Tissue-engineered medical device

#The present invention relates to the production of a tissue-engineered medical device for use in therapeutic applications, such as tissue replacement interventions, especially for use in cardiovascular applications. The medical device comprises a hybrid structure of a biodegradable synthetic scaffold and a tissue engineered extracellular matrix grown from human or animal cells.

#Tissue-engineered constructs are useful as prostheses in the repair or replacement of damaged tissues or even organs. In cardiovascular surgery there is a large need for grafts, patches and valves to replace failing tissues due to congenital disorders or for example calcification and degeneration. Currently used materials for soft tissue repair are either non-degradable synthetic grafts or fixated tissues from allo-/xenogenic origin and therefore inherently associated with progressive dysfunctional degeneration, risk for disease transmission, and lack of regenerative capacity. These drawbacks limit their broader use in younger patient populations or require several reoperations. Non-degradable synthetic polymer constructs bear the risk of infection, calcification, or inflammation following implantation. Degradable synthetic polymers have found a wide use as tissue culture scaffolds, however, fragments of degradable polymers can cause inflammatory reactions. Alternatively, scaffolds of non-human (e.g. bovine or rat) collagen gels or meshes show limited tensile strength and entail the risk of contamination or immunogenic reactions after implant into a human patient.

#Biodegradable scaffold matrices are used to form the basis of any in vitro tissue engineering approach by acting as a temporary matrix for cell proliferation and extracellular matrix deposition until the scaffold is replaced by neo-tissue. While the engineered living substitute develops, the biocompatible scaffold should degrade ideally without leaving remnants in the body. PGA is most commonly used because it degrades at predictable time point and into (generally) biocompatible components. Besides, the high porosity of PGA meshes permits a good diffusion, neovascularization and cellular infiltration2. Unfortunately, PGA meshes are biodegraded rapidly within few weeks and can therefore not withstand mechanical forces exerted to the materials and guide the shape of the bioengineered construct over longer culturing periods2,3. As a result, hybrid polymers have been designed in order to combine the shape-memory and mechanical stability of slowly degrading polymers with the fast degrading properties of polymers, such as PGA4. For instance, combinations of PGA with polymers such as (poly-4-hydroxybutyrate) P4HB, PLA, or PGA have been explored [5,6]. Unlike PGA, which is synthetized chemically, P4HB is produced naturally by microorganisms, making it more challenging to be synthesized7. After implantation into the body, P4HB degrades mainly by bulk hydrolysis producing 4HB, a normal component of the mammalian body8. In 1998, Shinoka et al. reported surgical implantation of tissue engineered vascular grafts in lambs, in which scaffolds were constructed from autologous cells seeded onto PGA grafts9.

#Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

#FIG. 1 shows a systematic process overview of the production method according to the present invention, including various quality control steps;

#FIG. 2 shows pictures of the fabrication process of a tubular polymer scaffold for the production of a tissue-engineered medical device according to a first preferred embodiment in the form of a tissue-engineered vascular graft (TEVG), wherein in A, the forming of the mesh into a tube is shown; in B, the fusion of the overlapping edges is shown; in C, the spray coating of the tubular polymer scaffold is shown; and in D, the final tubular polymer scaffold on a mount prior to sterilization;

#In FIG. 1, the systematic process overview shows the process steps for producing a polymer scaffold and isolating cells as preparatory processes. The products of these preparatory processes, i.e. the polymer scaffold and/or the isolated cells, can individually either be prepared as part of the inventive method of production of the TEMD, as further described below, or separately can be purchased or obtained otherwise for use in the method of production of the TEMD starting with the equilibration of the polymer scaffold and the expansion of the isolated cells to prepare both for the cell seeding step.

#Isolation and Expansion of Cells:

#Human umbilical cords (n=3) were collected after full-term births with informed consent according to the cantonal ethics commission of Zurich, Switzerland [KEK-ZH-2009-0095] and processed for isolation of venous fibroblasts according to established protocols13. The umbilical cord vein was isolated surgically and small tissue pieces were cut out using a dissecting scissors. Tissue pieces were placed on a sterile petri dish and were left to adhere to the bottom for 30+/−5 min. Culture medium was gently added and changed every third or fourth day. The preferred medium composition used for the first expansion of the isolated cells is as follows: 500 ml A-DMEM (Advanced-Dulbecco's Modified Eagle Medium), 50 ml. Fetal Bovine Serum (FBS), 5 ml Glutamax (200 mM), 1.25 ml Gentamycin (10 mg/ml). Tissue pieces were removed after first cellular outgrowth after approximately 1-2 weeks of incubation under humidified incubator conditions at 5% CO2 at 37° C.