Progenitor cells with high chondrogenic potential are present in the adult human meniscus

Abstract

Purpose: Due to the limited regenerative capacity of the meniscus, (partial) meniscectomy is often the treatment of choice. Consequential loss of contact area and abnormal distribution of forces lead to osteoarthritis. Therefore, there is an unmet clinical need for meniscus regeneration. Recently the presence of multipotent mesenchymal stromal (stem) cells (MSCs) or progenitor cells in different intra-articular tissues, for example in articular cartilage has been acknowledged. If progenitor cells are also present in the meniscus, they could be targeted for meniscus regeneration. Moreover, meniscus progenitors could be a new and possibly superior source of MSCs for meniscus repair strategies. Therefore, the purpose of this study is to isolate and characterize meniscus-derived progenitor cells from osteoarthritic meniscus tissue according to the MSC guidelines of the International Society for Cellular Therapy (ISCT). Method(s): Osteoarthritic menisci of 5 donors were digested for cellular isolation an progenitor cells were selected by fibronectin adhesion. Progenitors were cultured up to passage 4. Trilineage potential of meniscus-derived progenitor cells was compared to non-selected meniscus cells that were cultured up to passage 2. After 3 weeks of culturing in differentiation medium, the cells were stained with Alizarin red for osteogenic differentiation, Oil red O for adipogenic differentiation, and Fast Green / Safranin O staining for chondrogenic differentiation. Expression of positive (CD105, CD73 and CD90) and negative (CD45, CD34, CD11b, CD79A, and HLA-DR) MSC markers was assessed by flow cytometry. Meniscus cells were co-cultured with progenitor cells in a 20:80 ratio in the absence of growth factors (n=2 donors, 3 pellets per donor). Glycosaminoglycan and DNA content was determined using a dimethylmethylene-Blue (DMMB) and PicoGreen assay. Result(s): All progenitor and non-selected meniscus donors demonstrated osteogenic and adipogenic differentiation. All meniscus progenitors showed glycosaminoglycan deposition, indicating chondrogenic differentiation. In none of the of non-selected meniscus cells glycosaminoglycans could be detected by Safranin O staining (figure 1). Of the progenitor cells, 73-87% expressed the surface marker profile according to the ISCT MSC criteria(figure 2). Co-culture of meniscus cells with progenitor cells increased glycosaminoglycan deposition (figure 3). Conclusion(s): Meniscus progenitor cells are present in the osteoarthritic human meniscus. In our experimental set-up, meniscus progenitor cells have trilineage potential with higher chondrogenic capacity than the total meniscus cell population. Flow cytometry indicates that meniscus progenitor cells express MSC markers. Due to the high chondrogenic potential, easy isolation and fast proliferation, meniscus progenitor cells are a promising cell source for regeneration of meniscus tissue. [Formula presented] [Formula presented] [Formula presented] Copyright © 2020