CCN2/CTGF expression does not correlate with fibrosis in myeloproliferative neoplasms, consistent with noncanonical TGF-ß signaling driving myelofibrosis.

The classical BCR::ABL1-negative myeloproliferative neoplasms (MPN) form a group of bone marrow (BM) diseases with the potential to progress to acute myeloid leukemia or develop marrow fibrosis and subsequent BM failure. The mechanism by which BM fibrosis develops and the factors that drive stromal activation and fibrosis are not well understood. Cellular Communication Network 2 (CCN2), also known as CTGF (Connective Tissue Growth Factor), is a profibrotic matricellular protein functioning as an important driver and biomarker of fibrosis in a wide range of diseases outside the marrow. CCN2 can promote fibrosis directly or by acting as a factor downstream of TGF-ß, the latter already known to contribute to myelofibrosis in MPN.To study the possible involvement of CCN2 in BM fibrosis in MPN, we assessed CCN2 protein expression by immunohistochemistry in 75 BM biopsies (55 × MPN and 20 × normal controls). We found variable expression of CCN2 in megakaryocytes with significant overexpression in a subgroup of 7 (13%) MPN cases; 4 of them (3 × essential thrombocytemia and 1 × prefibrotic primary myelofibrosis) showed no fibrosis (MF-0), 2 (1 × post-polycythemic myelofibrosis and 1 × primary myelofibrosis) showed moderate fibrosis (MF-2), and 1 (primary myelofibrosis) severe fibrosis (MF-3). Remarkably, CCN2 expression did not correlate with fibrosis or other disease parameters such as platelet count or thrombovascular events, neither in this subgroup nor in the whole study group. This suggests that in BM of MPN patients other, CCN2-independent pathways (such as noncanonical TGF-ß signaling) may be more important for the development of fibrosis.

Cellular senescence in kidney biopsies is associated with tubular dysfunction and predicts CKD progression in childhood cancer patients with karyomegalic interstitial nephropathy.

Karyomegalic interstitial nephropathy (KIN) has been reported as an incidental finding in patients with childhood cancer treated with ifosfamide. It is defined by the presence of tubular epithelial cells (TECs) with enlarged, irregular, and hyperchromatic nuclei. Cellular senescence has been proposed to be involved in kidney fibrosis in hereditary KIN patients. We report that KIN could be diagnosed 7-32 months after childhood cancer diagnosis in 6/6 consecutive patients biopsied for progressive chronic kidney disease (CKD) of unknown cause between 2018 and 2021. The morphometry of nuclear size distribution and markers for DNA damage (γH2AX), cell-cycle arrest (p21+, Ki67-), and nuclear lamina decay (loss of lamin B1), identified karyomegaly and senescence features in TECs. Polyploidy was assessed by chromosome fluorescence in situ hybridization (FISH). In all six patients the number of p21-positive TECs far exceeded the typically small numbers of truly karyomegalic cells, and p21-positive TECs contained less lysozyme, testifying to defective resorption, which explains the consistently observed low-molecular-weight (LMW) proteinuria. In addition, polyploidy of TEC was observed to correlate with loss of lysozyme staining. Importantly, in the five patients with the largest nuclei, the percentage of p21-positive TECs tightly correlated with estimated glomerular filtration rate loss between biopsy and last follow-up (R2 = 0.93, p < 0.01). We conclude that cellular senescence is associated with tubular dysfunction and predicts CKD progression in childhood cancer patients with KIN and appears to be a prevalent cause of otherwise unexplained CKD and LMW proteinuria in children treated with DNA-damaging and cell stress-inducing therapy including ifosfamide. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Cellular communication network 2 (connective tissue growth factor) aggravates acute DNA damage and subsequent DNA damage response-senescence-fibrosis following kidney ischemia reperfusion injury.

Chronic allograft dysfunction with progressive fibrosis of unknown cause remains a major issue after kidney transplantation, characterized by ischemia-reperfusion injury (IRI). One hypothesis to account for this is that spontaneous progressive tubulointerstitial fibrosis following IRI is driven by cellular senescence evolving from a prolonged, unresolved DNA damage response (DDR). Since cellular communication network factor 2 ((CCN2), formerly called connective tissue growth factor), an established mediator of kidney fibrosis, is also involved in senescence-associated pathways, we investigated the relation between CCN2 and cellular senescence following kidney transplantation. Tubular CCN2 overexpression was found to be associated with DDR, loss of kidney function and tubulointerstitial fibrosis in both the early and the late phase in human kidney allograft biopsies. Consistently, CCN2 deficient mice developed reduced senescence and tubulointerstitial fibrosis in the late phase; six weeks after experimental IRI. Moreover, tubular DDR markers and plasma urea were less elevated in CCN2 knockout than in wild-type mice. Finally, CCN2 administration or overexpression in epithelial cells induced upregulation of tubular senescence-associated genes including p21, while silencing of CCN2 alleviated DDR induced by anoxia-reoxygenation injury in cultured proximal tubule epithelial cells. Thus, our observations indicate that inhibition of CCN2 can mitigate IRI-induced acute kidney injury, DNA damage, and the subsequent DDR-senescence-fibrosis sequence. Hence, targeting CCN2 might help to protect the kidney from transplantation-associated post-IRI chronic kidney dysfunction.

CCN2 Aggravates the Immediate Oxidative Stress-DNA Damage Response following Renal Ischemia-Reperfusion Injury.

AKI, due to the fact of altered oxygen supply after kidney transplantation, is characterized by renal ischemia-reperfusion injury (IRI). Recent data suggest that AKI to CKD progression may be driven by cellular senescence evolving from prolonged DNA damage response (DDR) following oxidative stress. Cellular communication factor 2 (CCN2, formerly called CTGF) is a major contributor to CKD development and was found to aggravate DNA damage and the subsequent DDR-cellular senescence-fibrosis sequence following renal IRI. We therefore investigated the impact of CCN2 inhibition on oxidative stress and DDR in vivo and in vitro. Four hours after reperfusion, full transcriptome RNA sequencing of mouse IRI kidneys revealed CCN2-dependent enrichment of several signaling pathways, reflecting a different immediate stress response to IRI. Furthermore, decreased staining for γH2AX and p-p53 indicated reduced DNA damage and DDR in tubular epithelial cells of CCN2 knockout (KO) mice. Three days after IRI, DNA damage and DDR were still reduced in CCN2 KO, and this was associated with reduced oxidative stress, marked by lower lipid peroxidation, protein nitrosylation, and kidney expression levels of Nrf2 target genes (i.e., HMOX1 and NQO1). Finally, silencing of CCN2 alleviated DDR and lipid peroxidation induced by anoxia-reoxygenation injury in cultured PTECs. Together, our observations suggest that CCN2 inhibition might mitigate AKI by reducing oxidative stress-induced DNA damage and the subsequent DDR. Thus, targeting CCN2 might help to limit post-IRI AKI.

Extracellular Granzyme K Modulates Angiogenesis by Regulating Soluble VEGFR1 Release From Endothelial Cells.

Angiogenesis is crucial for normal development and homeostasis, but also plays a role in many diseases including cardiovascular diseases, autoimmune diseases, and cancer. Granzymes are serine proteases stored in the granules of cytotoxic cells, and have predominantly been studied for their pro-apoptotic role upon delivery in target cells. A growing body of evidence is emerging that granzymes also display extracellular functions, which largely remain unknown. In the present study, we show that extracellular granzyme K (GrK) inhibits angiogenesis and triggers endothelial cells to release soluble VEGFR1 (sVEGFR1), a decoy receptor that inhibits angiogenesis by sequestering VEGF-A. GrK does not cleave off membrane-bound VEGFR1 from the cell surface, does not release potential sVEGFR1 storage pools from endothelial cells, and does not trigger sVEGFR1 release via protease activating receptor-1 (PAR-1) activation. GrK induces de novo sVEGFR1 mRNA and protein expression and subsequent release of sVEGFR1 from endothelial cells. GrK protein is detectable in human colorectal tumor tissue and its levels positively correlate with sVEGFR1 protein levels and negatively correlate with T4 intratumoral angiogenesis and tumor size. In conclusion, extracellular GrK can inhibit angiogenesis via secretion of sVEGFR1 from endothelial cells, thereby sequestering VEGF-A and impairing VEGFR signaling. Our observation that GrK positively correlates with sVEGFR1 and negatively correlates with angiogenesis in colorectal cancer, suggest that the GrK-sVEGFR1-angiogenesis axis may be a valid target for development of novel anti-angiogenic therapies in cancer.

Connective Tissue Growth Factor Is Overexpressed in Explant Lung Tissue and Broncho-Alveolar Lavage in Transplant-Related Pulmonary Fibrosis.

Background: Connective tissue growth factor (CTGF) is an important mediator in several fibrotic diseases, including lung fibrosis. We investigated CTGF-expression in chronic lung allograft dysfunction (CLAD) and pulmonary graft-versus-host disease (GVHD). Materials and Methods: CTGF expression was assessed by quantitative real-time polymerase chain reaction (qPCR) and immunohistochemistry in end-stage CLAD explant lung tissue (bronchiolitis obliterans syndrome (BOS), n=20; restrictive allograft syndrome (RAS), n=20), pulmonary GHVD (n=9). Unused donor lungs served as control group (n=20). Next, 60 matched lung transplant recipients (BOS, n=20; RAS, n=20; stable lung transplant recipients, n=20) were included for analysis of CTGF protein levels in plasma and broncho-alveolar lavage (BAL) fluid at 3 months post-transplant, 1 year post-transplant, at CLAD diagnosis or 2 years post-transplant in stable patients. Results: qPCR revealed an overall significant difference in the relative content of CTGF mRNA in BOS, RAS and pulmonary GVHD vs. controls (p=0.014). Immunohistochemistry showed a significant higher percentage and intensity of CTGF-positive respiratory epithelial cells in BOS, RAS and pulmonary GVHD patients vs. controls (p<0.0001). BAL CTGF protein levels were significantly higher at 3 months post-transplant in future RAS vs. stable or BOS (p=0.028). At CLAD diagnosis, BAL protein content was significantly increased in RAS patients vs. stable (p=0.0007) and BOS patients (p=0.042). CTGF plasma values were similar in BOS, RAS, and stable patients (p=0.74). Conclusions: Lung CTGF-expression is increased in end-stage CLAD and pulmonary GVHD; and higher CTGF-levels are present in BAL of RAS patients at CLAD diagnosis. Our results suggest a potential role for CTGF in CLAD, especially RAS, and pulmonary GVHD.

Correction to: FoxD1-driven CCN2 deletion causes axial skeletal deformities, pulmonary hypoplasia, and neonatal asphyctic death.

Pulmonary fibrosis is a severely disabling disease often leading to death. CCN2 (Cellular Communication Network factor 2, also known as CTGF) is a known mediator of fibrosis and clinical trials studying anti-CCN2 efficacy in pulmonary fibrosis are currently underway. Fork head box D1 (FoxD1) transcription factor is transiently expressed in several mesenchymal cell types, including those of fetal lungs. Differentiation of FoxD1-progenitor derived pericytes into myofibroblasts involves CCN2 expression and contributes importantly to maladaptive tissue remodeling in for example kidney and lung fibrosis models. To generate a model for studying the contribution of CCN2 expression in FoxD1-progenitor derived cells to development of fibrotic tissue remodeling, we set out to establish a FoxD1Cre - CCN2flox/flox mouse colony. However, all double-transgenic mice died soon after birth due to asphyxia. Histopathological examination revealed a reduction in alveolar space and lung weight, and subtle axial (thoracic and cervical) skeletal deformities. Together with the previously reported association of a FoxD1 containing locus with human adolescent idiopathic scoliosis, our data suggest that the fatal pulmonary hypoplasia resulting from selective deletion of CCN2 from FoxD1-progenitor derived mesenchymal cells developed secondary to impaired breathing movements due to aberrant axial skeletogenesis.

FoxD1-driven CCN2 deletion causes axial skeletal deformities, pulmonary hypoplasia, and neonatal asphyctic death.

Pulmonary fibrosis is a severely disabling disease often leading to death. CCN2 (Cellular Communication Network factor 2, also known as CTGF) is a known mediator of fibrosis and clinical trials studying anti-CCN2 efficacy in pulmonary fibrosis are currently underway. Fork head box D1 (FoxD1) transcription factor is transiently expressed in several mesenchymal cell types, including those of fetal lungs. Differentiation of FoxD1-progenitor derived pericytes into myofibroblasts involves CCN2 expression and contributes importantly to maladaptive tissue remodeling in e.g. kidney and lung fibrosis models. To generate a model for studying the contribution of CCN2 expression in FoxD1-progenitor derived cells to development of fibrotic tissue remodeling, we set out to establish a FoxD1Cre - CCN2flox/flox mouse colony. However, all double-transgenic mice died soon after birth due to asphyxia. Histopathological examination revealed a reduction in alveolar space and lung weight, and subtle axial (thoracic and cervical) skeletal deformities. Together with the previously reported association of a FoxD1 containing locus with human adolescent idiopathic scoliosis, our data suggest that the development of fatal pulmonary hypoplasia caused by selective deletion of CCN2 from FoxD1-progenitor derived mesenchymal cells was secondary to aberrant axial skeletogenesis.

Prognostic relevance of tumor-infiltrating lymphocytes and immune checkpoints in pediatric medulloblastoma.

Pediatric medulloblastomas are the most frequently diagnosed embryonal tumors of the central nervous system. Current therapies cause severe neurological and cognitive side effects including secondary malignancies. Cellular immunotherapy might be key to improve survival and to avoid morbidity. Efficient killing of tumor cells using immunotherapy requires to overcome cancer-associated strategies to evade cytotoxic immune responses. Here, we examined the immune response and immune evasion strategies in pediatric medulloblastomas. Cytotoxic T-cells, infiltrating medulloblastomas with variable activation status, showed no correlation with overall survival of the patients. We found limited numbers of PD1+ T-cells and complete absence of PD-L1 on medulloblastomas. Medulloblastomas downregulated immune recognition molecules MHC-I and CD1 d. Intriguingly, expression of granzyme inhibitors SERPINB1 and SERPINB4 was acquired in 23% and 50% of the tumors, respectively. Concluding, pediatric medulloblastomas exploit multiple immune evasion strategies to overcome immune surveillance. Absence of PD-L1 expression in medulloblastoma suggest limited or no added value for immunotherapy with PD1/PD-L1 blockers.

Tamoxifen for induction of Cre-recombination may confound fibrosis studies in female mice.

A variety of conditional knock-out mice relying on Tamoxifen-driven ERT2/Cre -mediated recombination are available and have been used to study involvement of specific genes in kidney disease. However, recent data suggest that Tamoxifen itself might attenuate fibrosis when administered during experimental models of kidney disease. It has remained unclear whether this still applies also if kidney damage is initiated after a wash-out period has been implemented. Here we report that the commonly applied regimen of administration of 4 alternate day doses of 1mg Tamoxifen per mouse until 14 days prior to start of the actual experiment, in this case the induction of obstructive nephropathy by Unilateral Ureteral Obstruction (UUO), still attenuated fibrosis in female obstructed mouse kidneys, whereas this effect was not seen in male obstructed kidneys. Attenuation of fibrosis was accompanied by a reduction in nuclear ERα positivity despite absence of detectable levels of the active tamoxifen metabolite endoxifen throughout the UUO experiment. In conclusion, these results indicate that the Tamoxifen dosing regimen commonly applied in conditional gene targeting experiments might have prolonged confounding effects in female mice through attenuation of renal fibrosis independent of modulation of the expression of the targeted gene(s).

Proteomic profiling of the spinal cord in ALS: decreased ATP5D levels suggest synaptic dysfunction in ALS pathogenesis.

BACKGROUND: We aimed to gain new insights into the pathogenesis of sporadic ALS (sALS) through a comprehensive proteomic analysis. METHODS: Protein profiles of the anterior and posterior horn in post-mortem spinal cord samples of 10 ALS patients and 10 controls were analysed using 2D-differential gel electrophoresis. The identified protein spots with statistically significant level changes and a spot ratio >2.0 were analysed by LC-MS/MS. RESULTS: In the posterior horn only 3 proteins were differentially expressed. In the anterior horn, 16 proteins with increased levels and 2 proteins with decreased levels were identified in ALS compared to controls. The identified proteins were involved in mitochondrial metabolism, calcium homeostasis, protein metabolism, glutathione homeostasis, protein transport and snRNP assembly. The two proteins with decreased levels, ATP5D and calmodulin, were validated by Western blot and immunostaining. Immunohistochemical and immunofluorescent double staining of ATP5D and synaptophysin showed that the reduction of ATP5D was most pronounced at synapses. CONCLUSIONS: We speculate that mitochondrial dysfunction in synaptic clefts could play an important role in sALS pathogenesis. A similar approach revealed decreased calmodulin expression mainly in the neuronal body and dendrites of ALS patients. These findings contribute to a deeper understanding of the disease process underlying ALS.

Plasma CTGF is independently related to an increased risk of cardiovascular events and mortality in patients with atherosclerotic disease: the SMART study.

AIMS: Connective tissue growth factor (CTGF) plays a key role in tissue fibrogenesis and growing evidence indicates a pathogenic role in cardiovascular disease. Aim of this study is to investigate the association of connective tissue growth factor (CTGF/CCN2) with cardiovascular risk and mortality in patients with manifest vascular disease. METHODS AND RESULTS: Plasma CTGF was measured by ELISA in a prospective cohort study of 1227 patients with manifest vascular disease (mean age 59.0 ± 9.9 years). Linear regression analysis was performed to quantify the association between CTGF and cardiovascular risk factors. Results are expressed as beta (ß) regression coefficients with 95% confidence intervals (CI). The relation between CTGF and the occurrence of new cardiovascular events and mortality was assessed with Cox proportional hazard analysis. Adjustments were made for potential confounding factors. Plasma CTGF was positively related to total cholesterol (ß 0.040;95%CI 0.013-0.067) and LDL cholesterol (ß 0.031;95%CI 0.000-0.062) and inversely to glomerular filtration rate (ß -0.004;95%CI -0.005 to -0.002). CTGF was significantly lower in patients with cerebrovascular disease. During a median follow-up of 6.5 years (IQR 5.3-7.4) 131 subjects died, 92 experienced an ischemic cardiac complication and 45 an ischemic stroke. CTGF was associated with an increased risk of new vascular events (HR 1.21;95%CI 1.04-1.42), ischemic cardiac events (HR 1.41;95%CI 1.18-1.67) and all-cause mortality (HR 1.18;95%CI 1.00-1.38) for every 1 nmol/L increase in CTGF. No relation was observed between CTGF and the occurrence of ischemic stroke. CONCLUSIONS: In patients with manifest vascular disease, elevated plasma CTGF confers an increased risk of new cardiovascular events and all-cause mortality.

Age-dependent shifts in renal response to injury relate to altered BMP6/CTGF expression and signaling.

Age is associated with an increased prevalence of chronic kidney disease (CKD), which, through progressive tissue damage and fibrosis, ultimately leads to loss of kidney function. Although much effort is put into studying CKD development experimentally, age has rarely been taken into account. Therefore, we investigated the effect of age on the development of renal tissue damage and fibrosis in a mouse model of obstructive nephropathy (i.e., unilateral ureter obstruction; UUO). We observed that after 14 days, obstructed kidneys of old mice had more tubulointerstitial atrophic damage but less fibrosis than those of young mice. This was associated with reduced connective tissue growth factor (CTGF), and higher bone morphogenetic protein 6 (BMP6) expression and pSMAD1/5/8 signaling, while transforming growth factor-ß expression and transcriptional activity were no different in obstructed kidneys of old and young mice. In vitro, CTGF bound to and inhibited BMP6 activity. In summary, our data suggest that in obstructive nephropathy atrophy increases and fibrosis decreases with age and that this relates to increased BMP signaling, most likely due to higher BMP6 and lower CTGF expression.

Biological responses of human solid tumor cells to X-ray irradiation within a 1.5-Tesla magnetic field generated by a magnetic resonance imaging-linear accelerator.

Devices that combine magnetic resonance imaging with linear accelerators (MRL) represent a novel tool for MR-guided radiotherapy. However, whether magnetic fields (MFs) generated by these devices affect the radiosensitivity of tumors is unknown. We investigated the influence of a 1.5-T MF on cell viability and radioresponse of human solid tumors. Human head/neck cancer and lung cancer cells were exposed to single or fractionated 6-MV X-ray radiation; effects of the MF on cell viability were determined by cell plating efficiency and on radioresponsiveness by clonogenic cell survival. Doses needed to reduce the fraction of surviving cells to 37% of the initial value (D0s) were calculated for multiple exposures to MF and radiation. Results were analyzed using Student's t-tests. Cell viability was no different after single or multiple exposures to MRL than after exposure to a conventional linear accelerator (Linac, without MR-generated MF) in 12 of 15 experiments (all P > 0.05). Single or multiple exposures to MF had no influence on cell radioresponse (all P > 0.05). Cells treated up to four times with an MRL or a Linac further showed no changes in D0s with MF versus without MF (all P > 0.05). In conclusion, MF within the MRL does not seem to affect in vitro tumor radioresponsiveness as compared with a conventional Linac. Bioelectromagnetics. 37:471-480, 2016. © 2016 Wiley Periodicals, Inc.

Pediatric Primitive Neuroectodermal Tumors of the Central Nervous System Differentially Express Granzyme Inhibitors.

BACKGROUND: Central nervous system (CNS) primitive neuroectodermal tumors (PNETs) are malignant primary brain tumors that occur in young infants. Using current standard therapy, up to 80% of the children still dies from recurrent disease. Cellular immunotherapy might be key to improve overall survival. To achieve efficient killing of tumor cells, however, immunotherapy has to overcome cancer-associated strategies to evade the cytotoxic immune response. Whether CNS-PNETs can evade the immune response remains unknown. METHODS: We examined by immunohistochemistry the immune response and immune evasion strategies in pediatric CNS-PNETs. RESULTS: Here, we show that CD4+, CD8+, γδ-T-cells, and Tregs can infiltrate pediatric CNS-PNETs, although the activation status of cytotoxic cells is variable. Pediatric CNS-PNETs evade immune recognition by downregulating cell surface MHC-I and CD1d expression. Intriguingly, expression of SERPINB9, SERPINB1, and SERPINB4 is acquired during tumorigenesis in 29%, 29%, and 57% of the tumors, respectively. CONCLUSION: We show for the first time that brain tumors express direct granzyme inhibitors (serpins) as a potential mechanism to overcome cellular cytotoxicity, which may have consequences for cellular immunotherapy.

Connective tissue growth factor and the cicatrization of cellular crescents in ANCA-associated glomerulonephritis.

BACKGROUND: Outcome in patients with anti-neutrophil cytoplasmic antibodies (ANCA)-associated glomerulonephritis (AGN) is difficult to predict. Scoring of renal biopsies has significant but limited predictive value. We investigated whether analysis of plasma and urine levels, and immunostaining of biopsies for the pro-fibrotic peptide connective tissue growth factor (CTGF), might improve prediction of renal outcome. METHODS: ANCA-positive patients were included. Renal biopsies were classified according to the AGN classification. Biopsies were stained for CTGF protein. CTGF was measured by ELISA at the time of renal biopsy in plasma and urine, and during follow-up in plasma. RESULTS: Eighty-two patients were included. CTGF staining was positive in crescentic lesions. Plasma CTGF at the time of renal biopsy was 2.4 ± 1.7 pmol/mL when compared with 0.5 ± 0.0 pmol/mL in healthy controls (P < 0.01). Plasma CTGF was associated with cellular crescents, but not when corrected for renal function. Plasma CTGF at baseline was associated with fibrous crescents in the follow-up biopsy, also after correction for renal function. Plasma CTGF at baseline predicted renal survival more accurately than the AGN classification. CONCLUSION: In AGN patients, CTGF was overexpressed in crescentic glomeruli. Baseline plasma CTGF predicted the percentage of fibrous crescents in later biopsies, and renal survival, suggesting that CTGF is involved in the cicatrization, as opposed to resolution of cellular crescents in AGN.

Urinary connective tissue growth factor is associated with human renal allograft fibrogenesis.

BACKGROUND: Connective tissue growth factor (CTGF) is a key mediator of tissue fibrogenesis in kidney disease. Its involvement in renal allograft fibrosis was recently demonstrated in a mouse model. METHODS: We prospectively studied the association between urinary CTGF (CTGFu) levels and renal allograft fibrosis during the first 2 years after transplantation. Histologic and biochemical data were collected from 315 kidney transplant recipients enrolled in a protocol biopsy-based clinical program. RESULTS: At 3, 12, and 24 months after transplantation, CTGFu levels were independently associated with the degree of interstitial fibrosis in protocol biopsies, scored according to the revised 1997 Banff criteria. In a subgroup of 164 patients with pristine biopsies at 3 months, higher CTGFu levels at 3 months were associated with moderate and severe interstitial fibrosis developed at 24 months after transplantation. CONCLUSIONS: As it is readily quantifiable in urine, a role for CTGFu as a noninvasive candidate biomarker and predictor of human renal allograft fibrogenesis deserves further study.

Hemizygous deletion of CTGF/CCN2 does not suffice to prevent fibrosis of the severely injured kidney.

BACKGROUND: Connective Tissue Growth Factor (CTGF/CCN2) is an important mediator of kidney fibrosis. Previous observations indicated that attenuation of CCN2 expression sufficed to alleviate early kidney damage. However, little is known about the role of CCN2 in fibrosis of severely damaged and more chronically injured kidneys. Therefore, we examined the effects of CCN2 haploinsufficiency on the progression of renal scarring in long-term STZ-induced diabetic nephropathy, in a more advanced stage of obstructive nephropathy following unilateral ureteric obstruction (UUO), and in severe aristolochic acid (AA)-induced tubulotoxic nephritis. METHODS: Wild-type (WT, CCN2(+/+)) and hemizygous CCN2(+/-) C57Bl/6 mice were studied. In the diabetes experiment, streptozotocin-injected and control mice were followed for 6 months, with regular blood pressure, glycaemia and albuminuria recordings. In the UUO experiment, the left ureter was obstructed for 14 days with the contralateral kidney serving as control. For the AA experiment, mice were followed for 25 days after 5 intraperitoneal injections with AA and compared to control mice injected with buffer alone. Organs were harvested for histology, mRNA and protein measurements. Collagen content was determined by HPLC and expressed as hydroxyproline/proline ratio. RESULTS: CCN2 expression was significantly increased in the damaged as compared to control kidneys. In all three models, CCN2 levels in the damaged kidneys of CCN2(+/-) mice averaged about 50% of those in damaged WT kidneys. After 6 months of diabetes, albuminuria was increased 2.5-fold in WT mice, compared to 1.5-fold in CCN2(+/-) mice, mesangial matrix was expanded 5-fold in WT and 4.4-fold in CCN2(+/-) mice and the glomerular basement membrane was thickened 1.3-fold in WT and 1.5-fold in CCN2(+/-) mice (all differences between WT and CCN2(+/-) mice are NS). Tubular damage and interstitial fibrosis scores were also not different between Wt and CCN2(+/-) mice in the diabetes (1.8 vs. 1.7), UUO (2.8 vs. 2.6), and AA (1.4 vs. 1.2) models, as was the case for macrophage influx and collagen content in these three models. CONCLUSION: Unlike in mild and relatively early STZ-induced diabetic nephropathy, scarring of severely and chronically damaged kidneys is not attenuated by a 50% reduction of CCN2 to (near) normal levels. This suggests that CCN2 is either redundant in severe and chronic kidney disease, or that it is a limiting factor only at subnormal concentrations requiring further reduction by available or emerging therapies to prevent fibrosis of the severely injured kidney.