Addition of soluble PDGFRβ, EGFR, and ErbB4 receptor traps leads to decreased pericyte recruitment and proliferation. GFP-pericytes were allowed to coassemble with ECs for a period of 72 hours, at which time cultures were fixed for further analysis. (A) Addition of soluble PDGFRβ, EGFR, and ErbB4 receptor traps (50 μg/mL) as individual molecules leads to approximately 60% of pericytes being associated with EC tubes and 40% being nonassociated. However, under conditions in which these soluble proteins are added in combination, only 30%-40% of pericytes are associated with EC tubes, and 60%-70% are nonassociated. Data are reported as percent pericyte association. (B) After treatment with soluble protein inhibitors, there is a dramatic increase in EC tube width in all conditions with marked disruption of pericyte recruitment. (C) Addition of these soluble protein inhibitors also leads to decreased pericyte proliferation, as quantified by assessing the total number of GFP-pericytes per high-powered field. (D) Representative images of EC-pericyte coassembly are shown in which pericytes are GFP-labeled and ECs are CD31-immunostained red. Associated pericytes are denoted by arrows; nonassociated pericytes are denoted by arrowheads. Bar equals 20 μm. n ≥ 5; P ≤ .01. *Significance from control conditions. +Significance from individual factor addition.