The study investigates whether Platelet Lysate (PL), a protein-rich component derived from blood platelets, could enhance the differentiation of bone marrow-derived mesenchymal stromal cells (BM-MSCs) into chondrocytes and osteocytes – vital for treating musculoskeletal injuries. Despite having higher levels of transforming growth factor-Beta (TGF-β1), a protein implicated in cellular differentiation, results proved PL is an adequate supplement for cell culture but does not significantly enhance BM-MSC chondrogenic differentiation as initially hypothesized.

Introduction and Background

• The research revolves around bone marrow-derived mesenchymal stromal cells (BM-MSCs), which are being explored for therapeutic applications to treat musculoskeletal injuries including tendon, ligament, and cartilage damages.
• BM-MSCs are traditionally cultured in medium supplemented with fetal bovine serum (FBS). However, concerns around antigenicity and potential viral or prion contamination of FBS led the researchers to explore alternative supplements such as Platelet Lysate (PL).
• PL contains elevated concentrations of growth factors, including transforming growth factor-beta (TGF-β), platelet-derived growth factors, and fibroblast growth factor, making it an interesting alternative culture medium. However, the effects of PL on MSC growth and differentiation hadn’t been fully established.

Methods and Procedures

• The scientists hypothesized that PL medium would have significantly higher amounts of TGF-β1 than FBS medium and would be associated with enhanced osteogenic and chondrogenic differentiation – the process where MSCs transform into osteocytes and chondrocytes, the cells that make up bone and cartilage respectively.
• MSCs were harvested from the bone marrow of five adult horses and cultured in either the traditional medium with FBS or medium supplemented with fibrinogen-depleted PL (FD-PL).
• The cells were monitored and their characteristics inspected through a procedure known as immunophenotyping. The differentiation was assessed through histology, gene expression analysis, and the amount of TGF-β1 was quantified in both types of media.

Findings

• The BM-MSCs cultured in both types of medium had similar profiles. Both cultures contained cells positive for stromal cell markers and negative for exclusion markers, indicating successful culture and growth.
• The FD-PL medium had significantly higher TGF-β1 concentrations compared to the FBS medium. Still, both supplements led to similar rates of chondrogenic and osteogenic differentiation.

Conclusion

• Due to the similar results between PL and FBS supplemented cultures, the authors conclude that PL can be considered an appropriate alternative medium for the culture of equine BM-MSCs up to the third generation of cells (passage 3).
• Despite this, and contrary to the initial hypothesis, the higher concentration of TGF-β1 in the PL medium did not result in a significant increase in chondrogenic differentiation compared to the FBS medium.