CLCF-1 is a cytokine known for B-cell stimulation and for neurotrophic properties. We have identified CLCF-1 as a potential injurious factor in the human renal disease focal segmental glomerulosclerosis (FSGS). We investigated its effects on renal cells and renal function inin vitroandin vivostudies. Methods include measurement of the effect of CLCF-1 on phosphorylation of target molecules of the JAK/STAT pathway, on cytoskeleton and cell morphology in cultured podocytes, on albumin permeability of isolated rat glomeruli, and on tissue phosphorylation and urine albumin after acute or chronic CLCF-1 injection. In addition, cell sorting was performed to determine the presence of cells expressing CLCF-1 in spleen and bone marrow of normal mice and the effect of CLCF-1 infusion on splenic B-cell populations. CLCF-1 increased phosphorylation of STAT3 in multiple cell types, activated podocytes leading to formation of lamellipodia and decrease in basal stress fibers, increased glomerular albumin permeability, and increased STAT3 phosphorylation of peripheral blood cells and renal cortex. CLCF-1 increased urine albumin/creatinine ratio in mice and increased B-cell expression of IgG in mouse spleen. We conclude that CLCF-1 has potentially important systemic effects, alters podocyte function, and may contribute to renal dysfunction and albuminuria.

Patients with resistant focal segmental glomerulosclerosis (FSGS) who are unresponsive to corticosteroids and other immunosuppressive agents are at very high risk of progression to end stage kidney disease. In the absence of curative treatment, current therapy centers on renoprotective interventions that reduce proteinuria and fibrosis. The FONT (Novel Therapies for Resistant FSGS) Phase II clinical trial (NCT00814255, Registration date December 22, 2008) was designed to assess the efficacy of adalimumab and galactose compared to standard medical therapy which was comprised of lisinopril, losartan, and atorvastatin. Key eligibility criteria were biopsy confirmed primary FSGS or documentation of a causative genetic mutation, urine protein:creatinine ratio >1.0 g/g, and estimated glomerular filtration rate (eGFR) >40 ml/min/1.73 m2. The experimental treatments – adalimumab, galactose, standard medical therapy-- were administered for 26 weeks. The primary endpoint was a 50 % reduction in proteinuria with stable eGFR. Thirty-two subjects were screened and 21 were assigned to one of the three study arms. While none of the adalimumab-treated subjects achieved the primary outcome, 2 subjects in the galactose and 2 in the standard medical therapy arm had a 50 % reduction in proteinuria without a decline in eGFR. The proteinuria response did not correlate with serial changes in the serum glomerular permeability activity measured by the Palb assay or soluble urokinase plasminogen activator receptor (suPAR). There were no serious adverse effects related to treatments in the study. Recruitment into this trial that addressed patients with resistant FSGS fell short of the enrollment goal. Our findings suggest that future studies of novel therapies for rare glomerular diseases such as FSGS may benefit from enrollment of patients earlier in the course of their disease. In addition, better identification of patients who are likely to respond to a new treatment based on biomarkers suggesting involvement of the disease pathway targeted by the experimental agent may reduce the required sample size and increase the likelihood of a favorable outcome.

A plasma component is responsible for altered glomerular permeability in patients with focal segmental glomerulosclerosis. Evidence includes recurrence after renal transplantation, remission after plasmapheresis, proteinuria in infants of affected mothers, transfer of proteinuria to experimental animals, and impaired glomerular permeability after exposure to patient plasma. Therapy may include decreasing synthesis of the injurious agent, removing or blocking its interaction with cells, or blocking signaling or enhancing cell defenses to restore the permeability barrier and prevent progression. Agents that may prevent the synthesis of the permeability factor include cytotoxic agents or aggressive chemotherapy. Extracorporeal therapies include plasmapheresis, immunoadsorption with protein A or anti-immunoglobulin, or lipopheresis. Oral or intravenous galactose also decreasesPalbactivity. Studies of glomeruli have shown that several strategies prevent the action of FSGS sera. These include blocking receptor-ligand interactions, modulating cell reactions using indomethacin or eicosanoids 20-HETE or 8,9-EET, and enhancing cytoskeleton and protein interactions using calcineurin inhibitors, glucocorticoids, or rituximab. We have identified cardiotrophin-like cytokine factor 1 (CLCF-1) as a candidate for the permeability factor. Therapies specific to CLCF-1 include potential use of cytokine receptor-like factor (CRLF-1) and inhibition of Janus kinase 2. Combined therapy using multiple modalities offers therapy to reverse proteinuria and prevent scarring.

Sharma, M., Sharma, R., McCarthy, E. T., Ge, X. L., Fish, B. L., Savin, V. J., Cohen, E. P. and Moulder, J. E. Early Detection of Radiation-Induced Glomerular Injury by Albumin Permeability Assay. Renal irradiation leads predictably to glomerular vascular injury, cell lysis, matrix accumulation, sclerosis and loss of renal function. The immediate effects of renal irradiation that may be associated with glomerular pathology and proteinuria are not clear in the human disease or its rat model. We hypothesized that radiation-induced injury causes immediate and subtle alterations in glomerular physiology independent of the neurohumoral and hemodynamic regulatory mechanisms. We employed a sensitive in vitro functional assay of glomerular albumin permeability (P_alb) to demonstrate radiation-induced damage to the glomerular filtration barrier immediately after total-body irradiation of rats. In blinded experiments, control rats were sham-treated, and experimental rats received 9.5 Gy X rays. Rats were killed humanely at 1 h to 9 weeks after irradiation and glomeruli were isolated. In parallel experiments, glomeruli were isolated from normal rats and irradiated in vitro. The change in glomerular capillary permeability due to an experimental oncotic gradient was determined using videomicroscopy and P_alb was calculated. Results show that in vivo or in vitro irradiation of glomeruli caused an increased P_alb at 1 h. Increased P_alb was observed up to 3 weeks after irradiation. Glomeruli from mice irradiated with 9.5 or 19.0 Gy X rays did not show increased P_alb at 1 h postirradiation. We conclude that glomerular protein permeability of irradiated rats increases in a dose-dependent manner immediately after irradiation and that it appears to be independent of hemodynamic or systemic influences.