Perichondrial progenitor cells promote proliferation and chondrogenesis of mature chondrocytes

Autologous chondrocytes are effective sources of cell therapy for engineering cartilage tissue to repair chondral defects, such as degenerative arthritis. The expansion of cells with chondrocyte characteristics has become a major challenge due to inadequate donor sites and poor proliferation of mature chondrocytes. The perichondrial progenitor cells (P cells) from the cambium layer of the perichondrium possessed significantly higher mesenchymal stem cell markers than chondrocytes (C cells). In the transwell co-culture system, P cells increased the passaging capacity of C cells from P6 to P9, and the cell number increased 128 times. This system increased the percentage of Alcian blue-positive chondrocytes from 40% in P6 to 62% in P9, contributing about 198 times more Alcian blue-positive chondrocytes than the control group. C cells co-cultured with P cells also exhibited higher proliferation than C cells cultured with P cell-conditioned medium. Similar results were obtained in nude mice that were subcutaneously implanted with C cells, P cells, or a mixture of the two cell types, in which the presence of both cells enhanced neocartilage formation in vivo. In aggregate, P cells enhanced the proliferation of C cells in a dose-dependent manner and prolonged the longevity of mature chondrocytes for clinical applications.