CoolCell Aids Research on MSC Mediated Therapy

An optometrist carefully checks her patient’s retinal health. Conditions such as diabetes affect blood flow into and out of the retina, which can lead to ischemia, and potential loss of vision if left untreated. Image credit: Wikimedia Commons.

An independent study [1] at the University of Iowa is using BioCision’s CoolCell® freezing container to cryopreserve human mesenchymal stromal cells that are being evaluated in a reperfusion injury model.

In any cell-based therapy model, the ability to use cells directly out of cryostorage is a huge plus; it gives clinicians and surgeons the ability to treat medical conditions on demand, a critically important benefit during emergency situations.

During events such as a heart attack or stroke, cells and tissues are cut off from the nutrients and oxygen carried by a healthy blood supply; a condition known as “ischemia”. Without rapid treatment, the return of normal circulation can trigger an inflammatory cascade that causes widespread and permanent tissue damage. Scientists now think this type of damage, called “reperfusion injury” can be reversed or even prevented through the use of stem cells, namely mesenchymal stromal cells (MSCs). The problem is, there is an ongoing debate about whether the viability and potency of MSCs is damaged by cryopreservation, rendering the cells unsuitable for this type of therapy.

Retinal ischemia is a common cause of visual impairment and blindness, and is often associated with poorly controlled diabetes. The authors of this study are using a murine model of retinal ischemia and reperfusion injury to compare the therapeutic potential of freshly isolated MSCs and cryopreserved MSCs. Their first move was to establish a cryopreservation protocol they considered optimal for their MSCs. The cells were re-suspended in CryoStor CS5 freezing medium, and frozen using a CoolCell freezing container at a controlled rate of -1°C/min. The cells were stored in a -80°C freezer prior to being placed in liquid nitrogen storage for 7-30 days.

For thawing, all vials were removed from liquid nitrogen and placed directly in a 37 °C water bath until only a small ice pellet remained. It’s worth noting that it’s unlikely this thawing method would be used in the more tightly regulated environment of a human clinical trial, due to the risk of contamination. In that case, a controlled rate dry thawing method  would be more suitable.

Thawing considerations aside, the author’s methods resulted in an admirable 95% MSC viability rate. The cryostored MSCs remained responsive to inflammatory signals, and were able to suppress activated human peripheral blood mononuclear cells. All MSC injections occurred within 1 hour of thawing; the authors purposely avoided any post-thaw recovery period in keeping with their goal of creating an “on-demand” cell therapy treatment. ‘Fresh’ MSCs in this study were all maintained in culture for at least 7 days prior to use. When injected into the eyes of mice 3 hours after the onset of ischemia and 2 hours after the onset of reperfusion, cryopreserved MSCs performed just as well as fresh MSC to rescue retinal cells.

The data in this study suggests that as long as viability is protected, cryopreserved mesenchymal stromal cells retain their therapeutic potential. The success of MSC clinical therapy will largely depend on the availability of reliably effective cells. Cryopreservation greatly simplifies the logistics of developing off-the-shelf cell-based therapeutics.

[1] Gramlich, O. W., et al. Cryopreserved Mesenchymal Stromal Cells Maintain Potency in a Retinal Ischemia/Reperfusion Injury Model: Toward an off-the-shelf Therapy. Nature: Scientific Reports 6, Article number: 26463, 1-12. 2016.