The rising popularity of platelet rich plasma (PRP) treatments has given birth to several competing PRP kits. The efficacy of PRP treatments depends on delivering a therapeutic dose of viable platelets directly to damaged tissues, and platelet recovery rates vary substantially between commercially available kits, according to third party research. This article discusses the primary differences between the Stryker Regenkit and EmCyte Pure PRP kits, including centrifugation protocols and platelet recovery rates.
Physicians seeking to improve patient outcomes with PRP treatments would be interested to learn that EmCyte Pure PRP kits, have been shown to produce PRP with platelet concentrations 7x higher than whole blood while Regnekit was shown to produce PRP with 30% fewer platelets than whole blood. These substantial differences are rooted in divergent approaches to centrifugation. Regenkit relies on the simplicity of single spin preparation while EmCyte PRP further concentrates platelets with a dual spin approach.¹
Centrifugation and PRP Platelet Recovery
Both kits rely on the principles of differential centrifugation to isolate platelets. While under the radial force of centrifugation, the various components of whole blood are separated by weight. The heaviest elements, red blood cells, travel at a faster rate and settle at the bottom of the kit followed by white blood cells, platelets followed by plasma at the top.
Emcyte Pure PRP kit protocols call for the initial supernatant to undergo a secondary centrifugation. During this subsequent centrifugation blood elements become more clearly stratified and additional platelets fall out of the plasma solution. The secondary centrifugation yields PRP serums with higher platelet recovery rates.
Single spin PRP kits rely on centrifugation as well as a gel polymer to stratify blood elements. The exact chemical makeup of the Regenkit polymer isn’t mentioned under the product’s description. Our scientific advisor suspects the polymer to have a specific gravity just above white blood cells. This is reasonable to deduce because of the extremely low granulocyte and hematocrit levels found in Regenkit PRP serums. The polymer settles above red and white blood cells and the lighter blood elements, which excludes nearly all of the red and white blood cells from the injectate.
Hematocrit Levels and Patient Comfort in PRP Treatment
Low hematocrit levels can benefit patients by decreasing pain at the injection site. Outside of vascular pathways, red blood cells cause oxidative stress and patients report a stinging sensation. Though Rengenkit eliminates potential pain caused by red blood cells at the injection site, the final serum may not contain ideal concentrations of platelets. In fact, third party research found that Regenkit PRP serums contained fewer platelets than whole blood, technically platelet poor plasma.
A PRP kit that produces PPP?
The Regenkit gel polymer effectively isolates red blood cells but, the RegenKit system leaves behind most of the patient’s platelets because the polymer only captures platelets of a specific gravity. Platelets are non-nucleated fragments of megakaryocytes. Megakaryocytes are large progenitor cells located in the bone marrow that extend into sinusoidal blood vessels to release platelets into the bloodstream. Platelets are not uniform in size. Unfortunately, it seems that a majority of platelets have a higher specific gravity than the gel polymer and are likely to be trapped within or settled below the polymer. This results in a PRP serum with fewer platelets than whole blood and therefore limited healing potential.
Details of Scientific Study
Third party research was conducted by Robert Mandel, PhD of BioSciences Research Associates (BSR). In 2016, Dr. Mandel lead a team of researchers to compare platelet concentration and growth factor release between 5 different PRP kits:
- Emcyte GS30-PurePRP II
- Emcyte GS60-PurePRP II
- Arteriocyte MAGELLAN
- REGENKIT THT Tube
- ECLIPSE PRP
BioSciences Research Associates (BSR) is an independent contract research laboratory located in Cambridge and once academically affiliated with Harvard Medical School. BSR is currently affiliated with the Immune Disease Institute at Harvard and as such draws from a community of nearly 400 bioscience researchers. The BSR laboratory complies with the Food and Drug Administration’s (FDA) Current Good Manufacturing Practice (cGMP) to assist pharmaceutical and biotech companies in product development and clinical trial support.
The researchers drew approximately 200 ml of blood from 4 “healthy” donors and recorded the concentration levels of platelets, stromal cell-derived factor 1 (SDF-1α), and platelet derived growth factor (PDGF) in the final serum produced by each PRP kit. Donors were referenced with code numbers; age, sex and ethnicity were not tracked.
Blood was drawn into the presence of an anticoagulant according the manufacturer’s protocol to keep platelets from degranulating during centrifugation. Anticoagulants included sodium citrate, and ACD-A citrate dextrose solution (see anticoagulant table for proportions according to kit).
Anticoagulants Used in Study
|PRP Kit||Anticoagulant||Blood volume|
|Emcyte GS30-PurePRP®II||5mL Na Citrate||25 ml|
|Emcyte GS60-PurePRP®II||10mL Na Citrate||50 ml|
|Arteriocyte MAGELLAN||8mL ACD-A||52 ml|
|REGENKIT®THT Tube||1mL Citrate||8 ml|
|ECLIPSE PRP||≈1mL*||≈ 9mL|
*material not listed (unknown polymer/anticoagulant mix)
Anticoagulants and PRP Platelet Viability
PRP preparation starts with a blood draw in the presence of an anticoagulant agent. Anticoagulants have the vital role of preventing platelet activation during the mechanical force of centrifugation. If platelets where to activate during the preparation process, a blood clot will form and the resulting serum will no longer contain many of the platelets central to effective PRP therapy. This clot cascade (PRP activation) signals the release of growth factors, which would diverge from the platelets and rise to the top of the supernatant, resulting in an injectate with a greatly diminished therapeutic potential.
In the aforementioned study, both preparation techniques utilize citrate concentrate as an anticoagulant, which controls for the potential influence of various anticoagulants on platelet function. The use of different anticoagulants affect the resulting PRP. A 2016 study out of Brazil found that PRP prepared with sodium citrate as an anticoagulant yielded serums with higher platelet concentrations compared to PRP prepared with citrate dextrose solution A or ethylenediaminetetraacetic acid.²
Platelet Concentration and Growth Factors
Platelets function to stop bleeding wherever the vascular wall is ruptured. If the vascular wall is ruptured, collagen present in subendothelial tissues initiates a clotting cascade. Platelets bind to collagen directly via the glycoprotein (GP) receptor complex. After binding, collagen receptors on the platelets initiate phospholipase C-mediated cascades. This leads to an increase in intracellular calcium which initiates morphological changes in platelet structure (such as the presentation of pro-coagulant surfaces) and the secretion of platelet granular content: growth factors.³ Growth factors increase angiogenesis, collagen secretion, cell mitogenesis and chemotaxis in a wide variety of cells including chondrocytes, osteoblasts, and mesenchymal stem cells.⁴ Higher platelet concentration increases the beneficial role of growth factors in tissue repair.
- Mandel R. Research Study: Comparisons of Emcyte GS30-PurePRP II, EmCyte GS60-PurePRP II, Arteriocyte Magellan, Stryker REGENKIT THT, and ECLIPSE PRP. Biosciences Research Associates. 2016; May. [pdf]
- DCorrêa do Amaral R, Pereira da Silva N, Haddad N, Lopes L, Ferreira F, Filho R, Cappelletti P, Mello W, Cordeiro-Spinetti E, and Balduino A. Platelet-rich plasma obtained with different anticoagulants and their effect on platelet numbers and mesenchymal stromal cells behavior in vitro. Stem Cells International. 2016; Article ID 7414036, 11 pages.[ncbi]
- Sangkuhl K, Shuldiner AR, Klein TE, Altman RB. Platelet aggregation pathway. Pharmacogenetics and Genomics. 2011;21(8):516-521. doi:10.1097/FPC.0b013e3283406323.[ncbi]
- Dhurat R, Sukesh M. Principles and Methods of Preparation of Platelet-Rich Plasma: A Review and Author’s Perspective. Journal of Cutaneous and Aesthetic Surgery. 2014;7(4):189-197. doi:10.4103/0974-2077.150734.[ncbi]