Cyanidin suppresses autophagic activity regulating chondrocyte hypertrophic differentiation

Abstract

Cartilage is a kind of special connective tissue which does not contain neither blood vessels nor lymphatics and nerves. Therefore, the damage in cartilage is difficult to be repaired spontaneously. Constructing tissue engineered cartilage provides a new technique for cartilage repairing. Mesenchymal stem cells (MSCs) possess a unique capability of self-renew and can differentiate into pre-chondrocytes which are frequently applied as seed cells in tissue engineering. However, in regenerated cartilage the chondrocytes derived from MSCs can hardly maintain homeostasis and preferentially present hypertrophic like phenotype. We investigated the effects of cyanidin, a natural organic compound, on chondrogenic and subsequent hypertrophic differentiation of MSCs in order to seek approaches to inhibit chondrocyte hypertrophy. We evaluated the effects of cyanidin on expression of chondrogenic and hypertrophic marker genes through RT-PCR, Western blot, alcian blue staining, and immunocytochemistry. The results showed that both chondrogenic related genes Sox9, Col2a1, and hypertrophic marker genes Runx2, Col10a1 were inhibited by cyanidin. In addition, we found that cyanidin promoted Nrf2 and p62 expression and suppressed LC3B expression during chondrogenic stage of MSCs. Meanwhile phosphorylation of IκBα and autophagosome related protein LC3B were inactivated by cyanidin during chondrocyte hypertrophic stage. Furthermore, rapamycin, an autophagy activator, abrogated the inhibitory effect of cyanidin on chondrogenic, and hypertrophic differentiation of MSCs. In conclusion, one potential mechanism of cyanidin, by which the chondrogenic and hypertrophic differentiation of MSCs were inhibited, was due to decreased autophagy activity. Our results indicated that cyanidin was a potential therapeutic agent for keeping mature chondrocyte functions.

Nrf2/ARE Signaling Directly Regulates SOX9 to Potentially Alter Age-Dependent Cartilage Degeneration

“…Importantly, we also provided evidence that a systemic Nrf2 deficiency results in Sox9 suppression in murine articular chondrocytes in vivo. At an older age, Nrf2-KO mice developed a mild osteoarthritic articular cartilage degeneration, which is in line with earlier reported proteoglycan loss upon postnatal Sox9 depletion [26]. Thus, we postulate that accumulative oxidative stress age-dependently contributes to cartilage degeneration in the knee and that Nrf2 helps protect its ECM integrity through maintaining Sox9-mediated postnatal tissue homeostasis.…”

“…Further, a successful, direct pharmacological activation of Nrf2 target genes by methysticin has already been shown in vitro and in vivo in another context [ 24 , 25 ]. Interestingly, Cao et al [ 26 ] reported that cyanidin-induced Nrf2 overexpression reduced the relative mRNA expression of Sox9 and Col II in the murine embryonic mesenchymal progenitor cell line C3H10T1/2. At first glance, these data seemingly contradict our findings.…”

“…Importantly, SOX9-mediated responses are well known to be largely context dependent [ 28 ]. Since Cao et al used murine progenitor cells [ 26 ], while we used adult human chondrocytes, contrasting responses may result from differences in species and developmental stages as well.…”

Osteoclast-derived exosomal let-7a-5p targets Smad2 to promote the hypertrophic differentiation of chondrocytes

“…One microgram of total RNA was reverse transcribed to single-stranded cDNA with a PrimeScript RT Reagent Kit (Takara, Nojihigashi, Japan). Table 1 shows the specific primers used in the quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) (6). The cycling conditions were set as 95°C for 30 s and 40 cycles at 95°C for 5 s and 60°C for 30 s. The reference gene GAPDH was used for normalization to obtain the relative mRNA Western blot analysis.…”

Autophagy Is a Crucial Path in Chondrogenesis of Adipose-Derived Mesenchymal Stromal Cells Laden in Hydrogel

“…Modulation of autophagy is fundamental for cell differentiation in different cell types (i.e., myocytes, osteoblasts, neuronal cells, adipocytes, chondrocytes) [ 2 , 20 , 21 , 22 , 23 ]. The use of positive and negative modulators of autophagy have contributed to confirming this direct relation with chondrogenic differentiation [ 15 , 24 ]. It has been shown that autophagy activation contributes to suppressing the chondrogenesis of MSCs, while the reduction of the autophagic process contributes to the activation of MSCs chondrogenesis [ 25 ].…”