Purpose
Investigating the effects of Platelet Rich Plasma (PRP) and Hyaluronic Acid (HA) on bone marrow-derived stem cells (BMSCs) proliferation.

Methods
Sprague-Dawley rat (SDR) blood centrifuged via RegenKit® protocols in BCT tubes produced 4-5 ml PRP with 1.6-fold platelet count increase and >85% WBC depletion. CaCl2 activation (100 nM) of pooled PRP prevented gelling reaction with media ensuring nutrient diffusion to cells.
SDR femur BMSCs were cultured (DMEM/low glucose media, 1% antibiotic/antimycotic, 10% FBS) until P4 and plated at 3.6 x 104 cells/well.
Twelve experimental media contained PRP at 1%, 5%, 10%, 20%, HA at 0.25 mg, 0.5 mg, 0.75 mg, and 1.0 mg, 1% PRP + 0.25 mg or 0.5 mg HA (1550 kDA non-crosslinked, Regen Lab SA), and 5% PRP + 0.25 mg or 0.5 mg HA. Samples were prepared in quadruplicate with media changes at days 3 and 6.
Cellular proliferation was measured with MTS formazan assay and Mann-Whitney U nonparametric tests for statistical analysis.

Results
Significant increases in BMSC proliferation were observed with 1% (p = 0.0006), 5% (p = 0.0059), 10% (p = 0.006), and 20% (p = 0.0015) PRP but not with HA. A trend across PRP groups (p = 0.007) suggests dose-response effects.

Conclusion
We observed a significant increase in BMSC proliferation in culture with PRP and a negative proliferative trend at high PRP concentrations,possibly from cell surface receptor downregulation. It is unclear why enhanced proliferation was not observed with HA.
Whether use of rat blood in a system designed for human blood affects PRP preparations remains unknown. Our research coordinates with a multi-center placebo-controlled RCT comparing the effects of intraarticular PRP-HA and HA-alone knee supplementation in patients who previously received intraarticular HA but continue to have knee pain.