LDL Receptor Identified as Therapeutic Target for Alzheimer’s

By the time people with Alzheimer’s disease start exhibiting difficulty remembering and thinking, the disease has been developing in their brains for two decades or more, and their brain tissue already has sustained damage. As the disease progresses, the damage accumulates, and their symptoms worsen.

Researchers at Washington University School of Medicine in St. Louis have found that high levels of a normal protein associated with reduced heart disease also protect against Alzheimer’s-like brain damage – at least in mice. The findings, published in Neuron, suggest that raising levels of the protein — known as low-density lipoprotein receptor (LDL receptor) — could potentially be a way to slow or stop cognitive decline.

The discovery of LDL receptor as a potential therapeutic target for dementia is surprising since the protein is much better known for its role in cholesterol metabolism. Statins and PCSK9 inhibitors, two groups of drugs widely prescribed for cardiovascular disease, work in part by increasing levels of LDL receptor in the liver and some other tissues. It is not known whether they affect LDL receptor levels in the brain.

There are not yet clearly effective therapies to preserve cognitive function in people with Alzheimer’s disease,” said senior author David Holtzman, MD, the Andrew B. and Gretchen P. Jones Professor and head of the Department of Neurology. “We found that increasing LDL receptor in the brain strongly decreases neurodegeneration and protects against brain injury in mice. If you could increase LDL receptor in the brain with a small molecule or other approach, it could be a very attractive treatment strategy.”

The key to the importance of LDL receptor lies in a different protein, APOE, that also is linked to both cholesterol metabolism and Alzheimer’s disease. High cholesterol in the blood is associated with increased risk of Alzheimer’s disease, although the exact nature of the association is unclear.

During the long, slow development of Alzheimer’s disease, plaques of a protein called amyloid gradually accumulate in the brain. After many years, another brain protein called tau starts forming tangles that become detectable just before Alzheimer’s symptoms arise. The tangles are thought to be toxic to neurons, and their spread through the brain foretells the death of brain tissue and cognitive decline. First author Yang Shi, PhD, a postdoctoral researcher, and Holtzman previously showed that APOE drives tau-mediated degeneration in the brain by activating microglia, the brain’s cellular janitorial crew. Once activated, microglia can injure neural tissue in their zeal to clean up molecular debris.

Higher levels of LDL receptor limit the damage APOE can do in part by binding to APOE and degrading it. Higher levels of LDL receptor in the brain, therefore, should pull more APOE out of the fluid surrounding brain cells and mitigate damage even further, the researchers reasoned.

How To Substantially Lower LDL Cholesterol Levels

Verve Therapeutics, a next-generation cardiovascular company, today announced the presentation of new preclinical proof-of-concept data in non-human primates that demonstrate the successful use of base editing to turn off a gene in the liver and thereby lower blood levels of either LDL cholesterol or triglyceride-rich lipoproteins, two factors leading to coronary atherosclerosis. Verve is developing one-time gene editing medicines that safely edit the adult human genome and mimic naturally-occurring cardioprotective variants to permanently knock out cholesterol-raising genes in the liver and treat coronary heart disease. The data were presented at the International Society for Stem Cell Research (ISSCR) 2020 Virtual Annual Meeting.

In a keynote address titled, “From reading the genome for risk to rewriting it for health,” Sekar Kathiresan, M.D., co-founder and chief executive officer of Verve Therapeutics, presented the results of recent studies utilizing adenine base editing (ABE) technology, licensed from Beam Therapeutics, in which substantial lowering of plasma LDL cholesterol or triglycerides was successfully demonstrated in non-human primates. Base editing is a gene editing technology developed to enable precise and permanent rewriting of a single DNA letter in the genome.

At Verve, our goal is to develop medicines, given once in life, that precisely edit targeted genes in the liver to permanently reduce LDL cholesterol and triglyceride levels in adults with coronary heart disease, the leading cause of death in the U.S. and worldwide,” said Dr. Kathiresan. “These proof-of-concept data, which to the best of our knowledge represent the first successful application of the base editing technology in non-human primates, show that we can safely edit the primate genome at highly efficacious levels to significantly lower blood LDL cholesterol and triglycerides. The findings are very encouraging and add to our growing body of evidence in using both base editing and CRISPR-Cas9 in vivo against various gene targets. We expect to choose a lead program by year-end 2020 with the goal of initiating human clinical studies within the next three years.”

The studies were conducted in a total of 14 non-human primates and evaluated in vivo liver base editing to turn off proprotein convertase subtilisin/kexin type 9 (PCSK9), a gene whose protein product elevates blood LDL cholesterol or angiopoietin-like protein 3 (ANGPTL3), a gene whose protein product elevates blood triglyceride-rich lipoproteins. Verve’s proprietary drug product consisting of the ABE mRNA and an optimized guide RNA packaged in an engineered lipid nanoparticle was delivered through a single intravenous infusion. Across two separate studies, seven animals were treated with the drug product targeting the PCSK9 gene and seven additional animals with the drug product targeting the ANGPTL3 gene.

Whole liver editing, blood protein and lipid levels were measured at two weeks and compared to baseline. The program targeting PCSK9 showed an average of 67% whole liver PCSK9 editing, which translated into an 89% reduction in plasma PCSK9 protein and resulted in a 59% reduction in blood LDL cholesterol levels. The program targeting ANGPTL3 showed an average of 60% whole liver ANGPTL3 editing, which translated into a 95% reduction in plasma ANGPTL3 protein and resulted in a 64% reduction in blood triglyceride levels and 19% reduction in LDL cholesterol levels.

Source: https://www.vervetx.com/

3D Printed Mini Livers

Using human blood cells, Brazilian researchers have succeeded in obtaining hepatic organoids (“mini-livers”) that perform all of the liver’s typical functions, such as producing vital proteins, storing vitamins, and secreting bile, among many others. The innovation permits the production of hepatic tissue in the laboratory in only 90 days and may in the future become an alternative to organ transplantation.
The study was conducted at the Human Genome and Stem Cell Research Center (HUG-CELL). Hosted by the University of São Paulo (USP), HUG-CELL is one of the Research, Innovation and Dissemination Centers (RIDCs) funded by FAPESP.

This study combined bioengineering techniques, such as cell reprogramming and the cultivation of pluripotent stem cells, with 3D bioprinting. Thanks to this strategy, the tissue produced by the bioprinter maintained hepatic functions for longer than reported by other groups in previous studies.

More stages have yet to be achieved until we obtain a complete organ, but we’re on the right track to highly promising results. In the very near future, instead of waiting for an organ transplant, it may be possible to take cells from the patient and reprogram them to make a new liver in the laboratory. Another important advantage is zero probability of rejection, given that the cells come from the patient,” said Mayana Zatz, director of HUG-CELL and last author of the article published in Biofabrication.

The innovative part of the study resided in how the cells were included in the bioink used to produce tissue in the 3D printer. “Instead of printing individualized cells, we developed a method of grouping them before printing. These ‘clumps’ of cells, or spheroids, are what constitute the tissue and maintain its functionality much longer,” said Ernesto Goulart, a postdoctoral fellow in USP’s Institute of Biosciences and first author of the article. The researchers thereby avoided a problem faced by most human tissue bioprinting techniques, namely, the gradual loss of contact among cells and hence loss of tissue functionality.

Spheroid formation in this study already occurred in the differentiation process, when pluripotent cells were transformed into hepatic tissue cells (hepatocytes, vascular cells, and mesenchymal cells). “We started the differentiation process with the cells already grouped together. They were cultured in agitation, and groups formed spontaneously,” Goulart told Agência FAPESP.

According to the researchers, the complete process from collection of the patient’s blood to functional tissue production takes approximately 90 days and can be divided into three stages: differentiation, printing, and maturation.

In this study, researchers developed mini-livers using blood cells from three volunteers as raw material and compared markers relating to functionality, such as the maintenance of cell contact and protein production and release. “Our spheroids worked much better than those obtained from single-cell dispersion. As expected, during maturation, the markers of hepatic function were not reduced,” Goulart said. Although the study was limited to producing miniature livers, the technique can be used in the future to produce complete organs suitable for transplantation, according to Goulart. “We did it on a small scale, but with investment and interest, it can easily be scaled up,” he said.

The article can be retrieved from iopscience.iop.org/.

Source: http://agencia.fapesp.br/

Nanomachines To Deliver Cancer Drugs to Hard-to-reach Areas

In a recent study in mice, researchers found a way to deliver specific drugs to parts of the body that are exceptionally difficult to access. Their Y-shaped block catiomer (YBC) binds with certain therapeutic materials forming a package 18 nanometers wide. The package is less than one-fifth the size of those produced in previous studies, so can pass through much smaller gaps. This allows YBCs to slip through tight barriers in cancers of the brain or pancreas.

The fight against cancer is fought on many fronts. One promising field is gene therapy, which targets genetic causes of diseases to reduce their effect. The idea is to inject a nucleic acid-based drug into the bloodstream — typically small interfering RNA (siRNA) — which binds to a specific problem-causing gene and deactivates it. However, siRNA is very fragile and needs to be protected within a nanoparticle or it breaks down before reaching its target.

siRNA can switch off specific gene expressions that may cause harm. They are the next generation of biopharmaceuticals that could treat various intractable diseases, including cancer,” explained Associate Professor Kanjiro Miyata of the University of Tokyo, who jointly supervised the study. “However, siRNA is easily eliminated from the body by enzymatic degradation or excretion. Clearly a new delivery method was called for.”

Presently, nanoparticles are about 100 nanometers wide, one-thousandth the thickness of paper. This is small enough to grant them access to the liver through the leaky blood vessel wall. However some cancers are harder to reach. Pancreatic cancer is surrounded by fibrous tissues and cancers in the brain by tightly connected vascular cells. In both cases the gaps available are much smaller than 100 nanometers. Miyata and colleagues created an siRNA carrier small enough to slip through these gaps in the tissues.

We used polymers to fabricate a small and stable nanomachine for the delivery of siRNA drugs to cancer tissues with a tight access barrier,” said Miyata. “The shape and length of component polymers is precisely adjusted to bind to specific siRNAs, so it is configurable.”

Source: https://www.u-tokyo.ac.jp/