Towards a full characterization of a proprietary GMP human platelet lysate

Background \u0026 Aim Human platelet lysate (hPL) has long been used as a xeno-free culture supplement to expand different cell types. Its use is currently thriving given its potential therapeutic properties and its increasing importance in a clinical manufacturing context. hPL has been described to exert beneficial effects in bone and cartilage regeneration, ophthalmologic or autoimmune diseases, such as dry eye disease or graft-versus-host disease. Furthermore, regulatory agencies require the replacement of FBS for medicinal product manufacturing, and hPL is a highly suitable alternative. Methods, Results \u0026 Conclusion At the moment, there is no consensus on the hPL manufacturing process, hindering standardization and characterization. We have previously standardized the production of a clinical grade hPL for clinical applications within a public health system setting, taking advantage of platelets that are routinely discarded in blood transfusion centres. Quality control tests and a robust manufacturing protocol were validated, ensuring safety, efficacy and traceability of our product. Here, we have further characterized our in-house manufactured hPL by means of a proteomic study. Interestingly, after high-abundance protein depletion, the enrichment analysis of the common proteins identified in 3 batches highlighted biological processes related to protein activation cascade, vesicle-mediated transport and immune system process, among others. Moreover, to examine the effects of hPL on fibroblast culture at a transcriptomic level, we performed a microarray analysis comparing explant-derived fibroblast cultured either with FBS (10%) or with our hPL (at 5 and 15%, n=3, respectively). 129 differentially expressed genes were obtained when comparing hPL versus FBS. Notably, we found downregulated genes associated with cellular senescence and cell proliferation inhibition in our hPL. No significant differences were found between hPL at 5 and 15%. In conclusion, we present a new step towards an in-depth characterization of an in-house-GMP hPL that can be a medicinal product itself or a raw material for the manufacturing of cell-based therapies.