Cryopreservation of adipose-derived stromal/stem cells using 1–2% Me2SO (DMSO) in combination with pentaisomaltose: An effective and less toxic alternative to comparable freezing media

Mesenchymal stromal/stem cells (MSCs) derived from bone marrow, umbilical cord and especially adipose tissue are increasingly being explored for their therapeutic potential to treat a wide variety of diseases. A prerequisite for most allogeneic off-the-shelf and some autologous MSC therapies is the ability to safely and efficiently cryopreserve cells during production or for storage prior to treatment. Dimethyl sulfoxide (Me2SO) is still the commonly used gold standard cryoprotectant (CPA). However, undesirable cellular impacts and side effects of Me2SO have led to an increasing demand for the development of safe and effective alternatives. This study investigated the effect of pentaisomaltose as a CPA for cryopreservation of adipose-derived stromal/stem cells (ASCs). We compared pentaisomaltose-based freezing media containing 1% Me2SO (PIM1) or 2% Me2SO (PIM2) to our in-house freezing media formulation containing 10% Me2SO (STD10) and to CryoStor freezing media containing 2% or 10% Me2SO (CS2 and CS10). We assessed the recovery of viable ASCs, their phenotype, differentiation potential, proliferation potential, and migratory potential. Further, their immunomodulatory potential was assessed by measuring their ability to suppress T cell proliferation and express immunomodulatory markers. The results showed that the post-thaw viability of ASCs cryopreserved with STD10, CS10 and PIM2 was improved compared to that of CS2. The recovery of ASCs with PIM1 and PIM2 was also improved compared to that of CS2. Proliferation and migration were comparable among the tested freezing media. The results showed no difference in the induction of PDL1, PDL2 or IDO1 expression. Nevertheless, the potential of cryopreserved ASCs to suppress T cell proliferation was reduced when the Me2SO concentration was reduced (CS10>STD10>CS2 and PIM2>PIM1). Altogether, the migratory and immunomodulatory potential combined with improved recovery indicate that the addition of pentaisomaltose in the freezing media may allow for the reduction of the Me2SO concentration to 2% while retaining a more potent cell product that what is recovered using comparable freezing media. With the desire to reduce the amount of Me2SO, these results suggest that 2% and potentially even 1% Me2SO in combination with 10% pentaisomaltose could be an effective and less toxic alternative to comparable freezing media.