely on a robust and feasible method to assess the treatment effects on the DNA in a cell cycle-specific manner. This is not possible with single-endpoint assays and an important advantage of the presented method. The method is not restricted to any particular cell line and has been thoroughly tested in a multitude of tumor and normal tissue cell lines. It can be widely applied as a comprehensive genotoxicity assay in many fields of oncology besides radio-oncology, including environmental risk factor assessment, drug screening and evaluation of genetic instability in tumor cells.

The presented method combines the quantitative analysis of DNA double-strand breaks (DSBs), cell cycle distribution and apoptosis to enable cell cycle-specific evaluation of DSB induction and repair as well as the consequences of repair failure.

The presented method or slightly modified versions have been devised to study specific treatment responses and side effects of various anti-cancer ...

Use of a Caspase Multiplexing Assay to Determine Apoptosis in a Hypothalamic Cell Model

The ability to multiplex assays in studies of complex cellular mechanisms eliminates the need for repetitive experiments, provides internal controls, and decreases waste in costs and reagents. Here we describe optimization of a multiplex assay to assess apoptosis following a palmitic acid (PA) challenge in an in vitro hypothalamic model, using both fluorescent and luminescent based assays to measure viable cell counts and caspase-3/7 activity in a 96-well microtiter plate format. Following PA challenge, viable cells were determined by a resazurin-based fluorescent assay. Caspase-3/7 activity was then determined using a luminogenic substrate, DEVD, and normalized to cell number. This multiplexing assay is a useful technique for determining change in caspase activity following an apoptotic stimulus, such as saturated fatty acid challenge. The saturated fatty acid PA can increase hypothalamic oxidative stress and apoptosis, indicating the potential importance of assays such as that described here in studying the relationship between saturated fatty acids and neuronal function.

Multiplex assays can provide beneficial information for basic cellular mechanisms&#160;and eliminate waste of reagents and unnecessary repetitive experiments. We describe here a multiplex caspase-3/7 activity assay, using fluorescent- and luminescent-based methods, to determine cell viability in an in vitro hypothalamic model following oxidative challenge with palmitic acid.

The ability to multiplex assays in studies of complex cellular mechanisms eliminates the need for repetitive experiments, provides internal controls, and ...

Neuroscience

Through the Looking Glass: Time-lapse Microscopy and Longitudinal Tracking of Single Cells to Study Anti-cancer Therapeutics

The response of single cells to anti-cancer drugs contributes significantly in determining the population response, and therefore is a major contributing factor in the overall outcome. Immunoblotting, flow cytometry and fixed cell experiments are often used to study how cells respond to anti-cancer drugs. These methods are important, but they have several shortcomings. Variability in drug responses between cancer and normal cells, and between cells of different cancer origin, and transient and rare responses are difficult to understand using population averaging assays and without being able to directly track and analyze them longitudinally. The microscope is particularly well suited to image live cells. Advancements in technology enable us to routinely image cells at a resolution that enables not only cell tracking, but also the observation of a variety of cellular responses. We describe an approach in detail that allows for the continuous time-lapse imaging of cells during the drug response for essentially as long as desired, typically up to 96 hr. Using variations of the approach, cells can be monitored for weeks. With the employment of genetically encoded fluorescent biosensors numerous processes, pathways and responses can be followed. We show examples that include tracking and quantification of cell growth and cell cycle progression, chromosome dynamics, DNA damage, and cell death. We also discuss variations of the technique and its flexibility, and highlight some common pitfalls.

Here, we describe a method of long-term time-lapse microscopy to longitudinally track single cells in response to anti-cancer therapeutics.

The response of single cells to anti-cancer drugs contributes significantly in determining the population response, and therefore is a major contributing ...

Medicine

Detecting Anastasis In Vivo by CaspaseTracker Biosensor

Anastasis (Greek for &#8220;rising to life&#8221;) is a recently discovered cell recovery phenomenon whereby dying cells can reverse late-stage cell death processes that are generally assumed to be intrinsically irreversible. Promoting anastasis could in principle rescue or preserve injured cells that are difficult to replace such as cardiomyocytes or neurons, thereby facilitating tissue recovery. Conversely, suppressing anastasis in cancer cells, undergoing apoptosis after anti-cancer therapies, may ensure cancer cell death and reduce the chances of recurrence. However, these studies have been hampered by the lack of tools for tracking the fate of cells that undergo anastasis in live animals. The challenge is to identify the cells that have reversed the cell death process despite their morphologically normal appearance after recovery. To overcome this difficulty, we have developed Drosophila and mammalian CaspaseTracker biosensor systems that can identify and permanently track the anastatic cells in vitro or in vivo. Here, we present in vivo protocols for the generation and use of the CaspaseTracker dual biosensor system to detect and track anastasis in Drosophila melanogaster after transient exposure to cell death stimuli. While conventional biosensors and protocols can label cells actively undergoing apoptotic cell death, the CaspaseTracker biosensor can permanently label cells that have recovered after caspase activation - a hallmark of late-stage apoptosis, and simultaneously identify active apoptotic processes. This biosensor can also track the recovery of the cells that attempted other forms of cell death that directly or indirectly involved caspase activity. Therefore, this protocol enables us to continuously track the fate of these cells and their progeny, facilitating future studies of the biological functions, molecular mechanisms, physiological and pathological consequences, and therapeutic implications of anastasis. We also discuss the appropriate controls to distinguish cells that undergo anastasis from those that display non-apoptotic caspase activity in vivo.

Detecting Anastasis In Vivo by CaspaseTracker Biosensor

Anastasis is technically challenging to detect in vivo because the cells that have reversed the cell death process can be morphologically indistinguishable from normal healthy cells. Here we describe protocols for detecting and tracking cells that undergo anastasis in live animals by using our newly developed in vivo CaspaseTracker biosensor system.

Anastasis (Greek for &#8220;rising to life&#8221;) is a recently discovered cell recovery phenomenon whereby dying cells can reverse late-stage cell death ...

Preparation of Cell-lines for Conditional Knockdown of Gene Expression and Measurement of the Knockdown Effects on E4orf4-Induced Cell Death

Functional inactivation of gene expression in mammalian cells is crucial for the study of the contribution of a protein of interest to various pathways1,2. However, conditional knockdown of gene expression is required in cases when constitutive knockdown is not tolerated by cells for a long period of time3-5. Here we describe a protocol for preparation of cell lines allowing conditional knockdown of subunits of the ACF chromatin remodeling factor. These cell lines facilitate the determination of the contribution of ACF to induction of cell death by the adenovirus E4orf4 protein6. Sequences encoding short hairpin RNAs for the Acf1 and SNF2h subunits of the ACF chromatin remodeling factor were cloned next to a doxycycline-inducible promoter in a plasmid also containing a gene for the neomycin resistance gene. Neomycin-resistant cell clones were selected in the presence of G418 and isolated. The resulting cell lines were induced by doxycycline treatment, and once Acf1 or SNF2h expression levels were reduced, the cells were transfected with a plasmid encoding E4orf4 or an empty vector. To confirm the specific effect of the shRNA constructs, Acf1 or SNF2h protein levels were restored to WT levels by cotransfection with a plasmid expressing Acf1 or SNF2h which were rendered resistant to the shRNA by introduction of silent mutations. The ability of E4orf4 to induce cell death in the various samples was determined by a DAPI assay, in which the frequency of appearance of nuclei with apoptotic morphologies in the transfected cell population was measured7-9.
The protocol described here can be utilized for determination of the functional contribution of various proteins to induction of cell death by their protein partners in cases when constitutive knockdown may be cell lethal.

Contribution of the ACF chromatin remodeling factor to E4orf4-induced cell death was measured. The protocol includes selection of cell clones in which doxycycline treatment induces conditional knockdown of the ACF subunits Acf1 and SNF2h, and use of the DAPI assay to measure E4orf4-induced cell death in the inducible cell lines.

Functional inactivation of gene expression in mammalian cells is crucial for the study of the contribution of a protein of interest to various ...

Temporal Tracking of Cell Cycle Progression Using Flow Cytometry without the Need for Synchronization

This protocol describes a method to permit the tracking of cells through the cell cycle without requiring the cells to be synchronized. Achieving cell synchronization can be difficult for many cell systems. Standard practice is to block cell cycle progression at a specific stage and then release the accumulated cells producing a wave of cells progressing through the cycle in unison. However, some cell types find this block toxic resulting in abnormal cell cycling, or even mass death. Bromodeoxyuridine (BrdU) uptake can be used to track the cell cycle stage of individual cells. Cells incorporate this synthetic thymidine analog, while synthesizing new DNA during S phase. By providing BrdU for a brief period it is possible to mark a pool of cells that were in S phase while the BrdU was present. These cells can then be tracked through the remainder of the cell cycle and into the next round of replication, permitting the duration of the cell cycle phases to be determined without the need to induce a potentially toxic cell cycle block. It is also possible to determine and correlate the expression of both internal and external proteins during subsequent stages of the cell cycle. These can be used to further refine the assignment of cell cycle stage or assess effects on other cellular functions such as checkpoint activation or cell death.

This protocol describes the use of bromodeoxyuridine (BrdU) uptake to permit the temporal tracking of cells that were in S phase at a specific point in time. Addition of DNA dyes and antibody labeling facilitates detailed analysis of the fate of the S phase cells at later times.

This protocol describes a method to permit the tracking of cells through the cell cycle without requiring the cells to be synchronized. Achieving cell ...

Techniques to Induce and Quantify Cellular Senescence

In response to cellular stress or damage, proliferating cells can induce a specific program that initiates a state of long-term cell-cycle arrest, termed cellular senescence. Accumulation of senescent cells occurs with organismal aging and through continual culturing in vitro. Senescent cells influence many biological processes, including embryonic development, tissue repair and regeneration, tumor suppression, and aging. Hallmarks of senescent cells include, but are not limited to, increased senescence-associated &#946;-galactosidase activity (SA-&#946;-gal); p16INK4A, p53, and p21 levels; higher levels of DNA damage, including &#947;-H2AX; the formation of Senescence-associated Heterochromatin Foci (SAHF); and the acquisition of a Senescence-associated Secretory Phenotype (SASP), a phenomenon characterized by the secretion of a number of pro-inflammatory cytokines and signaling molecules. Here, we describe protocols for both replicative and DNA damage-induced senescence in cultured cells. In addition, we highlight techniques to monitor the senescent phenotype using several senescence-associated markers, including SA-&#946;-gal, &#947;-H2AX and SAHF staining, and to quantify protein and mRNA levels of cell cycle regulators and SASP factors. These methods can be applied to the assessment of senescence in various models and tissues.

Cellular senescence, the irreversible state of cell-cycle arrest, can be induced by various cellular stresses. Here, we describe protocols to induce cellular senescence and methods to assess markers of senescence.

In response to cellular stress or damage, proliferating cells can induce a specific program that initiates a state of long-term cell-cycle arrest, termed ...

An Introduction to Cell Death

Necrosis, apoptosis, and autophagic cell death are all manners in which cells can die, and these mechanisms can be induced by different stimuli, such as cell injury, low nutrient levels, or signaling proteins. Whereas necrosis is considered to be an &#8220;accidental&#8221; or unexpected form of cell death, evidence exists that apoptosis and autophagy are both programmed and &#8220;planned&#8221; by cells.In this introductory video, JoVE highlights key discoveries pertaining to cell death, including recent work done in worms that helped identify genes involved in apoptosis. We then explore questions asked by scientists studying cell death, some of which look at different death pathways and their interactions. Finally, several methods to assess cell death are discussed, and we note how researchers are applying these techniques in their experiments today.

Cell Death: Apoptosis, Autophagy and Necrosis

Necrosis, apoptosis, and autophagic cell death are all manners in which cells can die, and these mechanisms can be induced by different stimuli, such as ...

Strategies for Tracking Anastasis, A Cell Survival Phenomenon that Reverses Apoptosis

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