Mm. Clowes et al., LONG-TERM BIOLOGICAL RESPONSE OF INJURED RAT CAROTID-ARTERY SEEDED WITH SMOOTH-MUSCLE CELLS EXPRESSING RETROVIRALLY INTRODUCED HUMAN GENES, The Journal of clinical investigation, 93(2), 1994, pp. 644-651
Cultured vascular smooth muscle cells (SMCs) containing retrovirally i
ntroduced genes are a potential vehicle for gene replacement therapy.
Because the cultured SMCs are selected for their ability to proliferat
e in vitro, it is possible that the SMCs might be permanently altered
and lose their capacity to respond to growth-suppressing conditions af
ter being seeded back into blood vessels. To investigate this possibil
ity we measured SMC proliferation and intimal thickening in balloon-in
jured Fischer 344 rat carotid arteries seeded with SMCs stained with t
he fluorescent marker dioctadecyl-3,3,3',3'-tetramethylindo-carbocyani
ne perchlorate (DiI) and infected with replication-defective retroviru
s expressing human adenosine deaminase or human placental alkaline pho
sphatase. The majority of the seeded SMCs remained in the intima while
a few of the cells appeared to migrate into the first layer of the me
dia. Intimal SMC proliferation returned to background levels (< 0.1% t
hymidine labeling index) by 28 d. At late times (1 and 12 mo) the morp
hological appearance of the intima was the same for balloon-injured ar
teries with or without seeded SMC, except that the seeded arteries con
tinued to express human adenosine deaminase or alkaline phosphatase. T
hese results support the conclusion that cultured SMC infected with a
replication-defective virus containing human adenosine deaminase or al
kaline phosphatase are not phenotypically altered and do not become tr
ansformed. After seeding onto the surface of an injured artery, they s
top replicating but continue to express the introduced human genes eve
n over the long term.