Philipp Niemeyer

Influence of Platelet-Rich Plasma on Osteogenic Differentiation of Mesenchymal Stem Cells and Ectopic Bone Formation in Calcium Phosphate Ceramics

Platelet-rich plasma (PRP) contains a mixture of growth factors that play an important role in wound and fracture healing. While PRP enhanced bone formation by autogenous cancellous bone grafts, its influence in combination with different bone substitutes remained unknown. This study evaluated the effect of PRP on osteogenic differentiation and ectopic bone formation of human mesenchymal stem cells (MSC) in distinct resorbable calcium phosphate ceramics. Calcium-deficient hydroxyapatite (CDHA) blocks with a large specific surface area (48 m2/g) and β-tricalcium phosphate (β-TCP) with a low specific surface area (<0.5 m2/g) were loaded with 2 × 105 bone marrow-derived MSC. Half of the specimens were treated with 5-fold concentrated PRP. Biocomposites were implanted subcutaneously into SCID mice or kept under osteogenic culture conditions for 2 weeks before implantation. The addition of PRP increased the specific alkaline phosphatase (ALP) activity (p = 0.012) in undifferentiated MSC/CDHA composites but not in MSC/β-TCP composites. Osteogenic preinduction was ineffective for CDHA and reduced ALP activity of β-TCP composites significantly at explantation. Ectopic bone formation was stronger in MSC/CDHA (7/32) compared to MSC/β-TCP (2/30) composites, but no influence of PRP was evident. In conclusion, the effect of PRP depended on the type of ceramic and the differentiation status of the MSC, and enhanced ALP activity of MSC on the high surface scaffold CDHA only, but PRP did not improve osteogenesis in our setting.

Combined Meniscus and Cartilage Lesions

The intimate connections between the menisci and the osteochondral unit of the femoro-tibial compartment are based on their specific anatomical structure. Understanding the underlying structural and anatomical basis helps to understand the causes why meniscal lesions (and meniscus extrusion) may lead to cartilage loss and why cartilage loss may also induce meniscal damage. In turn, the reconstructive surgical consequences are also based on these topographical correlations.