Predominant promotion by tacrolimus of chondrogenic differentiation to proliferating chondrocytes.
"Tacrolimus (FK506) has been used as a therapeutic drug beneficial for the treatment of rheumatoid arthritis in humans. In this study, we investigated the effects of FK506 on cellular differentiation in cultured chondrogenic cells. Culture with FK506 led to a significant and concentration-dependent increase in Alcian blue staining for matrix proteoglycan at 0.1 to 1,000 ng/ml, but not in alkaline phosphatase (ALP) activity, in ATDC5 cells, a mouse pre-chondrogenic cell line, cultured for 7 to 28 days, while the non-steroidal anti-inflammatory drug indomethacin significantly decreased Alcian blue staining in a concentration-dependent manner, without altering ALP activity. FK506 significantly increased the expression of mRNA for both type II and type X collagen, but not for osteopontin, in ATDC5 cells. Similar promotion was seen in chondrogenic differentiation in both mouse metatarsals and chondrocytes cultured with FK506. However, FK506 failed to significantly affect transcriptional activity of the reporter construct for either sry-type HMG box 9 (Sox9) or runt-related transcription factor-2 (Runx2), which are both transcription factors responsible for chondrocytic maturation as a master regulator. These results suggest that FK506 may predominantly promote cellular differentiation into proliferating chondrocytes through a mechanism not relevant to the transactivation by either Sox9 or Runx2 in chondrogenic cells."
"FK506 preferentially inhibits the production of inflammatory cytokines, such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β, through suppression of T-cell activation in human peripheral blood mononuclear cells, without markedly affecting proliferation and differentiation of bone marrow cells"
"The immunosuppressant drugs FK506 and cyclosporine A inhibit the activity of the ubiquitously expressed Ca2+/calmodulin–dependent protein phosphatase, calcineurin, through an interaction between the calcineurin subunit A and different immunophilins such as FK506-binding protein for FK506 and cyclophilins for cyclosporine A, which consequently leads to the inhibition of calcineurin-mediated dephosphorylation of the nuclear factor of activated T cells in T-lymphocyte cells"
"In chondrogenic ATDC5 cells, chondrogenic differentiation is promoted by FK506, but not by cyclosporine A, in terms of matrix proteoglycan production and type II collagen (Col II) expression."
Insulin increased proteoglycan matrix accumulation by ATDC5 cells.
"FK506 would predominantly promote cellular differentiation from pre-chondrocytes to proliferating chondrocytes, without markedly altering that from proliferating to hypertrophic chondrocytes or from hypertrophic to calcified chondrocytes, in cultured metatarsals ex vivo." See Figure 9 for a great graphic explaining the different stages of chondrogenic differentiation.
The immunosuppressant FK506 promotes development of the chondrogenic phenotype in human synovial stromal cells via modulation of the Smad signaling pathway.
"hSSCs were isolated from synovium of the knee joint and 2x10(5) cells were subjected to pellet culture in chondrogenic culture medium for 3 weeks with or without growth factors [bone morphogenetic protein 2 (BMP2) or transforming growth factor beta(1) (TGFbeta(1))] and +/- addition of FK506 in chondrogenic culture media was evaluated. Chondrogenesis was assessed by the size of the pellet, the production of proteoglycans, and messenger RNA (mRNA) levels for chondrogenic markers. Furthermore, levels and intracellular location of phosphorylated Smad proteins related to BMP signaling and TGFbeta signaling were evaluated following exposure to FK506.
FK506 enhanced the differentiation of hSSCs toward a chondrogenic phenotype in a dose-dependent manner associated with increases in glycosaminoglycan synthesis and increased mRNA levels for chondrogenic marker genes. Additionally, FK506 further enhanced chondrogenesis of synovial stromal cells (SSCs) induced by BMP2 and TGFbeta(1), also in a dose-dependent manner. Notably, phosphorylation of Smad1/5/8 and Smad3 was significantly increased by FK506. Also, the ratio of nuclear translocation to cytoplasmic levels of phosphorylated Smad1/5/8 and Smad3 were increased following exposure of SSCs to FK506. Moreover, inhibition of Smad signaling significantly abrogated FK506-induced chondrogenic differentiation of SSCs."
"The immunosuppressive effect of FK506 is believed to be related to its ability to inhibit calcineurin, an enzyme involved in the activation of the nuclear factor of activated T cells (NFAT)"<-inhibiting calcineurin may help make you taller. Although some NFATs seem to pro-chondrogenic whereas others are anti-.
"SSCs were isolated from human synovium which was harvested from the knee joint of four patients during arthroscopic surgery"<-Ages 19 to 57.
"To assess chondrogenic differentiation, a pellet culture system was used24. Approximately 2 × 105 cells (passages 3–5) were placed in a 15-ml polypropylene tube, and centrifuged at 500g for 10 min. The pellets were cultured at 37°C with 5% CO2 in 500 μl of chondrogenic culture medium that contained HG-DMEM with 10% FBS, supplemented with 50 μg/ml ascorbate-2-phosphate, 100 μg/ml sodium pyruvate, and 50 mg/ml insulin, transferrin, and selenious acid (ITS) + Premix"
Inhibition of the ERK, PI3K, and the p38 pathways did not affect Tacrolimus' enhancement of chondrogenesis.
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