The cellular composition significantly affects the properties of platelet concentrates. In particular, leukocyte platelet concentrates due to the increased number of monocytes and granulocytes have increased levels of proinflammatory cytokines, which contribute to the destruction of extracellular matrix, reduce synthesis of its components and enhance inflammation in tissues. The purpose. To determine the blood cells number in leukocyte (L-PCP) or leukocyte-poor platelet-concentrated plasma (LP-PCP) and compare it with whole venous blood, plasma and platelet-poor plasma. Materials and methods. 20 L-PCP and 21 LP-PCP samples were obtained by double centrifugation from the venous blood of 30 donors aged 26 to 78 with local pathology of the musculoskeletal system. In the first stage, plasma was isolated after the separation of whole blood, and in the second stage, platelets were concentrated in a small volume of platelet-poor plasma. The number of blood cells in the test samples was determined by hematology analyzer.

Platelet-rich plasma (PRP) is plasma with high platelet count. Currently, PRP is used in many fields of medicine [1, 2, 9]. It is believed that the platelet count in PRP should be about 1 million per 1 μl, or 2-5 times higher than in whole blood of a healthy person, where their content is 150,000 to 450,000 per 1 μl. This platelet concentration is considered necessary for effective tissue regeneration. PRP is usually obtained from the patient's own blood (autologous PRP) [10]. There are many methods and techniques to obtain PRP [18, 21], which significantly complicates the development of its classification. The most commonly used classification is developed by D. Dohan Ehrenfest, who divided platelet concentrates by leukocyte concentration and fibrin content into 4 groups [11]. According to this classification, PRP is divided by the content of leukocytes into leukocyte-containing and pure. Leukocyte-containing PRP has a high concentration of leukocytes, pure PRP is characterized by their low content. Other classifications of platelet concentrates have been proposed, in particular by J. Magalon. It uses the number of platelets, the percentage of platelets and other cells in PRP. This classification takes into account the effectiveness of techniques and devices for platelet isolation [20]. TGF-β1 level in platelet-rich plasma in patients with diseases and injuries of the musculoskeletal system