Human Platelet Lysate (HPL) is a highly potent biological supplement derived from human blood platelets. It is a turbid, light-yellow liquid created to be a rich source of biological signaling molecules that stimulate cell growth and tissue repair. HPL is increasingly utilized in both research laboratories and clinical settings, most notably as a human-derived alternative to animal-based serums for growing cells outside the body.
What Human Platelet Lysate Contains
HPL is fundamentally a concentrated mixture of the bioactive molecules platelets store in their granules, which are released upon activation or injury. The resulting lysate contains a wide array of growth factors that promote cell proliferation and survival. These include Platelet-Derived Growth Factor (PDGF), Transforming Growth Factor beta (TGF-β), and Vascular Endothelial Growth Factor (VEGF).
Insulin-like Growth Factor 1 (IGF-1), Epidermal Growth Factor (EGF), and basic Fibroblast Growth Factor (bFGF) are also present. These factors stimulate various cell types, encouraging them to divide and migrate to sites of damage. Concentrations often range between 0.1 and 300 nanograms per milliliter, with IGF-1 and PDGF-AB typically being the most abundant.
HPL also includes numerous cytokines and chemokines, which regulate immune response and cell trafficking, such as CCL5 (RANTES). The product contains plasma proteins like albumin and immunoglobulins, essential minerals, glucose, and lipids. These components provide basic nourishment and support the expansion of human cells in laboratory environments.
How HPL is Prepared
HPL preparation begins by sourcing platelet units from healthy, screened donors, often using units near or past their expiration date for standard transfusion. Large quantities of platelet concentrate are pooled together to minimize donor-to-donor variation and ensure predictable performance. A single batch of HPL may be derived from pooling ten to fifteen platelet units.
Once pooled, “lysis” is performed to break open the platelets and release the concentrated growth factors. The most common method involves multiple cycles of freezing at very low temperatures, followed by thawing. This physical stress ruptures the platelet membranes, releasing the contents of the internal granules.
Alternative lysis methods include chemical activation using substances like thrombin or calcium chloride, or mechanical disruption through sonication. After release, the mixture is typically centrifuged to remove platelet debris and cellular fragments. The resulting supernatant is then subjected to quality control measures, including sterility checks, pathogen testing, and virus inactivation procedures like solvent/detergent treatment or gamma irradiation.
Essential Applications in Regenerative Medicine
The primary non-clinical application of HPL is its use as a cell culture supplement in laboratory research and biomanufacturing. HPL now serves as a human-derived alternative to animal serums, removing the risk of introducing animal-derived pathogens or proteins that could cause adverse reactions in a clinical setting. It is effective for expanding difficult cell types, such as Mesenchymal Stem Cells (MSCs), which are used extensively in regenerative therapies.
By providing an optimal mix of human growth factors, HPL supports the large-scale, robust expansion of these therapeutic cells. The regulatory environment increasingly favors these “xenogeneic-free” supplements for clinical-grade cell production, solidifying HPL’s role in the field.
Beyond the laboratory, HPL is applied directly in clinical regenerative treatments. It is used to stimulate healing in areas with poor circulation or chronic damage because of its high concentration of tissue-repairing molecules. Direct applications include topical gels for non-healing chronic wounds, such as diabetic foot ulcers, where local delivery of growth factors accelerates tissue formation. HPL is also used in orthopedic procedures to promote cartilage and tendon regeneration, and in specialized ophthalmology for treating severe ocular surface conditions.