Stem cell secretome as a new booster for regenerative medicine.

Stem cells are an undifferentiated cell population that has the ability to develop into many different cell types and also has the ability to repair damaged tissues in some cases. For a long time, the stem cell regenerative paradigm has been based on the assumption that progenitor cells play a critical role in tissue repair by means of their plasticity and differentiation potential. However, recent works suggest that the mechanism underlying the benefits of stem cell transplantation might relate to a paracrine modulatory effect rather than the replacement of affected cells at the site of injury. This paracrine modulatory effect derives from secretome which comprises a diverse host of growth factors, cytokines, chemokines, angiogenic factors, and exosomes which are extracellular vesicles that are produced in the endosomal compartment of most eukaryotic cells and are from about 30 to several hundred nanometers in diameter. The role of these factors is being increasingly recognized as key to the regulation of many physiological processes including leading endogenous and progenitor cells to sites of injury as well as mediating apoptosis, proliferation, migration, and angiogenesis. In reality, the immunomodulatory and paracrine role of these factors may mainly account for the therapeutic effects of stem cells and a number of in vitro and in vivo researches have proved limited stem cell engraftment at the site of injury. As a cell-free way for regenerative medicine therapies, stem cell secretome has shown great potential in a variety of clinical applications including prevention of cardiac disfunction, neurodegenerative disease, type 1 diabetes, hair loss, tumors, and joint osteoarthritis.

Meta-Analysis of Fecal Microbiota and Metabolites in Experimental Colitic Mice during the Inflammatory and Healing Phases.

The imbalance of gut microbiota is known to be associated with inflammatory bowel disease, but it remains unknown whether dysbiosis is a cause or consequence of chronic gut inflammation. In order to investigate the effects of gut inflammation on microbiota and metabolome, the sequential changes in gut microbiota and metabolites from the onset of colitis to the recovery in dextran sulfate sodium-induced colitic mice were characterized by using meta 16S rRNA sequencing and proton nuclear magnetic resonance (¹H-NMR) analysis. Mice in the colitis progression phase showed the transient expansions of two bacterial families including Bacteroidaceae and Enterobacteriaceae and the depletion of major gut commensal bacteria belonging to the uncultured Bacteroidales family S24-7, Rikenellaceae, Lachnospiraceae, and Ruminococcaceae. After the initiation of the recovery, commensal Lactobacillus members promptly predominated in gut while other normally abundant bacteria excluding the Erysipelotrichaceae remained diminished. Furthermore, ¹H-NMR analysis revealed characteristic fluctuations in fecal levels of organic acids (lactate and succinate) associated with the disease states. In conclusion, acute intestinal inflammation is a perturbation factor of gut microbiota but alters the intestinal environments suitable for Lactobacillus members.