Platelet lysate (PL) is expected to replace fetal bovine serum (FBS) as a medium additive for expansion cultures of mesenchymal stem cells (MSCs). As a material for PL, we used whole blood-derived platelet concentrate (WB-PC), prepared from leukocyte-reduced whole blood using a platelet-saving leukocyte reduction filter. We compared the usefulness of the WB-PC-derived PL (WB-PL) for MSC expansion culture with that of apheresis PC (Aph-PC) -derived PL (Aph-PL).

The concentrations of growth factors involved in MSC proliferation were comparable between WB-PL and Aph-PL. The MSC proliferation-promoting activity of WB-PL was significantly weaker than that of Aph-PL, but the difference was slight, and significantly stronger than that of FBS. MSCs cultured in WB-PL or Aph-PL maintained the membrane antigen expression pattern characteristics of MSC and tri-lineage differentiation potential into adipocytes, osteocytes, and chondrocytes.

These results suggest that WB-PL may be an alternative to Aph-PL in MSC expansion culture.

Background: We investigated risks associated with performing pre-freezing preparation of cells harvested for chimeric antigen receptor (CAR) T-cell therapy within a clean booth using non-sterile clothing.

Methods: An Air Barrier Booth^® (ABB, Dai-Dan Co., Ltd.), was installed in a general hospital environment. Two operators conducted cell preparation inside a safety cabinet within the ABB, wearing sterile gloves but non-sterile sandals, gowns, masks, and caps, which were reused for the same lot. Sixty-five procedures for tisagenlecleucel (Kymriah^®) were examined for airborne falling bacteria at eight locations around the ABB, and sterility tests were performed on pre-freeze products.

Results: Cleanliness during non-operation met Grade A standards inside the safety cabinet and Grade B in the work area. Positive rates of falling bacteria during the operation were 2% inside the safety cabinet, 0% upstream of the ABB, 13% in the work area downstream of operators at workbench height, 26% at floor level, and 43% in the support area. Various bacteria were detected. All pre-freeze products were culture-negative, with no manufacturing failure due to contamination.

Conclusions: Due to the frequent presence of airborne bacteria downstream of operators, special attention should be paid to processing cellular material in a clean booth with non-sterile clothing.