Human Platelet Lysate (or hPL) is a substitute supplement for fetal bovine serum (FBS) in experimental and clinical cell culture. It corresponds to a turbid, light-yellow liquid that is obtained from human blood platelets after freeze/thaw cycle(s). The freeze/thaw cycle causes the platelets to lyse, releasing a large quantity of growth factors necessary for cell expansion.
Platelets have a life span of 5 to 9 days. Because of this, the U.S. Food and Drug Administration (FDA) expires transfuse-able platelets 5 days post-collection. Typically, hPL is produced from expired platelets that have been stored in frozen conditions no later than 7 days post-collection.
hPL is created from single or pooled donor-donated platelets isolated from whole blood or by apheresis, distributed in a standard platelet collection bag. There are some differences between hPL manufacturing protocols, but they all share the same core of being frozen at very low temperatures and thawed. This process may be repeated two or three times to cause complete platelet lysis. The resultant hPL can then undergo different manufacturing steps to achieve multiple grades of hPL.
The most common form of hPL undergoes few processing steps, producing a raw product made up of supernatent following the freeze/thaw process. Because of this raw form, many clotting factors found in platelets saturate the product. These clotting factors require the end user to add heparin to the cell culture media to prevent coagulation during incubation.
An emerging form of hPL is one that can be used in cell culture without the need of heparin, or any anticoagulant, addition. This grade of hPL goes through further manufacturing steps to inhibit the effect the clotting factors have.
Many labs around the world are creating small amounts of hPL to suit their laboratory needs. The disadvantages of this process are: cost and consistency. When creating small batches of hPL (single or few donors pooled), the lot-to-lot consistency of the hPL becomes variable. Large-scale manufacturing by pooling many platelet donors is a necessity to mitigate the donor-to-donor variability. Consistency is a top priority for experimental designs to provide reproducible results.
Platelet lysate is commonly used for supplementation of basal media in mesenchymal stem cells culture. Prior the use, the pathogen inactivation process is recommended to prevent pathogen transmission. 
In 1991, the FDA recalled two lots of FBS processed in the US. The serum had arrived from Brazil labelled as human serum and thereby evading the U.S. Department of Agriculture (USDA). The source of FBS and all serum is critical when considering the purchase of serum. The source now determines whether or not a bio therapeutic agent will receive approval by certain regulatory bodies including the USDA.
Human Platelet Lysate is available commercially through Compass Biomedical, Inc., Cook Medical, Macopharma SA and iBiologics, LLC under the product lines PLUS, Stemulate, Human Platelet Lysate and XcytePlus, respectively. All companies provide different grades of platelet lysate including GMP versions for use in human clinical trials. Platelet lysate offers a true xenofree platform which requires no addition of heparin (anticoagulant). Platelet lysate has been tested in various cell culture applications including use in advanced bioreactor systems.
- Iudicone P (Jan 2014). "Pathogen-free, plasma-poor platelet lysate and expansion of human mesenchymal stem cells..". J Transl Med. 12. doi:10.1186/1479-5876-12-28. PMC 3918216. PMID 24467837.