Month: September 2022

Posted on

A how-to guide for improving the potency of stem cells

You may remember Dolly, the sheep that became famous in the ‘90s as the first mammal to be cloned from an adult cell. Dolly was created through somatic cell nuclear transfer (SCNT), in which the nucleus from a somatic donor cell, i.e., a cell from the body other than a sperm or egg cell, is transferred into an enucleated egg cell. In this case, the donor cell was derived from a sheep’s mammary glands, a medical term for the breasts. The scientists named the cloned sheep Dolly since they could not think of a more impressive pair of mammary glands than Dolly Parton’s, or so the story goes. Aside from generating viable embryos in the laboratory, SCNT can be used to generate human stem cell lines for research and therapeutic purposes. However, this procedure is technically challenging and requires egg cells, which raises ethical concerns.

Artist’s impression of Dolly Parton, the famous American country singer, holding the cloned sheep named after her.
© 2022, Maaike Schilperoort

In 2007, a lab in Kyoto, Japan, found another way of generating human stem cells. The group infected human skin cells with a virus that carried a set of genes known to be important for embryonic stem cells. This resulted in so-called “induced pluripotent stem cells”, or iPSCs, that are functionally identical to embryonic stem cells. Although therapeutically promising, these iPSCs do not have the same potency as the cells generated through SCNT. SCNT generates cells that are totipotent at an early stage, meaning that they can form viable embryos as well as extraembryonic tissues such as the placenta and yolk sack. In contrast, iPSCs are pluripotent and are not able to give rise to extraembryonic tissues. They also have an inferior differentiation potential and lower proliferation rate as compared to totipotent cells.

Efforts have been made by scientists to make embryonic stem cells and iPSCs more totipotent by treating them with small molecule inhibitors, resulting in so-called expanded potential stem cells (EPSCs) that that can give rise to the embryo as well as placenta tissues and thus are more versatile as compared to their pluripotent counterparts. However, the developmental potential of EPSCs is still inferior to true totipotent cells or cells generated through SCNT. To gain insight into how the developmental potential of EPSCs can be improved, Columbia postdoc Vikas Malik and colleagues performed a deep analysis of pluripotent embryonic stem cells vs. the more totipotent EPSCs. They examined gene expression, DNA accessibility, and protein expression, and found some unique genes and proteins that are upregulated in EPSCs as compared to embryonic stem cells, such as Zscan4c, Rara, Zfp281, and UTF1. This pioneering work, published in Life Science Alliance, shows us which genes and proteins to target to generate authentic totipotent stem cells in a petri dish.

The work of Dr. Malik and colleagues has improved our understanding of how to generate totipotent cells outside of the human body without having to deal with the technical and ethical challenges of SCNT. These cells can further improve stem cell therapy through a greater ability to regenerate and repair tissues affected by damage or disease. In addition, totipotent cells are more suitable to study early development and problems of the reproductive system, and are optimal for gene therapy to correct genetic defects that cause disease. As the word indicates, totipotent cells really hold all the power, and could greatly advance scientific knowledge and regenerative medicine.

More information on the pursuit of totipotency can be found in this comprehensive review article by Dr. Malik and his PI Jianlong Wang published in Trends in Genetics.

Reviewed by: Trang Nguyen and Vikas Malik

Posted on

Lactic acid – a new energy fuel source in brain tumor

What does lactic acid do to the body?

Lactic acid is produced when the body breaks down carbohydrates in low oxygen levels to generate energy. It is mainly found in muscle cells and red blood cells. An example of lactic production is when we perform intense exercise. 

Glucose, glutamine, fatty acids, and amino acids are well-known energy sources for cell growth and division. In the past, lactic acid has been known as a by-product of glycolysis, a process in which glucose is broken down through several enzyme reactions without the involvement of oxygen. However, recent studies showed that lactic acid is a key player in cancer cells to regulate tumor cell growth and division, blood vessel formation, and invasion. The tumor cells prefer to use glycolysis to produce energy and lactic acid despite the abundance of oxygen levels. Lactic acid is an alternative fuel source for glucose-deprived tumors to avoid cell death.

Lactic acid is transported through the membrane via the monocarboxylate transporter 1 (MCT1). A research group at Columbia University led by Dr. Markus Siegelin in the department of Pathology and Cell Biology showed a substantial presence of lactic acid in the citric acid cycle (TCA cycle), a series of chemical reactions to generate energy, in the glioblastoma cells cultured in the nutrient deprivation condition (low glucose and glutamine concentration). When the glucose and/or glutamine concentrations increased, less lactic acid was involved in the TCA-cycle metabolites. The uptaken lactic acid in the TCA-cycle was traced by using a method called C13 carbon tracing and was analyzed by liquid chromatography-mass spectrometry to identify the structure of different molecules. The researchers concluded that lactic acid is used as a fuel source to generate the energy in the brain tumor cells. Furthermore, lactic acid is converted to Actetyl-CoA and contributed to the gene modification in glioblastoma cells (Figure 1). These novel findings were published in a prestigious journal,  Molecular Cell. 

Figure 1: Role of lactic acid in the epigenetic modification of glioblastoma cells. Lactic acid is transported to the membrane via the monocarboxylate transporter 1 (MCT1) and contributed to the TCA cycle as a fuel source to generate the energy. Lactic acid is converted to Actetyl-CoA and contributed to the gene modification in glioblastoma cells. Suppressing the TCA cycle by using the targeted drug, namely CPI-613 (devimistat) leads to the abrogation of lactic acid in the energy production. The figure was generated by Biorender.

From these findings, the authors proposed to use CPI-613 (devimistat) drug, which targets TCA-cycle metabolites (Figure 1), to  treat glioblastoma cells. Indeed, CPI-613 showed a suppression of cellular viability in vitro of glioblastoma cells and an extension of the animal survival curve in the mouse model. The authors suggested that the combination of CPI-613 with other standard care treatment in glioblastoma such as temozolomide and radiation could be a potential clinical therapy for patients with glioblastoma.

Read more about this exciting finding here:

https://www.sciencedirect.com/science/article/pii/S1097276522006475 

Reviewed by: Pei-Yin Shih, Sam Rossano, Emily Hokett

Posted on

Alcohol Use Disorder – are we making the right diagnosis?

Do you and your friends enjoy the occasional cocktail or two over the weekend? Maybe we know someone who enjoys the more-than-occasional cocktail. But, at what point do our drinking habits significantly affect our health? Recent studies suggest that 6% of adults in the United States report heavy or high-risk consumption of alcohol, which is defined as an average of more than 7 drinks/week for women and more than 14 drinks/week for men. This high risk-consumption may lead to Alcohol Use Disorder (AUD) if it is repeated for one year or more. AUD is associated with a number of medical and psychiatric problems, and can even increase risk of death in patients who have cancer and cardiovascular disease.

To diagnose AUD, medical and mental health professionals use the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), which explores 11 criteria, including alcohol-related cravings, strains on relationships caused by alcohol use, feeling unable to cut back or stop drinking, dangerous or risky behavior when under the influence of alcohol, etc. Unlike previous versions of the DSM, these AUD diagnoses are divided based on severity, where people who experience 0 or 1 of the diagnostic criteria do not have AUD (no-AUD), 2-3 criteria have mild AUD, 4-5 criteria have moderate AUD, and 6+ have severe AUD. However, it’s not well understood whether other factors like the extent of alcohol use, the degree of cravings or impairments, etc. can help classify mild, moderate, and severe AUD diagnoses. 

Last year, Dr. Zachary L. Mannes, a postdoc in the Department of Epidemiology at Columbia University Mailman School of Public Health and New York State Psychiatric Institute, and colleagues published a study in which they aimed to explore any potential relationships between the severity of AUD (no-AUD, mild, moderate, or severe, based on the DSM-5) and self-reported measures of other factors or “external validators”, such as levels of alcohol craving, functional impairment, and psychiatric conditions. To do this, they collected AUD diagnosis as well as measures of external validators in 588 participants. These validators included alcohol specific validators (i.e. Craving, Problematic Use, Harmful Use, Binge Drinking Frequency), psychiatric validators (i.e. Major Depressive Disorder/MDD and posttraumatic stress disorder/PTSD), and functioning validators (social impairments; physical and mental impairments).

Dr. Mannes and colleagues reported that in this cohort of subjects, participants with alcohol use validators had a significantly greater likelihood of a diagnosis with mild, moderate, and severe AUD than a no-AUD diagnosis. Psychiatric validators like MDD and PTSD had a significantly greater likelihood of a severe AUD diagnosis than no-AUD; this relationship was not seen for either mild or moderate AUD. Participants who had social, physical, and mental impairments had a greater likelihood of having severe AUD than no-AUD, but this was not seen for participants with mild or moderate AUD. When looking within participants with an AUD diagnosis (i.e. excluding a no-AUD diagnosis), participants with many alcohol-specific, psychiatric, and functional validators were more likely to have a severe AUD than either mild or moderate AUD.

Overall, the results of this study support the structure of the DSM-5 diagnosis for AUD, as those diagnoses with mild and moderate AUD had significant associations with alcohol use validators, while those with severe AUD had significant associations with alcohol use, psychiatric and functional validators. In other words, people with severe AUD had a higher likelihood of symptoms that affected other aspects of their lives including impairments in social functioning and presence of psychiatric conditions including MDD and BPD. This study emphasizes the importance of looking at levels of severity in AUD as the current DSM-5 does, as opposed to a binary yes/no diagnosis as older versions of the DSM had incorporated. This study also helps further the understanding of optimal ways to diagnose AUD and may help better understand potential treatment implications for various AUD severity. The study published by Dr. Mannes and colleagues supports and progresses the field of AUD research in order to better understand and characterize the symptoms, comorbidities, and diagnosis of AUD, so that medical professionals can better assist those who are struggling with the disorder. 

Edited by: Trang Nguyen, Maaike Schilperoort

Follow this blog

Get every new post delivered right to your inbox.