Protein misfolding cyclic amplification (PMCA) is a cell-free assay mimicking the prion replication process. However, constraints affecting PMCA have not been well-defined. Although cellular prion protein (PrPC) is required for prion replication, the influence of PrPC abundance on PMCA has not been assessed. Here, we show that PMCA was enhanced by using mouse brain material in which PrPC was overexpressed. Tg(MoPrP)4112 mice overexpressing PrPC supported more sensitive and efficient PMCA than wild type mice. As brain homogenate of Tg(MoPrP)4112 mice was diluted with PrPC-deficient brain material, PMCA became less robust. Our studies suggest that abundance of PrPC is a determinant that directs enhancement of PMCA. PMCA established here will contribute to optimizing conditions to enhance PrPSc amplification by using concentrated PrPC source and expands the use of this methodology. (C) 2009 Elsevier Inc. All rights reserved.