Tranexamic Acid—An Alternative to Aprotinin in Fibrin-Based Cardiovascular Tissue Engineering

Abstract

Recent clinical trials have led to the worldwide suspension of aprotinin, the most commonly used antifibrinolytic agent in fibrin-based tissue engineering. For future clinical applications of fibrin-based scaffolds, a suitable, alternative fibrinolysis inhibitor must be identified. The present study aimed to evaluate tranexamic acid (trans-4-aminomethyl-cyclohexane-1-carboxylic acid [t-AMCA]) as an alternative fibrinolysis inhibitor to aprotinin for cardiovascular tissue engineering applications. The effects of various concentrations of t-AMCA (30-160 microg/mL) and aprotinin on fibrin gel-lysis were spectrophotometrically quantified in vitro. Cytotoxic effects of t-AMCA and aprotinin on carotid artery-derived cells, in addition to their influence on fibrin gel mechanical strength, were examined. Further, the influence of t-AMCA versus aprotinin on three-dimensional fibrin-based constructs was analyzed using light microscopy, scanning electron microscopy, and transmission electron microscopy. The results demonstrated that neither t-AMCA (30-160 microg/mL) nor aprotinin elicited cytotoxic effects on cultured cells. Although aprotinin showed reduced fibrinolysis in the presence of plasmin compared to t-AMCA, no significant difference was obtained under standard culture conditions. Additionally, t-AMCA had no negative influence on the mechanical stability of fibrin gels, which also demonstrated excellent cell morphology, tissue development, and ultrastructure. The results from the present study demonstrate that t-AMCA may be a suitable alternative to aprotinin for controlling the in vitro degradation rate of fibrin-based tissue-engineered constructs.

Cardiovascular Tissue Engineering Based on Fibrin-Gel-Scaffolds

“…• Fibrin gel is a naturally-occurring scaffold that can be isolated as an autologous substrate from blood of the patient in question (Heselhaus, 2011); • Starting with a cell suspension in fibrinogen solution, fibrin gel scaffolds offer immediate high cell seeding efficiency and homogenous cell distribution by gelation entrapment, with a minimal loss of cells during the seeding procedure; furthermore, there is no time-consuming cell ingrowth from the scaffold surface to the deeper parts of the scaffold (Jockenhoevel et al, 2001a); • Polymerisation as well as degradation of the fibrin gel is controllable and can be adapted to tissue development through the use of the protease inhibitors, such as aprotinin and tranexamic acid (Cholewinski et al, 2009); • Local, covalent immobilisation of different growth factors is possible, while PRP gels can be developed to enhance the content and delivery of growth factors (Wirz et al, 2011); • Production of complex 3-D structures such as heart valve conduits or vascular grafts with complex side branches is possible through the use of an injection moulding technique (Flanagan et al, 2007;Jockenhoevel et al, 2001b); • Textile-reinforced fibrin-based grafts can be implanted in the arterial circulation and function for at least 6 months in vivo (Koch et al, 2010); • Fibrin-based tissue engineering can be merged with self-expanding stents to create a platform technology for cardiovascular, and other, diseases. These properties highlight the significant potential for creation of functional, autologous implantable cardiovascular prostheses in future using tissues derived from the patient.…”

“…Tranexamic acid is clinically approved and competitively inhibits the conversion of plasminogen into plasmin via reversibly binding to the lysine-binding site on plasminogen. Cholewinski et al (2009) demonstrated that tranexamic acid at a concentration of 160 mg per mL medium has a comparable inhibition effect on fibrinolysis in comparison with aprotinin. Furthermore, no negative side-effects with regard to proliferation, apoptosis, necrosis or the burst strength of the produced fibrin gel scaffolds could be demonstrated (Cholewinski et al, 2009).…”

The Effects of Constant Flow Bioreactor Cultivation and Keratinocyte Seeding Densities on Prevascularized Organotypic Skin Grafts Based on a Fibrin Scaffold

“…After three additional days, dermal and fullthickness skin grafts were exposed to air contact, by lowering culture media levels. In addition, total Ca 2 + concentration was increased to 1.2 mM for the airlift culture and all media were supplemented with 0.1% Gentamicin, 0.16 mg/mL tranexamic acid (Cyklokapron Ò ; Pfizer, Inc., New York, NY) 13 , and 0.5 mM vitamin C (Sigma-Aldrich). Culture medium was exchanged once per week with daily medium level controls and adjustments were made, if deemed necessary.…”

Hydrogels for Cardiac Tissue Engineering

“…Normally, in the fibrin gel culture medium, a chemical like aprotinin is used to inhibit fibrinolysis. However, it is possibly toxic to the cells [35]. Without aprotinin, a high degradation rate results in a rapid loss of the supporting matrix before the maturation of the delivered cells and the establishment of angiogenesis.…”