Mechanosensory Pathways in Angiocrine Mediated Tissue Regeneration - Mechanical and Chemical Signaling in Angiogenesis - page 35

Fig. 8 Injection of VEGF-A 164 , but not VEGFR1-specific ligand PlGF, accelerates the
regeneration of liver mass (a), associated with an incremental increase in VEGFR + CD34 - liver
SEC number (b)(n= 4). c Regenerative liver section of Id1 VenusYFP mouse. Id1 is selectively
upregulated by partial hepatectomy in VE-cadherin + vessels. d VEGFR2 deletion diminishes Id1
upregulation in the regenerative liver d (n = 5).; *P \ 0.05, **P \ 0.01. Scale bars, 50 lm
placental growth factor (PlGF), as the latter selectively activates VEGFR1 [ 69 ].
After partial PH, VEGF 164 , but not PlGF, accelerated the regeneration of both liver
mass and the number of VEGFR3 + CD34 - LSECs, which were sustained for at
least 28 days (Fig. 8 a, b). Therefore, after partial hepatectomy, the activation of
VEGF-A/VEGFR2, but not PlGF/VEGFR1, is crucial for priming LSECs to ini-
tiate and maintain hepatic proliferation.
5.2 Microarray Analysis
To identify the angiocrine signals that stimulate liver regeneration, we used
microarray analysis (Fig. 9 ). Among the endothelial-specific genes, the tran-
scription factor Id1 was specifically upregulated in the endothelial cells activated
by PH [ 70 ]. Using Id1 venusYFP reporter mice in which the venus YFP expression is