Platelet lysate is beneficial for chondrocyte expansion but ineffective in 3d culture

Abstract

Purpose: The purpose of this study is to define the potential of platelet lysate as a xeno-free alternative in expansion of human chondrocytes for cell therapy purposes. Additionally, the effects of using platelet lysate for redifferentiation of chondrocytes in 3D pellets are assessed. Methods: Platelet lysate was prepared from human blood and platelet enrichment was measured. Chondrocytes were isolated from human osteoarthritic cartilage (age 55-84, mean 66 years) and subjected to a range of concentrations of platelet lysate in monolayer culture. Cell proliferation and morphology were assessed after 7 days. In addition, expression of chondrogenic genes was determined by quantitative real-time PCR. Next, platelet lysate-expanded chondrocytes (passage 2) were cultured in 3D cell pellets without any additional growth factors and cartilage matrix production was assessed after 28 days. Glycosaminoglycan (GAG) and collagen production in the pellets were quantified by biochemical analyses as well as (immuno)histochemistry. Moreover, platelet lysate was supplemented into redifferentiation medium of chondrocytes in 3D pellets. Cartilage matrix production was assessed with similar outcomes. Results: Platelet lysate had a dose-dependent effect on chondrocyte proliferation, but expression of chondrogenic markers was decreased in monolayers when compared to bovine serum-expanded monolayers. After 28 days of subsequent 3D pellet culture, GAG production was significantly higher in pellets consisting of chondrocytes expanded with 1% platelet lysate compared to controls (figure 1). When used for redifferentiation of chondrocyte pellets, platelet lysate significantly decreased the production of GAGs and collagen. This was confirmed by (immuno)histochemistry. Conclusions: In conclusion, low concentrations of platelet lysate stimulate chondrocyte proliferation in 2D monolayer and cartilage extracellular matrix production in subsequent 3D pellet culture. However, this does not work for high concentrations of platelet lysate. Furthermore, this study showed unfavourable effects on redifferentiation of 3D chondrocyte cultures in platelet lysate. Thus, platelet lysate can be seen as a promising xeno-free alternative to be used for in vitro expansion of chondrocytes for cartilage tissue engineering or cartilage repair therapies.