Multifaceted regenerative lives of ‘expired’ platelets

There is great interest in using expired platelet concentrates for producing human platelet lysates (hPLs) for cell therapy procedures and, potentially, regenerative medicine. The scientific rationale lies in the richness of platelets in growth factors and cytokines and other cell growth‐promoting biomolecules. The main use of hPL is to replace fetal bovine serum (FBS) for cell therapy protocols for clinical‐grade xeno‐free nutritional supplementation of propagation media. To improve consistency, hPLs may be currently manufactured by pooling the lysates from approximately 16 to 50 frozen platelet concentrates, depending upon jurisdiction. hPL is used as growth medium supplement to expand primary mesenchymal stromal cells (MSCs) from different tissues, as well as various differentiated primary cells. hPLs avoid immunological and zoonotic infectious risks linked to FBS, exhibit potent capacity at expanding cells, shortening the cell population doubling time while maintaining cell physiological, biochemical and functional properties, and, for MSCs, capacity to differentiate. Nonexpired autologous or allogeneic platelet‐derived biomaterials are used in regenerative medicine to enhance the healing and repair of damaged or injured tissues. However, the variability in these products does not generally allow to draw evidence‐based conclusions, and recommendations on best clinical practices remain needed. Future trends may include the development of large‐scale virally inactivated hPLs manufactured following controlled conditions meeting specifications tailored‐made for dedicated clinical applications. In conclusion, there is a scientific rationale for making optimal use of expired platelets to produce standardized growth factor preparations for both cell therapy procedures and dedicated regenerative medicine applications.