What Are Exosomes?
Exosomes are loosely described as extracellular vesicles of fluid first used in inter-cell communication ( paracrine signaling) and these fluid-filled structures are usually released by cells after fusion of multivesicular body (MVB) and the plasma membrane. This process helps release intraluminal vesicles (ILVs) into the extracellular membrane (milieu) and the release vesicles are what we refer to as exosomes.
These extracellular vesicles can also be used in stem cell therapies as a vehicle to take advantage of the beneficial cell signaling that occurs in the natural regeneration process to help control behavior of surrounding cells or to carry treatment doses in the bloodstream throughout the body including the ability to cross the blood-brain barrier  for promoting neurogenesis in treatments in neurodegenerative conditions, spinal cord injuries, strokes, brain injuries & bypass all other immune checkpoints in the body. The therapeutic potential in homing/migration of MSC cells and to hijack the neural stem cell messaging system via laboratory produced extracellular vesicles is especially powerful considering the same vesicles are also used by the body to spread disease, damaged proteins & genetic information for many conditions including Dementia, Parkinson’s disease along with metabolic disorders like obesity & diabetes.
Cancer cell-derived exosomes is another promising field with the goal of using exosomes to deliver vaccines or drugs in cancer immunotherapies, lung cancer treatments, prostate cancer treatment & treatment for pancreatic cancers.  These manufactured cancer exosome markers are able to send antigens to dendritic cells when then induces a T-cell-mediated response to surrounding cancer cells.
By enhancing the beneficial signals given out by stem cells scientist are able to manipulate exosomes behavior to solve medication delivery problems for many types of therapies including:
Doctors are hoping these isolate and purified exosomes vesicles (for immunoregulation) could one day become a new sector in regenerative medicine and stem cell treatments where MSC-derived exosomes are already being used for its healing properties in patients with COPD and pulmonary fibrosis lung disease. 
Potential Sources & Exosome Isolation Methods
There are several natural sources of extracting exosome including immature dendritic cells (imDCs). Learn more about dendritic cells in our glossary or FAQ sections. The exosomes that are secreted by dendritic cells lack surface markers resulting in very low risk for an immune response (immunogenicity.) Exosomes can also be produced from CD34+ stem cells that are isolated from peripheral blood, amniotic membrane, cord tissue ( Wharton’s jelly), bone marrow, adipose fat, and dental pulp.
Published Clinical Citations
 ^ Chen, Claire C, Linan Liu, Fengxia Ma, Chi W Wong, Xuning E Guo, Jenu V Chacko, Henry P Farhoodi, et al. 2016. Elucidation of Exosome Migration across the Blood-Brain Barrier Model In Vitro. Cellular and molecular bioengineering, no. 4 (July 7). doi:10.1007/s12195-016-0458-3. https://www.ncbi.nlm.nih.gov/pubmed/28392840
 ^ Chen, Wen, Mingcan Yang, Jian Bai, Xiang Li, Xiangrui Kong, Yu Gao, Lili Bi, Li Xiao, and Bingyi Shi. 2017. Exosome-Modified Tissue Engineered Blood Vessel for Endothelial Progenitor Cell Capture and Targeted siRNA Delivery. Macromolecular bioscience, no. 2 (December 4). doi:10.1002/mabi.201700242. https://www.ncbi.nlm.nih.gov/pubmed/29205878
 ^ Sung, Bong Hwan, and Alissa M Weaver. 2017. Exosome secretion promotes chemotaxis of cancer cells. Cell adhesion & migration, no. 2 (January 27). doi:10.1080/19336918.2016.1273307. https://www.ncbi.nlm.nih.gov/pubmed/28129015
 ^ Urbanelli, Lorena, Sandra Buratta, Krizia Sagini, Giuseppina Ferrara, Marco Lanni, and Carla Emiliani. 2015. Exosome-based strategies for Diagnosis and Therapy. Recent patents on CNS drug discovery, no. 1. https://www.ncbi.nlm.nih.gov/pubmed/26133463