Application of Millifluidics to Encapsulate and Support Viable Human Mesenchymal Stem Cells in a Polysaccharide Hydrogel.

Human adipose-derived stromal cells (hASCs) are widely known for their immunomodulatory and anti-inflammatory properties. This study proposes a method to protect cells during and after their injection by encapsulation in a hydrogel using a droplet millifluidics technique. A biocompatible, self-hardening biomaterial composed of silanized-hydroxypropylmethylcellulose (Si-HPMC) hydrogel was used and dispersed in an oil continuous phase. Spherical particles with a mean diameter of 200 µm could be obtained in a reproducible manner. The viability of the encapsulated hASCs in the Si-HPMC particles was 70% after 14 days in vitro, confirming that the Si-HPMC particles supported the diffusion of nutrients, vitamins, and glucose essential for survival of the encapsulated hASCs. The combination of droplet millifluidics and biomaterials is therefore a very promising method for the development of new cellular microenvironments, with the potential for applications in biomedical engineering.

Patients' exposure to PVC plasticizers from ECMO circuits.

BACKGROUND: ECMO is a therapeutic act with a high risk of exposure to diethylhexylphthalate (DEHP), plasticizer from PVC tubings. The replacement of this plasticizer with alternative compounds is recommended but the risks associated with the use of new plasticizers have not been evaluated in ECMO situations. METHODS: Ex vivo ECMO models were performed with different flow rates over 6 days to evaluate the migration of plasticizers and their potential toxic risk for patient. The release of plasticizers during ECMO was measured and compared to reference value (derived no effect level, DNEL) and to cytotoxic concentration carried out with MTT test. RESULTS: Trioctyltrimellitate (TOTM), main plasticizer present in circuit (44% w/w), is weakly released during ECMO. Concentrations are not cytotoxic and exposure doses are lower than DNEL. In contrast, DEHP doses are higher than the DNEL despite a lower presence of DEHP in the circuit (0.2%). We have shown that DEHP is not coming from the circuit but from the priming bag. Replacing this bag with a multilayer one avoids the exposure to DEHP. CONCLUSION: Our study shows that circuits made of PVC plasticized with TOTM against DEHP improves the safety of ECMO.

Polysaccharide Hydrogels Support the Long-Term Viability of Encapsulated Human Mesenchymal Stem Cells and Their Ability to Secrete Immunomodulatory Factors.

While therapeutically interesting, the injection of MSCs suffers major limitations including cell death upon injection and a massive leakage outside the injection site. We proposed to entrap MSCs within spherical particles derived from alginate, as a control, or from silanized hydroxypropyl methylcellulose (Si-HPMC). We developed water in an oil dispersion method to produce small Si-HPMC particles with an average size of about 68 µm. We evidenced a faster diffusion of fluorescein isothiocyanate-dextran in Si-HPMC particles than in alginate ones. Human adipose-derived MSCs (hASC) were encapsulated either in alginate or in Si-HPMC, and the cellularized particles were cultured for up to 1 month. Both alginate and Si-HPMC particles supported cell survival, and the average number of encapsulated hASC per alginate and Si-HPMC particle (7102 and 5100, resp.) did not significantly change. The stimulation of encapsulated hASC with proinflammatory cytokines resulted in the production of IDO, PGE2, and HGF whose concentration was always higher when cells were encapsulated in Si-HPMC particles than in alginate ones. We have demonstrated that Si-HPMC and alginate particles support hASC viability and the maintenance of their ability to secrete therapeutic factors.