Osteoarthritis (OA) is a degenerative joint disease that affects a lot of people worldwide. Current treatment for OA mainly focuses on halting or slowing down the disease progress and to improve the patient’s quality of life and functionality. Autologous chondrocyte implantation (ACI) is a new treatment modality with the potential to promote regeneration of worn cartilage. Traditionally, foetal bovine serum (FBS) is used to expand the chondrocytes. However, the use of FBS is not ideal for the expansion of cells mean for clinical applications as it possesses the risk of animal pathogen transmission and animal protein transfer to host. Human platelet lysate (HPL) appears to be a suitable alternative to FBS as it is rich in biological factors that enhance cell proliferation. Thus far, HPL has been found to be superior in promoting chondrocyte proliferation compared to FBS. However, both HPL and FBS cannot prevent chondrocyte dedifferentiation. Discrepant results have been reported for the maintenance of chondrocyte redifferentiation potential by HPL. These differences are likely due to the diversity in the HPL preparation methods. In the future, more studies on HPL need to be performed to develop a standardized technique which is capable of producing HPL that can maintain the chondrocyte redifferentiation potential reproducibly. This review discusses the in vitro expansion of chondrocytes with FBS and HPL, focusing on its capability to promote the proliferation and maintain the chondrogenic characteristics of chondrocytes.

Human platelet lysate (hPL) has high levels of fibrinogen and coagulation factors, which can lead to gel and precipitate formation during storage and cell culture. Heparin derived from animals is commonly added to minimize these risks, but cannot completely eliminate them. Thus, this study proposes an alternative method to prepare fibrinogen-depleted hPL (Fd-hPL) that supports heparin-free expansion of mesenchymal stem cells (MSCs). hPL was added to heparin to prepare heparin-hPL (H-hPL), whilst Fd-hPL was prepared by adding calcium salt to hPL to remove the fibrin clot. The concentrations of calcium, fibrinogen, and growth factors in H-hPL and Fd-hPL were compared. The effects of H-hPL and Fd-hPL on umbilical cord-derived MSCs (UC-MSCs) were assessed. The results showed that Fd-hPL possessed a significantly higher calcium concentration and a lower fibrinogen level than H-hPL. The concentrations of BDNF, TGF-β1, and PDGF-BB showed no significant difference between H-hPL and Fd-hPL, but Fd-hPL had a lower VEGF concentration. Fd-hPL retained the characteristics of UC-MSCs, as it did not affect the cell viability, proliferation, multilineage differentiation potential, or surface marker expression. In conclusion, Fd-hPL effectively supported the in vitro expansion of MSCs without compromising their characteristics, positioning it as a potential substitute for FBS in MSC culture.

Background and aims: Enhanced cell proliferation is crucial for reducing production time and cost in cell therapy, and human platelet lysate (HPL) is often used to boost cell proliferation due to its favorable safety profile. Understanding the roles of different HPL components and their effects on cell culture can lead to more informed choices in medium formulation, which in turn can influence cell behavior and outcomes. Therefore, this study aimed to investigate the effects of two types of HPL, i.e., heparin-supplemented HPL (He-HPL) and fibrinogen-depleted HPL without heparin (Fd-HPL), on human osteoblasts. Materials and Methods: He-HPL and Fd-HPL were prepared from expired platelet concentrates. The presence of growth factors, i.e., brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF), and cytokines, i.e., interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α), in HPL was evaluated. Human fetal osteoblast (hFOB) cells were cultured in Dulbecco’s Modified Eagle Medium supplemented with either He-HPL or Fd-HPL. The cell morphology, viability, calcium deposition, and expression of osteogenic genes were assessed. Results: Comparable levels of BDNF (p > 0.05), VEGF (p > 0.05), and IL-6 (p > 0.05) were detected in both types of HPL, whereas He-HPL exhibited significantly higher levels of TNF-α (p < 0.05). However, there were no notable differences in cell morphology, viability, population doubling time, or total cell yield between the two HPL types. Similarly, no differences were observed in the mineralization of cells treated with He-HPL compared to Fd-HPL. Nonetheless, hFOB cells cultured with He-HPL demonstrated significantly higher expression of osteogenic markers Runx2 and ALP (p < 0.05) compared to those cultured with Fd-HPL. Conclusions: He-HPL and Fd-HPL demonstrate comparable performance in promoting osteoblast proliferation and mineralization, making both usable for bone tissue engineering. However, He-HPL might have a slight edge as it enhances osteogenic gene expression.