Hypoxia, a common environmental condition, influences cell signals and functions. Here, we compared the effects of hypoxia (1% oxygen) and normoxia (air) on chondrogenic differentiation of human mesenchymal stem cells (MSCs). For in vitro chondrogenic differentiation, MSCs were concentrated to form pellets and subjected to conditions appropriate for chondrogenic differentiation under normoxia and hypoxia, followed by the analysis for the expression of genes and proteins of chondrogenesis and endochondral ossification. MSCs induced for differentiation under hypoxia increased in chondrogenesis, but decreased in endochondral ossification compared to those under normoxia. MSCs induced for differentiation were more resistant to apoptosis under hypoxia compared to those under normoxia. The hypoxia-dependent protection of MSCs from chondrogenesis-induced apoptosis correlated with an increase in the activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/FoxO pathway. These results suggest that the PI3K/Akt/FoxO survival pathway activated by hypoxia in MSCs enhances chondrogenesis and plays an important role in preventing endochondral ossification.

Lipoma arborescens is a rare entity of the synovium and frequently occurs in the joints. Lipoma arborescens involving the synovial sheaths of the tendons is exceedingly rare. We report a case of a 12-year-old girl with lipoma arborescence affecting the synovial sheaths of the peroneal, posterior tibialis, and flexor tendons. Identification of the typical features of fat tissues in the proliferative synovium on MRI may help in making a correct diagnosis. The clinical presentation and MRI findings are described, and the entity is briefly reviewed.

The current results demonstrated the isolation of MSCs from LF. The cellular response to TGF-β1 implied that these cells might play an important role in the pathogenesis of LF hypertrophy. TSA, which blocks the effects of TGF-β1, may be a potent therapeutic choice for inhibiting LF hypertrophy.