Audience: High School Students
Matrix-Bound Nanovesicles, their presence depicted by the green stain in the perivascular stem cells*, were discovered in the extracellular matrix for the first time in 2016. DAPI was used to stain the nucleus of the cell, as visible by the blue stain. F-actin staining was used to stain the F-actin, a major component of the cell’s cytoskeleton, visible by the orange stain. Image from article "Matrix-Bound Nanovesicles: The Effects of Isolation Method upon Yield, Purity, and Function".
*Present in the area around blood vessels, perivascular stem cells differentiate into various specialized cell types.
2016, a year where promising stories began and other stories were fulfilled. While many individuals were out cheering in the Rio Olympics or watching Zootopia, scientists at the Stephen Badylak Lab at the McGowan Institution for Regenerative Medicine (University of Pittsburgh) were hard at work. Led by doctors Luai Huleihel and George S. Hussey, the Badylak Lab team identified a distinct “character” in the extracellular matrix of cells – matrix-bound nanovesicles.
The extracellular matrix (ECM) is a huge network of various proteins, polysaccharides, and other molecules forming the tissues and the organs in the body. The ECM gives the cell support and structure. It is crucial in order for cells to “attach to and communicate with nearby cells.” [4]. Additionally, it largely contributes to various cell functions, including cell movement and cell growth. Not limited to only the extracellular matrix exists vesicles, small sacs filled with liquid that are surrounded by a membrane. They have numerous functions, such as moving proteins from one part of the cell to another, recycling within the cell, and moving particles out of cells in a process called exocytosis. Extracellular vesicles (EVs) are vesicles that float around outside the cell and play a vital role in intercellular communication because they are able to transfer RNA, enzymes, proteins, and lipids. In the past, there were very limited reports on extracellular vesicles within the ECM of connective tissue, mainly found just in mineralized tissues such as bone. However, this changed in 2016 when vesicles embedded within the ECM were identified and termed matrix-bound nanovesicles (MBVs) in other tissues. MBVs are a unique subpopulation of EVs not only because they do not move out of the ECM, but also because they have distinct miRNA and lipid profiles compared to other extracellular vesicles [8].
A study was performed to see what combination of solubilization and isolation methods resulted in the highest yield, purity, and biologic activity of MBVs. Urinary bladder-derived ECM was solubilized in four ways and four isolation methods were used. It was determined that the most effective method was the combination of collagenase or liberase for ECM solubilization followed by size exclusion chromatography for isolation. MBVs are bound to collagen – a structural protein found in the ECM of various connective tissues. Collagenase is an enzyme that breaks down collagen. Liberase includes various types of collagenases. Size exclusion chromatography (SEC) is a way to separate molecules by their size in numerous fractions by filtering them through a gel. The highest concentration of MBVs were found in fractions 3, 4, and 5.
But what is the point of doing all this? What is the role of MBVs? Most importantly, what do they hold for the future? There are so many questions, but since MBVs were identified only very recently, little is known about them. Scientists are still trying to figure out the precise role(s) of MBVs within the ECM, and specifically their mechanisms of interactions with the cells. However, despite not being too far into the years of MBV research, studies have shown that MBVs have regenerative properties.
The first paper published following the identification of MBVs revealed that MBVs have the capability to influence macrophage polarization, which is when macrophages (a type of white blood cell that has the role to kill microorganisms, remove dead cells, activate other immune system cells, and promote tissue repair) “produce distinct functional phenotypes as a reaction to specific microenvironmental stimuli and signals” [9]. MBVs influence macrophage polarization particularly toward the M2 macrophage phenotype, which is the anti-inflammatory – reduction of inflammation and/or swelling – phenotype of macrophages. M2 macrophages help in the repair and regeneration of tissues by providing support to the rebuilding of the tissue and reducing/resolving inflammation. Another study showed that IL-33, a type of cytokine (small proteins crucial in controlling the growth and activity of other blood and cells) found within the MBV supported skeletal muscle (an organ that controls movement and posture) regeneration. IL-33 did this by having local macrophages activate toward a “pro-remodeling phenotype,” which is referring to M2 macrophages. It was also seen that MBVs could possibly play a role in tissue development, wound healing, and homeostasis. Additionally, it is speculated that the contents of the MBVs may change when the ECM is altered in various diseases like fibrosis, so MBVs could potentially be used to help predict or monitor these conditions [11].
Matrix-bound nanovesicles may be a young identification, but they hold so much potential in medicine and bioengineering. Their unique cargo and location make scientists question their main function in the cell and, when isolated, what therapeutics it can contribute to.
Incase you are interested in reading more about matrix-bound nanovesicles, here are some great articles that go in depth of various studies done to better understand MBVs:
Special Thanks
This past summer, I interned at the Badylak Lab at the University of Pittsburgh for eight weeks. I’d like to thank Dr. Badylak, Dr. Hussey, and my amazing mentor, Dr. Catalina Pineda Molina for this once-in-a-lifetime opportunity. This experience has taught me many life skills and allowed me to gain an incredible wealth of knowledge both in and out of the lab. I worked with a vast amount of equipment and a variety of cells, ranging from learning how to use a micropipette to eventually myself isolating MBVs from a pig’s urinary bladder. I know this lab will continue to make stellar breakthroughs in research and medicine.
Bibliography:
[1] Collagenase ointment. (n.d.). Cleveland Clinic. Retrieved July 29, 2024, from https://my.clevelandclinic.org/health/drugs/18678-collagenase-ointment
[2] Collagen: What It Is, Types, Function & Benefits. (n.d.). Cleveland Clinic. Retrieved July 29, 2024, from https://my.clevelandclinic.org/health/articles/23089-collagen
[3] Cytokines and Their Side Effects. (2019, December 27). American Cancer Society. Retrieved July 29, 2024, from https://www.cancer.org/cancer/managing-cancer/treatment-types/immunotherapy/cytokines.html
[4] Definition of extracellular matrix - NCI Dictionary of Cancer Terms - NCI. (n.d.). National Cancer Institute. Retrieved July 29, 2024, from https://www.cancer.gov/publications/dictionaries/cancer-terms/def/extracellular-matrix
[5] Definition of macrophage - NCI Dictionary of Cancer Terms - NCI. (n.d.). National Cancer Institute. Retrieved July 29, 2024, from https://www.cancer.gov/publications/dictionaries/cancer-terms/def/macrophage
[6] Definition of vesicle - NCI Dictionary of Cancer Terms - NCI. (n.d.). National Cancer Institute. Retrieved July 29, 2024, from https://www.cancer.gov/publications/dictionaries/cancer-terms/def/vesicle
[7] Introduction to Size Exclusion Chromatography. (n.d.). Bio-Rad. Retrieved July 29, 2024, from https://www.bio-rad.com/en-us/applications-technologies/introduction-size-exclusion-chromatography?ID=LUSMV015
[8] Lipidomics and RNA sequencing reveal a novel subpopulation of nanovesicle within extracellular matrix biomaterials. (2020, March 20). PubMed. Retrieved August 14, 2024, from https://pubmed.ncbi.nlm.nih.gov/32219161/
[9] Macrophage Polarization in Physiological and Pathological Pregnancy. (2019, April 15). NCBI. Retrieved July 29, 2024, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6476302/
[10] Matrix-bound nanovesicle-associated IL-33 supports functional recovery after skeletal muscle injury by initiating a pro-regenerative macrophage phenotypic transition. (2024, January 27). PubMed. Retrieved July 29, 2024, from https://pubmed.ncbi.nlm.nih.gov/38280914/
[11] Matrix-bound nanovesicles within ECM bioscaffolds. (2016, June 10). PubMed. Retrieved July 29, 2024, from https://pubmed.ncbi.nlm.nih.gov/27386584/
[12] Physiology, Muscle - StatPearls. (n.d.). NCBI. Retrieved July 29, 2024, from https://www.ncbi.nlm.nih.gov/books/NBK532258/
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