How stem cells self-organize in the developing embryo

Embryonic development is a process of profound physical transformation, one that has challenged researchers for centuries. How do genes and molecules control forces and tissue stiffness to orchestrate the emergence of form in the developing embryo? How are the precise mechanics underlying emergence of the complexity of our organs and tissues encoded in our DNA?

One particular aspect of embryonic development: how a group of stem cells -- the endoderm -- moves from the surface of the developing embryo to the center, and in doing so transforms from a flat sheet to a hollow tube. This structure, known as the gut tube, then forms the lining of the entire respiratory and gastrointestinal tracts.

In a study published today in Nature, Nerurkar worked with colleagues at Harvard to shed new light on this critical step in early embryonic development. The team discovered gut tube formation is driven by collective cell movements of the endoderm, a process by which cells travel large distances en masse, without rearranging relative to one another. They also found that this collective movement is triggered by cells that are converting a molecular gradient to a force gradient that drives cells from the surface into the embryo. This discovery is one of the few examples, especially among vertebrates, of how molecular cues are converted into the physical forces that shape our organs.

The study findings could have important implications for how stem cells are used to create functional organs in the lab, and lead to a better understanding of the underlying causes of gastrointestinal birth defects. "Our major goal is to understand how we, as complex organisms, are formed with such precision from a seemingly disorganized ball of cells -- the early embryo," says Nandan Nerurkar, assistant professor of biomedical engineering at Columbia Engineering.

Identifying genes that drive differentiation of stem cells into mature cell types -- the primary focus in Nerurkar's field -- is an important step toward growing replacement organs in the lab. However, Nerurkar suggests this is only part of the picture: "It is equally important to understand how to instruct those cells to organize into functional three-dimensional organs. The developing embryo holds the recipe for this, and many research groups, including ours, are now leveraging the language of physics and mechanics to dissect it."

The team used an innovative approach at the leading edge of the developmental biology field. They combined conventional approaches of developmental biology, including analysis and manipulation of gene expression and live time lapse microscopy of cell movements in the developing chick embryo, with engineering methods, such as mathematical modeling and force and strain measurements.

They focused on one part of endoderm internalization: the hindgut, which gives rise to half of the small intestine, the large intestine, and colon. What was previously known of gut tube formation came from fate-mapping experiments, wherein cells are labeled early in development and then mapped to where the labeled cells end up later in development. This static analysis, which uses static images of the beginning and the end of the process to make an educated guess of what happens in the middle, has led to a view of gut tube formation that is present in most embryology textbooks. "Based on our recent findings, this view is at best incomplete, and at worst completely wrong," says Nerurkar.

Unlike earlier fate-mapping studies, Nerurkar and his colleagues used live imaging in the embryo to directly observe cell movements as the endoderm is internalized to form a tube. They next applied a combination of mechanical engineering and developmental biology approaches to understand just how those cell movements occur, and how the movements are coordinated to form this critical structure in the early embryo.

The team found that the movements are coordinated by the conversion of a molecular gradient into a force gradient from cells that are contracting in proportion to the amount of a molecular cue -- fibroblast growth factor (FGF) -- that they sense. This results in a tug of war among endoderm cells: as one "team" begins to win, the cells actually recruit players from the opposing team by pulling them from low to higher concentrations of FGF.

Irregularities in FGF function can lead to a number of developmental defects. "During human development, errors in gut tube formation would likely lead to miscarriage, something that is a relatively high risk during the first trimester, when this process is occurring," says Nerurkar.

While this study focused on just one part of endoderm internalization, the hindgut, it is still unknown how the foregut, which forms the trachea, lungs, esophagus, stomach, and liver, and the midgut, which forms the pancreas and small intestine, are formed. Nerurkar plans to use his new approach to study these other areas of embryonic development and investigate if and how FGF signaling acts more broadly to control mechanics in the development of other tissues and organs.

"I want to learn more about how mechanics and molecules are integrated to coordinate the formation of these very distinct tissues by disparate mechanisms, yet from the same initial pool of stem cells," he says. "By focusing on the tissue-level mechanics downstream of FGF signaling, we may now be able to understand what this important pathway does to shape other organs and tissues during development, including the heart, brain, and spinal column."

Nerurkar is continuing this research at Columbia Engineering, developing quantitative molecular-mechanical relationships that could be used to design and construct replacement tissues in the lab, using controlled delivery of these diffusible cues -- the instructional signals that are secreted by cells and then float away to neighboring cells -- to instruct the self organization of cells into functional tissues and organs. If he and others in this field can establish the design principles of embryonic tissue formation, it will be possible to repurpose those same principles for regenerative medicine and tissue engineering applications.

Researchers from different part of the world are invited to submit abstract on their unpublished latest research at our upcoming conference Cell Tissue Science 2019 which is focused on the complications and consequences of Stem Cell, Regenerative Medicine, Stem Cell Therapy, Cancer Cell Biology,Technical Advancements in cancer treatment and many more. We as committee members of the conference welcome you to be a part of the conference “ 12th World Congress on Cell & Tissue Science” in Singapore on March 11-12, 2019. 

You can submit your abstract on Session or Track : 09. Stem Cells and its Applications

Novel DNA nanoplatform delivers anticancer agents to multidrug-resistant tumors

A tailored DNA nanoplatform carries chemotherapeutic drugs and RNA interference toward multidrug-resistant tumors

One of the most successful techniques to combat multidrug resistance in cancer cells is the downregulation of those genes responsible for drug resistance. Chinese scientists have now developed a nanoplatform that selectively delivers small hairpin RNA transcription templates and chemotherapeutics into multidrug-resistant tumors. A deadly cocktail of gene-silencing elements and chemotherapeutic drugs effectively and selectively kills cells, they reported in the Journal Angewandte Chemie. The nanoplatform was assembled using established DNA origami techniques.

Multidrug-resistant cancer cells often remove potent drugs from the cell before they can become effective. As several genes for proteins that perform this job are known, scientists attempt to interfere on the gene expression level, which is possible with RNA interference (RNAi) techniques: small RNAi strands combine with messenger RNA and inhibit transcription. However, RNA transcription templates must be delivered and released into the cytoplasm of the cell, and at the same time, a potent drug must be present to kill the cell.

Baoquan Ding at the National Center for Nanoscience and Technology, Beijing, China, and his colleagues have now designed and built a platform that includes every item needed to intrude into tumor cells and release gene-silencing elements and chemotherapeutic drugs. They built the platform using the DNA origami technique, which allows the construction of nanosized DNA objects in multiple, and even very complicated shapes. In this case, the scientists constructed a relatively simple DNA origami structure, which self-assembled into a triangular nanoplatform with various sites to bind multiple functional units.

One of the key features of the platform was that it could include the hydrophobic potent drug doxorubicin (DOX), a cytostatic that is especially useful against malign tumors. Here, DOX did not bind to the nanoplatform by any covalent linkage, but was loaded onto it through intercalation (which is the way DOX works in the cell: it intercalates into DNA, inhibiting transcription). Instead, what was covalently linked to the platform was the multiple gene silencing and cell-targeting site, which consisted of two linear small hairpin RNA transcription templates for RNAi and gene therapy, a cell-specific unit for specific recognition and insertion by the tumor cell, and a disulfide linkage to be cleaved by cellular glutathione.

 

The authors examined their multipurpose nanoplatform with an in vitro assay (on cell cultures) and by administering it into mice containing multidrug-resistant tumors. They found both a high and selective delivery and release rate of DOX and RNA transcription templates, and a high and selective tumor-killing efficiency. In addition, the multifunctional platform itself was not harmful to mice; however, filled with drugs and delivery sites, it was effective and deadly to multidrug-resistant tumors, the authors reported.

This research demonstrates what is possible in cancer therapy. The scientists have designed a nanostructure that not only specifically targets cancer cells, thus reducing severe side effects in chemotherapy, but also carries a drug and everything needed to suppress resistance in the cell when releasing the drug. And the platform itself is modifiable; adaption to other delivery strategies and other therapeutic components is easily possible, according to the authors.

We welcome researchers from different part of the to submit abstract on their latest research at our upcoming conference Cell Tissue Science 2019 which is mainly focuses on the complications the consequences of Stem Cell, Regenerative Medicine, Stem Cell Therapy, Cancer Cell Biology , Technical Advancements in cancer treatment and many more.We welcome you to the our upcoming conference “ 12th World Congress on Cell & Tissue Science” . 

You can submit your abstract on Session or Track : 8.Advancement in Cancer Treatment

Study identifies potential therapeutic strategy for patients with clear cell renal cancer

Researchers have provided new insight on the mechanisms behind the development of clear cell Renal Cell Carcinoma (ccRCC), according to new findings published in eLife.

The study in human cells and mice could have implications for how we understand and treat ccRCC - a major subtype of human kidney cancer.

Kidney cancer is one of the top 10 causes of death from cancer in both men and women. Inactivation of the tumor suppressor gene VHL is the primary cause of ccRCC, which is the most frequently occurring subtype of the disease. Tumour suppressor genes slow down cell division, repair DNA mistakes, and tell cells when to die. Mutations or inactivation of these genes stop them from working properly, which can lead to uncontrolled cell growth and cancer development.

"The disabling of VHL is usually followed by mutations in other tumour suppressor genes that are involved in ccRCC, such as PBRM1 and KDM5C," says co-first author Lili Liao, Postdoctoral Fellow at Jefferson (Philadelphia University + Thomas Jefferson University) and researcher at the Sidney Kimmel Cancer Center - Jefferson Health.. "These secondary tumor suppressors each have their own unique functions and their mutations are associated with different survival risks, yet they all collaborate with VHL loss to promote cancer development. In this study, we wanted to investigate whether they share a common tumor suppressor pathway that might be implicated in future ccRCC treatment."

While probing the gene expression patterns (the processes whereby instructions within DNA are converted into messenger RNA), the research team found that VHL, PBRM1, KDM5C, SETD2 and BAP1 all regulate the interferon stimulated gene factor 3 (ISGF3) - a master regulator that is key to viral infection response.

"We also saw that ISGF3 is strongly tumor-suppressive in a xenograft mouse model of ccRCC, as its loss enables tumors to increase significantly in size," explains co-senior author Haifeng Yang, Assistant Professor at Jefferson. "Conversely, boosting ISGF3 in human ccRCC cancer cells shrinks the tumors they form into tiny nodules."

 

After VHL inactivation, it is known that the hypoxia-inducible factor (HIF)2 alpha becomes constantly active. HIFs respond to decreases in oxygen levels available within cellular environments. "We found that HIF2 alpha triggers the activation of ISGF3, which acts as a brake for tumor growth," Yang continues. "This brake can be disabled by the loss of any of the secondary tumor suppressors, suggesting that this is a key negative feedback loop in ccRCC."

"It is surprising to see that so many major tumor suppressor genes in ccRCC share the same target in ISGF3," adds co-senior author Qin Yan, Associate Professor of Pathology at Yale University. "As many critical cancer genes in kidney cancer converge on ISGF3, it might play significant roles in drug development, patient responses to treatments, and survival."

"There is a significant unmet clinical need to develop new strategies for treating ccRCC. Dr. Yang's breakthrough study brings us one step closer to this goal," concludes Dr. Karen E. Knudsen, Enterprise Director of the Sidney Kimmel Cancer Center at Jefferson Health.

We welcome researchers from different part of the to submit abstract on their latest research at our upcoming conference Cell Tissue Science 2019 which is mainly focuses on the complications the consequences of Stem Cell, Regenerative Medicine, Stem Cell Therapy, Cancer Cell Biology , Technical Advancements in cancer treatment and many more.We welcome you to the our upcoming conference “ 12th World Congress on Cell & Tissue Science” . 

You can submit your abstract on Session or Track : 8.Advancement in Cancer Treatment

Mitochondrial DNA may have strong influence on cellular metabolism and disease susceptibility

About 1.5 billion years ago, tiny visitors came to live inside the cells that later evolved into all plant and animal life including humans.

Those visitors were mitochondria, small organelles whose prominent role is producing 90 percent of the chemical energy cells need to survive. Evolutionarily speaking, humans, animals and plants are thus a combination of two organisms.

Mitochondria have their own DNA, but the 13 genes in human mitochondria along with DNA sequences for tRNAs, rRNAs and some small peptides are massively overshadowed by the 20,000 genes in the human nucleus. Nevertheless, these diminutive mitochondria may have a strong influence on cellular metabolism and susceptibility to metabolic diseases like heart failure or obesity, according to preliminary research by Scott Ballinger, Ph.D., professor of pathology at the University of Alabama at Birmingham.

"For 50 years, researchers have tried to find disease susceptibility using Mendelian genetics," Ballinger said while speaking about studies of the chromosomal genes in the cell nucleus. "But this explains only 10 percent of the reasons for susceptibility to disease."

The possible impact of mitochondrial DNA on disease susceptibility depends on two facts. First, all of a person's mitochondrial DNA comes from the mother, via her egg. This is distinct from the chromosomal genes in the nucleus, where, on average, half come from the mother and half from the father. Second, human mitochondrial DNA has evolved into distinct haplotypes, and each of these types has mitochondrial DNA variations that are inherited together. There are approximately 25 to 35 basic mitochondrial DNA haplogroups, and one of them is found in African populations and has many subtypes due the deep genetic diversity of that continent.

To investigate the impact of mitochondrial DNA, Ballinger and colleagues looked for changes in metabolism and nuclear gene expression when they exchanged mitochondrial backgrounds of strains of mice -- specifically those having different mitochondrial DNA sequences, and also having notable differences in susceptibility to diseases associated with metabolism.

After switching the mitochondrial DNA backgrounds, Ballinger and colleagues measured changes in body composition, metabolism and nuclear gene expression in fat tissue when mice switched from a low-fat chow diet to a high-fat diet.  

In the first report of its kind, they found that switching the mitochondrial genetic background had a significant impact on adiposity, whole body metabolism and nuclear gene expression in mice.

For example, gene expression in both visceral and subcutaneous fat was markedly changed between mice sharing the same nuclear genome but having different mitochondrial DNA backgrounds, when fed chow versus a high-fat diet. These changes ranged from 10- to 50-fold differences in the number of genes affected, and mitochondrial DNA background influenced whether the number of affected genes were increased or decreased. These studies also found that metabolic efficiency and percentage of body fat in the mice were impacted as well.

"These results are clearly consistent with the notion that different nuclear-mitochondrial genetic combinations influence metabolism, adiposity and gene expression in different ways," Ballinger said. "The overall implication of this work is that it can provide a new framework for understanding complex genetic disease susceptibility that both an individual's nuclear and mitochondrial genomes, in combination, can affect disease development. We are now trying to understand how the different combinations of nuclear and mitochondrial encoded genes interact to alter metabolism, and how this influences individual disease susceptibility."

We welcome researchers from different part of the to submit abstract on their latest research at our upcoming conference Cell Tissue Science 2019 which is mainly focuses on the complications the consequences of Stem Cell, Regenerative Medicine, Stem Cell Therapy, Cancer Cell Biology , Technical Advancements in cancer treatment and many more.We welcome you to the our upcoming conference “ 12th World Congress on Cell & Tissue Science” . 

You can submit your abstract on Session or Track :12.Epigenetics and Epigenome