Stories about: Vascular Biology Program

The softer the nanoparticle, the better the drug delivery to tumors

Nanolipogels, pictured here, are a promising drug delivery system
Nanolipogels of different stiffness, as seen through a transmission electron microscope. Credit: Moses lab/Boston Children’s Hospital.

For the first time, scientists have shown that the elasticity of nanoparticles can affect how cells take them up in ways that can significantly improve drug delivery to tumors.

A team of Boston Children’s Hospital researchers led by Marsha A. Moses, PhD, who directs the Vascular Biology Program, created a novel nanolipogel-based drug delivery system that allowed the team to investigate the exclusive role of nanoparticle elasticity on the mechanisms of cell entry.

Their findings — that softer nanolipogels more efficiently enter cells using a different internalization pathway than their stiffer counterparts — were recently published in Nature Communications.

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News Note: Modeling sepsis better to find a cure faster

In this SEM image, E. coli (green) bacteria, a common instigator of sepsis, is captured by bioengineered magnetic beads.
New assessment criteria for monitoring sepsis in pig models could help clinical researchers more accurately evaluate potential sepsis treatments in preclinical experiments. In this SEM image, E. coli (green) bacteria, a common instigator of sepsis, is captured by bioengineered magnetic beads. Credit: Wyss Institute at Harvard University

Sepsis, or blood poisoning, occurs when the body’s response to infection damages its own tissues, leading to organ failure. It is the most common cause of death in people who have been hospitalized, yet no new therapies have been developed in the last 30 years. Many treatments that have prevented death in animal experiments have failed in clinical trials, indicating that a more clinically-relevant sepsis model is needed for therapeutic development.

To bridge this gap, a team of scientists from the Wyss Institute at Harvard University and Boston Children’s Hospital think a better experimental model of sepsis in pigs could help weed out the therapies most likely to succeed in humans. Their method, a scoring criteria to evaluate sepsis in pigs that closely mirrors standard human clinical assessment, is reported in Advances in Critical Care Medicine.

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A “CRISPR” view of Sturge-Weber syndrome is coming into focus

Colorized laboratory image showing tissue model containing the Sturge-Weber syndrome genetic mutation
Living blood vessels inside a microfluidic chip containing the genetic mutation (green) responsible for Sturge-Weber syndrome (Credit: Bischoff lab)

Three-dimensional modeling and CRISPR-Cas9 gene editing technology are giving scientists a new view into Sturge-Weber syndrome, a rare congenital disorder that causes small blood vessels, called capillaries, to be malformed. These capillary malformations can cause port wine birthmarks on the face and neck, and in some cases, abnormal vasculature in the brain that can spark seizures.

Last year, a Boston Children’s Hospital research team — led by Joyce Bischoff, PhD, of the Vascular Biology Programdiscovered that the genetic mutation responsible for Sturge-Weber syndrome dwells in endothelial cells lining the affected capillaries in the brain. The team had previously found the same mutation present in the endothelial cells of skin capillaries of patients’ port wine birthmarks.

Together, their studies suggest that mutated endothelial cells could be causing surrounding cells to behave abnormally.

To explore this emerging hypothesis, Bischoff’s team is seeking lifelike ways of mimicking these hallmark capillary malformations in the laboratory.

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Organs-on-chips reveal breathing’s critical role in lung cancer development

Image of lung cancer cells grown alongside human lung small airway cells inside an organ-on-a-chip
Inside view of a lung cancer chip: Lung adenocarcinoma cells are grown as a tumor cell colony (blue) next to normal human lung small airway cells (purple). Credit: Wyss Institute at Harvard University

One of the biggest challenges facing cancer researchers — and lots of other medical researchers, in fact — is that experimental models cannot perfectly replicate human diseases in the laboratory.

That’s why human Organs-on-Chips, small devices that mimic human organ environments in an affordable and lifelike manner, have quickly been taken up into use by scientists in academic and industry labs and are being tested by the U.S. Food and Drug Administration.

Now, the chips have helped discover an important link between breathing mechanics and lung cancer behavior.

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An FDA-approved drug could prevent valve damage after heart attack

Losartan is shown to prevent thickening of the mitral valve after heart attack, in comparison with an untreated heart
An untreated mitral valve (left) shows much more thickening and fibrosis after heart attack than a mitral valve treated with losartan (right).

On average, one in four people who have a heart attack sustain long-lasting damage to the mitral valve, which has the important job of making sure blood pumps through the heart’s ventricles in the right direction. If the valve is damaged, the heart’s pumping efficiency is reduced and blood can flow backward, which can lead to heart failure and death.

Now, a team of collaborators from Boston Children’s Hospital, Massachusetts General Hospital and Brigham and Women’s Hospital has shown, for the first time, that it’s possible to treat and even prevent mitral valve damage after heart attack with an FDA-approved, anti-hypertension drug called losartan. Their findings are published in the Journal of the American College of Cardiology.

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Mitigating blood vessel damage from heart attack, stroke

Mouse hearts showing the impact of a therapeutic protein fusion on blood vessel health
Imaging of mouse hearts reveals widespread tissue damage (light-colored areas) after heart attack. At far right, however, mice that were treated with an engineered, optimized ApoM protein containing S1P have better tissue recovery than untreated mice (left) and mice that were given an inactive “dud” ApoM treatment (center). Credit: Hla lab/Boston Children’s Hospital

The average human has 60,000 miles of blood vessels coursing through their body. There are a number of mechanisms the body uses to keep that vast vascular network healthy, including a tiny fat molecule, a lipid called S1P, that plays a particularly important role.

S1P receptors dot the surface of the endothelium, a layer of cells that line the inside of all the body’s blood cells. Together, these so-called endothelial cells form a barrier between the body’s circulating blood and surrounding tissue. When S1P molecules activate their receptors, it suppresses endothelial inflammation and generally helps regulate cardiovascular health.

Now, researchers led by Timothy Hla, PhD, from the Boston Children’s Hospital Vascular Biology Program, report a novel therapeutic fusion that could trigger increased S1P receptor activity and recover blood vessel health following the onset of hypertension, atherosclerosis, stroke, heart attack and other cardiovascular diseases.

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A new inlet to treating neurological disease

Image of brains showing red tracer dye, indicating passage of molecules through the blood-brain barrier
These brain images tell a story about the blood-brain barrier: At left, the brain before injection of red tracer dye. At center, an injection of tracer dye shows only a small amount of molecules can infiltrate the blood brain barrier. At right, a new approach for crossing the blood-brain barrier increases the tracer’s penetration into brain tissue.

The blood-brain barrier was designed by nature to protect the brain and central nervous system (CNS) from toxins and other would-be invaders in the body’s circulating blood. Made up of tightly-packed cells, the barrier allows nutrients to pass into the CNS and waste products from the brain to be flushed out, while blocking entry of harmful substances.

A dysfunctional blood-brain barrier can contribute to CNS diseases including Alzheimer’s and multiple sclerosis (MS). But, ironically, the same blood-brain barrier can keep out drugs intended to treat CNS disease. Scientists have long been seeking ways to overcome this obstacle.

Now, Timothy Hla, PhD, and members of his laboratory in the Boston Children’s Hospital Vascular Biology Program have found a way to selectively control openings in the blood brain barrier to allow passage of small drug molecules.

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Flipping the switch on tumor growth

Pictures of angiogenic tumor cells
Time-lapse imaging can reveal tell-tale changes in cellular behaviors associated with tumor growth.

Without a blood supply, a tumor can remain dormant and harmless. But new blood vessel growth from an existing vessel, a process called angiogenesis, is a hallmark of both benign and malignant tumors. During angiogenesis, blood vessels invade tumors and activate them, fueling their growth.

Now, Marsha A. Moses, PhD, who directs the Vascular Biology Program at Boston Children’s Hospital, and members of her laboratory have revealed that a specialized imaging system can detect changes in cell behaviors. These changes predict when tumors are leaving a state of dormancy and becoming more likely to grow.

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Angiogenesis: The slow growth of a science

angiogenesis

Sometimes a scientific idea takes a long time to make its way forward. Angiogenesis is a case in point. As surgeon-in-chief at Boston Children’s Hospital, Judah Folkman, MD, noted that malignant tumors often had a bloody appearance. In The New England Journal of Medicine in 1971, he hypothesized that tumors cannot grow beyond a certain size without a dedicated blood supply, and that “successful” tumors secrete an unknown substance that encourages blood vessel growth, or angiogenesis.

If angiogenesis could be blocked, he argued, tumors might not grow or spread. Rather than waging a toxic chemical and radiation battle with a tumor, one could starve it into submission by shutting down its blood supply.

The idea was roundly criticized.

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Patients’ brain tissue unlocks the cellular hideout of Sturge-Weber’s gene mutation

A diagram of the skull and brain showing the leptomeninges, which is affected by Sturge-Weber syndrome
Sturge-Weber syndrome causes capillary malformations in the brain. They occur in the brain’s leptomeninges, which comprise the arachnoid mater and pia mater.

A person born with a port-wine birthmark on his or her face and eyelid(s) has an 8 to 15 percent chance of being diagnosed with Sturge-Weber syndrome. The rare disorder causes malformations in certain regions of the body’s capillaries (small blood vessels). Port-wine birthmarks appear on areas of the face affected by these capillary malformations.

Aside from the visible symptoms of Sturge-Weber, there are also some more subtle and worrisome ones. Sturge-Weber syndrome can be detected by magnetic resonance imaging (MRI). Such images can reveal a telltale series of malformed capillaries in regions of the brain. Brain capillary malformations can have potentially devastating neurological consequences, including epileptic seizures.

Frustratingly, since doctors first described Sturge-Weber syndrome over 100 years ago, the relationship between brain capillary malformations and seizures has remained somewhat unexplained. In 2013, a Johns Hopkins University team found a GNAQ R183Q gene mutation in about 90 percent of sampled Sturge-Weber patients. However, the mutation’s effect on particular cells and its relationship to seizures still remained unknown.

But recently, some new light has been shed on the mystery. At Boston Children’s Hospital, Sturge-Weber patients donated their brain tissue to research after it was removed during a drastic surgery to treat severe epilepsy. An analysis of their tissue, funded by Boston Children’s Translational Neuroscience Center (TNC), has revealed the cellular location of the Sturge-Weber mutation. The discovery brings new hope of finding ways to improve the lives of those with the disorder.

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