Comparative Motility of human Umbilical Vein Endothelial Cells (hUVEC) Established at Physiologic vs. Atmospheric Oxygen Tension
Authors: Cheu Jessica , Smith Anna Gray , Presnell Sharon Collins 
Published: April 2020

INTRODUCTION

Angiogenesis that occurs during development, wound healing, and tissue regeneration involves the active migration of endothelial cells in response to chemotactic, haptotactic, and mechanotactic stimuli. Oxygen tension at the site of angiogenesis may also modulate the efficiency of cell migration, by affecting secretion of angiogenic factors or production of matrix‐degrading enzymes such as matrix metalloproteases (MMPs). While the oxygen tension within the body varies from <1% in cartilage to around 13% in arteries, there are no tissues in the body (with the exception of an active, open wound bed) where cells are exposed to atmospheric levels of oxygen (i.e., 21%). We hypothesized that human umbilical vein endothelial cells (hUVEC) that were established at physiologic oxygen tension (5%) would exhibit differences in migration behavior compared to hUVEC established at 21% O2.

METHODS

Both hUVEC and well‐characterized human placental stem cells (hPSC) were established from the same donor placenta and umbilical cord using standard isolation techniques. Cultures were maintained at either 5% (hUVEC‐LO) or 21% (hUVEC‐HO) O2 in humidified incubators equipped with regulated CO2 and N2 gases. Cell motility was evaluated using Transwell™ migration assays (Corning Fluoroblok 356488) in basal conditions at both 5% and 21% O2 and in response to hPSC in the lower chamber. Crossover experiments were conducted wherein hUVEC‐LO and hUVEC‐HO were assessed for migration at both 5% and 21% O2 in the presence of hPSC.
Assay plates were analyzed from both top (cell disappearance) and bottom (cell appearance) and representative wells were visualized and photographed to confirm plate reader observations.

RESULTS

Both hUVEC‐LO and hUVEC‐HO migration at 5% and 21% O
2
occurred rapidly and reached a plateau within a 60‐minute time frame. The basal rate of hUVEC migration was higher in hUVEC‐LO compared to hUVEC‐HO, regardless of whether the migration assay was conducted at 5% or 21% O2. At 21% O2, hPSC seeded at 31,250 cells/cm2 in the lower chamber inhibited hUVEC migration in both hUVEC‐LO (p = 0.035) and hUVEC‐HO (p=0.039). At 5% O2, the effects of hPSC were not statistically significant.

CONCLUSIONS

hUVEC‐LO have a higher basal rate of migration compared to hUVEC‐HO established from the same donor tissue, and placing the hUVEC‐HO in the lower 5% O2 environment did not render them equivalent to the hUVEC‐LO. These data suggest that the inherent difference between hUVEC‐LO and hUVEC‐HO with respect to migration is determined primarily by the initial conditions of primary culture and expansion. The presence of hPSC, which have a phenotype consistent with pericyte‐like cells, inhibited migration in the 21% O2 assay environment but not in the 5% O2 environment, suggesting a significant difference in either the milieu created by the hPSC at 5% vs. 21% O2 and/or a mechanistic switch in the chemotactic response of the hUVEC at 21% vs. 5% O2. Isolating and maintaining hUVEC at physiologic O2 tension may enhance migration proficiency and positively impact early events in angiogenesis.

Support or Funding Information

This work supported by the Amnion Foundation.