SAN DIEGO The day after President Barack Obama lifted federal funding restrictions on human embryonic stem cell research, stem cells took center stage at the 34th annual scientific meeting of the Society of Interventional Radiology (SIR; Fairfax, Virginia), being held here this week.
Dara Kraitchman, associate professor at Johns Hopkins School of Medicine (Baltimore), presented preclinical data demonstrating that seaweed encapsulated stem cells delivered with perfluorooctylbromide (PFOB) and a firefly luminescent enzyme allowed for better visibility and targeting in a rabbit model of peripheral arterial disease (PAD).
The stem cells used in the study were bone marrow-derived adult allogeneic cells, but Kraitchman said there's no reason the approach couldn't be used with embryonic stem cells, as well as in other disease applications such as injection of stem cells into the spine for neurological disease or into the heart for cardiovascular disease.
In PAD, about 20% of patients have critical limb ischemia that would benefit from an interventional radiology treatment such as angioplasty or stent insertion, but the disease is so severe and affects so many vessels that revascularization isn't an option. In these patients, stem cell treatments may offer an alternative to amputation, Kraitchman explained. However, between 70 percent and 95 percent of injected stem cells die within 24 hours, and doctors can't tell where the injected cells are and if they are alive.
Kraitchman's team protected the injected stem cells in an alginate capsule and incorporated PFOB, which allows tracking via X-ray, ultrasound or MRI. They also transfected the stem cells with a trifusion multimodality reporter gene containing red fluorescence protein, truncated thymidine kinase, and firefly luciferase to track stem cell survival. The resulting cell viability and tracking could allow more targeted delivery of cell therapy, the researchers concluded.
Drug-eluting stents decrease PAD restenosis
In other PAD news, Dimitris Karnabatidis, assistant professor of interventional radiology at Patras University Hospital (Rion, Greece), presented data supporting the use of drug-eluting stents over bare stents.
Karnabatidis's team studied 103 patients with critical limb ischemia who underwent infrapopliteal revascularization with angioplasty followed by placement of either a sirolimus-eluting stent or a bare stent. After three years, the patients who received the drug-eluting stents had significantly improved blood flow, and 60% of the treated arteries remained open, compared to 10% in the bare stent group.
Additionally, only 15% of patients in the drug-eluting stent group required repeat angioplasties, compared to 35% in the bare stent group. There were no significant differences in mortality or limb salvage, Karnabatidis said.
Embolization helps avoid hysterectomies
Multiple studies at the SIR conference demonstrated that embolization can improve outcomes in women with severe bleeding following a cesarean section.
Cesarean sections, or C-sections, account for one in three deliveries in the U.S., for a total of more than 1.2 million procedures per year. Severe bleeding occurs in one of every 20 patients, on average, and may occasionally require a hysterectomy.
"There are far too many institutions where hysterectomies are done and they shouldn't be," said Robert Vogelzang, professor of radiology at Northwestern University (Chicago). But embolization a common interventional radiology technique in which a catheter is inserted through an artery to deliver clotting agents to the point of vessel rupture may present an alternative.
Michael Stecker, an interventional radiologist at Brigham and Women's Hospital (Boston), presented data from a study in which embolization was used to treat 13 women with bleeding following a C-section. All of the women did well and there were no recurrences of hemorrhage and no hysterectomies, Stecker reported. Vogelzang estimated for comparison that about 10% of such patients might have otherwise required hysterectomies.
In a separate study, Robert Beecroft, interventional radiologist at Mount Sinai Hospital (Toronto), reported data on 14 women with invasive placenta who received embolization to reduce bleeding during delivery. While historic data indicate that 80% of such patients would normally require a hysterectomy, the rate was 25% in his study. Additionally, his patients experienced less blood loss and required fewer blood transfusions, he said.
Stecker noted that while interventional radiology procedures such as embolization are available at most hospitals, many women and even some referring physicians "may not know" about this option.
Yet awareness is growing: Tarun Sabharwal, an interventional radiologist at Guy's and St. Thomas' Hospitals (both London), noted that a rash of C-section related deaths in the UK led to an inquiry and a recommendation that hospitals offering obstetrics retain an interventional radiologist on call.