Endothelial Progenitor Cells—Potential New Avenues to Improve Neoangiogenesis and Reendothelialization - International Review of Cell and Molecular Biology - page 60

volumes of acute lesion, final lesion, and lesion growth ( Bogoslovsky et al.,
2010 ). Based on these findings, an animal study proved that the transplantation
of EPC in mice improved the long-term outcome after ischemic stroke ( Fan
et al., 2010 ). Still, EPCs from patients with ischemic stroke show functional
impairments and differences in protein expressions ( Brea et al., 2011 ).
Whether this is related to known risk factors such as diabetes, hypertension,
etc., or if this is a postischemic reaction on EPC remains unclear.
3.2.3 Trauma
From several studies, we know that EPC are secreted in situations related to
tissue trauma. Common to all traumas are the disruption of vasculature and a
posttraumatic healing process involving angiogenesis. Therefore, the associ-
ation of EPC in different trauma situations has been studied.
3.2.3.1 Bone trauma
A bone fracture is a painful and traumatic condition, which also leads to
extensive regenerative processes. One part of these processes is the mobili-
zation of EPC fromBM to PB. The recruitment of mobilized EPC into frac-
ture sites augments neovascularization during the process of bone healing
( Matsumoto et al., 2008 ). This can also be documented during distraction
osteogenesis in human limb-lengthening patients ( Lee et al., 2010 ). Concur-
rent to EPC-increases during this phase, the plasma levels of EPC-related
cytokines, such as VEGF and SDF-1, can also be noticed ( Lee et al.,
2010 ). The augmentation of EPC during the bone-healing phase is therefore
a rational conclusion.
In a study by Li et al. (2011) , local EPC therapy significantly enhanced
fracture healing in a segmental defect model in a rat femur that resulted in
superior radiographic bone formation and healing when compared with con-
trols. This was further backed by a study where the coimplantation of EPC
together with MSC increased neovascularization around a bone-regenerating
area compared to MSC only. The bone area was greater in the MSC þ EPC
group, which also resulted in greater bone thickness ( Usami et al., 2009 ).
Overall, EPC may play an essential role in fracture healing by promoting a
favorable environment through neovascularization in damaged skeletal tissue.
3.2.3.2 Skin trauma
One of the most severe injuries to the skin is burn trauma. Several studies
have shown that burn trauma induces the recruitment of EPC into the
PB ( Foresta et al., 2011; Fox et al., 2008; Groger et al., 2010; Piatkowski