Simvastatin Enhances the Chondrogenesis But Not the Osteogenesis of Adipose-Derived Stem Cells in a Hyaluronan Microenvironment

Abstract

Directing adipose-derived stem cells (ADSCs) toward chondrogenesis is critical for ADSC-based articular cartilage regeneration. Simvastatin (SIM) is a lipid-lowering drug that also affects both chondrogenic and osteogenic differentiation of ADSCs by upregulating bone morphogenetic protein-2 (BMP-2). We previously found that ADSC chondrogenesis can be initiated and promoted in a hyaluronan (HA) microenvironment (HAM). Here, we further hypothesized that SIM can augment the HAM-induced chondrogenesis but not osteogenesis of ADSCs and that this synergism can be applied for articular cartilage regeneration. ADSCs were treated with SIM in a HAM in HA-coated wells or an HA-enriched fibrin (HA/Fibrin) hydrogel, and chondrogenic differentiation of ADSCs and formation of cartilage were evaluated. Treatment with SIM in a HAM (SIM plus HAM) induced the expression of BMP-2 and transcription factors for chondrogenesis (SOX-9) and osteogenesis (RUNX-2) in ADSCs, and these effects were reversed by CD44 blockade. Furthermore, ADSCs exposed to SIM plus HAM exhibited cell aggregation, chondrogenic gene (collagen type II and aggrecan) expression and sulfated glycosaminoglycan formation. By contrast, SIM-induced osteogenesis in ADSCs was reduced in a HAM, as determined by measuring osteogenic gene (osteocalcin and alkaline phosphatase) expression and calcium deposition. These inhibitory effects were not altered by changes in the HA molecular weight (80~2000 kDa). In addition, SIM enhanced articular cartilage regeneration, as demonstrated by implantation of an ADSCs/HA/Fibrin construct in an ex vivo porcine articular chondral defect model. These results indicate that a HAM may be used as a chondroinductive agent to enhance SIM-induced MSC chondrogenesis but prevent osteogenesis.