Bone marrow chimerism prevents atherosclerosis in arterial walls of mice deficient in apolipoprotein E.
OBJECTIVE
apolipoprotein E (apoE) is a key regulator in cholesterol-rich lipoprotein metabolism. Inherited deficiency of this protein results in type III hyperlipoproteinemia in humans. ApoE, especially that derived from macrophages, can efficiently protect against development of atherosclerotic lesion. To use stem cell gene therapy or mini-transplant in treating abnormal lipid metabolism and preventing atherosclerosis, a minimal level of bone marrow chimerism must be determined.


METHODS
lethally irradiated apoE deficient mice (12-16 weeks of age) fed on normal chow were transplanted with normal bone marrow cells (C57BL/6.Ly5.1) mixed with those of apoE deficient mice (C57BL/6.Ly5.2) at various ratios. Plasma cholesterol levels were determined every 3 weeks for up to 42 weeks. Areas of atherosclerotic lesion in the aortas were quantified 6 months post-transplant. Plasma apoE was measured by Western blot analysis.


RESULTS
bone marrow transplantation (BMT) in apoE (-/-) mice resulted in a detectable level of plasma apoE as determined by Western blot analysis. The plasma cholesterol levels in mice with > or = 60% chimerism were normalized by 6 weeks post-transplant. Mice with < or = 40% chimerism showed significant reductions, but not normalization, in the plasma cholesterol levels even at 42 weeks posttransplant. However, atherosclerotic areas observed in 10%-chimeric mice were significantly smaller than those in control mice (P<0.01). Immunohistochemical studies in 10%-chimeric mice revealed foam cells derived from donor marrow (apoE (+/+)) and expressed immunoreactive apoE in the atherosclerotic lesion. The positive signals by Western blot analysis were represented in the plasma of up to 8% of the chimeric mice.


CONCLUSIONS
chimerism of 10%, the minimum level analyzed, was sufficient to reduce the severity of atherosclerosis, although the plasma cholesterol levels were not completely normalized. The results indicate that stem cell gene therapy and mini-transplant may provide possible therapeutic approaches to treat patients with abnormal lipid metabolism and atherosclerosis.
Sakai
Yutaka
Y
Department of Immunology, Institute of Basic Medical Sciences, University of Tukuba, and CREST (Japan Science and Technology Corporation), 1-1-1 Ten-nodai, Tsukuba Science City, Ibaraki, 305-8575, Japan.
Kim
Dong Ku
DK
Iwasa
Satoshi
S
Liang
Jingxan
J
Watanabe
Teruo
T
Onodera
Masafumi
M
Nakauchi
Hiromitsu
H
D000818:Animals; D001057:Apolipoproteins E / Q000172:deficiency* / Q000502:physiology; D001161:Arteriosclerosis / Q000517:prevention & control*; D015153:Blotting, Western; D016026:Bone Marrow Transplantation; D002784:Cholesterol / Q000097:blood; D004730:Endothelium, Vascular / Q000378:metabolism / Q000473:pathology; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018183:Transplantation Chimera
D001057:Apolipoproteins E; D002784:Cholesterol