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Joyce Bischoff, PhD

An accompanying editorial calls the work "a significant step forward in the vascularization process necessary for tissue engineering and regenerative medicine."

The researchers combined two different types of progenitor cells in a culture dish of nutrients and growth factors, then washed off the nutrients and implanted the cells into mice with weakened immune systems. Once implanted, the progenitor cell mixture grew and differentiated into a small ball of healthy blood vessels.

The researchers used different combinations of the two types of progenitor cells. They found that a mixture of adult blood- and adult bone marrow-derived progenitor cells or a combination of umbilical cord blood-derived and adult bone marrow-derived cells resulted in the greatest density of new blood vessel formation.

The ability to rapidly grow two-layered blood vessels without using embryonic or umbilical cord blood stem cells could skirt many ethical concerns, Bischoff said. It would also solve a persistent problem in treating several medical conditions that result from ischemia--the inability of oxygen-rich blood to reach an organ or tissue--such as heart attacks, wound healing and many acute injuries.

"What we are most interested in right now is speeding up the vascularization (the formation of blood vessels)," said Bischoff, who is also an associate professor at Harvard Medical School. "We see very good and extensive vasculature in seven days and we'd like to see that in 24 or 48 hours. If you have an ischemic tissue, it's dying tissue, so the faster you can establish blood flow the better."

Bischoff said other findings include:

• The cells created a vigorous network of vessels that connected to one another and to the vessels of the host mouse within seven days and continued to transport blood during the four-week study.
• Once combined and implanted, the two progenitor cells arranged themselves into vessels with minimal outside help, i.e., without any genetic alteration or manipulation to improve their growth. This is important because many growth-promoting genes are the same genes that become activated in cancer.
• Mixtures of EPCs and MPCs from adult donors were as effective at generating vessels as those made from a mixture of cord blood EPCs and adult bone marrow MPCs. That finding increases the likelihood of someday being able to easily find clinically useful amounts of progenitor cells.

The research could also enhance tissue engineering - growing new organs for later implantation into patients, another medical research field that needs good sources of microvascularization to develop, Bischoff said.

Contacte:
Jamie Newton
617-919-3110
james.newton@childrens.harvard.edu

Children's Hospital Boston is home to the world's largest research enterprise based at a pediatric medical center, where its discoveries have benefited both children and adults since 1869. More than 500 scientists, including eight members of the National Academy of Sciences, 11 members of the Institute of Medicine and 12 members of the Howard Hughes Medical Institute comprise Children's research community. Founded as a 20-bed hospital for children, Children's Hospital Boston today is a 397-bed comprehensive center for pediatric and adolescent health care grounded in the values of excellence in patient care and sensitivity to the complex needs and diversity of children and families. Children's also is the primary pediatric teaching affiliate of Harvard Medical School. For more information about the hospital and its research visit: www.childrenshospital.org/newsroom.