Repair of the blood-brain barrier following implantation of polymer
capsules.
Brain Res., 551 (1-2):
163-70 (1991)Abstract
Past studies of polymer-encapsulated cell lines implanted in the brain
indicated their usefulness for transmitter replacement therapy in
animal models. Such grafts may have potentially important clinical
applications, but their placement into neural parenchyma may cause
a traumatic injury resulting in a leaky blood-brain barrier around
the implant. This study investigated whether or not injury repair
and reformation of the barrier takes place near a polymer capsule
implanted in the brain of Sprague-Dawley rats. The two methods used
for detection of a leaky barrier were immunocytochemical localization
of extravasated serum albumin and circulating Evans blue that binds
to serum albumin. Immunocytochemical staining for glial filament
protein provided a measure for evaluating injury associated gliosis.
Polymer capsules implanted for 10, 16 and 18 days were surrounded
by microvessels that leaked detectable quantities of serum albumin
into interstitial spaces and, by secondary uptake, into some nearby
neurons and reactive astrocytes. Reactive astroglia were observed
within the outer regions of the capsule wall and in the near vicinity
of the implant after these early survival times. In contrast, at
post-implantation times of 46 and 54 days, serum albumin was no longer
detected in the neural parenchyma near the macrocapsules and only
few reactive astrocytes remained. These findings show that polymer
capsules implanted within the cerebrum permit (a) reformation of
the blood-brain barrier and (b) occurrence of repair processes that
lead to minimal deposition of reactive astroglia near the implanted
polymer capsule.