Beyond FBS: Making Sense of Platelet-derived Supplement Terminology

September 25, 2026

Key Message: Human platelet lysate (hPL) is emerging as one of the most promising alternatives to fetal bovine serum (FBS); however, inconsistent and interchangeable terminology is holding the field back. Here, we propose a clear and discrete definition of what hPL is.

Since the late 1950s, fetal bovine serum (FBS) has been the default supplement in mammalian cell culture workflows. FBS is a complex, undefined supplement containing thousands of biomolecules that can support the growth of many cell types. Its universality and historic integration into standard protocols make FBS the preferred choice over other alternatives. Despite the technical, ethical, and economic challenges associated with FBS, reluctance to shift away from it is worsened by a lack of effective alternatives. Over the past few decades, human platelet-derived alternatives have emerged as an effective alternative to FBS. Like FBS, these alternatives are complex and undefined. However, compared to FBS, the supply chain is far more transparent, controllable, and less ethically ambiguous. As the interest in human platelet-derived alternatives grows, inconsistent terminology muddies the discussion, with stakeholders using overlapping terms interchangeably. Here, we aim to establish a clear definition of human platelet lysate (hPL), allowing scientists to distinguish it from supplements sometimes mislabelled as hPL. The definition is developed based on examining two key variables: where the platelets come from and how their contents are extracted.

Umbilical cord vs. peripheral blood-derived platelets

Platelets, or thrombocytes, are small, colorless, plate-like cell fragments found in our blood. Their primary function is to form blood clots and support cell growth when tissue is damaged or injured. They perform their function by releasing biomolecules that are stored in dense reserves, known as granules (𝛼- and dense granules). These biomolecules include growth factors and cytokines that are crucial to cell growth and maintenance.

A drop of blood contains approximately 4.5 × 10⁵ platelets. Blood can be collected from an individual from the severed umbilical cord immediately after birth (known as umbilical cord blood) or from a vein at a later stage (known as peripheral blood). Because cord blood is near-fetal, its biochemical profile differs from a supplement derived from peripheral blood platelets.

In a comparison study, umbilical cord blood platelet lysate (UCB-PL) showed 20% more total protein than peripheral-blood platelet lysate (PB-PL). Compared to PB-PL, UCB-PL was also significantly more enriched with growth factors (FGF-2, TGF-β1, IGF-1, and PDGF-AB), which resulted in higher proliferation in cell culture.

Nevertheless, peripheral blood platelets are more prevalent in studies and commercial applications as they are available in larger amounts. Umbilical cord blood yields a median volume of 60 mL per unit, obtained from ~1 in 200 births, and is generally reserved for autologous applications. Meanwhile, experts estimate that roughly 100 million peripheral-blood donations are collected worldwide each year, and could yield 100,000 – 250,000 L of PB-PL, without interfering with clinical demand for platelets. Thus, the term hPL typically refers to platelet lysate obtained from peripheral blood (PB-PL).

Human platelet Releasate vs. Lysate

To make an effective cell culture supplement, different methods may be employed. It is recommended that supplements should be classified into two main categories, based on the underpinning mechanism used to extract biomolecules from platelets.

Human Platelet Releasate (hPR)

In the body, activation of the membrane receptors shifts a resting, discoid platelet into a spiky, activated form. The spiky shape allows granules to fuse to the membrane and release their contents (“degranulation”). Numerous factors drive these changes. Outside the body, you can reproduce this by adding calcium salts, adenosine diphosphate (ADP), thrombin-receptor activated peptide-6, or thrombin. Different activation methods yield notable differences in final composition and cell culture performance. Therefore, a qualifier to indicate the activation method used should be included to avoid confusion (e.g., calcium-activated hPR or thrombin-activated hPR).

Human platelet lysate (hPL)

Shock-freezing (repeated freeze-thaw cycles), sonication (20 kHz for 30 min), and solvent-detergent methods commonly lyse the phospholipid bilayer to produce a platelet-derived supplement known as hPL. Studies have shown no significant differences in the biochemical profile or cell culture performance when comparing these lysis methods. However, a few studies comparing hPL and hPR show significant differences in total protein content, growth factor levels, and cell culture performance, which are cell-type dependent. Across all these studies, hPL outperforms hPR.

What we observed

When defining hPL, two findings matter in terms of its biochemical characterisation:

Source of blood; and
Production mechanism.

blog post diagram lysate releasate Download

Parameter	Human Platelet Releasate (hPR)	Human Platelet Lysate (hPL)
Total protein content	Low	High
Growth factor levels	Low	High
Clotting factors and Fibrinogen levels	Low*	High
Cell culture performance	Lower cell yields; especially in BM-MSC	Higher cell yields

*Dependent on activation method used.
Abbreviations: BM-MSC- bone marrow-derived Mesenchymal stem cells

Why it matters

Without shared terminology, validating manufacturing processes and comparing studies becomes difficult. For example, the FDA’s definition of “lysate” broadly encompasses what we separate here into UB-PL, hPL, and hPR. However, these have distinct properties that are scientifically meaningful.

Takeaways

hPL remains one of the strongest FBS alternatives available, but the field needs to agree on what it means. Peripheral blood is the commercially viable source; releasate and lysate are distinct products with different trade-offs in composition; and the production method used should be stated explicitly, not folded into a generic “platelet lysate” label. A shared vocabulary is the necessary first step toward comparable research and clearer phasing out of FBS.