Cryopreservation of swine colostrum-derived cells

Mesenchymal stromal cells (MSCs) have been demonstrated to possess anti-inflammatory and antimicrobial properties and are of interest in biotechnologies that will require cryopreservation. Recently, MSC-like cells were isolated from colostrum and milk. We used an interrupted slow freezing procedure to examine cryoinjury incurred during slow cooling and rapid cooling of MSC-like cells from swine colostrum. Cells were loaded with either dimethyl sulfoxide (Me₂SO) or glycerol, cooled to a nucleation temperature, ice-nucleated, and further cooled at 1 °C/min. At several temperatures along the cooling path, cells were either thawed directly, or plunged into liquid nitrogen for storage and later thawed. The pattern of direct-thaw and plunge-thaw responses was used to guide optimization of cryopreservation protocol parameters. We found that both 5% Me₂SO (0.65 M, loaded for 15 min on ice) or 5% glycerol (0.55 M, loaded for 1 h at room temperature) yielded cells with high post-thaw membrane integrity when cells were cooled to at least -30 °C before being plunged into, and stored in, liquid nitrogen. Cells cultured post-thaw exhibited osteogenic differentiation similar to fresh unfrozen control. Fresh and cryopreserved MSC-like cells demonstrated antimicrobial activity against S. aureus. Also, the antimicrobial activity of cell-conditioned media was higher when both fresh and cryopreserved MSC-like cells were pre-exposed to S. aureus. Thus, we were able to demonstrate cryopreservation of colostrum-derived MSC-like cells using Me₂SO or glycerol, and show that both cryoprotectants yield highly viable cells with osteogenic potential, but that cells cryopreserved with glycerol retain higher antimicrobial activity post-thaw.