RESUMEN
Herein, we report that VEGF-functionalized dextran (dexOx-VEGF) is comparatively superior to free VEGF in prolonging the phosphorylation of VEGF receptor 2 (VEGFR-2). Both dexOx-VEGF and free VEGF activate VEGFR-2, and the complexes are internalized into early endosomes (EEA1(+) vesicles) and then transported to lysosomes (Rab7(+) vesicles). However, after cell activation, dexOx-VEGF is preferentially colocalized in early endosomes where VEGF signaling is still active while free VEGF is preferentially transported to late endosomes or lysosomes. We further show that dexOx-VEGF after phosphorylation of VEGF receptor 2 induces an increase of intracellular Ca(2+) and activates VEGF downstream effectors such as Akt and extracellular signal-regulated kinase (ERK1/2) proteins. Under specific conditions, the activation level is different from the one observed for free VEGF, thus suggesting mechanistic differences, which is illustrated by cell migration and cord-like formation studies. DexOx-VEGF can be cross-linked with adipic acid dihydrazide to form a degradable gel, which in turn can be incorporated in a fibrin gel containing endothelial cells (ECs) to modulate their activity. We envision that these constructs might be beneficial to extend the pro-angiogenic activity of VEGF in ischemic tissues and to modulate the biological activity of vascular cells.
Asunto(s)
Dextranos/química , Endosomas/efectos de los fármacos , Células Endoteliales de la Vena Umbilical Humana/efectos de los fármacos , Lisosomas/efectos de los fármacos , Factor A de Crecimiento Endotelial Vascular/química , Calcio/metabolismo , Movimiento Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Citoplasma/efectos de los fármacos , Citoplasma/metabolismo , Endocitosis/efectos de los fármacos , Endosomas/metabolismo , Expresión Génica/efectos de los fármacos , Células Endoteliales de la Vena Umbilical Humana/citología , Células Endoteliales de la Vena Umbilical Humana/metabolismo , Humanos , Hidrogeles , Lisosomas/metabolismo , Proteína Quinasa 1 Activada por Mitógenos/genética , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/genética , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Fosforilación/efectos de los fármacos , Isoformas de Proteínas/química , Isoformas de Proteínas/metabolismo , Isoformas de Proteínas/farmacología , Proteínas Proto-Oncogénicas c-akt/genética , Proteínas Proto-Oncogénicas c-akt/metabolismo , Transducción de Señal/efectos de los fármacos , Factor A de Crecimiento Endotelial Vascular/metabolismo , Factor A de Crecimiento Endotelial Vascular/farmacología , Receptor 2 de Factores de Crecimiento Endotelial Vascular/química , Receptor 2 de Factores de Crecimiento Endotelial Vascular/metabolismoRESUMEN
In this study, we developed a methodology to improve the survival, vascular differentiation and regenerative potential of umbilical cord blood (UCB)-derived hematopoietic stem cells (CD34(+) cells), by co-culturing the stem cells in a 3D fibrin gel with CD34(+)-derived endothelial cells (ECs). ECs differentiated from CD34(+) cells appear to have superior angiogenic properties to fully differentiated ECs, such as human umbilical vein endothelial cells (HUVECs). Our results indicate that the pro-survival effect of CD34(+)-derived ECs on CD34(+) cells is mediated, at least in part, by bioactive factors released from ECs. This effect likely involves the secretion of novel cytokines, including interleukin-17 (IL-17) and interleukin-10 (IL-10), and the activation of the ERK 1/2 pathway in CD34(+) cells. We also show that the endothelial differentiation of CD34(+) cells in co-culture with CD34(+)-derived ECs is mediated by a combination of soluble and insoluble factors. The regenerative potential of this co-culture system was demonstrated in a chronic wound diabetic animal model. The co-transplantation of CD34(+) cells with CD34(+)-derived ECs improved the wound healing relatively to controls, by decreasing the inflammatory reaction and increasing the neovascularization of the wound.