SYNTHETIC ENROUTES TO ENGINEER ELECTROSPUN SCAFFOLDS FOR STEM CELLS AND TISSUE REGENERATION - Micro and Nanotechnologies in Engineering Stem Cells and Tissues - page 134

Human umbilical cord blood (UCB) stem cells 98 are an alternative source of
hematopoietic precursors for allogeneic stem cell transplantation in children with
inborn errors or malignant diseases. HSCs, originating from bone marrow, are used
for the treatment of many bloodborne and other diseases, including sickle cell
anemia, thalassemia, aplastic anemia, leukemia, metabolic disorders, and certain
genetic immunodeficiencies. 99 The cord blood stem cells show a higher proliferative
capacity and expansion potential. Allogeneic stem cell transplantation is limited
because of the lack of suitable bone marrow donors and the risk of graft-versus-host
diseases. The percentage of stem cells is higher in cord blood than in the bone
marrow, and the main merits of UCB stem cells over the other stem cell sources are
(1) easy to recover, (2) no health risks for the mother or newborn, (3) immediate
disposition at the cryobank, (4) low incidence of rejection of the transplant, (5) high
cellular plasticity, (6) low possibilities of transmission of viral diseases, (7) low cost
of the procedure, and (8) easy possibilities to create cord blood banks so as to store
samples.
Transplantation protocols into adults is limited because of the low number of
progenitors in cord blood harvest and due to this, expanding HSCs ex vivo to get
sufficient number of cells for transplantation became a need. Several studies have
demonstrated 100 the application of nanofibrous scaffolds for enhancement of
cellular responses such as cell adhesion and cell phenotype maintenance. Researches
on the influence of nanotopographical cues and biochemical cues on the nanofiber
surface and their synergistic influence toward HSC adhesion, proliferation and
phenotypic maintenance are also established. The highest expansion efficiency of
CD34 cells, and colony-forming unit potential was observed in surface-

aminated electrospun nanofibrous scaffolds compared with the unmodified, surface-
hydroxylated, surface-carboxylated 101 nanofibrous scaffolds. Amino groups were
conjugated as spacers to nanofiber surfaces, and it was found 102 that the cell-
substratum interaction dictated the HSC-progenitor cell proliferation and self-
renewal in cytokine supplemented expansion. Aminated nanofiber scaffolds and
PCL-collagen nanofiber scaffolds were found to enhance the HSC-substrate adhe-
sion and proliferation of progenitor cells. This formed the basis for research on
specific cell adhesion molecules such as fibronectin in combination with the nano-
fiber substratum toward HSC adhesion and expansion ex vivo to solve various
diseases.
Unrestricted somatic stem cells (USSCs) were seeded on electrospun PES
nanofiber mats with plasma treatment and collagen grafting, and their bio-
compatibility and application in tissue engineering was investigated. Imam
et al. 103 observed the infiltration of stem cells into the collagen grafted nanofibers
after 7 days of cell culture, thus making collagen-grafted PES nanofibers an ideal
candidate to form 3D structures in tissue engineering. They further observed that the
PES-collagen nanofibers 104 have the highest capacity to support osteogenic differ-
entiation and infiltration of stem cells into the 3D nanostructure, which they
confirmed via assessment of osteogenic markers and histologic examination. Results
from their study concluded that the PES-collagen scaffolds could act as a potential
3D bone graft with capacity for bone healing and regeneration in vivo.

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