Targeting of chondrocyte plasticity via connexin43 modulation attenuates cellular senescence and fosters a pro-regenerative environment in osteoarthritis

Abstract

Osteoarthritis (OA), a chronic disease characterized by articular cartilage degeneration, is a leading cause of disability and pain worldwide. In OA, chondrocytes in cartilage undergo phenotypic changes and senescence, restricting cartilage regeneration and favouring disease progression. Similar to other wound-healing disorders, chondrocytes from OA patients show a chronic increase in the gap junction channel protein connexin43 (Cx43), which regulates signal transduction through the exchange of elements or recruitment/release of signalling factors. Although immature or stem-like cells are present in cartilage from OA patients, their origin and role in disease progression are unknown. In this study, we found that Cx43 acts as a positive regulator of chondrocyte-mesenchymal transition. Overactive Cx43 largely maintains the immature phenotype by increasing nuclear translocation of Twist-1 and tissue remodelling and proinflammatory agents, such as MMPs and IL-1β, which in turn cause cellular senescence through upregulation of p53, p16INK4a and NF-κB, contributing to the senescence-associated secretory phenotype (SASP). Downregulation of either Cx43 by CRISPR/Cas9 or Cx43-mediated gap junctional intercellular communication (GJIC) by carbenoxolone treatment triggered rediferentiation of osteoarthritic chondrocytes into a more differentiated state, associated with decreased synthesis of MMPs and proinflammatory factors, and reduced senescence. We have identified causal Cx43-sensitive circuit in chondrocytes that regulates dedifferentiation, redifferentiation and senescence. We propose that chondrocytes undergo chondrocyte-mesenchymal transition where increased Cx43-mediated GJIC during OA facilitates Twist-1 nuclear translocation as a novel mechanism involved in OA progression. These findings support the use of Cx43 as an appropriate therapeutic target to halt OA progression and to promote cartilage regeneration.

Mitochondria and metabolic transitions in cardiomyocytes: lessons from development for stem cell-derived cardiomyocytes

“…Reduced Cx43 is considered a marker for senescence in fibroblasts [285], glomerular mesangial cells [286], and hematopoietic stem cells (HSCs) [287], although upregulation of Cx43 increases senescence of chondrocytes [288]. Cx43 prevents senescence in HSCs by forming Fig.…”

Reprogramming of human fibroblasts into osteoblasts by insulin-like growth factor-binding protein 7

“…Cellular senescence is regarded as detrimental for tissue repair and regeneration since it induces replicative aging in cells, which directly contributes to their loss of regenerative capacity in tissue repair . Additionally, SASP proteins released by senescent cells can disrupt tissue homeostasis and potentially act on neighboring cells in a paracrine signaling manner . Thus, induction of cell senescence in the reprograming of fibroblast into OB appears contradictory.…”

“…[43][44][45][46] Additionally, SASP proteins released by senescent cells can disrupt tissue homeostasis and potentially act on neighboring cells in a paracrine signaling manner. 45,[47][48][49] Thus, induction of cell senescence in the reprograming of fibroblast into OB appears contradictory. Nevertheless, emerging evidence in embryonic and adult tissues indicates that cell senescence is beneficial in tissue homeostasis.…”

Applications of CRISPR for musculoskeletal research

“…For example, deletion of the gap junction channel protein connexin43 attenuates cellular senescence and promotes chondrocyte regeneration in osteoarthritis. 46 The power of CRISPR-mediated gene deletion to ‘cleanly’ dissect the contribution of closely related family members to cartilage biology was nicely demonstrated in a study of the WNT signalling pathway members. 47 Here, CRISPR was used to delete three WNT family members independently, thereby allowing the investigators to separately determine the contribution of each WNT factor to chondrocyte differentiation.…”