SRY-related high-mobility-group box 9 (Sox9) gene is a cartilage-specific
transcription factor that plays essential roles in chondrocyte differentiation and
cartilage formation. The aim of this study was to investigate the feasibility of
genetic delivery of Sox9 to enhance chondrogenic differentiation of human umbilical
cord blood-derived mesenchymal stem cells (hUC-MSCs). After they were isolated from
human umbilical cord blood within 24 h after delivery of neonates, hUC-MSCs were
untreated or transfected with a human Sox9-expressing plasmid or an empty vector. The
cells were assessed for morphology and chondrogenic differentiation. The isolated
cells with a fibroblast-like morphology in monolayer culture were positive for the
MSC markers CD44, CD105, CD73, and CD90, but negative for the differentiation markers
CD34, CD45, CD19, CD14, or major histocompatibility complex class II. Sox9
overexpression induced accumulation of sulfated proteoglycans, without altering the
cellular morphology. Immunocytochemistry demonstrated that genetic delivery of Sox9
markedly enhanced the expression of aggrecan and type II collagen in hUC-MSCs
compared with empty vector-transfected counterparts. Reverse transcription-polymerase
chain reaction analysis further confirmed the elevation of aggrecan and type II
collagen at the mRNA level in Sox9-transfected cells. Taken together, short-term Sox9
overexpression facilitates chondrogenesis of hUC-MSCs and may thus have potential
implications in cartilage tissue engineering.