Mesenchymal stem cells (MSCs) were first isolated more than 50 years ago from the bone marrow. Currently MSCs may also be isolated from several alternative sources and they have been used in more than a hundred clinical trials worldwide to treat a wide variety of diseases. The MSCs mechanism of action is undefined and currently under investigation. For in vivo purposes MSCs must be produced in compliance with good manufacturing practices and this has stimulated research on MSCs characterization and safety. The objective of this review is to describe recent developments regarding MSCs properties, physiological effects, delivery, clinical applications and possible side effects.

Extracellular vesicles (EVs) from a variety of stem cell sources are believed to harbour regenerative capacity, which may be exploited for therapeutic purposes. Because of EV interaction with other soluble secreted factors, EV activity may depend on the employed purification method, which limits cross‐study comparisons and therapeutic development. Raman spectroscopy (RS) is a quick and easy method to assess EV purity and composition, giving in‐depth biochemical overview on EV preparation. Hereby, we show how this method can be used to characterise EVs isolated from human liver stem cells and bone marrow mesenchymal stem/stromal cells by means of conventional ultracentrifugation (UC) and size exclusion chromatography (SEC) protocols. The obtained EV preparations were demonstrated to be characterised by different degrees of purity and a specific Raman fingerprint that represents both the cell source and the isolation procedure used. Moreover, RS provided useful hints to explore the factors underlying the functional diversity of EV preparations from the same cell source, thus representing a valuable tool to assess EV quality prior to functional assays or therapeutic application.

Mast cells and basophils, which are activated by IgE and allergens through the high affinity IgE receptor (Fc ε RI), play a prominent role in anaphylaxis in the mouse. Mice deficient in this receptor become resistant to passive anaphylaxis. As a first step in developing an in vivo model that more closely mimics the IgE-mediated responses in man, we used a combination of transgenic and embryonic stem cell technology to generate a mouse line in which the murine Fc ε RI α-chain has been replaced with its human homologue. We demonstrate here that these mice express a tetrameric high affinity IgE receptor, in which the human α-chain associates with the murine β- and γ-chains, and that upon triggering with relevant Ag, this receptor mediates the initiation of the expected intracellular events. In addition, we show that the human α-chain restores an anaphylactic response to the nonresponsive α-deficient parental mouse line. This "humanized" mouse represents a potentially important model system, not only for studying the role of IgE in human immune responses, but also for testing potential therapeutic reagents that can interfere with responses mediated through the human Fc ε RI receptor.