Arteries and veins are blood vessels that transport gases and nutrients in and out of the body by circulating blood across the circulation. Each type of blood vessel has a specific structure and set of features that enable the blood vessels to function at an optimal level.
For example, arteries, which are the vessels responsible for carrying oxygenated blood from the heart to the rest of the body are generally thicker and more elastic than their counterpart, veins. Veins carry the deoxygenated blood from the body back to the heart and are generally thinner than arteries.
It is important to note that the thickness or thinness of the blood vessel refers to the wall size and not the diameter of the vessel.
The blood vessels become less elastic and can be calcified over time. This is referred to as an age-related change, something everyone goes through. The entire body undergoes these types of changes as one gets older. Most of the changes are associated with the general weakness of body physiology. Over time, these changes, after being affected by comorbidities can be severely detrimental to an individual’s health.
Previous studies on aging and age-related effects on blood vessels
As people age, the blood vessels in the body become weaker and lose their elasticity. This age-related weakness presents in the form of increased permeability across the blood vessels. Furthermore, the loss of elasticity results in rigid and hardened vessels. All of this can result in serious consequences to one’s health, thereby, making blood vessels an important topic of research. However, this research topic comes riddled with limitations as the study of blood vessels requires a sample that can only be obtained in an invasive manner. This is not a suitable method for long-term research to study blood vessels and the effect of age on them. Previous studies on blood vessels have been performed using pluripotent stem cells which is both an invasive and a time-consuming methodology for large-scale research.
Moreover, the use of stem cells by researchers was responsible for another significant limitation in the research of blood vessels. Stem cells are the undifferentiated cells in the embryonic stage that can differentiate into any other type of cell. These are the cells that all human cells start off as. However, differentiating them into cells of blood vessels to study them further didn’t provide the results that scientists had hoped for.
Martin Hetzer, Salk’s vice president and chief science officer is the head of the new research team in which he and his team claim to have found a solution to this problem. However, in 2015, Hetzer was in the team that initially used stem cells to form cells of the blood vessels. The major limitation of this study was that the blood vessel formed had no age-markers and was brand new and therefore could not be used for the purpose of studying the effects of aging on blood vessels.
Effects of age on blood vessels finally understood
A recent study published in the eLife Journal in September 2020, performed by a team of scientists from Salk headed by Hetzer found that using fibroblasts may be more useful than pluripotent stem cells. Fibroblasts, a type of cells in the connective tissue, were derived from skin cells and used in this study to form induced vascular endothelial cells (iVECs) and induced smooth muscle cells (iSMCs)
Method of the study
For this study, researchers used skin cells from three groups of subjects; young subjects between the ages of 19 and 30 years, older subjects between the ages of 62 and 87 years, and patients suffering from Hutchinson-Gilford progeria syndrome (HGPS), an accelerated aging disorder.
Three samples from young subjects, three from older subjects, and 8 from patients affected by Hutchinson-Gilford Progeria Syndrome were taken and stimulated to develop into iVECs and iSMCs.
Results of the study
Hetzer and his team found that the iVECs and iSMCs had all the age-markers and also showed different genetic expressions dependent on the age of the participant. This aided the researchers in finding genes and proteins associated with aging and understand their age-related effects on blood vessels.
One such protein, namely BMP4, was found in higher amounts in the samples from older individuals and the iSMCs from the HGPS patients. Researchers assumed that this protein might be the reason for the accelerated aging seen in HGPS.
To test their hypothesis, they used antibodies against BMP4 in volunteers with vascular disease. Hetzer and the team found that blocking BMP4 in these volunteers resulted in lesser vascular leaking, a feature of vascular disease. This finding is being recommended by the researchers as the new target for the treatment of HGPS or progeria.
Hetzer and his team have decided to continue working to isolate the genes associated with aging in order to better understand their underlying mechanism, especially at the molecular level.