MicroRNA-21 controls the development of osteoarthritis by targeting GDF-5 in chondrocytes

Osteoarthritis is a common cause of functional deterioration in older adults and is an immense burden on the aging population. Altered chondrogenesis is the most important pathophysiological process involved in the development of osteoarthritis. However, the molecular mechanism underlying the regulation of chondrogenesis in patients with osteoarthritis requires further elucidation, particularly with respect to the role of microRNAs. MiR-21 expression in cartilage specimens was examined in 10 patients with knee osteoarthritis and 10 traumatic amputees. The effect of miR-21 on chondrogenesis was also investigated in a chondrocyte cell line. The effect of miR-21 on the expression of growth differentiation factor 5 (GDF-5) was further assessed by luciferase reporter assay and western blot. We found that endogenous miR-21 is upregulated in osteoarthritis patients, and overexpression of miR-21 could attenuate the process of chondrogenesis. Furthermore, we identified GDF-5 as the direct target of miR-21 during the regulation of chondrogenesis. Our data suggest that miR-21 has an important role in the pathogenesis of osteoarthritis and is a potential therapeutic target.

Identification of a GDF5 Mutation in a Korean Patient with Brachydactyly Type C without Foot Involvement

Brachydactyly type C (BDC) is characterized by shortening of the middle phalanges of the index, middle, and little fingers. Hyperphalangy of the index and middle finger and shortening of the first metacarpal can also be observed. BDC is a rare genetic condition associated with the GDF5 gene, and this condition has not been confirmed by genetic analysis so far in the Korean population. Herein, we present a case of a 6-yr-old girl diagnosed with BDC confirmed by molecular genetic analysis. The patient presented with shortening of the second and third digits of both hands. Sequence analysis of the GDF5 gene was performed and the pathogenic mutation, c.1312C>T (p.Arg438Cys), was identified. Interestingly, this mutation was previously described in a patient who presented with the absence of the middle phalanges in the second through fifth toes. However, our patient showed no involvement of the feet. Considering intrafamilial and interfamilial variability, molecular analysis of isolated brachydactyly is warranted to elucidate the genetic origin and establish a diagnosis.