p16INK4a and its regulator miR-24 link senescence and chondrocyte terminal differentiation-associated matrix remodeling in osteoarthritis

Abstract

IntroductionRecent evidence suggests that tissue accumulation of senescent p16INK4a-positive cells during the life span would be deleterious for tissue functions and could be the consequence of inherent age-associated disorders. Osteoarthritis (OA) is characterized by the accumulation of chondrocytes expressing p16INK4a and markers of the senescence-associated secretory phenotype (SASP), including the matrix remodeling metalloproteases MMP1/MMP13 and pro-inflammatory cytokines interleukin-8 (IL-8) and IL-6. Here, we evaluated the role of p16INK4a in the OA-induced SASP and its regulation by microRNAs (miRs).MethodsWe used IL-1-beta-treated primary OA chondrocytes cultured in three-dimensional setting or mesenchymal stem cells differentiated into chondrocyte to follow p16INK4a expression. By transient transfection experiments and the use of knockout mice, we validate p16INK4a function in chondrocytes and its regulation by one miR identified by means of a genome-wide miR-array analysis.Resultsp16INK4a is induced upon IL-1-beta treatment and also during in vitro chondrogenesis. In the mouse model, Ink4a locus favors in vivo the proportion of terminally differentiated chondrocytes. When overexpressed in chondrocytes, p16INK4a is sufficient to induce the production of the two matrix remodeling enzymes, MMP1 and MMP13, thus linking senescence with OA pathogenesis and bone development. We identified miR-24 as a negative regulator of p16INK4a. Accordingly, p16INK4a expression increased while miR-24 level was repressed upon IL-1-beta addition, in OA cartilage and during in vitro terminal chondrogenesis.ConclusionsWe disclosed herein a new role of the senescence marker p16INK4a and its regulation by miR-24 during OA and terminal chondrogenesis.

Cellular senescence impact on immune cell fate and function

“…On the other hand, by interfering with MDM2 (mouse double minute 2)‐dependent degradation of p53, p14/p19 ARF controls p53/p21 WAF1 ‐induced G1 or G2 cell cycle arrest (Gil & Peters, 2006). Remarkably, using knockout mice models for this locus, it was possible to reveal that these senescence features could be associated with the terminal differentiation program in some specific cell types including keratinocytes (Paramio et al ., 2001; Bachoo et al ., 2002), chondrocytes (Philipot et al ., 2014), myofibers (Pajcini et al ., 2010), and also megakaryocytic cells (Muñoz‐Espín & Serrano, 2014). Megakaryocytic cells, myeloid‐derived immune cells from which blood platelets originate, are required for wound healing and immune responses (Besancenot et al ., 2010), opening new avenues to explore features of senescence in other types of immune cells.…”

Expression of p16INK4a is a biomarker of chondrocyte aging but does not cause osteoarthritis

“…OA progression is driven by inflammatory cytokines that initiate a cascade of matrix degradation, and the prominent role for SASP factors such as matrix metalloproteinase 13 (MMP‐13) and interleukin 1 alpha (IL‐1α) implicates senescent cells in the joint as a source of these catabolic molecules (Loeser, Collins & Diekman, 2016). The functional role of p16 INK4a in cartilage aging and OA is less clear, although knockdown and overexpression studies in cultured chondrocytes have confirmed that p16 INK4a expression is associated with the production of catabolic factors involved in dedifferentiation and OA (Philipot et al., 2014; Zhou, Lou & Zhang, 2004). Further evidence that non‐cell‐autonomous effects of senescence contribute to OA has come from a recent study showing that selective elimination of senescent cells can mitigate the development of OA (Jeon et al., 2017).…”

Ascorbic acid provides protection for human chondrocytes against oxidative stress

“…Cell viability and senescence are characterized by a loss of function and integrity, which contribute to the progressive degeneration of tissues (25,26). The cell viability and senescence of chondrocytes were determined under oxidative stress conditions mediated by H 2 O 2 or AA pretreatment using an MTT assay or the SA-β-gal assay, as shown in Fig.…”