Endothelial Cells and Angiogenesis
Endothelial cells line the blood vessels of the circulatory and lymphatic systems and play a major role in regulating vascular and lymphatic homeostasis. Vascular endothelial cells respond to inflammation by recruiting immune cells and assist in the formation of new blood vessels from existing blood vessels in a process called angiogenesis. Upon the receipt of pro-angiogenic signals, endothelial cells begin to proliferate and migrate, forming tube-like structures that will eventually become new blood vessels.
Importantly, endothelial cell dysfunction is implicated in a number of cardiovascular diseases, such as atherosclerosis, coronary artery disease, and high blood pressure (hypertension).
Interested in Lifeline® endothelial cell systems? Check out our catalog, which includes the following:
- Pulmonary artery endothelial cells
- Aortic endothelial cells
- Coronary artery endothelial cells
- Lung microvascular endothelial cells
- Dermal microvascular endothelial cells (adult and neonatal)
- Cardiac microvascular endothelial cells
- Iliac artery endothelial cells
- Umbilical vein endothelial cells (primary and 10-donor pool)
Lifeline Endothelial Cells in Periodontitis and Angiogenesis Research
Periodontitis is an oral disease characterized by damage to the gum tissue and associated loss of alveolar bone (the bone that holds tooth sockets). Additionally, the subgingival capillary network may become distorted as a result of a remodeling process thought to be due to endothelial cell exposure to inflammatory signals and bacterial toxins.
In a study from this year in the Journal of Oral Microbiology, Reyes and colleagues set out to determine how infection with Porphyromonas gingivalis (a common oral bacterial pathogen) affects the microvascular endothelium in the oral cavity.
The authors first examined the effects of P. gingivalis using a rat model. Following oral infection over 12 weeks, rats infected with P. gingivalis displayed chronic inflammation and disruption of microvascular structure, characterized by increased vessel density and lumen diameter.
Next, the authors looked at P. gingivalis infection in vitro using Lifeline human dermal microvascular endothelial cells (HD-MVECs) cultured in VascuLife® EnGS-MV medium. By 2.5 hours after inoculation, bacteria could be isolated from HD-MVEC lysates; by 6 hours, an increased number of bacteria were isolated, but this number was reduced by 24 hours. Viable P. gingivalis could also be isolated from cell culture supernatants 6 and 24 hours after inoculation.
To define how P. gingivalis enters human microvascular endothelial cells, the authors next evaluated the colocalization of P. gingivalis with different internal trafficking components inside MD-HVECs. Their results demonstrated that most of the internalized P. gingivalis colocalized with vesicles positive for intracellular adhesion molecule 1 (ICAM-1).
Finally, the authors assessed whether P. gingivalis infection impacted the angiogenic capability of HD-MVECs. Using an endothelial branching assay, where the ability of endothelial cells to grow and form branching networks on Matrigel is measured, the authors found that compared with uninfected control cells, P. gingivalis-infected HD-MVECs did not form branching networks.
Together, the results of this study demonstrate that P. gingivalis enters MD-HVECs in an ICAM-1-dependent manner and disrupts endothelial cell function, which may contribute to the pathogenesis of P. gingivalis infection.
Cell surface proteins are important players in angiogenesis. In particular, the C-terminal fragment of perlecan—a heparan sulfate proteoglycan—called endorepellin, has anti-angiogenic properties. In a study this year, published in the Journal of Biological Chemistry, Kapoor and co-authors studied the role of endorepellin in cellular stress signaling.
First, the authors tested the ability of endorepellin to induce growth arrest and expression of DNA damage-inducible protein (GADD45a), which is increased following DNA damage or cellular stress. Using Lifeline human umbilical cord endothelial cells (HUVECs), they found that GADD45a levels increased following endorepellin treatment; this increase was associated with increased activating transcription factor 4 (ATF4) levels (an upstream activator of GADD45a) and increased phosphorylation of PKR-like ER kinase (PERK; an upstream activator of ATF4).
Using microscopy, the authors next confirmed that endorepellin stimulated nuclear translocation of GADD45a and ATF4 in Lifeline HUVECs. Using RNAi, they also demonstrated that endorepellin stimulation of stress signaling was dependent on PERK and eukaryotic translation initiation factor 2A (eIF2a).
Finally, to show that the endorepellin-activated stress pathway inhibits angiogenesis, the group used an ex vivo model system, whereby aortic rings from mice were cultured in 3D Type I fibrillar collagen. They found that endorepellin treatment of aortic rings increased phosphorylation of PERK and expression of GADD45a. Using a PERK inhibitor, they showed that treatment with endorepellin disrupted aortic ring sprouting, which was blocked following addition of the PERK inhibitor.
Together, the results of this study demonstrate that endorepellin has anti-angiogenic activity that depends on activation of the PERK-GADD45a stress signaling axis.
How are you using Lifeline cell systems in your research? Let us know and your published study could be featured next time!