Cartilage Tissue Engineering using Chondrocyte-Derived Extracellular Matrix Scaffold Suppressed Vessel Invasion During Chondrogenesis of Mesenchymal Stem Cells In Vivo

Loss of chondrogenic phenotypes of tissue engineered cartilage using mesenchymal stem cells (MSCs) in vivo are thought to be influenced by environmental factors like vessel invasion in particular. This study investigated effect of a chondrocyte-derived extracellular matrix (CD-ECM) scaffold on the hypertrophic changes and vessel invasion into tissue engineered cartilage using rabbit MSCs in comparison with a synthetic polyglycolic acid (PGA) scaffold. Rabbit MSCs in CD-ECM or PGA scaffold were differentiated for 1 week in vitro and implanted in the back of nude mice for 6 weeks in vivo. Gross observation showed red stains, indicative of vessel invasion, increased along with the loss of chondrogenic phenotype in safranin-O stains, which was more prominent in the PGA constructs. The area showing loss of chondrogenic phenotypes in safranin-O stain was correlated well with the mineralized area in the von kossa stain and the area with vessel-like structures in the gomori aldehyde fuchsin stain at 6 weeks in terms of their size and distribution. Also, vessel invasion took place more deeply and intensively into the constructs, in accordance with the expression of angiogenic markers (CD31, VEGF-A and HIF-1 alpha) and a macrophage marker (CD68). This phenomenon progressed much more rapidly in the PGA constructs than in the CD-ECM constructs, and correlated well with the loss of chondrogenic phenotypes. In conclusion, this study showed that tissue engineered cartilage using the CD-ECM scaffold maintained better chondrogenic phenotypes in vivo and showed lower levels of hypertrophic changes and vessel invasion.