Stories about: blood vessels

Helping tissue grafts build a blood supply: Less is more

blood vessels in vivo

For a tissue graft to survive in the body — whether it’s a surgical graft or bioengineered tissue — it needs to be nourished by blood vessels, and these vessels must connect with the recipient’s circulation. While scientists know how to generate blood vessels for engineered tissue, efforts to get them to connect with the recipient’s vessels have mostly failed.

“Surgeons will tell you that when putting tissue in a new location in the body, the small blood vessels don’t connect at the new site,” says Juan Melero-Martin, PhD, a researcher in Cardiac Surgery in Boston Children’s Hospital. “If you want to engineer a tissue replacement, you’d better understand how the vessels get connected, because if the vessels go, the graft goes.”

Melero-Martin and colleagues have uncovered several strategies to help these connections form, as they describe online today in Nature Biomedical Engineering. The strategies could help improve the success of such procedures as heart patching, bone grafting, fat transplants and islet transplantation.

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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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Getting the most of mesenchymal stem cell transplants

Fat cells from mesenchymal stem cell transplant
The fat cells shown in yellow are descended from transplanted human mesenchymal stem cells (green) inside of a mouse after co-transplantation. The red stain shows native mouse fat cells.(Courtesy Juan Melero-Martin)
Joseph Caputo originally wrote this post for the Harvard Stem Cell Institute (HSCI). Vector editor Nancy Fliesler contributed.

Stem cell scientists had what first appeared to be an easy win for regenerative medicine when they discovered mesenchymal stem cells several decades ago. These cells, found in the bone marrow, can give rise to bone, fat and muscle tissue, and have been used in hundreds of clinical trials for tissue repair.

Uses range from tissue protection in heart attack and stroke to immune modification in multiple sclerosis and diabetes. Unfortunately, the results of these trials have been underwhelming. One challenge is that these stem cells don’t stick around in the body long enough to benefit the patient.

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Looking within cells to control inflammation

blood_vessel_shutterstock_142125664Chronic, unresolved inflammation can be quite harmful, right down to the cellular level. At the macro level, it has links to cancer, diabetes, heart disease and other degenerative conditions.

This is why the body keeps a tight rein on the inflammatory response and maintains a host of factors that resolve inflammation once the need for it (for instance, to clear an infection or heal an injury) has passed.

We know pretty well which factors work between cells to turn on and turn off inflammation. That knowledge has led to the development of drugs like ibuprofen, acetaminophen and naproxen, all of which temper pro-inflammatory factors.

However, when you look at the signals and signaling pathways within cells, things get more complex, especially when it comes to factors that turn off inflammation. We haven’t completely grasped the full complement of proteins that transmit these internal anti-inflammatory signals. If we did, we could potentially add new drugs to our pharmacopeia to regulate or resolve inflammation or maintain cells in a non-inflamed state, and perhaps help prevent rejection of transplanted organs and tissues.

David Briscoe, MD, and his team at Boston Children’s Hospital’s Transplant Research Program, has taken the field one step closer to grasping those internal pathways by studying a cellular protein called DEPTOR.

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