HHV-8 induced in vitro neoangiogenesis and MCP-1 production in HMECs but not in HMEC-AS. The ability of endothelial cells to form capillary-like structures within Matrigel was evaluated. Uninfected and HHV-8-infected HMECs and HMEC-AS (5 × 10⁴) harvested 3 days after infection were seeded on growth factor–reduced Matrigel in RPMI plus 1% FCS, and the extent of capillary-like structure formation was observed after 6 and 24 hours. (A-D) Representative micrographs showing the network of capillary-like structures formed by HMECs (A) and HMEC-AS (B) infected with HHV-8, by HMECs coincubated with blocking MCP-1 antibody (C), and uninfected HMECs (D) after 24 hours of incubation. (E) Morphometric evaluation of ring-like structures formed within Matrigel (gray columns, uninfected HMEC; black columns, infected HMEC; white columns, infected HMEC-AS). Data are mean plus or minus SD of 3 independent experiments performed in triplicate detected by Nikon Eclipse TE 200 inverted microscope (objectives, 10×/0.25; Tokyo, Japan), analyzed by the Micro-image system (Casti Imaging), and expressed as arbitrary units by the computer analysis system at ×100 magnifications. Analysis of variance with Newman-Keuls multiple comparison test was performed (*P < .05, infected HMECs vs uninfected HMEC; #P < .05, infected HMEC-AS vs infected HMECs). (F) HMECs or HMEC-AS were infected with HHV-8. At the indicated productively infected times, culture supernatant was analyzed for the release of the MCP-1 by standard quantitative ELISA assays. Levels of chemokines are total pg/mL. Columns represent the same variables as listed for panel E. Bars represent the mean plus or minus SD of triplicate samples. Control is represented by supernatant of uninfected HMECs.