Bone marrow stem cells, especially, endothelial precursor cells (EPC), mesenchymal stem cells (MSC) or hematopoietic stem cell (HSC) are expected as reparative cells for the repair of a variety of tissue damages such as stroke and myocardial infarction, even though their role in the repair is not demonstrated. This report was investigated to find a role of Substance-p (SP) as a reparative agent in the tissue repair requiring EPC and MSC.
In order to examine EPC (EPCSP) and MSC (MSCSP) mobilized by SP, we injected SP intravenously for consecutive 2 days and saline was injected as a vehicle. At 3 post injection, peripheral blood (PB) was collected.To get mesenchymal stem cells or endothelial progenitor cells, MNCs were incubated in MSCGM or EGM-2 respectively for 10 days.
Functional characteristics of the EPCSP were proven by the capacity to form endothelial tubule network in the matrigel in vitro and in the matrigel plug assay in vivo. In contrast, MSCSP did not form a tube-like structure but formed a pellet-structure on matrigel. However, when both cells were premixed before the matrigel assay, much longer and branched tubular network was formed, in which a-SMA expressing MSCSP were decorating outside of the endothelial tube, especially enriched at the bifurcating point. MSCSP may contribute and reinforce elaborate vascular network formation in vivo by working as pericyte-like cells. Thus, the EPCSP and MSCSP were labeled with PKH green and PKH red respectively and their tubular network was examined. Well organized tubular network was formed, which was covered by PKH green labeled cells and was decorated in a punctate pattern by PKH red labeled cells. In order to investigate the role of EPCSP and MSCSP specifically in vivo, rabbit EPCSP and MSCSP were transplanted to full thickness skin wound. The vessel of EPCSP-transplanted groups was UEA-lectin+, which was not covered with a-SMA+ pericytes but EPCSP + MSCSP-transplanted groups showed, in part, a-SMA+ pericyte-encircled UEA-lectin+ vessels. This proved the specific role of MSCSP as pericytes.
From these data, we have postulated that the collaboration of MSC and EPC is essential for normal vessel structure and furthermore, accelerated wound healing as ischemia diseases, which can be stimulated through by SP injection.