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ABSTRACT:
TITLE: Smooth Muscle Cells effect on the angiogenic invasion of Human-Umbilical Vein Endothelial Cells in fibrin- based Tissue Engineered Blood Vessels Analogs subjected to 10% 3-D Cyclic Strain
INTRODUCTION:
T i s s u e s g r e a t e r t h a n 2 0 0 m f r o m a v a s c u l a r s u p p l y a r e s u s c e p t i b l e t o b o t h i s c h e m i a a n d s u b s e q u e n t n e c r o s i s . E n g i n e e r e d t i s s u e s , i n c l u d i n g t i s s u e e n g i n e e r e d b l o o d v e s s e l s ( T E B V s ) , h a v e t h e s a m e r e q u i r e m e n t s . A s s u c h , t h e d e v e l o p m e n t o f g r a f t s w i t h t h i c k e r media layers will likely require the development of a microvasculature within these vessels walls to nourish the smooth muscle cells (SMCs) of the tunica media which add both structural integrity and elasticity. ADDIN EN.CITE Folkman197319191917Folkman, J.Hochberg, M.Self-regulation of growth in three dimensionsJ Exp MedJ Exp Med745-5313841973/10/01AgarAnimalsCell Count*Cell DivisionCricetinae*Culture TechniquesLeukemia, Experimental/pathologyLung/pathologyMelanoma/pathologyMiceTime Factors1973Oct 10022-1007 (Print)4744009http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=47440092180571eng(1) Recent developments in tissue culture techniques have demonstrated that dynamic mechanical stimulation can augment cellular proliferation, alignment, and matrix protein synthesis. To achieve these same benefits TEBVs have been cultured with dynamic mechanical stimulation. Cyclic strain has been shown to particularly augment the mechanical strength of TEBVs. ADDIN EN.CITE ADDIN EN.CITE.DATA (2) Preliminary results within the lab of Dr. Howard Greisler have shown that, when compared to static controls, endothelial cells (ECs) seeded alone within fibrin-based TEBVs and cultured in a dynamic environment of 10% cyclic strain demonstrate shorter, more robust, and wider multi-cellular angiogenic sprouts. Additionally, work in the same lab has shown that ECs co-cultured with SMCs (both homogenous distribution and co-aggregated) in a fibrin matrix have both longer and more robust angiogenic sprouting.
HYPOTHESIS:
Within a dynamic culture environment, the homogenous addition of SMCs to the extracellular matrix will augment the development and angiogenic invasion of EC sprouts into a fibrin hydrogel.
METHODS:
TEBVs will be formed from fibrin, over silicone sleeves. Prior to formation of the TEBV and pelleting of the ECs, both cell types identities will be confirmed using immunohistochemistry and then labeled seperatly with two distinct membrane bound immunoflourescent surface dyes. A tubular hydrogel will be formed from a suspension of human-umbilical vein EC (HUVEC) pellets (2k cells/pellet, 20 pellets/mL), canine carotid SMCs (100k /mL), fibrinogen (2.5mg/mL), thrombin (0.32 U/mL), heparin (5U/mL), vascular endothelial growth factor (VEGF) (1 ng/mL), fibroblast growth factor-1 (FGF-1) (10ng/mL), and aprotinin (100KIU/mL). The hydrogel TEBV analog will then be mounted within a bioreactor chamber. The constructs will then be covered with assay media comprised of all of the same reagents and concentrations as the TEBV except the cells, fibrinogen and thrombin. This media will be replaced every 3 days. A Windkessel effect pump system will deliver fluid pulsations through the bioreactor distending the TEBV another 10% of the silicones sleeves original volume. Angiogenic invasion will be documented at Day 7 by measuring average sprout length and sprout number by both light and confocal fluorescence microscopy. The samples that have large multi-cellular sprouts will be sent for TEM sectioning and imaging to confirm lumen formation
ANTICIPATED RESULTS:
ECs and SMCs co-cultured in a fibrin-based TEBV subjected to 10% 3-D cyclic strain will likely demonstrate a robust network of angiogenic sprouts that are longer than sprouts formed by endothelial cells alone and wider than sprouts formed in co-culture without mechanical stimulation.
Research Plan:
Background and rationale
Tissue Engineered Blood Vessels: The current standard for small diameter (<6mm) functional arterial grafts in vascular medicine is the autologous graft. The use of these grafts is limited in many patients since a suitable replacement is not available due to vascular disease, amputation, or previous harvests. Experiments have shown that with lower flow velocities in the smaller grafts, the incidence of thrombogenesis, aneurysm formation, and atherosclerotic plaque formation is increased. There is currently a need for an alternative option for small diameter functional arterial grafts, and this absence has spurred interest into TEBVs. ADDIN EN.CITE Barron200344417Barron, V.Lyons, E.Stenson-Cox, C.McHugh, P. E.Pandit, A.National Centre for Biomedical Engineering Science, National University of Ireland, Galway, Galway, Ireland. valerie.barron@nuigalway.ieBioreactors for cardiovascular cell and tissue growth: a reviewAnn Biomed EngAnn Biomed Eng1017-303192003/10/30AnimalsArteries/growth & developmentBiomimetics/instrumentation/methods/trends*BioreactorsCell Culture Techniques/*instrumentation/methods/trendsCoronary Vessels/*growth & developmentHeart/*growth & developmentHeart Valves/growth & developmentHumansMyocytes, Cardiac/*physiologyTissue Engineering/*instrumentation/*methods/trends2003Oct0090-6964 (Print)14582605http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=14582605eng(3) Originally described by Weinberg and Bell, TEBVs are comprised of a complex network of cells and tubular support scaffolding. ADDIN EN.CITE Weinberg198612121217Weinberg, C. B.Bell, E.A blood vessel model constructed from collagen and cultured vascular cellsScienceScience397-40023147361986/01/24AnimalsAorta/anatomy & histology/cytologyBlood Vessels/*anatomy & histology/physiologyCattleCells, CulturedCollagen/*physiologyEndothelium/anatomy & histology/cytologyMicroscopy, Electron, Scanning*Models, CardiovascularMuscle, Smooth, Vascular/anatomy & histology/cytologyPolyethylene Terephthalates/diagnostic use1986Jan 240036-8075 (Print)2934816http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=2934816eng(4) Within these constructs, scaffolding materials typically include synthetic alternatives as well as biologic hydrogels such as fibrin and collagen. Fibrin hydrogels have been shown to stimulate ECs and pericytes (i.e. vascular SMCs and fibroblasts) to up-regulate cellular proliferation, synthesis of cytokines and both elastin and collagen genesis. ADDIN EN.CITE Isenberg200677717Isenberg, B. C.Williams, C.Tranquillo, R. T.Department of Chemical Engineering & Materials Science, University of Minnesota, Minneapolis, MN 55455, USA.Small-diameter artificial arteries engineered in vitroCirc ResCirc Res25-359812006/01/07AnimalsArteries/*cytology/physiologyBiocompatible MaterialsBiomechanicsBioreactorsBlood CirculationCollagenEndothelium, Vascular/physiologyFibrinHumansMuscle, Smooth, Vascular/physiologyPolymersTissue Engineering/*methods2006Jan 61524-4571 (Electronic)16397155http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=1639715598/1/25 [pii]
10.1161/01.RES.0000196867.12470.84eng(5)
Dynamic Stimulation: Dynamic mechanical stimulation, within a bioreactor cell culture, has been shown to promote tissue organization in engineered constructs. ADDIN EN.CITE Ziegler199533317Ziegler, T.Alexander, R. W.Nerem, R. M.Bioengineering Center, Georgia Institute of Technology, Atlanta 30332-0405, USA.An endothelial cell-smooth muscle cell co-culture model for use in the investigation of flow effects on vascular biologyAnn Biomed EngAnn Biomed Eng216-252331995/05/01AnimalsBlood Flow VelocityCell DivisionCell SizeCells, CulturedEndothelium, Vascular/*physiologyExtracellular Matrix/physiologyMuscle, Smooth, Vascular/*physiologyStress, MechanicalSwine1995May-Jun0090-6964 (Print)7631978http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=7631978eng(6) Cyclic 2-D uniaxial strain has been shown to augment ECs migration, cytokine production, proliferation, matrix remodeling and inhibit EC apoptosis. ADDIN EN.CITE ADDIN EN.CITE.DATA (7) Dynamic culture techniques have shown that subsequent mechanical stimulation after hydrogel formation increases the constructs mechanical structural characteristics (i.e. burst pressure, suture retention strength, etc). ADDIN EN.CITE ADDIN EN.CITE.DATA (2) The dynamically conditioned TEBVs are able to develop these characteristics secondary to proliferation of the cellular components of tunica media (i.e. SMCs). As these structural layers thicken to handle their mechanical load (>200 m ) a m i c r o v a s c u l a r s u p p o r t n e t w o r k a k i n t o n a t i v e v e s s e l s v a s a v a s o r u m m u s t b e c o n s i d e r e d t o a l l o w n u t r i e n t s a n d g a s e x c h a n g e i n t o t h e d e e p e r l a y e r s o f t i s s u e . A D D I N E N . C I T E <