Background:

Apoptosis was reported to take crucial role in mesenchymal stem cell (MSC)-mediated immunomodulation, in which apoptotic MSCs were shown to be superior compared to living MSCs. Furthermore, extracellular vesicles (Evs) derived from MSCs were revealed more specific advantages for patient safety such as lower propensity to trigger innate and adaptive immune responses. As a safety and simple operation, high hydrostatic pressure (HHP), a physical technique that uses only fluid pressure to inactivate cells or tissues, has been developed and applied in a lot of field of biosciences, including biotechnology, biomaterials, or tissue engineering.

Methods:

MSCs isolated from human bone marrow were suspended cultured in appropriate medium and subjected to pressurization at 50 MPa for 36 h. Then cells were collected and investigated apoptotic pathway by transmission electron microscopy (TEM), phosphatidylserine membrane translocations, cleaved caspase-3/7 and terminal deoxy-nucleotidyl transferase dUTP nick-end labeling (TUNEL) staining. Besides, viability assays and live cell imaging were also used for assessement of cell survival after pressurization.

Results:

We found that HHP at 50 MPa for ≥36 h completely induced MSC death by Live/Dead assay, live cell imaging and WST-8 assay up to 7 days after pressurization. The large amount of apoptotic MSCs death was found based on morphological changes in TEM, phosphatidylserine exposure, caspase activation and detection of DNA fragmentations via TUNEL staining.

Conclusions:

In the current study, our data revealed that HHP treatment was convenient processing which safety and effectively induced MSCs undergo apoptosis. Especially, by capable of manufacture expanding, this technique might provide numbers of manipulated products using for industrial cell-based therapies.