Friday, September 28, 2018

Scientists grow human esophagus in lab

This confocal microscopic image shows a two-month-old human esophageal organoid bioengineered by scientists from pluripotent stem cells. About 700 micrometers (0.027 inches) in size, the organoid is stained to visualize key structural proteins expressed in mature esophagus, such as involucrin (green) and cornulin (blue). Researchers report in the journal Cell Stem Cell the organoids enhance the study of esophageal disorders, personalized medical and the development of regenerative tissue therapies for people.
Credit: Cincinnati Children's

Scientists working to bioengineer the entire human gastrointestinal system in a laboratory now report using pluripotent stem cells to grow human esophageal organoids.
Published in the journal Cell Stem Cell the study is the latest advancement from researchers at the Cincinnati Children's Center for Stem Cell and Organoid Medicine (CuSTOM). The center is developing new ways to study birth defects and diseases that affect millions of people with gastrointestinal disorders, such as gastric reflux, cancer, etc. The work is leading to new personalized diagnostic methods and focused in part on developing regenerative tissue therapies to treat or cure GI disorders.
The newly published research is the first time scientists have been able to grow human esophageal tissue entirely from pluripotent stem cells (PSCs), which can form any tissue type in the body, according to the authors. Cincinnati Children's scientists and their multi-institutional collaborators already have used PSCs to bioengineer human intestine, stomach, colon and liver.
"Disorders of the esophagus and trachea are prevalent enough in people that organoid models of human esophagus could be greatly beneficial," said Jim Wells, PhD, chief scientific officer at CuSTOM and study lead investigator. "In addition to being a new model to study birth defects like esophageal atresia, the organoids can be used to study diseases like eosinophilic esophagitis and Barrett's metaplasia, or to bioengineer genetically matched esophageal tissue for individual patients."
The study involves collaboration from researchers in the divisions of Developmental Biology, Oncology, Allergy and Immunology, and Endocrinology at Cincinnati Children's and the Gladstone Institutes in San Francisco. This includes study first author Stephen Trisno, a graduate student and member of the Wells laboratory.
The Food Channel
The esophagus is a muscular tube that actively passes food from the mouth to the stomach. The organ can be affected by congenital diseases, such as esophageal atresia -- a narrowing or malformation of the esophagus caused by genetic mutations.
Additionally, there are several diseases that can afflict people later in life. Some include esophageal cancer, gastroesophageal reflux disease (GERD), or a rare ailment called achalasia -- a disease affecting the muscles of the lower esophagus that prevents contraction of the organ and the passage of food.
All of the conditions need better treatments, researchers note. This requires a more precise understanding of the genetic and biochemical mechanisms behind their cause -- a need filled by the ability to generate and study robust, functional, genetically matched models of human esophageal tissue that can be grown from a person's own cells.
Tracing Nature's Path
The scientists based their new method for using human PSCs to general esophageal organoids on precisely timed, step-by-step manipulations of genetic and biochemical signals that pattern and form embryonic endoderm and foregut tissues. They focused in part on the gene Sox2 and its associated protein -- which are already known to trigger esophageal conditions when their function is disrupted. -- The scientists used mice, frogs and human tissue cultures to identify other genes and molecular pathways regulated by Sox2 during esophagus formation.
The scientists report that during critical stages of embryonic development, the Sox2 gene blocks the programming and action of genetic pathways that direct cells to become respiratory instead of esophageal. In particular, the Sox2 protein inhibits the signaling of a molecule called Wnt and promotes the formation and survival of esophageal tissues.
In another test to help confirm the importance of Sox2 expression on esophageal formation, researchers studied the complete loss of Sox2 during the development process in mice. The absence of Sox2 resulted in esophageal agenesis -- a condition in which the esophagus terminates in a pouch and does not connect to the stomach.
After successfully generating fully formed human esophageal organoids -- which grew to a length of about 300-800 micrometers in about two months -- the bioengineered tissues were compared biochemically to esophageal tissues from patient biopsies. Those tests showed the bioengineered and biopsies tissues were strikingly similar in composition, according to the authors.
The research team is continuing its studies into the bioengineering process for esophageal organoids and identifying future projects to advance the technology's eventual therapeutic potential, according to Wells. This includes using the organoids to examine the progression of specific diseases and congenital defects affecting the esophagus.

Journal Reference:
  1. Stephen L. Trisno, Katherine E.D. Philo, Kyle W. McCracken, Emily M. Catá, Sonya Ruiz-Torres, Scott A. Rankin, Lu Han, Talia Nasr, Praneet Chaturvedi, Marc E. Rothenberg, Mohammad A. Mandegar, Susanne I. Wells, Aaron M. Zorn, James M. Wells. Esophageal Organoids from Human Pluripotent Stem Cells Delineate Sox2 Functions during Esophageal Specification. Cell Stem Cell, 2018; DOI: 10.1016/j.stem.2018.08.008 
Courtesy: ScienceDaily

Wednesday, September 26, 2018

Proof-of-concept HIV immunotherapy study passes Phase 1 safety trial

Preliminary results from a phase I clinical trial have demonstrated the safety and tolerability of a cell therapy involving the ex vivo expansion of T cells and their subsequent infusion into HIV-infected individuals previously treated with antiretroviral therapy (ART). The study appears September 21st in the journal Molecular Therapy.
"This study is focused on finding a way to re-educate the body's immune system to better fight HIV infection," says co-senior study author David Margolis of the University of North Carolina (UNC) at Chapel Hill. "We found that this approach of re-educating the immune cells and reinfusing them was safe, which was the primary goal of the study. The data from this trial will continue to help us design improved immunotherapies against HIV."
A game changer for patients living with HIV, ART has turned what was once a death sentence into a chronically managed disease. But it is not a cure, and the virus continues to persist within a latent reservoir that remains hidden from the immune system. Approaches using pharmacological HIV-latency-reversal agents to induce latent virus to express viral protein could make this reservoir vulnerable to T cells. However, the existing HIV-specific immune response in ART-treated individuals is insufficient to clear persistent infection, even in the presence of latency-reversal agents that induce HIV expression.
One safe avenue for harnessing T cell responses to fight HIV is adoptive cellular therapy. This procedure involves collecting T cells from a patient, growing them in the laboratory to increase their numbers, and then giving them back to the patient to help the immune system fight disease. Earlier adoptive-T-cell-therapy approaches for HIV had limited efficacy as a result of multiple factors. Since these earlier attempts, the adoptive-T-cell-therapy field has made significant advances, largely in the oncology field, that could help to overcome some of the pitfalls encountered with earlier T-cell-therapy approaches for HIV. T cells generated by these sophisticated methods of expansion have been safe and well tolerated, as well as highly effective.
"Before we can combine this approach with treatments meant to bring HIV out from hiding so the improved immune response can clear it from the body, we need to first establish that this immunotherapy approach is safe on its own," says co-senior study author Catherine Bollard of the Children's National Health System. "We have long-standing experience treating patients with virus-specific T cells targeting latent viruses such as Epstein-Barr virus and cytomegalovirus. Therefore, we were extremely excited to work with the UNC team to adapt this virus-specific T-cell-therapy approach to the HIV setting."
In the small proof-of-concept study, Margolis, Bollard, and their collaborators produced ex vivo expanded HIV-specific T cells (HXTCs); their long-term goal was to use HXTCs as part of a strategy to clear persistent HIV infection. The researchers administered two infusions of HXTCs over a 2 week period to six HIV-infected participants whose viral load had been reduced to an undetectable level by ART.
This treatment was well tolerated and had few adverse events. Moreover, two patients exhibited a detectable increase in T-cell-mediated antiviral activity after the two infusions, although the clinical significance of this mild-to-modest impact is unknown. When evaluating participants in aggregate, the research team found no overall enhancement of the magnitude of the HIV-specific immune response. This could be due to the low dose of the two infusions and the lack of strategies to promote the expansion of the T cells once they are in the body.
There was also no decrease in the size of the latent reservoir, most likely because of the absence of therapies such as latency-reversal agents, which are designed to perturb the reservoir and induce recognizable expression of HIV proteins that trigger immune responses. In the future, a critical question will be whether HXTC therapy in combination with latency-reversal agents can deplete the HIV reservoir to an extent that is measurable by current gold-standard assays of HIV latency. A study of HXTC in combination with the latency-reversal agent vorinostat is currently undergoing evaluation in an ongoing clinical trial.
"This is a promising advancement for the field," says first author Julia Sung of UNC, although she also cautions people against over-interpreting the results. "The study did not cure HIV and should not be interpreted as doing so, but we also are very encouraged by the safety data, so it should not be considered discouraging either. This paves the way for the next step, which is to combine this immunotherapy approach with latency-reversal therapy in order to wake up the HIV out of its latent state, where it is invisible to the immune system, then clear it out with the immunotherapy."

Journal Reference:
  1. Julia A. Sung, Shabnum Patel, Matthew L. Clohosey, Lauren Roesch, Tamara Tripic, JoAnn D. Kuruc, Nancie Archin, Patrick J. Hanley, C. Russell Cruz, Nilu Goonetilleke, Joseph J. Eron, Clio M. Rooney, Cynthia L. Gay, Catherine M. Bollard, David M. Margolis. HIV-Specific, Ex Vivo Expanded T Cell Therapy: Feasibility, Safety, and Efficacy in ART-Suppressed HIV-Infected Individuals. Molecular Therapy, 2018; DOI: 10.1016/j.ymthe.2018.08.015 

Courtesy: ScienceDaily