PTHrP promotes chondrogenesis and suppresses hypertrophy from both bone marrow-derived and adipose tissue-derived MSCs.

During chondrogenesis from mesenchymal stem cells (MSCs), inadequate differentiation and hypertrophic differentiation are two important limitations. The purpose of this study was to test the hypothesis that chondrogenesis is enhanced and unwanted hypertrophic changes are suppressed by treating bone marrow-derived (BMMSCs) and adipose tissue-derived mesenchymal stem cells (ATMSCs) with parathyroid hormone-related peptide (PTHrP). To induce chondrogenesis, in vitro pellet cultures were carried out using 2.5x10(5) MSCs at passage 3 in chondrogenic medium containing 5 ng/ml of TGF-beta(2) for BMMSCs, and 5 ng/ml of TGF-beta(2) and 100 ng/ml of BMP-7 for ATMSCs. From the 14th day of culture, subsets of pellets were treated with PTHrP [0, 10, 100 ng/ml], and after two more weeks of in vitro culture, pellets were harvested for analysis. The addition of PTHrP dose-dependently increased DNA contents in both BMMSCs and ATMSCs. GAG contents also increased after PTHrP treatment. The gene expression of COL1A1 decreased by three-fourths, while the decrease was not evident in ATMSCs after PTHrP treatment. SOX-9 mRNA increased up to four fold in both BMMSCs and ATMSCs, and COL2A1 gene expression sharply increased to sevenfold in BMMSCs and to 4 fold in ATMSCs. COL10A1 gene expression decreased by a third in both cell types, and Runx-2 expression dropped sharply in both cell types after PTHrP treatment. Safranin-O and immunohistochemistry for type I, II, X collagen and Runx-2 generally paralleled qRT-PCR findings with minor variations. In conclusion, PTHrP was found to promote chondrogenesis and suppress hypertrophy during in vitro chondrogenesis from both BMMSCs and ATMSCs, which supports its use for cartilage tissue engineering.