At present, various clinical trials using mesenchymal stem cells (MSCs) have taken place with increasing success rates. Given that their clinical efficacy is mainly attributed to paracrine effects, recent studies have drawn much attention to extracellular vesicles (EVs) secreted from MSCs. These bilipid-layered and nano-sized vesicles retaining medicinal potency equivalent to that of MSCs could reach a safe and effective cell-free treatment while circumventing current limitations of stem cell infusion therapies.

1) Technical challenges in obtaining sufficient amounts of EVs have limited further progress in clinical applications. Of the multiple efforts to reinforce the therapeutic capacity of MSCs, few studies have reportedly examined the scale-up of MSC-derived EV production. In our lab, we successfully amplified EV secretion from MSCs compared to the conventional culture method using a simple and efficient 3D-bioprocessing method. Size-controlled human MSC spheroids were homogeneously formed on a large scale by using a microfabricated microwell array. By subsequently providing a dynamic culture environment, the production of MSC-derived EVs was significantly increased compared to that using a conventional monolayer culture method.​

2) Conventional MSC culture methods only deliver an arbitrary cocktail of therapeutic molecules to collected EVs. Therefore, desired recruitment of the multifaceted therapeutic compounds in EVs should be addressed to customize their therapeutic capacity as primed for a targeted disease. In our lab, we regulated cytokine inclusions packaging into EVs by 3D-organizing different physical interactions between MSCs and culture matrices. We used gelatin methacryloyl (GelMA) hydrogel that was amenable to highly cell-friendly microenvironments as well as tuneable mechanical properties. Therefore, MSCs could be encapsulated in different 3D-microenvironments with varying mechanical properties. EVs were collected from each condition and their therapeutic properties and efficacies were compared by various biological analyses and different culture models.

Our study showed an efficient and scalable method to manipulate therapeutic compositions of MSC-derived EVs, which would practically contribute to translation of EVs to clinics.
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