Podocyte injury at young age causes premature senescence and worsens glomerular aging.

As life expectancy continues to rise, age-related diseases are becoming more prevalent. For example, proteinuric glomerular diseases typified by podocyte injury have worse outcomes in the elderly compared with young patients. However, the reasons are not well understood. We hypothesized that injury to nonaged podocytes induces senescence, which in turn augments their aging processes. In primary cultured human podocytes, injury induced by a cytopathic antipodocyte antibody, adriamycin, or puromycin aminonucleoside increased the senescence-related genes CDKN2A (p16INK4a/p14ARF), CDKN2D (p19INK4d), and CDKN1A (p21). Podocyte injury in human kidney organoids was accompanied by increased expression of CDKN2A, CDKN2D, and CDKN1A. In young mice, experimental focal segmental glomerulosclerosis (FSGS) induced by adriamycin and antipodocyte antibody increased the glomerular expression of p16, p21, and senescence-associated ß-galactosidase (SA-ß-gal). To assess the long-term effects of early podocyte injury-induced senescence, we temporally followed young mice with experimental FSGS through adulthood (12 m of age) and middle age (18 m of age). p16 and Sudan black staining were higher at middle age in mice with earlier FSGS compared with age-matched mice that did not get FSGS when young. This was accompanied by lower podocyte density, reduced canonical podocyte protein expression, and increased glomerular scarring. These results are consistent with injury-induced senescence in young podocytes, leading to increased senescence of podocytes by middle age accompanied by lower podocyte lifespan and health span.NEW & NOTEWORTHY Glomerular function is decreased by aging. However, little is known about the molecular mechanisms involved in age-related glomerular changes and which factors could contribute to a worse glomerular aging process. Here, we reported that podocyte injury in young mice and culture podocytes induced senescence, a marker of aging, and accelerates glomerular aging when compared with healthy aging mice.

Inhibiting NLRP3 signaling in aging podocytes improves their life- and health-span.

The decrease in the podocyte's lifespan and health-span that typify healthy kidney aging cause a decrease in their normal structure, physiology and function. The ability to halt and even reverse these changes becomes clinically relevant when disease is superimposed on an aged kidney. RNA-sequencing of podocytes from middle-aged mice showed an inflammatory phenotype with increases in the NLRP3 inflammasome, signaling for IL2/Stat5, IL6 and TNF, interferon gamma response, allograft rejection and complement, consistent with inflammaging. Furthermore, injury-induced NLRP3 signaling in podocytes was further augmented in aged mice compared to young ones. The NLRP3 inflammasome (NLRP3, Caspase-1, IL1ß IL-18) was also increased in podocytes of middle-aged humans. Higher transcript expression for NLRP3 in human glomeruli was accompanied by reduced podocyte density and increased global glomerulosclerosis and glomerular volume. Pharmacological inhibition of NLRP3 with MCC950, or gene deletion, reduced podocyte senescence and the genes typifying aging in middle-aged mice, which was accompanied by an improved podocyte lifespan and health-span. Moreover, modeling the injury-dependent increase in NLRP3 signaling in human kidney organoids confirmed the anti-senescence effect of MC9950. Finally, NLRP3 also impacted liver aging. Together, these results suggest a critical role for the NLRP3 inflammasome in podocyte and liver aging.

Upregulated PD-1 signaling antagonizes glomerular health in aged kidneys and disease.

With an aging population, kidney health becomes an important medical and socioeconomic factor. Kidney aging mechanisms are not well understood. We previously showed that podocytes isolated from aged mice exhibit increased expression of programmed cell death protein 1 (PD-1) surface receptor and its 2 ligands (PD-L1 and PD-L2). PDCD1 transcript increased with age in microdissected human glomeruli, which correlated with lower estimated glomerular filtration rate and higher segmental glomerulosclerosis and vascular arterial intima-to-lumen ratio. In vitro studies in podocytes demonstrated a critical role for PD-1 signaling in cell survival and in the induction of a senescence-associated secretory phenotype. To prove PD-1 signaling was critical to podocyte aging, aged mice were injected with anti-PD-1 antibody. Treatment significantly improved the aging phenotype in both kidney and liver. In the glomerulus, it increased the life span of podocytes, but not that of parietal epithelial, mesangial, or endothelial cells. Transcriptomic and immunohistochemistry studies demonstrated that anti-PD-1 antibody treatment improved the health span of podocytes. Administering the same anti-PD-1 antibody to young mice with experimental focal segmental glomerulosclerosis (FSGS) lowered proteinuria and improved podocyte number. These results suggest a critical contribution of increased PD-1 signaling toward both kidney and liver aging and in FSGS.

Application of Cryopreserved Human Intestinal Mucosa and Cryopreserved Human Enterocytes in the Evaluation of Herb-Drug Interactions: Evaluation of CYP3A Inhibitory Potential of Grapefruit Juice and Commercial Formulations of Twenty-Nine Herbal Supplements.

Commercial formulations of 29 commonly used herbal supplements (HSs) and grapefruit juice were evaluated for drug interaction potential via quantification of their CYP3A inhibitory potential in two in vitro experimental models of human small intestine, cryopreserved human intestinal mucosa (CHIM), and cryopreserved human enterocytes (CHEs). Two CYP3A substrates were used-in the studies with CHIM, CYP3A activity was quantified via liquid chromatography tandem mass spectrometry quantification of midazolam 1'-hydroxylation, whereas in CHE, luciferin-IPA metabolism to luciferin was quantified by luminescence. Upon treatment of CHIM with the estimated lumen concentration of the HS upon each oral administration (manufacturers' recommended dosage dissolved in 200 ml of culture medium), >80% CYP3A inhibition was observed for green tea extract, St. John's wort, valerian root, horehound, and grapefruit juice. Less than 50% inhibition was observed for fenugreek, aloe vera, guarana, soy isoflavone, maca, echinacea, spirulina, evening primrose, milk thistle, cranberry, red yeast rice, rhodiola, ginkgo biloba, turmeric, curcumin, white kidney bean, garlic, cinnamon, saw palmetto berries, panax ginseng, black elderberry, wheat grass juice, flaxseed oil, black cohosh, and ginger root. The results were confirmed in a a dose-response study with HSs obtained from three suppliers for the four inhibitory HSs (green tea extract, horehound, St. John's wort, valerian root) and three representative noninhibitory HSs (black cohosh, black elderberry, echinacea). Similar results were obtained with the inhibitory HSs in CHE. The results illustrate that CHIM and CHE represent physiologically relevant in vitro experimental models for the evaluation of drug interaction potential of herbal supplements. Based on the results, green tea extract, horehound, St. John's wort, and valerian root may cause drug interactions with orally administered drugs that are CYP3A substrates, as was observed for grapefruit juice. SIGNIFICANCE STATEMENT: In vitro evaluation of 29 popular herbal supplements in cryopreserved human intestinal mucosa identified green tea extract, horehound, St. John's wort, and valerian root to have CYP3A inhibitory potential similar to that for grapefruit juice, suggesting their potential to have clinically significant pharmacokinetic interaction with orally administered drugs that are CYP3A substrates. The results suggest that cryopreserved human intestinal mucosa can be used for in vitro evaluation of drug interactions involving enteric drug metabolism.

Global transcriptomic changes occur in aged mouse podocytes.

Glomerular podocytes undergo structural and functional changes with advanced age, that increase susceptibility of aging kidneys to worse outcomes following superimposed glomerular diseases. To delineate transcriptional changes in podocytes in aged mice, RNA-seq was performed on isolated populations of reporter-labeled (tdTomato) podocytes from multiple young (two to three months) and advanced aged mice (22 to 24 months, equivalent to 70 plus year old humans). Of the 2,494 differentially expressed genes, 1,219 were higher and 1,275 were lower in aged podocytes. Pathway enrichment showed that major biological processes increased in aged podocytes included immune responses, non-coding RNA metabolism, gene silencing and MAP kinase signaling. Conversely, aged podocytes showed downregulation of developmental, morphogenesis and metabolic processes. Canonical podocyte marker gene expression decreased in aged podocytes, with increases in apoptotic and senescence genes providing a mechanism for the progressive loss of podocytes seen with aging. In addition, we revealed aberrations in the podocyte autocrine signaling network, identified the top transcription factors perturbed in aged podocytes, and uncovered candidate gene modulations that might promote healthy aging in podocytes. The transcriptional signature of aging is distinct from other kidney diseases. Thus, our study provides insights into biomarker discovery and molecular targeting of the aging process itself within podocytes.

Cryopreserved Human Intestinal Mucosal Epithelium: A Novel In Vitro Experimental System for the Evaluation of Enteric Drug Metabolism, Cytochrome P450 Induction, and Enterotoxicity.

We report here a novel in vitro enteric experimental system, cryopreserved human intestinal mucosa (CHIM), for the evaluation of enteric drug metabolism, drug-drug interaction, drug toxicity, and pharmacology. CHIM was isolated from the small intestines of four human donors. The small intestines were first dissected into the duodenum, jejunum, and ileum, followed by collagenase digestion of the intestinal lumen. The isolated mucosa was gently homogenized to yield multiple cellular fragments, which were then cryopreserved in a programmable liquid cell freezer and stored in liquid nitrogen. After thawing and recovery, CHIM retained robust cytochrome P450 (P450) and non-P450 drug-metabolizing enzyme activities and demonstrated dose-dependent induction of transcription of CYP24A1 (approximately 300-fold) and CYP3A4 (approximately 3-fold) by vitamin D3 as well as induction of CYP3A4 (approximately 3-fold) by rifampin after 24 hours of treatment. Dose-dependent decreases in cell viability quantified by cellular ATP content were observed for naproxen and acetaminophen, with higher enterotoxicity observed for naproxen, consistent with that observed in humans in vivo. These results suggest that CHIM may be a useful in vitro experimental model for the evaluation of enteric drug properties, including drug metabolism, drug-drug interactions, and drug toxicity.

A Novel In Vitro Experimental System for the Evaluation of Drug Metabolism: Cofactor-Supplemented Permeabilized Cryopreserved Human Hepatocytes (MetMax Cryopreserved Human Hepatocytes).

We report here a novel experimental system, cryopreserved MetMax human hepatocytes (MMHHs), for in vitro drug metabolism studies. MMHHs consist of cofactor-supplemented permeabilized cryopreserved human hepatocytes. The use procedures for MMHHs are significantly simplified from that for conventional cryopreserved human hepatocytes (CCHHs): 1) storage at -80°C instead of in liquid nitrogen and 2) usage directly after thawing without centrifugation and microscopic evaluation of cell density and viability and cell density adjustment. In this study, we compared MMHHs and CCHHs in CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2D6, CYP2E1, CYP3A4, CYP2J2, monoamine oxidase A, aldehyde oxidase, flavin-containing monooxygenase, UDP-glucuronyl transferase, SULT, N-acetyltransferase 1, and acetaminophen glutathione (GSH) conjugation activities based on liquid chromatography-tandem mass spectrometry quantification of substrate metabolism. MMHHs were prepared from CCHHs consisting of hepatocytes pooled from 10 individual donors. The drug metabolizing enzyme activities of both CCHHs and MMHHs were cell concentration and time dependent, with specific activities of MMHHs ranging from 27.2% (carboxylesterase 2) to 234.2% (acetaminophen GSH conjugation) of that for CCHHs. As observed in CCHHs, sequential oxidation and conjugation was observed in MMHHs for coumarin, 7-ethoxycoumarin, and acetaminophen. 7-Hydroxycoumarin conjugation results showed that metabolic pathways in MMHHs could be selected via the choice of cofactors, with glucuronidation but not sulfation observed in the presence of UDP-glucuronic acid and not 3-phosphoadenosine-5-phosphosulfate, and vice versa. Results with noncytotoxic and cytotoxic concentrations of acetaminophen showed that drug metabolism was compromised in CCHHs but not in MMHHs. Our results suggest that the MMHHs system represents a convenient and robust in vitro experimental system for the evaluation of drug metabolism.

In vitro evaluation of hepatotoxic drugs in human hepatocytes from multiple donors: Identification of P450 activity as a potential risk factor for drug-induced liver injuries.

A possible risk factor for drug-induced hepatotoxicity is drug metabolizing enzyme activity, which is known to vary among individuals due to genetic (genetic polymorphism) and environmental factors (environmental pollutants, foods, and medications that are inhibitors or inducers of drug metabolizing enzymes). We hypothesize that hepatic cytochrome P450-dependent monooxygenase (CYP) activity is one of the key risk factors for drug induced liver injuries (DILI) in the human population, especially for drugs that are metabolically activated to cytotoxic/reactive metabolites. Human hepatocytes from 19 donors were evaluated for the activities of 8 major P450 isoforms: CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4. Extensive individual variations were observed, consistent with what is known to be in the human population. As CYP3A4 is known to be one of the most important P450 isoforms for drug metabolism, studies were performed to evaluate the relationship between the in vitro cytotoxicity of hepatotoxic drugs and CYP3A4 activity. In a proof of concept study, hepatocytes from six donors (lots) representing the observed range of CYP3A4 activities were chosen for the evaluation of in vitro hepatotoxicity of four drugs known to be associated with acute liver failure: acetaminophen, cyclophosphamide, ketoconazole, and tamoxifen. The hepatocytes were cultured in collagen-coated plates and treated with the hepatotoxicants for approximately 24 h, followed by viability determination based on cellular adenosine triphosphate (ATP) contents. HH1023, the lot of hepatocytes with the highest CYP3A4 activity, was found to be the most sensitive to the cytotoxicity of all 4 hepatotoxic drugs, thereby suggesting that high CYP3A4 activity may be a risk factor. To further validate the relationship, a second study was performed with hepatocytes from 16 donors. In this study, the hepatocytes were quantified for CYP3A4 activity at the time of treatment. Results of the second study show confirm the correlation between with high CYP3A4 activity and sensitivity to hepatotoxic drugs. Our results with primary cultured hepatocytes from multiple donors support the hypothesis that elevated P450 activity may be a risk factor for drug-induced liver injuries.

Inducible costimulator (ICOS) up-regulation on activated T cells in chronic graft-versus-host disease after dog leukocyte antigen-nonidentical hematopoietic cell transplantation: a potential therapeutic target.

BACKGROUND: Inducible costimulator (ICOS), a member of the CD28 family of costimulatory molecules, is induced on CD4 and CD8 T cells after their activation. ICOS functions as an essential immune regulator and ICOS blockade is a potential approach to immune modulation in allogeneic transplantation. Here, we describe the expression profile of ICOS in dogs and determine whether ICOS expression is up-regulated during chronic graft-versus-host disease (GVHD) and host-versus-graft reactions in the canine hematopoietic cell transplantation model. METHODS: Monoclonal antibodies (mAbs) against cell surface-expressed ICOS were produced and tested in vitro for suppression of canine mixed leukocyte reactions (MLR). Expression of ICOS on CD3 cells was evaluated by flow cytometry using peripheral blood, lymph nodes, and splenocytes obtained from dogs undergoing graft-versus-host and host-versus-graft reactions. RESULTS: Canine ICOS was expressed in an inducible pattern on T cells activated by concanavalin A, anti-CD3 mAb in combination with anti-CD28 mAb, and alloantigen stimulation. Immunosuppressive effects of ICOS blockade were observed in MLR using peripheral blood mononuclear cells from dog leukocyte antigen-nonidentical dogs. Immunosuppressive effects of ICOS blockade were observed in MLR when anti-ICOS was combined with suboptimal concentrations of cytotoxic T-lymphocyte antigen 4-Ig or cyclosporine. ICOS expression was significantly up-regulated on T cells in dogs undergoing graft rejection or chronic GVHD after allogeneic hematopoietic cell transplantation. CONCLUSIONS: These studies suggest that ICOS plays a role in graft rejection and GVHD in an outbred animal model, and ICOS blockade may be an approach to prevention and treatment of chronic GVHD.

Activation of Notch signaling during ex vivo expansion maintains donor muscle cell engraftment.

Transplantation of myogenic stem cells possesses great potential for long-term repair of dystrophic muscle. However, a single donor muscle biopsy is unlikely to provide enough cells to effectively transplant the muscle mass of a patient affected by muscular dystrophy. Expansion of cells ex vivo using traditional culture techniques significantly reduces engraftment potential. We hypothesized that activation of Notch signaling during ex vivo expansion would maintain donor cell engraftment potential. In this study, we expanded freshly isolated canine muscle-derived cells on tissue culture plates coated with Delta-1(ext) -IgG to activate Notch signaling or with human IgG as a control. A model of canine-to-murine xenotransplantation was used to quantitatively compare canine muscle cell engraftment and determine whether engrafted donor cells could function as satellite cells in vivo. We show that Delta-1(ext) -IgG inhibited differentiation of canine muscle-derived cells and increased the level of genes normally expressed in myogenic precursors. Moreover, cells expanded on Delta-1(ext) -IgG resulted in a significant increase in the number of donor-derived fibers, as compared to cells expanded on human IgG, reaching engraftment levels similar to freshly isolated cells. Importantly, cells expanded on Delta-1(ext) -IgG engrafted to the recipient satellite cell niche and contributed to further regeneration. A similar strategy of expanding human muscle-derived cells on Notch ligand might facilitate engraftment and muscle regeneration for patients affected with muscular dystrophy.

Inhibition of CD26/DPP-IV enhances donor muscle cell engraftment and stimulates sustained donor cell proliferation.

BACKGROUND: Transplantation of myogenic stem cells possesses great potential for long-term repair of dystrophic muscle. In murine-to-murine transplantation experiments, CXCR4 expression marks a population of adult murine satellite cells with robust engraftment potential in mdx mice, and CXCR4-positive murine muscle-derived SP cells home more effectively to dystrophic muscle after intra-arterial delivery in mdx5cv mice. Together, these data suggest that CXCR4 plays an important role in donor cell engraftment. Therefore, we sought to translate these results to a clinically relevant canine-to-canine allogeneic transplant model for Duchenne muscular dystrophy (DMD) and determine if CXCR4 is important for donor cell engraftment. METHODS: In this study, we used a canine-to-murine xenotransplantation model to quantitatively compare canine muscle cell engraftment, and test the most effective cell population and modulating factor in a canine model of DMD using allogeneic transplantation experiments. RESULTS: We show that CXCR4 expressing cells are important for donor muscle cell engraftment, yet FACS sorted CXCR4-positive cells display decreased engraftment efficiency. However, diprotin A, a positive modulator of CXCR4-SDF-1 binding, significantly enhanced engraftment and stimulated sustained proliferation of donor cells in vivo. Furthermore, the canine-to-murine xenotransplantation model accurately predicted results in canine-to-canine muscle cell transplantation. CONCLUSIONS: Therefore, these results establish the efficacy of diprotin A in stimulating muscle cell engraftment, and highlight the pre-clinical utility of a xenotransplantation model in assessing the relative efficacy of muscle stem cell populations.

Antagonistic and agonistic anti-canine CD28 monoclonal antibodies: tools for allogeneic transplantation.

BACKGROUND: It has been presumed that antibody-mediated selective costimulatory molecule blockade of CD28 is superior to cytotoxic T lymphocyte antigen 4 (CTLA4)-Ig. This is based on the premise that specifically blocking CD28 allows inhibitory signals through CTLA-4 to proceed, which furthermore suppresses T-cell function. METHODS: The extracelluar domain of canine (ca)CD28 was cloned from dog peripheral blood mononuclear cells. Mice were immunized with a caCD28/murine IgG2a fusion protein. Hybridomas were produced by fusing splenocytes with mouse NSO cells and screened for caCD28 binding by ELISA. Agonistic and antagonistic activities of the monoclonal antibodies (mAb) were tested in mixed leukocyte reactions. Canine regulatory T cells were expanded using plate-bound anti-CD3 and an anti-CD28 agonist mAb. RESULTS: One agonistic and seven antagonistic mAbs to canine (ca)CD28 were cloned. Binding studies indicated that an agonistic (5B8) and an antagonistic (1C6) mAb bound equally well to a caCD28/caIgG1 fusion protein and to CD28 expressed on CD4+ and CD8+ peripheral blood T cells. Antagonistic antibody blocked mixed lymphocyte reactions (MLR) in a dose-dependent manner similar to CTLA4-Ig, whereas the agonistic antibody to caCD28 enhanced MLR. The 5B8 was superior to 1C6 when either was combined with anti-caCD3 to stimulate lymphocyte proliferation. Furthermore, the agonistic mAb, 5B8, together with anti-CD3 mAb induced 100-fold proliferation of canine regulatory T cells. Relative to untreated control cells, anti-caCD28 (1C6) and CTLA4-Ig equivalently inhibited cytotoxic T lymphocyte-mediated killing of alloreactive target cells. CONCLUSION: These studies demonstrated that mouse anti-caCD28 mAbs can be generated with agonistic or antagonistic function.

Establishment of long-term tolerance to SRBC in dogs by recombinant canine CTLA4-Ig.

BACKGROUND: Blockade of the CD28 costimulatory molecule by recombinant human cytotoxic T lymphocyte (CTL)-associated antigen (CTLA4)-Ig or CD40-CD154 interaction with the monoclonal antibody 5C8 together with donor-specific transfusion led to enhanced engraftment in the canine model of dog leukocyte antigen (DLA)-identical marrow transplantation after 1 Gy total body irradiation. To reduce or eliminate total body irradiation conditioning regimens, we have sought to develop canine specific reagents. METHODS: We have created a fusion protein of the extracellular domain of canine (c) CTLA-4 linked to the hinge-CH2-CH3 domains of canine IgG1 in a pcDNA3.1+ vector. Chinese hamster ovarian cells were cotransfected with CTLA4-Ig vector and a dihydrofolate reductase-containing vector. Stable, high producing clones were generated. RESULTS: Cell binding and mixed leukocyte reactions indicated no significant differences in activity between cCTLA4-Ig and human CTLA4-Ig. Mixed leukocyte reaction data indicated that combinations of cCTLA4-Ig and the monoclonal antibody 5C8 were superior in blocking H-thymidine uptake compared to either reagent alone. In dogs, the circulating half-life of cCTLA4-Ig was approximately 7 days with no immune response against the fusion protein. Finally, two injections of cCTLA4-Ig effectively tolerized two dogs against eight consecutive challenges with sheep red blood cells, given over 330 days as indicated by a complete block of IgG antibody production. Tolerance was broken in one of the two dogs when a ninth injection of sheep red blood cell was given subcutaneously in incomplete Freund's adjuvant. CONCLUSION: cCTLA4-Ig is an effective nonimmunogenic blocking reagent of the CD28 costimulatory pathway in dogs and is a promising reagent for studies of tolerance induction in hematopoietic cell transplantation in the canine model.

Long-term tolerance to kidney allografts in a preclinical canine model.

Durable immune tolerance supporting vascularized allotransplantation offers the possibility of extending graft survival and avoiding harmful complications of chronic immunosuppression. Immune tolerance to renal allografts was induced in a preclinical canine model through engraftment of donor hematopoietic cells using a combination of low-dose total body irradiation and a short course of immunosuppression. Subsequently, donor renal allografts were transplanted accompanied by bilateral native nephrectomies. With 5-year follow up, we found normal renal function in all recipients and no histological evidence of acute or chronic rejection. This tolerance does not extend universally to donor skin grafts, however, with two of four animals rejecting delayed donor skin grafts. Hematopoietic chimerism produces durable and robust immune tolerance to kidney allografts, although incomplete tolerance to donor skin grafting.

Molecular cloning and characterization of canine ICOS.

Inducible costimulatory receptor (ICOS) is one recently identified member of the CD28 family of costimulatory molecules. Evidence suggests ICOS functions as a critical immune regulator and, to evaluate these effects, we employed the canine model system that has been used to develop strategies currently in clinical use for hematopoietic stem cell transplantation. To investigate the effects of blocking the ICOS pathway in the canine hematopoietic cell transplantation model, we tested existing murine and human reagents and cloned the full length of the open reading frame of canine ICOS cDNA to allow the development of reagents specific for the canine ICOS. Canine ICOS contains a major open reading frame of 624 nucleotides, encoding a protein of 208 amino acids, and localizes to chromosome 37. Canine ICOS shares 79% sequence identity with human ICOS, 70% with mouse, and 69% with rat. Canine ICOS expression is limited to stimulated PBMC.