DYNAMIC CELL CULTURE METHODS FOR FUNCTIONALIZED BIOMATERIALS - Biologically-Responsive Hybrid Biomaterials - page 387

surface [81,82,83]. This is done through the use of a pulsatile flow system which
pumps the culture medium through the construct in conditions that resemble the
standard systolic and diastolic pressures [84]. There are many critical parameters
with such a system, including the level of pulsation [85]. It is now possible that
by combining bioresponsive materials with dynamic systems, a more complete
and functional heart valve could be constructed. Huang et al. created a
decellularized porcine valve construct which was coated with fibronectin and
seeded with cells transduced with the gene for hepatocyte growth factor (HGF)
[86]. This system included both a hybrid xenogeneic/ECM component scaffold
as well as cells programmed to express a growth factor shown to induce
proliferation and motility in endothelial cells [87]. The constructs were cultured
with the transduced marrow stromal cells in a pulse duplicator system, where the
media flow and pressure were gradually increased for up to 8 weeks [83]. High
levels of endothelial cell retention even under high flow and pressure were
demonstrated on the construct, due to the presence of HGF and fibronectin.
Although extensive cell growth was observed, little active matrix synthesis
occurred, so longer studies are necessary to evaluate the construct further. It is
clear that a bioreactor system is integral in creating a mechanically sound
engineered heart valve, but also that hybrid materials may be required to
maintain cell density and function so that ECM remodeling of a construct can
occur both in vitro and in vivo .
3.1.3. Cardiac tissue
The successful growth of heart muscle in vitro could be used to treat cases of
acute myocardial infarction by implanting the constructs to enhance the
contractile function of the left ventricle. The field has been therefore focused on
creating functional tissue constructs rather than the entire complex organ. This
requires a suitable scaffold as well as a cell source which can demonstrate
significant contractile ability as well as proliferative capabilities. Primary cardiac
myocytes are non-proliferative, so adult-derived stem cells as well as human
embryonic stem cells are also being investigated [88]. In addition, neonatal
and/or embryonic primary cardiac cells retain their contractile ability in 3D
culture. Papadaki et al. used rat neonatal cardiac myocytes on a variety of
materials in multiple culture conditions to investigate the feasibility of
engineered cardiac tissue [89]. By using a PGA mesh which had been surface-
hydrolyzed in NaOH then coated with laminin, they cultured cells in both a
stirred flask and a rotating vessel to compare culture conditions based on