Interleukin-10 and Transforming Growth Factor-ß Cytokines Decrease Immune Activation During Normothermic Ex Vivo Machine Perfusion of the Rat Liver.

Normothermic ex vivo liver perfusion (NEVLP) is a novel system for organ preservation that may improve over static cold storage clinically and offers the chance for graft modification prior to transplantation. Although recent studies have shown the presence of inflammatory molecules during perfusion, none have yet shown the effects of NEVLP on liver-resident immune cell activation. We investigated the effects of NEVLP on liver-resident immune cell activation and assessed the ability of anti-inflammatory cytokines interleukin 10 (IL10) and transforming growth factor ß (TGF-ß) to improve organ function and reduce immune activation during perfusion. Rat livers were perfused for 4 hours at 37°C with or without the addition of 20 ng/mL of each IL10 and TGF-ß (n = 7). Naïve and cold storage (4 hours at 4°C) livers served as controls (n = 4). Following preservation, gene expression profiles were assessed through single-cell RNA sequencing; dendritic cell and macrophage activation was measured by flow cytometry; and cytokine production was assessed by enzyme-linked immunosorbent assay. NEVLP induced a global inflammatory gene expression signature, most notably in liver-resident macrophages and dendritic cells, which was accompanied by an increase in cell-surface levels of major histocompatibility complex (MHC) II, CD40, and CD86. Immune activation was partially ameliorated by IL10 and TGF-ß treatment, but no changes were observed in inflammatory cytokine production. Overall levels of liver damage and cellular apoptosis from perfusion were low, and liver function was improved with IL10 and TGF-ß treatment. This is the first study to demonstrate that liver-resident immune cells gain an activated phenotype during NEVLP on both the gene and protein level and that this activation can be reduced through therapeutic intervention with IL10 and TGF-ß.

Treatment with the matricellular protein CCN3 blocks and/or reverses fibrosis development in obesity with diabetic nephropathy.

Fibrosis is at the core of the high morbidity and mortality rates associated with the complications of diabetes and obesity, including diabetic nephropathy (DN), without any US Food and Drug Administration-approved drugs with this specific target. We recently provided the first evidence that the matricellular protein CCN3 (official symbol NOV) functions in a reciprocal manner, acting on the profibrotic family member CCN2 to inhibit fibrosis in a mesangial cell model of DN. Herein, we used the BT/BR ob/ob mouse as a best model of human obesity and DN progression to determine whether recombinant human CCN3 could be used therapeutically, and the mechanisms involved. Eight weeks of thrice-weekly i.p. injections (0.604 and 6.04 µg/kg of recombinant human CCN3) beginning in early-stage DN completely blocked and/or reversed the up-regulation of mRNA expression of kidney cortex fibrosis genes (CCN2, Col1a2, TGF-ß1, and PAI-1) seen in placebo-treated diabetic mice. The treatment completely blocked glomerular fibrosis, as determined by altered mesangial expansion and deposition of laminin. Furthermore, it protected against, or reversed, podocyte loss and kidney function reduction (rise in plasma creatinine concentration); albuminuria was also greatly reduced. This study demonstrates the potential efficacy of recombinant human CCN3 treatment in DN and points to mechanisms operating at multiple levels or pathways, upstream (eg, protecting against cell injury) and downstream (eg, regulating CCN2 activity and extracellular matrix metabolism).

CCN3 (NOV) is a negative regulator of CCN2 (CTGF) and a novel endogenous inhibitor of the fibrotic pathway in an in vitro model of renal disease.

Fibrosis is a major cause of end-stage renal disease, and although initiation factors have been elucidated, uncertainty concerning the downstream pathways has hampered the development of anti-fibrotic therapies. CCN2 (CTGF) functions downstream of transforming growth factor (TGF)-beta, driving increased extracellular matrix (ECM) accumulation and fibrosis. We examined the possibility that CCN3 (NOV), another CCN family member with reported biological activities that differ from CCN2, might act as an endogenous negative regulator of ECM and fibrosis. We show that cultured rat mesangial cells express CCN3 mRNA and protein, and that TGF-beta treatment reduced CCN3 expression levels while increasing CCN2 and collagen type I activities. Conversely, either the addition of CCN3 or CCN3 overexpression produced a marked down-regulation of CCN2 followed by virtual blockade of both collagen type I transcription and its accumulation. This finding occurred in both growth-arrested and CCN3-transfected cells under normal growth conditions after TGF-beta treatment. These effects were not attributable to altered cellular proliferation as determined by cell cycle analysis, nor were they attributable to interference of Smad signaling as shown by analysis of phosphorylated Smad3 levels. In conclusion, both CCN2 and CCN3 appear to act in a yin/yang manner to regulate ECM metabolism. CCN3, acting downstream of TGF-beta to block CCN2 and the up-regulation of ECM, may therefore serve to naturally limit fibrosis in vivo and provide opportunities for novel, endogenous-based therapeutic treatments.

Constitutive expression of E2F-1 leads to p21-dependent cell cycle arrest in S phase of the cell cycle.

p21 is a potent inhibitor of cyclin-dependent kinases capable of arresting cell cycle progression. p21 is primarily regulated at the transcriptional level by several transcription factors, including p53. Previously, we reported that certain members of the E2F family of transcription factors may activate p21 transcription via a p53-independent mechanism. To further elucidate the consequences of E2F-1-regulated induction of p21, we developed cell lines with a tamoxifen-dependent form of E2F-1. We confirmed direct interaction of E2F-1 with the proximal region of the p21 promoter. Interestingly, elevated E2F-1 activity was sufficient to arrest a substantial subset of cells in S phase and this effect was correlated to and dependent on the induction of p21 protein. Since E2F proteins control genes required for cell cycle progression and are activated by various oncogenic events, we believe that the p21-dependent arrest described in this report represents an additional mechanism that guards against unrestricted cell proliferation.

Gadolinium-induced fibrosis is counter-regulated by CCN3 in human dermal fibroblasts: a model for potential treatment of nephrogenic systemic fibrosis.

We recently show that CCN3 is a counter-regulatory molecule for the pro-fibrotic protein CCN2, and a potentially novel fibrosis therapy. The goal of this study was to assess the role of CCN3 in fibroproliferative/fibrotic responses in human dermal fibroblasts exposed to Omniscan, one of the gadolinium-based contrast agents associated with development of nephrogenic systemic fibrosis (NSF) a rare but life-threatening disease thought to be complication of NMR diagnostics in renal impaired patients. Human dermal fibroblasts were exposed to Omniscan; or to platelet-derived growth factor (PDGF) and transforming growth factor-ß (TGF-ß) as controls. Proliferation was assessed along with matrix metalloproteinase-1, tissue inhibitor of metalloproteinases-1 and type 1 procollagen in the absence and presence of CCN3. In parallel, CCN3 production was assessed in control and Omniscan-treated cells. The results showed that PDGF stimulated fibroblast proliferation, production of Timp-1 and MMP-1 whereas exogenous CCN3 inhibited, in a dose response manner, cell proliferation (approx. 50 % max.) and production of MMP-1 (approx 35 % max.) but had little effect on TIMP-1. TGF-ß stimulated type 1 procollagen production but not proliferation, Timp-1 or MMP-1 compared to non-TGF-ß treated control cells, and CCN3 treatment blocked (approx. 80 % max.) this up-regulation. Interestingly, untreated, control fibroblasts produced high constitutive levels of CCN3 and concentrations of Omniscan that induced fibroproliferative/fibrogenic changes in dermal fibroblasts correspondingly suppressed CCN3 production. The use of PDGF and TGF-ß as positive controls, and the study of differential responses, including that to Omniscan itself, provide the first evidence for a role of fibroblast-derived CCN3 as an endogenous regulator of pro-fibrotic changes, elucidating possible mechanism(s). In conclusion, these data support our hypothesis of a role for fibroblast-derived CCN3 as an endogenous regulator of pro-fibrotic changes in these cells, and suggest that CCN3 may be an important regulatory molecule in NSF and a target for treatment in this and other fibrotic diseases.

CCN3/CCN2 regulation and the fibrosis of diabetic renal disease.

Prior work in the CCN field, including our own, suggested to us that there might be co-regulatory activity and function as part of the actions of this family of cysteine rich cytokines. CCN2 is now regarded as a major pro-fibrotic molecule acting both down-stream and independent of TGF-beta1, and appears causal in the disease afflicting multiple organs. Since diabetic renal fibrosis is a common complication of diabetes, and a major cause of end stage renal disease (ESRD), we examined the possibility that CCN3 (NOV), might act as an endogenous negative regulator of CCN2 with the capacity to limit the overproduction of extracellular matrix (ECM), and thus prevent, or ameliorate fibrosis. We demonstrate, using an in vitro model of diabetic renal fibrosis, that both exogenous treatment with CCN3 and transfection with the over-expression of the CCN3 gene in mesangial cells markedly down-regulates CCN2 activity and blocks ECM over-accumulation stimulated by TGF-beta1. Conversely, TGF-beta1 treatment reduces endogenous CCN3 expression and increases CCN2 activity and matrix accumulation, indicating an important, novel yin/yang effect. Using the db/db mouse model of diabetic nephropathy, we confirm the expression of CCN3 in the kidney, with temporal localization that supports these in vitro findings. In summary, the results corroborate our hypothesis that one function of CCN3 is to regulate CCN2 activity and at the concentrations and conditions used down-regulates the effects of TGF-beta1, acting to limit ECM turnover and fibrosis in vivo. The findings suggest opportunities for novel endogenous-based therapy either by the administration, or the upregulation of CCN3.

TNF-alpha, but not IFN-gamma, regulates CCN2 (CTGF), collagen type I, and proliferation in mesangial cells: possible roles in the progression of renal fibrosis.

Connective tissue growth factor (CCN2) is a profibrotic factor acting downstream and independently of TGF-beta to mediate renal fibrosis. Although inflammation is often involved in the initiation and/or progression of fibrosis, the role of inflammatory cytokines in regulation of glomerular CCN2 expression, cellular proliferation, and extracellular matrix accumulation is unknown. We studied two such cytokines, TNF-alpha and IFN-gamma, for their effects on cultured mesangial cells in the presence or absence of TGF-beta, as a model for progressive renal fibrosis. Short-term treatment with TNF-alpha, like TGF-beta, significantly increased secreted CCN2 per cell, but unlike TGF-beta inhibited cellular replication. TNF-alpha combined with TGF-beta further increased CCN2 secretion and mRNA levels and reduced proliferation. Surprisingly, however, TNF-alpha treatment decreased baseline collagen type I protein and mRNA levels and largely blocked their stimulation by TGF-beta. Long-term treatment with TGF-beta or TNF-alpha alone no longer increased CCN2 protein levels. However, the combination synergistically increased CCN2. IFN-gamma had no effect on either CCN2 or collagen activity and produced a mild inhibition of TGF-beta-induced collagen only at a high concentration (500 U/ml). In summary, we report a strong positive regulatory role for TNF-alpha, but not IFN-gamma, in CCN2 production and secretion, including that driven by TGF-beta. The stimulation of CCN2 release by TNF-alpha, unlike TGF-beta, is independent of cellular proliferation and not linked to increased collagen type I accumulation. This suggests that the paradigm of TGF-beta-driven CCN2 with subsequent collagen production may be overridden by an as yet undefined inhibitory mechanism acting either directly or indirectly on matrix metabolism.