We report the use of telomerase-immortalized human microvascular endothelial
cells
in the formation of functional capillary blood vessels in vivo. Previously we showed
the superior in vitro survival of human telomerase reverse transcriptase (hTERT)-transduced
human endothelial cells. Here we show that retroviral-mediated transduction of
hTERT in human dermal microvascular endothelial cells (HDMEC) results in cell lines
that form microvascular structures when subcutaneously implanted in severe combined
immunodeficiency (SCID) mice. The human origin of xenografted microvaculature was
confirmed both by basement membrane immunoreactivity with anti-human type IV collagen
staining and visualization of fluorescent vessels containing HDMEC that were co-transduced
with hTERT and green fluorescent protein (eGFP). The lack of human vascular structures
after implantation of HT1080 fibrosarcoma cells, 293 human embryonic kidney cells
or human skin fibroblasts demonstrated the specificity of HDMEC at forming capillaries.
Intravascular red fluorescent microspheres injected into the host circulation were
found within green "telomerized" microvessels indicating functional murine-human
vessel anastamoses. Whereas primary HDMEC-derived vessel density decreased steadily
with time, telomerized HDMEC maintained durable vessels 6 weeks after xenografting.
Modulation of implant vessel density by exposure to different angiogenic and angiostatic
factors demonstrated the utility of this system for the study of human microvascular
remodeling in vivo.
