Vascular Tissue Engineering

The WG generates bioartifical vascular grafts (either decellularized animal arteries or fibrin-based vascular grafts), which can be used to replace damaged or missing blood vessels. Other projects of the WG are the development of fibrin- based cardiac patches for the surgical correction of congenital heart defects and the development of pre-vascularized tissue constructs.

Research

Vascular Tissue Engineering

In western industrial nations, cardiovascular pathologies are still leading cause of death. Arteriosclerosis, the root of these diseases, often calls for the replacement of arterial blood vessels in e.g.: bypass surgeries. The needed vascular grafts should ideally be resistant to infections, anti-thrombogenic and should not cause immune adverse immune reactions. Commonly used graft materials, such as the synthetic polymer Polytetrafluoroethylene (PTFE) pose serious risks in this aspect, as alloplastic materials can act thrombotic per se, and can cause severe infections due to biofilm formation. A novel approach in tissue engineering is therefore the generation of bioartificial vascular grafts, which can be populated by the patient’s cells after implantation, thereby causing a remodeling of the vascular grafts and their complete integration into the host tissue. Especially the invasion of newly formed capillaries into the vascular graft (neovascularization) is of great interest in this context, as it provides the seeded cells with oxygen and nutrients, but also enables immune cells to invade the matrix to fight possible infections. The supply of oxygen and nutrients to the cells often poses a limitation in larger tissue constructs, as oxygen can only passively diffuse in the body over a few hundred micrometers. Therefore, cells in deeper layers of the tissue construct are often not supplied properly, which might lead to cell death and therefore implant failure. Pre-vascularization, which is the formation of a capillary network in the tissue construct in vitro, is a promising solution to this problem. The pre-formed capillary network can be connected to the host vasculature and thereby enable instant supply to the cells in the tissue construct, even in deeper layers.

Development of different approaches for the preparation and characterization of matrices for vascular tissue engineering

1.) Production of fibrin-based vascular prostheses.

Fibrin is a natural polymer involved in the blood clotting cascade, which can also serve as material for cardiovascular grafts. However, the low biomechanic stability of fibrin has limited its use for the generation of vascular prostheses so far. Here, we developed a method to compact fibrin by high-speed rotation resulting in vascular grafts, comprising sufficient stability and an enormous potential to be reseeded and remodeled in vivo, as already shown in an animal model.

2.) Fibrin-based cardiac patches

The generation of cardiac patches, as needed in constructive surgical therapy for congenital heart defects, also requires a material that is biomechanically stable, can be remodeled and bears not immunogenic risk. Thus, fibrin was compacted by pressure, thereby generating patches with sufficient biomechanical stability. Fibrin patches may be a promising alternative to xenogeneic cardiac patch materials.

3) Seeding of fibrin-based matrices with (autologous) vascular cells

To mimic the natural structure of arteries, fibrin grafts can be seeded in vitro, meaning before implantation, with vascular cells. Endothelial cells, smooth muscle cells and mesenchymal stem cells from autologous tissue sources were isolated and used to form the three layers of an artery comprising the endothelial lining, a contractile medial layer and network of capillaries in the outer layer. Furthermore, these cell types are also used for cellularization of larger tissue constructs, to enable quicker and more efficient integration of the constructs after implantation. Structures as such can be visualized by fluorescence microscopy and scanning laser optical tomography (SLOT) in cooperation with the Laserzentrum Hannover (LZH).

4.) Bioreactor technologies for the generation of an attachable, pre-vascularized tissue construct

A customized flow chamber, which acts as a bioreactor, was developed in which fibrin-based tissue constructs can be combined with fibrin-based vascular grafts and perfused with feeding medium. Endothelial cells, which were seeded into the construct and are supported by mesenchymal stem cells, can thereby form a capillary network, which is stabilized by flow for several days. The goal is to generate tissue-specific, attachable and pre-vascularized tissue constructs by the introduction of specific cell types into the scaffolds. These are especially needed in the field of plastic reconstructive surgery, where constructs for muscle-, skin-, and adipose tissue replacement are of specific interest. Another interesting application of these tissue constructs is the replacement of cardiac tissue after cardiac infarctions.

Previous projects

1.) Decellularization of equine arteries

Carotid arteries from the horse are ideal scaffolds for large diameter vascular grafts, such as hemodialysis shunts, due to their size and the low number of outlets. To avoid rejection after implantation, xenogeneic (= from a different species) cells in the native carotid arteries have to be removed by treatment with detergents and enzymes, leaving behind a cell-free scaffold. We developed an intensified decellularization protocol that extensively reduced the immunogenicity of the equine carotid arteries but maintained their biomechanical properties. Intensified decellularization of equine carotids resulted in scaffolds with excellent biocompatibility and a high potential to be reseeded and remodeled as shown in vitro and in several animal models (mouse, rat, and sheep).

2.) Evaluation of the immunogenicity of xenogeneic bioartificial grafts

To determine graft-specific antibody formation in patients after implantation of xenogeneic bioprosthetic heart valves, we developed an enzyme-linked immuno sorbent assay (ELISA). Tissue-specific antibody formation was most pronounced in patients implanted with glutaraldehyde-fixed porcine heart valves up to 5 years and was directed against cellular and extracellular proteins of the heart valve. After implantation of decellularized porcine valves this immune response was significantly reduced and even absent in patients implanted with human decellularized valves. This underlines the recommendation to use the latter in particular for valve replacement in young patients.

3.) Evaluation of nano-structured metals for the generation of vascular stents

Nitinol-based materials for the generation of stents, which were electropolished and structured by the deposition of nano particles, were tested for their repopulation properties by vascular cells (Cooperation project with Prof. Dr. Stefan Barcikowski, Technical Universitity of Duisburg-Essen).

4.) Ex-vivo perfusion model to study pathomechanisms of atherosclerosis

The pathogenesis of atherosclerosis involves changes in the so-called vasa vasorum, which are necessary for oxygen and nutrient supply of the vessel wall. Damage or obstruction of the vasa vasorum results in local hypoxic zonation and subsequently in inflammation, lipid accumulation and intimal thickening. To study the early mechanisms of atherosclerosis, porcine aortas were exposed to low oxygen conditions in an in vitro perfusion system and the effects of arterial wall hypoxia on cellular and molecular structures in the vessel wall were investigated.

5) The role of pericytes and endothelial cells in atherosclerosis.

Investigation of vascular remodeling during atherosclerosis and in the context of vascular tissue engineering. The focus is on microcirculation. In particular, molecular mechanisms in the interaction of endothelial cells and pericytes are investigated.

GROUP LEADER

Prof. Dr.

Mathias Wilhelmi

AG-Leader

Clinic for Cardiac, Thoracic, Transplantation and Vascular Surgery

GROUP LEADER

MD.

Thomas Aper

AG-Leader

Clinic for Cardiac, Thoracic, Transplantation and Vascular Surgery

GROUP LEADER

Dr. rer. nat.

Sarah Zippusch

AG-Leader

Clinic for Cardiac, Thoracic, Transplantation and Vascular Surgery

Publications

Helms F, Zippusch S, Aper T, Kalies S, Heisterkamp A, Haverich A, Böer U, Wilhelmi M. Mechanical stimulation induces vasa vasorum capillary alignment in a fibrin-based tunica adventitia. Tissue Eng Part A. 2022 May 25. doi: 10.1089/ten.TEA.2022.0042. epub ahead of print. PMID: 35611972.

Helms F, Zippusch S, Theilen J, Haverich A, Wilhelmi M, Böer U. An encapsulated fibrin-based bioartificial tissue construct with integrated macrovessels, microchannels, and capillary tubes. Biotechnol Bioeng. 2022 Apr 29. doi: 10.1002/bit.28111. epub ahead of print. PMID: 35485750.

Helms F, Haverich A, Wilhelmi M, Böer U. Establishment of a Modular Hemodynamic Simulator for Accurate In Vitro Simulation of Physiological and Pathological Pressure Waveforms in Native and Bioartificial Blood Vessels. Cardiovasc Eng Technol. 2022 Apr;13(2):291-306. doi: 10.1007/s13239-021-00577-0. epub 2021 Sep 23. PMID: 34558032; PMCID: PMC9114050.

Bobylev D, Wilhelmi M, Lau S, Klingenberg M, Mlinaric M, Petená E, Helms F, Hassel T, Haverich A, Horke A, Böer U. Pressure-compacted and spider silk-reinforced fibrin demonstrates sufficient biomechanical stability as cardiac patch in vitro. J Biomater Appl. 2022 Jan;36(6):1126-1136. doi: 10.1177/08853282211046800. epub 2021 Oct 7. PMID: 34617818.

Helms F, Haverich A, Böer U, Wilhelmi M. Transluminal compression increases mechanical stability, stiffness and endothelialization capacity of fibrin-based bioartificial blood vessels. J Mech Behav Biomed Mater. 2021 Dec;124:104835. doi: 10.1016/j.jmbbm.2021.104835. epub 2021 Sep 10. PMID: 34530301.

Zippusch S, Besecke KFW, Helms F, Klingenberg M, Lyons A, Behrens P, Haverich A, Wilhelmi M, Ehlert N, Böer U. Chemically induced hypoxia by dimethyloxalylglycine (DMOG)-loaded nanoporous silica nanoparticles supports endothelial tube formation by sustained VEGF release from adipose tissue-derived stem cells. Regen Biomater. 2021 Aug 14;8(5):rbab039. doi: 10.1093/rb/rbab039. PMID: 34408911; PMCID: PMC8363767.

Helms F, Lau S, Aper T, Zippusch S, Klingenberg M, Haverich A, Wilhelmi M, Böer U. A 3-Layered Bioartificial Blood Vessel with Physiological Wall Architecture Generated by Mechanical Stimulation.
Ann Biomed Eng. 2021 Jan 22. doi: 10.1007/s10439-021-02728-9.

Zippusch S, Helms F, Lau S, Klingenberg M, Schrimpf C, Haverich A, Wilhelmi M, Böer U.
Perfusion promotes endothelialized pore formation in high concentration fibrin gels otherwise unsuitable for tube development.
Int J Artif Organs. 2021 Feb;44(2):130-138. doi: 10.1177/0391398820936700. epub 2020 Jul 2. PMID: 32611278.

Helms F, Lau S, Klingenberg M, Aper T, Haverich A, Wilhelmi M, Böer U.
Complete Myogenic Differentiation of Adipogenic Stem Cells Requires Both Biochemical and Mechanical Stimulation.
Ann Biomed Eng. 2020 Mar;48(3):913-926. doi: 10.1007/s10439-019-02234-z. Epub 2019 Feb 27. PMID: 30815762.

Lau S, Klingenberg M, Mrugalla A, Helms F, Sedding D, Haverich A, Wilhelmi M, Böer U.
Biochemical Myogenic Differentiation of Adipogenic Stem Cells Is Donor Dependent and Requires Sound Characterization.
Tissue Eng Part A. 2019 Jul;25(13-14):936-948. doi: 10.1089/ten.TEA.2018.0172. epub 2019 Jun 14. PMID: 30648499.

Aper T, Wilhelmi M, Boer U, Lau S, Benecke N, Hilfiker A, Haverich A.
Dehydration improves biomechanical strength of bioartificial vascular graft material and allows its long-term storage.
Innov Surg Sci. 2018 Jul 23;3(3):215-224. doi: 10.1515/iss-2018-0017. eCollection 2018 Sep.PMID: 31579785.

Jeinsen N, Mägel L, Jonigk D, Klingenberg M, Haverich A, Wilhelmi M, Böer U.
Biocompatibility of Intensified Decellularized Equine Carotid Arteries in a Rat Subcutaneous Implantation Model and in a Human In Vitro Model.
Tissue Eng Part A. 2018 Feb;24(3-4):310-321. doi: 10.1089/ten.TEA.2016.0542. epub 2017 Jun 29. PMID: 28530164.

Lau S, Eicke D, Carvalho Oliveira M, Wiegmann B, Schrimpf C, Haverich A, Blasczyk R, Wilhelmi M, Figueiredo C, Böer U.
Low Immunogenic Endothelial Cells Maintain Morphological and Functional Properties Required for Vascular Tissue Engineering.
Tissue Eng Part A. 2018 Mar;24(5-6):432-447. doi: 10.1089/ten.TEA.2016.0541. epub 2017 Dec 19. PMID: 28978275.

Böer U, Buettner FFR, Schridde A, Klingenberg M, Sarikouch S, Haverich A, Wilhelmi M.
Antibody formation toward porcine tissue in patients implanted with crosslinked heart valves is directed to antigenic tissue proteins and αGal epitopes and is reduced in healthy vegetarian subjects.
Xenotransplantation. 2017 Mar;24(2). doi: 10.1111/xen.12288. epub 2017 Jan 18. PMID: 28101961.

Kolster M, Wilhelmi M, Schrimpf C, Hilfiker A, Haverich A, Aper T.
Outgrowing endothelial and smooth muscle cells for tissue engineering approaches.
J Tissue Eng. 2017 Mar 15;8:2041731417698852. doi: 10.1177/2041731417698852. eCollection 2017 Jan-Dec.PMID: 28540031.
Aper T, Wilhelmi M, Hoeffler K, Benecke N, Haverich A.
Engineering of small diameter tubular compacted fibrin matrices.
BioNanoMaterials, vol. 17, no. 1-2, 2016, pp. 13-17. https://doi.org/10.1515/bnm-2015-0029
Aper T, Wilhelmi M, Gebhardt C, Hoeffler K, Benecke N, Hilfiker A, Haverich A.
Novel method for the generation of tissue-engineered vascular grafts based on a highly compacted fibrin matrix.
Acta Biomater. 2016 Jan; 29:21-32. doi: 10.1016/j.actbio.2015.10.012. Epub 2015 Oct 21. PMID: 26472610.

Böer U, Hurtado-Aguilar LG, Klingenberg M, Lau S, Jockenhoevel S, Haverich A, Wilhelmi M.
Effect of Intensified Decellularization of Equine Carotid Arteries on Scaffold Biomechanics and Cytotoxicity.
Ann Biomed Eng. 2015 Nov;43(11):2630-41. doi: 10.1007/s10439-015-1328-1. epub 2015 Apr 29. PMID: 25921001.

Böer U, Schridde A, Anssar M, Klingenberg M, Sarikouch S, Dellmann A, Harringer W, Haverich A, Wilhelmi M.
The immune response to crosslinked tissue is reduced in decellularized xenogeneic and absent in decellularized allogeneic heart valves.
Int J Artif Organs. 2015 Apr;38(4):199-209. doi: 10.5301/ijao.5000395. epub 2015 Apr 21. PMID: 25907532.

Böer U, Spengler C, Jonigk D, Klingenberg M, Schrimpf C, Lützner S, Harder M, Kreipe HH, Haverich A, Wilhelmi M.
Coating decellularized equine carotid arteries with CCN1 improves cellular repopulation, local biocompatibility, and immune response in sheep.
Tissue Eng Part A. 2013 Aug;19(15-16):1829-42. doi: 10.1089/ten.TEA.2012.0558. epub 2013 Apr 26. PMID: 23521030.
Aper T, Teebken OE, Krüger A, Heisterkamp A, Hilfiker A, Haverich A.
Development of implantable autologous small-caliber vascular grafts from peripheral blood samples.
Zentralbl Chir. 2013 Apr;138(2):173-9. doi: 10.1055/s-0032-1315112. epub 2013 Jan 22. PMID: 23341132.
Böer U, Spengler C, Klingenberg M, Jonigk D, Harder M, Kreipe HH, Haverich A, Wilhelmi M.
Cytotoxic effects of polyhexanide on cellular repopulation and calcification of decellularized equine carotids in vitro and in vivo.
Int J Artif Organs. 2013 Mar;36(3):184-94. doi: 10.5301/IJAO.5000182. epub 2013 Feb 13. PMID: 23404640.

Böer U, Lohrenz A, Klingenberg M, Pich A, Haverich A, Wilhelmi M.
The effect of detergent-based decellularization procedures on cellular proteins and immunogenicity in equine carotid artery grafts.
Biomaterials. 2011 Dec;32(36):9730-7. doi: 10.1016/j.biomaterials.2011.09.015. Epub 2011 Sep 23. PMID: 21944468.

Aper T, Schmidt A, Duchrow M, Bruch HP.
Autologous blood vessels engineered from peripheral blood sample.
Eur J Vasc Endovasc Surg. 2007 Jan;33(1):33-9. doi: 10.1016/j.ejvs.2006.08.008. epub 2006 Oct 25. PMID: 17070080.

Keywords

Vascular prostheses, cardiac patches, decellularization, xenoimmunogenicity, fibrin-based implants, pathomechanisms of atherosclerosis, (pre)-vascularization, autologous (autologous) vascular cells, bioreactor technologies.

Contact

Sarah Zippusch

+49 511 532 1436

zippusch.sarah(at)mh-hannover.de

NIFE
H0 Room 2410
Stadtfelddamm 34
30625 Hanover

Specials

Alumni

Dr. rer. nat. Skadi Lau, PhD, dissertation "Strategies for the development of fully-autologous tissue-engineered fibrin-based vascular prostheses similar to three-layer and natural arteries."

Alena Richter, MD, PhD, dissertation "Biomimetic Modification of Stent Surfaces by Nanoparticles: The influence of nanostructured nitinol and biochemically modified alginate on viability and morphology of vascular cells."

Niklas Jeinsen, MD, PhD, dissertation "Characterization of local immune response, vascularization and remodeling after subcutaneous implantation of decellularized CCN1-coated matrices in the rat."

Lisa-Marie Pudrycki, Master's thesis "Development of fibrin patches for cardiovascular use".

Andrea Lohrenz, Bachelorthesis "Characterization of potentially immunogenic structures in decellularized equine vascular matrices by Western blot analysis".

Anna Mrugalla, Master's thesis "Differentiation of human adipogenic mesenchymal stem cells into contractile smooth muscle cells for vascular tissue engineering".

Heike Jansen, Bachelorthesis "Development of an automated protocol for the production of bioartificial vascular prostheses and the comparison with the manual process".

Stefanie Lützner, diploma thesis "Investigation of the immunogenicity of bioartificial vascular prostheses by recording the humoral and cellular immune response in the heterogeneous animal model sheep".

Andreas Brinkmann, Bachelorthesis "Development and verification of an automated method for parallel decellularization of equine vascular matrices".

Claas Spengler, MD, PhD, dissertation "Studies on cellular repopulation and cytotoxicity with CCN1-coated and polyhexanide-disinfected equine vascular grafts in ovine animal models."

Jonathan Theilen, student research project "Development of a novel flow chamber to study capillary formation in fibrin hydrogels under flow."

More additional info

Cooperations

AG Behrens, Institute for Inorganic Chemistry, Leibniz Universität Hannover

AG Kampmann, Clinic for Oral and Maxillofacial Surgery, Hanover Medical School

AG Vogt, Clinic for Plastic, Aesthetic, Hand and Reconstructive Surgery, Hannover Medical SchoolAG

Barcikowski, Institute for Technical Chemistry I, University of Duisburg-Essen

AG Jockenhövel, Institute for Applied Medical Technology, RWTH Aachen University

AG Heisterkamp, Institute for Quantum Optics, Leibniz Universität Hannover

AG Wiegmann, Clinic for Cardiac, Thoracic, Transplantation and Vascular Surgery, Hannover Medical School

AG Hoffmann, Clinic for Orthopedics, Hanover Medical School

AG Hilfiker, LEBAO, Hanover Medical School

Laser Center Hanover

Fraunhofer ITEM, Hanover

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