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Doctoral dissertation about optimal expansion and differentiation conditions for mesenchymal stromal cells

10/9/2020 9:00

The study focuses on determining optimal expansion and differentiation conditions for clinical-grade bone marrow-derived MSCs. It also aimed to improve quality of MSCs products by introducing an imaging-based screening method to detect aging-related morphological changes in MSC cultures. Finally, we investigated how additional freezing steps during the manufacturing process affect the basic manufacturing parameters and alter the cellular aging process.

Sofia Oja, FM will defend the doctoral dissertation entitled "Culture Systems and Quality Parameters for Clinical-grade Mesenchymal stromal cells" in the Faculty of Biological and Environmental Sciences, University of Helsinki, on 9 October 2020 at 12:00.

Mesenchymal stromal cells (MSC) are a potential tool for cell-based therapies subject to intensive investigation. MSCs display immunomodulatory functions and a broad differentiation capacity, and thus have several potential therapeutic applications, such as treatment of immunological disorders and correction of tissue defects.

MSCs have been widely studied and utilized in treatment of Graft-versus-Host disease, a severe complication of stem cell transplantation, and have also been evaluated in treatment of Crohn’s disease, multiple sclerosis, and chronic inflammation. The repair of bone and cartilage defects is another application of significant interest.

MSCs are classified as advanced therapy medicinal products (ATMPs), which are manufactured under supervision by regulatory authorities. The aim of regulation is to produce safe and effective medicinal products, and therefore safety risks and sources of alterations or impairment of functionality should be evaluated carefully.

MSCs are somatic cells, which can be isolated from various sources, such as from bone marrow, adipose tissue, or umbilical cord. For production of medicinal products, MSCs are usually expanded extensively in cell cultures. Culture conditions are known to affect to the characteristic and functionality of MSCs. Animal-derived components during culture such as bovine serum are to be avoided if possible, due to risks of immune reactions and zoonotic infections. Therefore, animal serum-free culture medium is considered safe option for MSC cultures.

This thesis focuses on determining optimal expansion and differentiation conditions for clinical-grade bone marrow-derived MSCs by using platelet-derived culture medium supplements to replace bovine serum. This study also aimed to improve quality of MSCs products by introducing an imaging-based screening method to detect aging-related morphological changes in MSC cultures. Finally, we investigated how additional freezing steps during the manufacturing process affect the basic manufacturing parameters and alter the cellular aging process.

We found in this study that platelet lysate with two freeze-thaw cycles effectively supported MSC expansion and maintained their functionality in ambient oxygen concentration. Platelet lysate also promoted osteogenic differentiation at least equally with bovine serum in two-dimensional plate culture and slightly better if a three-dimensional matrix was used. We were able to detect and quantify aging-related morphological changes from MSCs cultures and found that a rapid increase in cell size reflects the expression of aging markers. We found that freezing at early phases of cell cultures did not alter the characteristics or functionality of the MSC.

This study has yielded insights into the establishment and scaling up of animal-serum free MSC cultures. In addition, our screening method for aged cells could be implemented into the clinical-grade manufacturing of MSCs to monitor cell quality during processing. 

The dissertation will be published in the series Academic Dissertations from The Finnish Red Cross Blood Service. It is the 66th doctoral dissertation in the series.

The dissertation is also available in electronic form through the E-thesis service.