FOR RELEASE                 
February 26, 1996                  

NHLBI RESEARCHERS GROW LUNG TISSUE IN ANIMALS

Scientists supported by the National Heart, Lung, and Blood
Institute (NHLBI) have been able to grow new tissue in the
lungs of laboratory animals for the first time.  Dr. Gloria
De Carlo Massaro and Dr. Donald Massaro of the Georgetown
University School of Medicine showed a 50 percent increase
in the number of alveoli in the lungs of newborn rats
treated with retinoic acid, a drug that is a derivative of
Vitamin A.  The alveoli are the smallest air spaces in the
lungs and the site of the exchange of oxygen and carbon
dioxide between the lungs and the bloodstream.  The
Massaros' study appears in the February issue of the
American Journal of Physiology: Lung Cellular and Molecular
Physiology.

"This is extremely exciting news," said NHLBI Director Dr.
Claude Lenfant.  "This is the first time that anyone has
been able to grow new lung tissue in laboratory animals.  It
provides the first suggestion that some day we may be able
to use an existing agent like retinoic acid to treat lung
diseases like bronchopulmonary dysplasia in which the
patient has insufficient alveoli to breathe efficiently.

"Nonetheless," he added, "a great deal more basic research
is needed before we can begin work in patients.  Until then,
we caution that there is absolutely no evidence that Vitamin
A supplementation is useful in treating lung disorders."  

Bronchopulmonary dysplasia (BPD) is a condition that is
becoming increasingly common as physicians improve their
ability to save very low-birth-weight premature infants. 
Ten thousand new cases are now reported each year.  

In babies who develop BPD, the lungs are immature and the
structures that form the gas-exchange region of the lung
don't subdivide as they should to form a sufficient number
of alveoli to meet the body's oxygen needs.  BPD has serious
health and developmental consequences and represents a major
health care cost to the nation, with initial treatment costs
averaging $90,000 per baby.

In their study, the Massaros set out to test whether
retinoic acid could reverse the effects of dexamethasone, an
anti-inflammatory compound that is known to inhibit alveolar
formation in rats.  Using morphometry to quantify the
alveoli, the Massaros found that administering retinoic acid
to newborn rats also receiving dexamethasone reduced the
effects of the dexamethasone.  The rats formed three times
more alveoli than they would have if they'd been treated
with dexamethasone alone.  Morphometry is a method of
counting cell numbers.  

The NHLBI is part of the National Institutes of Health,
located in Bethesda, MD.