원저 Korean Circulation J 2004;34(10):983-991 흰쥐의경동맥풍선손상모델에서경구 Everolimus 투여에의한외막세포활성화와신내막형성감소 가톨릭대학교의과대학내과학교실 문건웅 이종민 장기육 유기동 전두수 윤호중정욱성 이만영 김종진 승기배 김철민 홍순조 Oral Everolimus Reduces dventitial Cell ctivation and Neointima Formation in alloon-injured Rat Carotid rtery Keon-Woong Moon, MD, Jong-Min Lee, MD, Kiyuk Chang, MD, Ki-Dong Yoo, MD, Doo-Soo Jeon, MD, Ho-Joong Youn, MD, Wook-Sung Chung, MD, Man-Young Lee, MD, Jong-Jin Kim, MD, Ki-ae Seung, MD, Chul-Min Kim, MD and Soon-Jo Hong, MD Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea STRCT ackground and Objectives:Previous studies suggest that phenotypic conversion, proliferation and migration of adventitial fibroblasts after balloon injury have an important role in neointimal formation and vascular remodeling. The present study evaluated whether orally administered everolimus (a macrolide of the same family as sirolimus) reduces adventitial cell activation and neointimal formation in balloon-injured rat carotid arteries. Materials and Methods:Oral everolimus (1.25 mg/kg/day), or a matching placebo, was administered daily to 30 rats by gavage, starting 3 days before balloon injury. The treatment effects were assessed 3, 7 and 14 days after injury. Results:The oral everolimus group showed a significant reduction in adventitial cell proliferation at 3 days after injury and significant neointimal formation reduction compared to the control group at 7 and 14 days after injury (control group 0.06±0.01 mm 2, everolimus group 0.01±0.01 mm 2, p<0.01 and control group 0.28±0.06 mm 2, everolimus group 0.08±0.03 mm 2, p<0.01). Conclusion:Oral everolimus reduces adventitial cell activation and neointima formation in balloon injured rat carotid arteries. (Korean Circulation J 2004;34(10):983-991) KEY WORDS:Everolimus;Restenosis;ngioplasty. 서 관동맥질환에서풍선도자또는스텐트를이용한관동 논문접수일 :2004 년 6 월 3 일심사완료일 :2004 년 7 월 6 일교신저자 : 유기동, 442-723 경기도수원시팔달구지동 93 가톨릭대학교의과대학내과학교실전화 :(031) 249-7139 전송 :(031) 247-7139 E-mail:yookd@dreamwiz.com 론 맥중재시술은외과적치료법인관동맥우회로술과비교될정도로효과가좋은것으로인정되고있다. 풍선확장술후 30~40% 에달하던재협착률은관동맥내스텐트의광범위한사용으로 15~20% 로감소하였으나 1) 아직재협착은관동맥중재시술의주요한계이며재협착의주된기전은신내막형성 (neointima formation) 과혈관재형성 (vascular remodeling) 으로알려져있다. 혈관의외막은중막의근육층에적절한영양을공급하 983
는것이주된기능으로알려져왔으나최근외막이신내막형성및혈관재형성에영향을미친다는사실이알려지면서외막의역할이주목받고있다. 2) 혈관손상후신내막형성은중막에있는혈관평활근세포의활성화및보다미숙한세포로의형질전환과증식, 유주가주된기전으로생각되고있으나 3-5) 외막의섬유모세포또한혈관손상후평활근세포와비슷한근섬유모세포 (myofibroblast) 로형질전환을일으키고증식하는데 6-8) 증식은손상후약 3일째최고조에달하며 9)10) 약 28일후에는손상전수준으로회복된다고한다. 11) 외막의증식된근섬유모세포는혈관재형성과관련이있으며그중일부는내막으로유주하여신내막형성에참여하는것으로알려져있다. 6-8) Rapamycin(sirolimus) 은 mtor(mammalian target of rapamycin) 를억제하는마크로라이드계열의면역억제제로 late G1 phase 에서세포주기를멈춤으로써조혈세포및혈관내평활근세포의증식을억제한다. Rapamycin 은실험실에서혈관내평활근세포의증식및유주를억제할뿐만아니라 12) 풍선도자를이용한쥐와돼지의생체실험에서도신내막의증식을억제하는것으로보고되고있으며 13)14) 돼지의관동맥에삽입된 sirolimus-coated stent 는스텐트내신내막증식을억제하는것으로알려졌다. 15) 30 명의환자를대상으로최초로사람의관동맥에시술된 sirolimus 용출스텐트 (sirolimuseluting stent) 의초기성적은 210 일재협착률 0% 로발표된바있고 16) 2년후추적관동맥조영술에서도 1명을제외하고스텐트내직경협착은 35% 이하로발표되었으며 17) 최근발표된 1,058 명의환자를대상으로한이중맹검무작위임상연구인 SIRIUS 연구에서도 1년후재협착률은대조군 16.6%, sirolimus 용출스텐트 4.1% 로재협착률을약 70~80% 감소시키는것으로나타났다. 18) 약물을용출하는스텐트는전신적부작용없이국소약물농도를높임으로써원하는효과를얻을수있다는장점은있지만동물실험결과에서신내막치유과정을지연시킨다는사실이밝혀져있으며 15)19) 스텐트내함유된약물의용출이끝난후신내막의증식이가속화되는후기신내막만회현상은약물용출스텐트의잠재된부작용으로남아있다. 19)20) 또한약물용출스텐트를사용하는경우전통적인스텐트보다비용이많이들며한환자에서 2~3 개이상의스텐트를삽입하는등다혈관질환에 984 대한중재시술이많이시행되면서약물용출스텐트의보조적인수단또는대체방법으로써전신적약물투여에관한연구가진행되고있다. 1) Sirolimus 는경구로투여할경우약역학적인개인차가매우큰것으로알려져있으나 21-23) sirolimus의유도체인 everolimus [40-O- (2- hydroxyethyl)-rapamycin] 는경구로투여하여도활성을나타내는면역억제제로신이식및심장이식후거부반응을예방하기위해사용되고있으며최근토끼의장골동맥을이용한동물실험에서경구로투여하였을때스텐트내신내막증식을억제한다는논문이발표된바있다. 24) 하지만풍선도자를이용한혈관손상모델에서 everolimus 의효과를연구한논문은아직없다. 본연구에서는풍선도자를이용한흰쥐의혈관손상모델에서 everolimus를경구로투여하였을경우외막세포의활성화와신내막형성을감소시키는효과가있는지알아보고자하였다. 재료및방법 대상동물 14~15주령의체중 350~450 g의 Sprague-Dawley 계의수컷흰쥐 30마리를대상으로 everolimus군 (N= 15) 과대조군 (N=15) 으로나누어실험을진행하였다. Everolimus 군은풍선도자로경동맥에손상을주기 3일전부터희생시키기전까지매일 gastric lavage 를통해 everolimus 1.25 mg/kg 를투여하였으며대조군은위약을투여하였다. Everolimus의준비 Everolimus 및위약은제조회사 (Novartis pharma G, asle, Switzerland) 로부터냉동된 2% microemulsion 상태로제공받았으며 4 에서냉장보관하다가 gastric lavage로투여직전 0.125 g의 microemulsion(everolimus 2.5 mg) 을증류수를사용하여 10 ml로희석하여 5 ml/kg 의용량을투여하였다. 경동맥의내막박리 Xylazine(4.6 mg/kg) 과 ketamine(70 mg/kg) 을복막내주사하여마취하고경부의정중앙을절개한후좌측총경동맥및외경동맥을노출시켰다. 좌측외경동맥을통하여 2F Fogarty 풍선도자를대동맥궁까지삽 Korean Circulation J 2004;34(10):983-991
입한후 0.3~0.4 ml 의공기를넣어풍선을확장시키고확장된풍선도자를회전시키면서총경동맥까지잡아당겨경동맥의내막을박리하였다. 이와같은술기를 3회반복하고풍선도자를제거한후외경동맥을결찰하고절개부위를봉합하였다. 조직검사대조군과 everolimus 군을각각 1/3 씩나누어경동맥의내막박리후 3일, 7일및 14일째마취후우측대퇴동맥을박리하여노출한뒤도관을삽입하여상행대동맥까지전진시킨후 4% 포르말린용액을사용하여 90~ 100 mmhg 의압력으로 5분간관류고정하였다. 관류고정이시작된후꼬리정맥을통하여과량의 thiopental sodium 을주사하여안락사시켰다. 관류-고정후좌측경동맥을채취하여 4% 포르말린용액에 24시간더고정후파라핀에포매한후 5 μm 두께의조직절편을만들어 histomorphometric study 및면역조직화학적검사를시행하였다. Histomorphometric study 중막의손상부위와정도를평가하기위해 Hematoxylin-Eosin 염색및 Verhoeff 탄력조직염색을실시하였다. 내탄력층의국소적인파열이있고외막이혈관내강으로노출되지않은경우경도의손상으로정의하였으며중막이파열되어외막이혈관내강으로노출된경우심한손상으로정의하였다 (Fig. 1). 10) 100 배확대시야에서현미경에장착된디지털카메라로촬영후 xiovision LE v 4.1.1(Carl Zeiss Vision GmbH, Germany) 을사용하여 histomorphometric analysis 를시행하였다. 신내막과중막의경계즉내탄력 층이이루는면적에서혈관내강의면적을빼서신내막의면적을구하였으며중막과외막의경계즉외탄력층이이루는면적에서내탄력층이이루는면적을빼서중막의면적을구하였다 (Fig. 1). 면역조직화학적검사 1) 세포의증식을평가하기위해안락사시키기 2시간전에 100 mg/kg 의 bromodeoxyuridine(rdu)(sigma-ldrich Co, St. Louis, MO, US) 를근육내주사하였다. 면역조직화학검사는 rdu 에대한단일클론항체 (DakoCytomation California Inc., Carpinteria, C, US) 를사용하여수행하였다. 400배확대시야에서외막또는내막에있는 rdu 로표지된세포의수를세고 rdu-labeling index(rdu-labeled nuclei의비율 100) 를계산하였다. 2) 외막에있는근섬유모세포를확인하기위해 mouse monoclonal anti-human α-smooth muscle actin antibody(sigma-ldrich Co, St. Louis, MO, US) 를사용하여면역조직화학검사를실시하였다. 통계분석통계분석은 SPSS for Windows 10.0 를사용하였으며두군간의정량적인비교는 Student t test를사용하여분석하였고 p<0.05 인경우유의한것으로판정하였다. 결과 모든실험동물은연구종료시까지생존하였다. Everolimus 투여군은초기약제투여및수술후약 10% 정도의체중감소를보였으나이후연구종료시까지체중 4000 * 45 40 * dventiti al cell density (cells/cross section) 3000 2000 1000 *p<0.01 * Cell proliferation (% rdu-positive cells) 35 30 25 20 15 10 *p<0.01 * 0 Control group Everolimus group 5 0 Control group Everolimus group Fig. 2. : bar graph showing that the adventitia was relatively hypocellular in everolimus group compared to control group 3 days after balloon injury. : adventitia cell proliferation (the ratio of rdu-positive adventitial cells to the total adventitial cell number) was decreased in everolimus group compared to control group 3 days after balloon injury. 985
의 변동은 없었다. 모든 실험동물 조직에서 경도의 혈관 모두에서 신내막의 형성은 관찰되지 않았다. 대조군은 경 손상이 관찰되었으며 중막이 파열되어 외막이 혈관 내강 동맥의 외막에서 세포가 많이 관찰된 반면 everolimus 으로 노출되는 심한 손상을 입은 경우는 없었다. 투여군은 외막에서 발견되는 세포가 적었다(대조군 3195 ±363, everolimus군 1260±197, p<0.01)(fig. 2, 경동맥 손상 3일후의 변화 경동맥의 내막 박리후 3일째 대조군과 everolimus군 Fig. 3). 외막에서 발견되는 세포들 중 rdu에 염색되는 세포 Fig. 1. : example of mild injury 14 days after balloon overstretch in rat carotid artery. reak in the internal elastic lamina (arrow) without medial dissection noted. : histomorphometric analysis. L indicates lumen area, N: neointima, M: media. Verhoeff s stain. Magnification 400 (), 100 (). Fig. 3. Hematoxylin and eosin staining of balloon-injured rat carotid arteries 3 days after angioplasty. large number of adventitial cells was noted in a control artery () whereas everolimus-treated artery showed few adventitial cells (). M: indicates media, : adventitia. Magnification 100. Fig. 4. Immunohistochemical staining using antibodies against bromodeoxyuridine (rdu) () and α-smooth muscle actin (). alloon-injured rat carotid arteries of control group 3 days after angioplasty. large number of adventitial cells was rapidly proliferating (). Most neo-adventitial cells of control artery showed positive α-actin staining () suggesting differentiation into the myofibroblast phenotype. Magnification 400. 986 Korean Circulation J 2004;34(10):983-991
Fig. 5. Carotid artery morphology of control group () and everolimus group () 7 days after balloon injury. Everolimus inhibits neointima formation 7 days after balloon injury. Hematoxylin and eosin staining. Magnification 100. C D Fig. 6. Carotid artery morphology of control group (, C) and everolimus group (, D) 7 days after balloon injury. C and D are higher magnification of the area indicated by rectangle in and, respectively. Everolimus reduces neointima cell proliferation 7 days after balloon injury. rdu immunostaining. Magnification 100 (, ), 400 (C, D). 들은대조군에비해 everolimus 군에서유의하게감소하였으며 ( 대조군 34.2±4.9%, everolimus군 6.5±3.5%, p<0.01) rdu 에염색되는세포들중대부분은 α-smooth muscle actin 에도염색되었다 (Fig. 2, Fig. 4). 경동맥손상 7일후의변화경동맥손상 7일후대조군에서는신내막의형성이관찰되었으나 everolimus 군에서는신내막의형성이현저히감소되었다 ( 대조군 0.06±0.02 mm 2, everolimus군 0.01±0.01 mm 2, p<0.01)(fig. 5, 6)(Table 1). 신내막내의세포수도 everolimus군에서대조군에비하여유의하게감소되었으며 everolimus군에서 rdu에염색되는세포의수가대조군의 6.9% 로현저히감소하였다 (Table 1). 경동맥손상 14일후의변화경동맥손상 14일후대조군과 everolimus 군모두에서신내막의형성이관찰되었다 (Fig. 7, 8)(Table 2). 987
Fig. 7. Carotid artery morphology of control group () and everolimus group () 14 days after balloon injury. Everolimus markedly reduces neointima formation 14 days after balloon injury. Verhoeff s stain for elastic tissue. Magnification 100. C D Fig. 8. Carotid artery morphology of control group (, C) and everolimus group (, D) 14 days after balloon injury. C and D are higher magnification of the area indicated by rectangle in and, respectively. Everolimus reduces neointima cell proliferation 14 days after balloon injury. rdu staining. Magnification 100 (, ), 400 (C, D). Histomorphometric analysis에서 신내막 형성은 eve- 감소하였다(대조군 4.8±0.6%, everolimus군 3.7± rolimus 군에서 유의하게 감소하였으며(대조군 0.28± 0.8%, p<0.05)(table 2). 2 2 0.06 mm, everolimus군 0.08±0.03 mm, p<0.01) 고 면적협착의 정도도 유의하게 감소하였다(대조군 62.6± 찰 4.4%, everolimus군 20.0±11.1%, p<0.01). 신내막의 세포들 중 rdu에 염색되는 세포 수는 eve- 혈관 손상 후 외막의 섬유모세포는 평활근세포와 비 rolimus군에서 유의하게 감소하였으며(대조군 184±26, 슷한 근섬유모세포(myofibroblast)로 형질전환을 일으 everolimus군 18±4, p<0.01) 신내막의 세포 중 rd- 키고 증식한다. U-labelling index 또한 everolimus군에서 유의하게 막으로 유주하여 신내막형성에 참여하는 것으로 알려져 988 6-8) 증식된 근섬유모세포 중 일부는 내 Korean Circulation J 2004;34(10):983-991
Table 1. Histomorphometric indices 7 days after balloon injury Control group Table 2. Histomorphometric indices 14 days after balloon injury Control group Everolimus group Neointima area (mm 2 ) 0.06±0.02 0.01±0.01 <0.01 Lumen area (mm 2 ) 0.35±0.06 0.42±0.06 NS rea stenosis (%) 14.6±5.80 3.3±1.4 <0.01 Media area (mm 2 ) 0.14±0.01 0.14±0.02 NS Neointimal cell count 828±120 35±70 <0.01 rdu (+) cell count 333±610 23±40 <0.01 rdu (+) cells (%) 40.3±5.40 68.7±15.4 <0.01 Values are mean±sd or percenatage Everolimus group Neointima area (mm 2 ) 0.28±0.06 0.08±0.03 <0.01 Lumen area (mm 2 ) 0.16±0.01 0.33±0.09 <0.01 rea stenosis (%) 62.6±4.40 20.0±11.1 <0.01 Media area (mm 2 ) 0.14±0.01 0.14±0.01 NS Neointimal cell count 3872±3120 503±101 <0.01 rdu (+) cell count 184±260 18±40 <0.01 rdu (+) cells (%) 4.8±0.6 3.7±0.8 <0.05 Values are mean±sd or percenatage 있다. 6-8) Li 등 8) 은흰쥐의경동맥손상모델에서리트로바이러스로형질을도입한섬유모세포를외막에직접이식하여손상후 7일, 10일, 14일째중막과내막에서형질이발현되는것을증명하였고 Shi 등 10) 은돼지의관동맥에서외막의섬유모세포가근섬유모세포로형질전환을일으켜혈관손상으로생긴중막의틈 (medial gap) 을통하여신내막으로유주한다고보고하였다. 하지만외막의섬유모세포가신내막으로이동하지않는다는연구결과도있는데 Faggin 등 7) 은토끼의경동맥손상모델에서 SM22 를외막의근섬유모세포의추적자로사용하여외막세포가내막으로이동하지않는다고보고한바있고 de Leon 등 25) 은흰쥐의경동맥손상모델에서형광염색시약인 PKH26 을사용하여외막세포가중막또는신내막으로유주하지는않는다고보고한바있다. 본연구는경구 everolimus를투여하는경우외막세포의활성화가억제되는지관찰하고자연구를시행하였는데경동맥손상 3일째대조군의외막에서 rdu 에염색되고 α-smooth muscle actin 에염색되는근섬유모세포의증식이관찰되었는데 rdu labelling index는 34.2 ±4.9% 로써 de Leon 등 25) 이보고한 27.5±3.8% 와 p p 유사하였다. Everolimus 군에서는이러한근섬유모세포의증식이유의하게감소하여경구 everolimus 는외막세포의활성화를감소시킨다는것을알수있었다. 1977년 ndreas Gruntzig 26) 가처음으로사람에서관동맥풍선확장술을실시한이래현재전세계적으로연간백만건이상의관동맥중재시술이시행되고있는데재협착은관동맥중재시술의주요한계이다. 재협착을줄이기위해체외및혈관내방사선치료, 국소및전신약물투여등이활발히연구되고있으며국내에서도동물실험을통하여김등 27) 이체외방사선치료를, 조등 28) 이국소약물요법을연구한바있다. 최근에는혈관내방사선치료의도입과약물용출스텐트의사용으로재협착률은더욱더감소될것으로예상된다. 1) 혈관내방사선치료는방사선치료자체가갖는안전성문제이외에도가장자리효과 (edge effect), 후기스텐트내혈전등의제한점이있으며약물용출스텐트는전신적부작용없이국소약물농도를높임으로써원하는효과를얻을수있다는장점은있지만동물실험결과에서신내막치유과정을지연시킨다는사실이밝혀져있다. 15)19) 최근미국의 FD 는 sirolimus 용출스텐트후 290 예이상의아급성혈전증및 50예이상의과민반응을보고한바있고 29) 스텐트내함유된약물의용출이끝난후신내막의증식이가속화되는후기신내막만회현상은약물용출스텐트의잠재된부작용으로남아있다. 19)20) 또한약물용출스텐트를사용하는경우전통적인스텐트보다비용이많이들며혈관의직경이너무작거나구불구불하여스텐트삽입의적응이되지않거나, 한환자에서 2~3 개이상의스텐트를삽입하는등다혈관질환에대한중재시술이많이시행되면서약물용출스텐트의보조적인수단또는대체방법으로써전신적약물투여에관한연구가진행되고있다. 1) 최근전신적약물투여에관한연구에사용되는약물은 taxol(paclitaxel) 과 sirolimus(rapamycin), everolimus 등이있다. 김등 30) 은흰쥐의풍선손상모델에서새로운경구용 paclitaxel 제제를투여하여신내막형성이억제되었다고보고한바있다. Sirolimus 는경구로투여할경우약역학적인개인차가매우큰것으로알려져있으며 21-23) rara 등 31) 은 22명의난치성재협착환자들을대상으로관동맥중재술시행후경구 rapamycin 을투여한결과재협착률 59.1% 로만족스럽지못한결과를얻었다고보고한바있다. Sirolimus 의유도 989
체인 everolimus [40-O-(2-hydroxyethyl)-rapamycin] 는경구로투여하여도활성을나타내는면역억제제로신이식및심장이식후거부반응을예방하기위해사용되고있으며 everolimus 용출 stent의초기임상성적은 6개월재협착률 0%, 12개월임상추적결과사망, 심근경색, 및재관류치료등의주요임상사건은발생하지않은것으로발표되었다. 32) 토끼의장골동맥을이용한동물실험에서스텐트시술후경구로 everolimus 를투여할경우스텐트내신내막증식을억제한다는결과가발표된바있으며 24) 본연구에서는풍선도자를이용한흰쥐의혈관손상모델에서경구 everolimus를투여한결과외막세포의활성화가감소되고신내막형성이억제되는것을관찰하였다. 경동맥손상 14일째 everolimus 를투여한군에서대조군에비하여신내막면적이 71% 감소하였고면적협착비율은 67% 감소하였다. 본연구에사용한 everolimus의용량은 1.25 mg/kg/ day로써 Cole 등 33) 이대동맥이식모델에서사용한 2.5 mg/kg/day 에비해절반에해당되는데이용량의 everolimus 의투여는체중감소등의부작용없이효과적으로신내막형성을억제하는것으로나타났다. 본연구의제한점은약물투여후관찰기간이짧았다는점을들수있다. 특히후기신내막만회현상이발생하는지여부를보기위해서는일정기간의 everolimus 투여후약물투여없이일정기간이지난후조직검사를실시하는추가연구가필요하다. 향후본연구의결과를토대로다발성병변이있는경우스텐트시술여부에관계없이경구 everolimus 투여를고려하거나약물용출스텐트시술후후기신내막만회현상을예방하기위한보조적인수단으로서경구 everolimus 투여가시도될수있을것으로기대된다. 요약 배경및목적 : 혈관외막의섬유모세포는혈관손상후근섬유모세포로형질전환을일으키고증식하여혈관재형성및신내막형성에중요한역할을하는것으로알려져있다. 흰쥐의경동맥풍선손상모델에서 rapamycin 의유도체인 everolimus를경구로투여하였을경우외막세포의활성화와신내막형성의억제효과가있는지알아보고자하였다. 990 방법 : 30마리의흰쥐를대상으로경동맥풍선손상 3일전부터 everolimus(everolimus군, N=15) 또는위약 ( 대조군, N=15) 을 1.25 mg/kg 용량으로매일경구투여하였다. Everolimus 군과대조군동물들을각각 1/3 씩나누어혈관손상후 3일, 7일, 14일째조직을채취하여치료효과를판정하였다. 결과 : 혈관손상 3일후 everolimus군에서외막세포증식이유의하게감소하였으며신내막형성은 everolimus 군에서혈관손상 7일후 ( 대조군 0.06±0.01 mm 2, everolimus군 0.01±0.01 mm 2, p<0.01) 및 14일후 ( 대조군 0.28±0.06 mm 2, everolimus군 0.08±0.03 mm 2, p<0.01) 유의하게감소하였다. 결론 : 흰쥐의경동맥풍선손상모델에서 everolimus 경구투여는외막세포의활성화와신내막형성을감소시킨다. 중심단어 :Everolimus; 재협착 ; 혈관성형술. 본논문은가톨릭대학교의과대학부속성모자애병원의연구비보조로이루어졌음. REFERENCES 1) Faxon DP. Systemic drug therapy for restenosis: deja vu all over again. Circulation 2002;106:2296-8. 2) Sartore S, Chiavegato, Faggin E, Franch R, Puato M, usoni S, Pauletto P. Contribution of adventitial fibroblast to neointima formation and vascular remodeling: from innocent bystander to active participant. Circ Res 2001;89:1111-21. 3) Owens GK. Regulation and differentiation of vascular smooth muscle cells. Physiol Rev 1995;75:487-517. 4) Sartore S, Franch R, Roelofs M, Chiavegato. Molecular and cellular phenotypes and their regulation in smooth muscle. Rev Physiol iochem Pharmacol 1999;134:235-320. 5) Glass CK, Witztum JL. therosclerosis: the road ahead. Cell 2001;104:503-16. 6) Zalewski, Shi Y. Vascular myofibroblasts: lessons from coronary repair and remodeling. rterioscler Thromb Vasc iol 1997;17:417-22. 7) Faggin E, Puato M, Zardo L, Franch R, Millino C, Sarinella F, Pauletto P, Sartore S, Chiavegato. Smooth muscle-specific SM22 protein is expressed in the adventitial cells of the balloon-injured rabbit carotid artery. rterioscler Thromb Vasc iol 1999;19:1393-404. 8) Li G, Chen SJ, Oparil S, Chen YF, Thompson J. Direct in vivo evidence demonstrating neointimal migration of adventitial fibroblasts after balloon injury of rat carotid arteries. Circulation 2000;101:1362-5. 9) Scott N, Cipolla GD, Ross CE, Dunn, Martin FH, Si- Korean Circulation J 2004;34(10):983-991
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