Biology subjects

Brenner, R. E.

Publications and source records attributed to Brenner, R. E..

3 recordsLinked to original sources

bioRxiv2024

p53-induced GDF-15 expression promotes a pro-regenerative response in human chondrocytes upon cartilage injury

Posttraumatic osteoarthritis (PTOA) is a special form of OA, developing after joint injuries. Except for some minor differences between the clinical characteristics of patients suffering from idiopathic OA (IOA) and PTOA, no biologic marker has yet been identified to distinguish IOA from PTOA. In this study, we investigated the expression of the stress-responsive cytokine growth differentiation factor 15 (GDF-15) in clinical samples from the Ulm OA study cohort (PTOA: n =12; IOA: n=54) and in a human ex vivo cartilage trauma model. We found significantly higher GDF-15 levels in synovial fluid of end-stage PTOA patients as compared to IOA patients. Further, we confirmed that fibroblast-like synoviocytes secreted increased levels of GDF-15 after stimulation with medium of ex vivo-traumatized cartilage. GDF-15 and its receptor, GFRAL, were significantly elevated in highly degenerated OA cartilage. By means of a human cartilage trauma model, we discovered that chondrocytes produced GDF-15 upon tissue injury, while antioxidative treatment attenuated GDF-15 secretion. We confirmed that oxidative stress and subsequent activation of p53 resulted in GDF-15 expression. As a transcriptional target of p53, GDF-15 was associated with chondrosenescence. Although the cytokine might therefore represent a senescence-associated secretory phenotype (SASP) factor, stimulation with exogenous GDF-15 did not cause detrimental effects but induced a pro-regenerative response in chondrocytes, characterized by enhanced proliferation as well as chondro- and cell protection after cartilage trauma. Overall, this study first describes GDF-15 as a stress-responsive and potentially pro-regenerative cytokine in the context of human PTOA.

cell biology↗

bioRxiv2024

Senolytic therapy combining Dasatinib and Quercetin restores the chondrogenic phenotype of human osteoarthritic chondrocytes by promoting the release of pro-anabolic mediators

Cellular senescence is associated with various age-related disorders and is assumed to play a major role in the pathogenesis of osteoarthritis (OA). Based on this, we tested a senolytic combination therapy using Dasatinib (D) and Quercetin (Q) on aged isolated human articular chondrocytes (hACs), as well as in OA-affected cartilage tissue (OARSI grade 1-2). Stimulation with D+Q selectively eliminated senescent cells in both, cartilage explants and isolated hAC. Furthermore, the therapy significantly promoted chondroanabolism, as demonstrated by increased gene expression levels of COL2A1, ACAN, and SOX9, as well as elevated collagen type II and glycosaminoglycan biosynthesis. Additionally, D+Q treatment significantly reduced the release of SASP factors (IL6, CXCL1). RNA sequencing analysis revealed an upregulation of the anabolic factors, inter alia, FGF18, IGF1, and TGFB2, as well as inhibitory effects on cytokines and the YAP-1 signaling pathway, explaining the underlying mechanism of the chondroanabolic promotion upon senolytic treatment. Accordingly, stimulation of untreated hAC with conditioned medium of D+Q-treated cells similarly induced the expression of chondrogenic markers. Detailed analyses demonstrated that chondroanabolic effects could be mainly attributed to Dasatinib, while monotherapeutical application of Quercetin or Navitoclax did not promote the chondroanabolism. Overall, D+Q therapy restored the chondrogenic phenotype in OA hAC most likely by creating a pro-chondroanabolic environment through the reduction of SASP factors and upregulation of growth factors. This senolytic approach could therefore be a promising candidate for further testing as a disease-modifying osteoarthritis drug.

cell biology↗

bioRxiv2023

Increase of cell surface vimentin (CSV) is associated with vimentin network disruption and subsequent stress-induced premature senescence (SIPS) in human chondrocytes

Accumulation of dysfunctional chondrocytes has detrimental consequences on the cartilage homeostasis and is thus thought to play a crucial role during the pathogenesis of osteoarthritis (OA). However, the underlying mechanisms of phenotypical alteration in chondrocytes are incompletely understood. Here, we provide evidence that disruption of the intracellular vimentin network and consequent phenotypical alteration in human chondrocytes results in an externalization of the intermediate filament. The presence of so-called cell surface vimentin (CSV) on chondrocytes was associated with the severity of tissue degeneration in clinical OA samples and was enhanced after mechanical injury of cartilage tissue. By means of a doxorubicine-based in vitro model of stress-induced premature senescence (SIPS), we could confirm the connection between cellular senescence and amount of CSV. Although siRNA-mediated silencing of CDKN2A clearly reduced the senescent phenotype as well as CSV levels of human chondrocytes, cellular senescence could not be completely reversed. Interestingly, knockdown of vimentin resulted in a SIPS-like phenotype and consequently increased CSV. Therefore, we concluded that the integrity of the intracellular vimentin network is crucial to maintain cellular function in chondrocytes. This assumption could be confirmed by chemically-induced collapse of the vimentin network, which resulted in cellular stress and enhanced CSV expression. Regarding its biological function, CSV was found to be associated with enhanced chondrocyte adhesion and plasticity. While osteogenic capacities seemed to be enhanced in chondrocytes expressing high levels of CSV, the chondrogenic potential was clearly compromised. Overall, our study reinforces the importance of the vimentin network in maintenance of the chondrogenic phenotype and introduces CSV as a novel membrane-bound marker of dysfunctional chondrocytes.

cell biology↗