151
the myocardial structure and can potentially aid in signal transduction between cardiomyocytes. They can be found in the wound healing environment post injury and
provide paracrine signaling [88, 91]. Cardiac fibroblasts have perivascular potential
and serve as a suitable source of cardiomyocyte co-culture. Twardowski et al.
focused on the role of vascular development with cardiac fibroblasts coupled with
endothelial cells. The study specifically looked at using rat aortic endothelial cells
(rAEC) coupled with neonatal cardiac fibroblasts (nCF) in fibrin hydrogels. As a
positive control for pericyte-like cells, rat bone marrow-derived mesenchymal stem
cells (BM-MSCs) were used to compare vessel assembly. Seeding support cells and
endothelial cells at 1:1 ratio, this study demonstrated that nCF-rAEC developed
longer sprouting networks compared to when endothelial cells were co-cultured
with BM-MSCs [120].
As indicated above, BM-MSCs can potentially serve as pericyte-like cells/mural
cells and stabilize vascular structures. While these cells have many potential benefits, there is high morbidity associated with their extraction, and cell yields are relatively low. In contrast, adipose-derived stem/stromal cells (ASCs) can be procured
in high numbers from a minimally invasive liposuction procedure. In addition to
acting as mural cells, ASCs secrete an abundance of proangiogenic growth factors.
ASCs are also capable of modulating inflammatory responses, reducing apoptosis,
preventing fibrosis, and stimulating endogenous repair and neovascularization and
can withstand temporary ischemia [49, 90, 124]. ASCs have also been shown to
electrically couple with neonatal rat cardiomyocytes by forming gap junctions,
which would indicate that these cells have the potential to behave as cardiac fibroblasts [18]. There are no studies to date that demonstrate the potential of hASCs to
behave as both cardiac fibroblasts and perivascular cells, within the same cultures.
Merfeld-Clauss et al. have monitored vessel assembly of hASCs coupled with
cord-blood endothelial colony-forming cells (cbECFCs). In the monolayer culture,
there was dense vessel network assembly which appeared to regress over time.
When cbECFCs were cultured with coronary artery smooth muscle cells (SMCs),
aortic SMCs, normal human dermal fibroblasts, or human ASCs, the hASCs had
statistically higher tube lengths [76]. In a 2015 report, this group reported that
Activin A expression directed hASC differentiation down the smooth muscle lineage, when in direct contact with cbECFCs [77]. Hutton et al. found that heterogeneous hASCs contained a small amount of endothelial cells with the ability to
expand and form vessel networks. These cells, cultured in high-density (20,000 cells/
cm
2
) monolayer, resulted in the development of CD31+ vessel structures [47]. This
study was followed up with 3D vascular development in fibrin hydrogels [48].
Freiman et al. developed vessel networks with co-cultures of hASCs or normal
human dermal fibroblasts and human adipose-derived microvascular endothelial
cells (HAMECs) or HUVECs. It was found that the co-culture of hASCs and
HAMECs resulted in the greatest increase in vessel length by day 7 and maintained
the vessel length up until day 14 [34].
6 Strategies for Tissue Engineering Vascularized Cardiac Patches to Treat Myocardial…
the myocardial structure and can potentially aid in signal transduction between cardiomyocytes. They can be found in the wound healing environment post injury and
provide paracrine signaling [88, 91]. Cardiac fibroblasts have perivascular potential
and serve as a suitable source of cardiomyocyte co-culture. Twardowski et al.
focused on the role of vascular development with cardiac fibroblasts coupled with
endothelial cells. The study specifically looked at using rat aortic endothelial cells
(rAEC) coupled with neonatal cardiac fibroblasts (nCF) in fibrin hydrogels. As a
positive control for pericyte-like cells, rat bone marrow-derived mesenchymal stem
cells (BM-MSCs) were used to compare vessel assembly. Seeding support cells and
endothelial cells at 1:1 ratio, this study demonstrated that nCF-rAEC developed
longer sprouting networks compared to when endothelial cells were co-cultured
with BM-MSCs [120].
As indicated above, BM-MSCs can potentially serve as pericyte-like cells/mural
cells and stabilize vascular structures. While these cells have many potential benefits, there is high morbidity associated with their extraction, and cell yields are relatively low. In contrast, adipose-derived stem/stromal cells (ASCs) can be procured
in high numbers from a minimally invasive liposuction procedure. In addition to
acting as mural cells, ASCs secrete an abundance of proangiogenic growth factors.
ASCs are also capable of modulating inflammatory responses, reducing apoptosis,
preventing fibrosis, and stimulating endogenous repair and neovascularization and
can withstand temporary ischemia [49, 90, 124]. ASCs have also been shown to
electrically couple with neonatal rat cardiomyocytes by forming gap junctions,
which would indicate that these cells have the potential to behave as cardiac fibroblasts [18]. There are no studies to date that demonstrate the potential of hASCs to
behave as both cardiac fibroblasts and perivascular cells, within the same cultures.
Merfeld-Clauss et al. have monitored vessel assembly of hASCs coupled with
cord-blood endothelial colony-forming cells (cbECFCs). In the monolayer culture,
there was dense vessel network assembly which appeared to regress over time.
When cbECFCs were cultured with coronary artery smooth muscle cells (SMCs),
aortic SMCs, normal human dermal fibroblasts, or human ASCs, the hASCs had
statistically higher tube lengths [76]. In a 2015 report, this group reported that
Activin A expression directed hASC differentiation down the smooth muscle lineage, when in direct contact with cbECFCs [77]. Hutton et al. found that heterogeneous hASCs contained a small amount of endothelial cells with the ability to
expand and form vessel networks. These cells, cultured in high-density (20,000 cells/
cm
2
) monolayer, resulted in the development of CD31+ vessel structures [47]. This
study was followed up with 3D vascular development in fibrin hydrogels [48].
Freiman et al. developed vessel networks with co-cultures of hASCs or normal
human dermal fibroblasts and human adipose-derived microvascular endothelial
cells (HAMECs) or HUVECs. It was found that the co-culture of hASCs and
HAMECs resulted in the greatest increase in vessel length by day 7 and maintained
the vessel length up until day 14 [34].
6 Strategies for Tissue Engineering Vascularized Cardiac Patches to Treat Myocardial…