Sr. Mallery et al., MODULATION OF HUMAN MICROVASCULAR ENDOTHELIAL-CELL BIOENERGETIC STATUS AND GLUTATHIONE LEVELS DURING PROLIFERATIVE AND DIFFERENTIATED GROWTH, Journal of cellular biochemistry, 53(4), 1993, pp. 360-372
During angiogenesis, formerly differentiated human microvascular endot
helial cells (HMECs) return to a proliferative growth state. Many fund
amental questions regarding HMEC function, such as how HMECS adapt to
changes in bioenergetic requirements upon return to proliferative grow
th, remained unanswered. In this study, we evaluated whether modificat
ions in HMEC bioenergetic profiles and glutathione (GSH) levels accomp
anied the cellular transition between differentiated and proliferative
growth. To provide insight into the continuum of cellular adaptations
that occur during this transition, we used a method recently develope
d in our laboratory that induces a state of morphological and function
al predifferentiation in HMECs. Cellular morphology, in conjunction wi
th flow cytometric DNA analyses and HMEC functional assays (the direct
ed migration and intercellular association involved in microtubule for
mation) were employed to validate the HMEC culture state of growth. An
alysis of the HPLC nucleotide profiles disclosed several findings comm
on to all culture growth states. These uniform findings, e.g., cellula
r energy charges > 0.90, and highly reduced redox states, revealed tha
t cultured HMECs maintain high rates of oxidative metabolism. However,
there were also significant, culture growth state related differences
in the nucleotide profiles. Proliferative HMECs were shown to possess
significantly higher (relative to both large vessel endothelial cells
, and differentiated HMECs) levels of GSH and specific nucleotides whi
ch were related with a return to the active cell cycle-ATP, GTP, UTP,
and CTP, and NADPH. Further, the nucleotide profiles and GSH levels of
the predifferentiated HMECs were determined to be intermediate betwee
n-levels obtained for the proliferative and differentiated HMECs. The
results of this study demonstrate that the capacity to modulate their
cellular bioenergetic status during growth state transitions is one of
the adaptations that enable HMECs to retain a growth state reciprocit
y. In addition, our findings also show that HMECs, especially during t
he proliferative growth state, are biochemically distinct from endothe
lial cells harvested from large vessels, and therefore suggest that HM
ECs are the cells of choice to employ when studying diseases that affe
ct the human microvasculature. (C) 1993 Wiley-Liss, Inc.