Background: Platelet-rich plasma (PRP) has been considered a promising tool for cartilage regeneration. However, increasing evidence has demonstrated the controversial effects of PRP on tissue regeneration, partially due to the unsatisfactory cell source. Chondrogenic progenitor cells (CPCs) have gained increasing attention as a potential cell source due to their self-renewal and multipotency, especially toward the chondrogenic lineage, and, thus, may be an appropriate alternative for cartilage engineering. Purpose: To compare the effects of PRP on CPC, mesenchymal stem cell (MSC), and chondrocyte proliferation, chondrogenesis, and cartilage regeneration. Study Design: Controlled laboratory study. Methods: Whole blood samples were obtained from 5 human donors to create PRPs (0, 1000 × 109, and 2000 × 109 platelets per liter). The proliferation and chondrogenesis of CPCs, bone marrow–derived MSCs (BMSCs), and chondrocytes were evaluated via growth kinetic and CCK-8 assays. Immunofluorescence, cytochemical staining, and gene expression analyses were performed to assess chondrogenic differentiation and cartilaginous matrix formation. The in vivo effects of CPCs, BMSCs, and chondrocytes on cartilage regeneration after PRP treatment were measured by use of histopathological, biochemical, and biomechanical techniques in a cartilage defect model involving mature male New Zealand White rabbits (critical size, 5 mm). Results: The CPCs possessed migration abilities and proliferative capacities superior to those of the chondrocytes, while exhibiting a chondrogenic predisposition stronger than that of the BMSCs. The growth kinetic, CCK-8, cytochemical staining, and biochemical analyses revealed that the CPCs simultaneously displayed a higher cell density than the chondrocytes and stronger chondrogenesis than the BMSCs after PRP stimulation. In addition, the in vivo study demonstrated that the PRP+CPC construct yielded better histological (International Cartilage Repair Society [ICRS] score, mean ± SEM, 1197.2 ± 163.2) and biomechanical (tensile modulus, 1.523 ± 0.194) results than the PRP+BMSC (701.1 ± 104.9, P < .05; 0.791 ± 0.151, P < .05) and PRP+chondrocyte (541.6 ± 98.3, P < .01; 0.587 ± 0.142, P < .01) constructs at 12 weeks after implantation. Conclusion: CPCs exhibit superiority over MSCs and chondrocytes in PRP scaffold-based cartilage regeneration, and PRP+CPC treatment may be a favorable strategy for cartilage repair. Clinical Relevance: These findings provide evidence highlighting the preferable role of CPCs as a cell source in PRP-mediated cartilage regeneration and may help researchers address the problem of unsatisfactory cell sources in cartilage engineering.
The Role of Chondrocyte Morphology and Volume in Controlling Phenotype—Implications for Osteoarthritis, Cartilage Repair, and Cartilage Engineering