Associations of systemic inflammatory regulators with CKD and kidney function: evidence from the bidirectional mendelian randomization study

BACKGROUND

Previous observational studies have reported that systemic inflammatory regulators are related to the development of chronic kidney disease (CKD); however, whether these associations are causal remains unclear. The current study aimed to investigate the potential causal relationships between systemic inflammatory regulators and CKD and kidney function.

METHOD

We performed bidirectional two-sample Mendelian randomization (MR) analyses to infer the underlying causal associations between 41 systemic inflammatory regulators and CKD and kidney function. The inverse-variance weighting (IVW) test was used as the primary analysis method. In addition, sensitivity analyses were executed via the Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) test and the weighted median test.

RESULTS

The findings revealed 12 suggestive associations between 11 genetically predicted systemic inflammatory regulators and CKD or kidney function in the forward analyses, including 4 for CKD, 3 for blood urea nitrogen (BUN), 4 for eGFRcrea and 1 for eGFRcys. In the other direction, we identified 6 significant causal associations, including CKD with granulocyte-colony stimulating factor (GCSF) (IVW β = 0.145; 95% CI, 0.042 to 0.248; P = 0.006), CKD with stem cell factor (SCF) (IVW β = 0.228; 95% CI, 0.133 to 0.323; P = 2.40 × 10- 6), eGFRcrea with SCF (IVW β =-2.90; 95% CI, -3.934 to -1.867; P = 3.76 × 10- 8), eGFRcys with GCSF (IVW β =-1.382; 95% CI, -2.404 to -0.361; P = 0.008), eGFRcys with interferon gamma (IFNg) (IVW β =-1.339; 95% CI, -2.313 to -0.366; P = 0.007) and eGFRcys with vascular endothelial growth factor (VEGF) (IVW β =-1.709; 95% CI, -2.720 to -0.699; P = 9.13 × 10- 4).

CONCLUSIONS

Our findings support causal links between systemic inflammatory regulators and CKD or kidney function both in the forward and reverse MR analyses.

PGR-KITLG signaling drives a tumor-mast cell regulatory feedback to modulate apoptosis of breast cancer cells

The immune microenvironment constructed by tumor-infiltrating immune cells and the molecular phenotype defined by hormone receptors (HRs) have been implicated as decisive factors in the regulation of breast cancer (BC) progression. Here, we found that the infiltration of mast cells (MCs) informed impaired prognoses in HR(+) BC but predicted improved prognoses in HR(-) BC. However, molecular features of MCs in different BC remain unclear. We next discovered that HR(-) BC cells were prone to apoptosis under the stimulation of MCs, whereas HR(+) BC cells exerted anti-apoptotic effects. Mechanistically, in HR(+) BC, the KIT ligand (KITLG), a major mast cell growth factor in recruiting and activating MCs, could be transcriptionally upregulated by the progesterone receptor (PGR), and elevate the production of MC-derived granulin (GRN). GRN attenuates TNFα-induced apoptosis in BC cells by competitively binding to TNFR1. Furthermore, disruption of PGR-KITLG signaling by knocking down PGR or using the specific KITLG-cKIT inhibitor iSCK03 potently enhanced the sensitivity of HR(+) BC cells to MC-induced apoptosis and exerted anti-tumor activity. Collectively, these results demonstrate that PGR-KITLG signaling in BC cells preferentially induces GRN expression in MCs to exert anti-apoptotic effects, with potential value in developing precision medicine approaches for diagnosis and treatment.

Physiological and regenerative functions of sterile-α motif protein-14 in hematopoiesis

Sterile α-motif domain-14 (Samd14) protein expression increases the regenerative capacity of the erythroid system. Samd14 is transcriptionally upregulated and promotes cell signaling via the receptor tyrosine kinase Kit in a critical window of acute erythroid regeneration. We generated a hematopoietic-specific conditional Samd14 knockout mouse model (Samd14-CKO) to study the role of Samd14 in hematopoiesis. The Samd14-CKO mouse was viable and exhibited no steady-state hematopoietic phenotype. Samd14-CKO mice were hypersensitive to 5-fluorouracil, resulting in more severe anemia during recovery and impaired erythroid progenitor colony formation. Ex vivo, Samd14-CKO hematopoietic progenitors were defective in their ability to form mast cells. Samd14-CKO mast cells exhibited altered Kit/stem cell factor (SCF), IL-3/IL-3R signaling, and less granularity than Samd14-FL/FL cells. Our findings indicate that Samd14 promotes both erythroid and mast cell functions. The Samd14-CKO mouse phenotype exhibits striking similarities to the KitW/W-v mice, which carry Kit mutations resulting in reduced tyrosine kinase-dependent signaling, causing mast cell and erythroid abnormalities. The Samd14-CKO mouse model is a new tool for studying hematologic pathologies involving Kit signaling.

Epigenetic histone modification by butyrate downregulates KIT and attenuates mast cell function

Short-chain fatty acid butyrate is produced from the bacterial fermentation of indigestible fiber in the intestinal lumen, and it has been shown to attenuate lung inflammation in murine asthma models. Mast cells (MCs) are initiators of inflammatory response to allergens, and they play an important role in asthma. MC survival and proliferation is regulated by its growth factor stem cell factor (SCF), which acts through the receptor, KIT. It has previously been shown that butyrate attenuates the activation of MCs by allergen stimulation. However, how butyrate mechanistically influences SCF signalling to impact MC function remains unknown. Here, we report that butyrate treatment triggered the modification of MC histones via butyrylation and acetylation, and inhibition of histone deacetylase (HDAC) activity. Further, butyrate treatment caused downregulation of SCF receptor KIT and associated phosphorylation, leading to significant attenuation of SCF-mediated MC proliferation, and pro-inflammatory cytokine secretion. Mechanistically, butyrate inhibited MC function by suppressing KIT and downstream p38 and Erk phosphorylation, and it mediated these effects via modification of histones, acting as an HDAC inhibitor and not via its traditional GPR41 (FFAR3) or GPR43 (FFAR2) butyrate receptors. In agreement, the pharmacological inhibition of Class I HDAC (HDAC1/3) mirrored butyrate's effects, suggesting that butyrate impacts MC function by HDAC1/3 inhibition. Taken together, butyrate epigenetically modifies histones and downregulates the SCF/KIT/p38/Erk signalling axis, leading to the attenuation of MC function, validating its ability to suppress MC-mediated inflammation. Therefore, butyrate supplementations could offer a potential treatment strategy for allergy and asthma via epigenetic alterations in MCs.

Embryonic stem cell factor FOXD3 (Genesis) defects in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are mesenchymal neoplasms, believed to originate from the interstitial cells of Cajal (ICC), often caused by overexpression of tyrosine kinase receptors (TKR) KIT or PDGFRA. Here, we present evidence that the embryonic stem cell factor FOXD3, first identified as 'Genesis' and involved in both gastrointestinal and neural crest cell development, is implicated in GIST pathogenesis; its involvement is investigated both in vitro and in zebrafish and a mouse model of FOXD3 deficiency. Samples from a total of 58 patients with wild-type GISTs were used for molecular analyses, including Sanger sequencing, comparative genomic hybridization, and methylation analysis. Immunohistochemistry and western blot evaluation were used to assess FOXD3 expression. Additionally, we conducted in vitro functional studies in tissue samples and in transfected cells to confirm the pathogenicity of the identified genetic variants. Germline partially inactivating FOXD3 sequence variants (p.R54H and p.Ala88_Gly91del) were found in patients with isolated GISTs. Chromosome 1p loss was the most frequent chromosomal abnormality identified in tumors. In vitro experiments demonstrate the impairment of FOXD3 in the presence of those variants. Animal studies showed disruption of the GI neural network and changes in the number and distribution in the ICC. FOXD3 suppresses KIT expression in human cells; its inactivation led to an increase in ICC in zebrafish, as well as mice, providing evidence for a functional link between FOXD3 defects and KIT overexpression leading to GIST formation.

Multiple intratumoral sources of kit ligand promote gastrointestinal stromal tumor

Gastrointestinal stromal tumor (GIST) is the most common human sarcoma and is typically driven by a single mutation in the Kit or PDGFRA receptor. While highly effective, tyrosine kinase inhibitors (TKIs) are not curative. The natural ligand for the Kit receptor is Kit ligand (KitL), which exists in both soluble and membrane-bound forms. While KitL is known to stimulate human GIST cell lines in vitro, we used a genetically engineered mouse model of GIST containing a common human KIT mutation to investigate the intratumoral sources of KitL, importance of KitL during GIST oncogenesis, and contribution of soluble KitL to tumor growth in vivo. We discovered that in addition to tumor cells, endothelia and smooth muscle cells produced KitL in KitV558Δ/+ tumors, even after imatinib therapy. Genetic reduction of total KitL in tumor cells of KitV558Δ/+ mice impaired tumor growth in vivo. Similarly, genetic reduction of tumor cell soluble KitL in KitV558Δ/+ mice decreased tumor size. By RNA sequencing, quantitative PCR, and immunohistochemistry, KitL expression was heterogeneous in human GIST specimens. In particular, PDGFRA-mutant tumors had much higher KitL expression than Kit-mutant tumors, suggesting the benefit of Kit activation in the absence of mutant KIT. Serum KitL was higher in GIST patients with tumors resistant to imatinib and in those with tumors expressing more KitL RNA. Overall, KitL supports the growth of GIST at baseline and after imatinib therapy and remains a potential biomarker and therapeutic target.

Cryo-EM analyses of KIT and oncogenic mutants reveal structural oncogenic plasticity and a target for therapeutic intervention

The receptor tyrosine kinase KIT and its ligand stem cell factor (SCF) are required for the development of hematopoietic stem cells, germ cells, and other cells. A variety of human cancers, such as acute myeloid leukemia, gastrointestinal stromal tumor, and mast cell leukemia, are driven by somatic gain-of-function KIT mutations. Here, we report cryo electron microscopy (cryo-EM) structural analyses of full-length wild-type and two oncogenic KIT mutants, which show that the overall symmetric arrangement of the extracellular domain of ligand-occupied KIT dimers contains asymmetric D5 homotypic contacts juxtaposing the plasma membrane. Mutational analysis of KIT reveals in D5 region an "Achilles heel" for therapeutic intervention. A ligand-sensitized oncogenic KIT mutant exhibits a more comprehensive and stable D5 asymmetric conformation. A constitutively active ligand-independent oncogenic KIT mutant adopts a V-shaped conformation solely held by D5-mediated contacts. Binding of SCF to this mutant fully restores the conformation of wild-type KIT dimers, including the formation of salt bridges responsible for D4 homotypic contacts and other hallmarks of SCF-induced KIT dimerization. These experiments reveal an unexpected structural plasticity of oncogenic KIT mutants and a therapeutic target in D5.

Sertoli cells are the source of stem cell factor for spermatogenesis

Several cell types have been proposed to create the required microenvironment for spermatogenesis. However, expression patterns of the key growth factors produced by these somatic cells have not been systematically studied and no such factor has been conditionally deleted from its primary source(s), raising the question of which cell type(s) are the physiological sources of these growth factors. Here, using single-cell RNA sequencing and a series of fluorescent reporter mice, we found that stem cell factor (Scf), one of the essential growth factors for spermatogenesis, was broadly expressed in testicular stromal cells, including Sertoli, endothelial, Leydig, smooth muscle and Tcf21-CreER+ stromal cells. Both undifferentiated and differentiating spermatogonia were associated with Scf-expressing Sertoli cells in the seminiferous tubule. Conditional deletion of Scf from Sertoli cells, but not any other Scf-expressing cells, blocked the differentiation of spermatogonia, leading to complete male infertility. Conditional overexpression of Scf in Sertoli cells, but not endothelial cells, significantly increased spermatogenesis. Our data reveal the importance of anatomical localization for Sertoli cells in regulating spermatogenesis and that SCF produced specifically by Sertoli cells is essential for spermatogenesis.

Proteomics Analysis of Genetic Liability of Abdominal Aortic Aneurysm Identifies Plasma Neogenin and Kit Ligand: The ARIC Study

BACKGROUND

Genome-wide association studies have reported 23 gene loci related to abdominal aortic aneurysm (AAA)-a potentially lethal condition characterized by a weakened dilated vessel wall. This study aimed to identify proteomic signatures and pathways related to these risk loci to better characterize AAA genetic susceptibility.

METHODS

Plasma concentrations of 4870 proteins were determined using a DNA aptamer-based array. Linear regression analysis estimated the associations between the 23 risk alleles and plasma protein levels with adjustments for potential confounders in a race-stratified analysis of 1671 Black and 7241 White participants. Significant proteins were then evaluated for their prediction of clinical AAA (454 AAA events in 11 064 individuals), and those significantly associated with AAA were further interrogated using Mendelian randomization analysis.

RESULTS

Risk variants proximal to PSRC1-CELSR2-SORT1, PCIF1-ZNF335-MMP9, RP11-136O12.2/TRIB1, ZNF259/APOA5, IL6R, PCSK9, LPA, and APOE were associated with 118 plasma proteins in Whites and 59 were replicated in Black participants. Novel associations with clinical AAA incidence were observed for kit ligand (HR, 0.59 [95% CI, 0.42-0.82] for top versus first quintiles) and neogenin (HR, 0.64 [95% CI, 0.46-0.88]) over a median 21.2-year follow-up; neogenin was also associated with ultrasound-detected asymptomatic AAA (N=4295; 57 asymptomatic AAA cases). Mendelian randomization inverse variance weighted estimates suggested that AAA risk is promoted by lower levels of kit ligand (OR per SD=0.67; P=1.4×10-5) and neogenin (OR per SD=0.50; P=0.03).

CONCLUSIONS

Low levels of neogenin and kit ligand may be novel risk factors for AAA development in potentially causal pathways. These findings provide insights and potential targets to reduce AAA susceptibility.

Endothelial cell-specific expression of serine/threonine kinase 11 modulates dendritic cell differentiation

In the bone marrow, classical and plasmacytoid dendritic cells (DC) develop from the macrophage-DC precursor (MDP) through a common DC precursor (CDP) step. This developmental process receives essential input from the niche in which it takes place, containing endothelial cells (EC) among other cell types. Here we show that targeted deletion of serine/threonine kinase 11 (Stk11) encoding tumor suppressor liver kinase b1 (Lkb1) in mouse ECs but not DCs, results in disrupted differentiation of MDPs to CDPs, severe reduction in mature DC numbers and spontaneous tumorigenesis. In wild type ECs, Lkb1 phosphorylates polypyrimidine tract binding protein 1 (Ptbp1) at threonine 138, which regulates stem cell factor (Scf) pre-mRNA splicing. In the absence of Lkb1, exon 6 of Scf is spliced out, leading to the loss of Scf secretion. Adeno-associated-virus-mediated delivery of genes encoding either soluble Scf or the phosphomimetic mutant Ptbp1T138E proteins rescued the defects of MDP to CDP differentiation and DC shortage in the endothelium specific Stk11 knockout mice. In summary, endothelial Stk11 expression regulates DC differentiation via modulation of Scf splicing, marking the Stk11-soluble-Scf axis as a potential cause of DC deficiency syndromes.

Tissue distribution of stem cell factor in adults

Stem cell factor (SCF) is an essential cytokine during development and is necessary for gametogenesis, hematopoiesis, mast cell development, stem cell function, and melanogenesis. Here, we measure SCF concentration and distribution in adult humans and mice using gene expression analysis, tissue staining, and organ protein lysates. We demonstrate continued SCF expression in many cell types and tissues into adulthood. Tissues with high expression in adult humans included stomach, spleen, kidney, lung, and pancreas. In mice, we found high SCF expression in the esophagus, ovary, uterus, kidney, and small intestine. Future studies may correlate our findings of increased, organ-specific SCF concentrations within adult tissues with increased risk of SCF/CD117-related disease.

Atractylodes oil alleviates diarrhea-predominant irritable bowel syndrome by regulating intestinal inflammation and intestinal barrier via SCF/c-kit and MLCK/MLC2 pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Atractylodes lancea (Thunb.) DC. is a widely used traditional herb that is well known for treating spleen deficiency and diarrhea. According to traditional Chinese medicine (TCM) theory, diarrhea-predominant irritable bowel syndrome (IBS-D) is caused by cold and dampness, resulting in diarrhea and abdominal pain. Nevertheless, the effect and mechanism of Atractylodes on IBS-D are still unclear.

AIM OF THE STUDY

This study was designed to confirm the therapeutic effect of Atractylodes lanceolata oil (AO) in a rat model of IBS-D, and to determine the mechanisms by which AO protects against the disease.

MATERIALS AND METHODS

The chemical components in AO were determined using gas chromatography-mass spectrometry (GC-MS). The expression levels of 5-hydroxytryptamine (5-HT), vasoactive intestinal peptide (VIP), and surfactant protein (SP) in serum and colon tissue were measured using enzyme-linked immunosorbent assay (ELISA). Reverse transcription-polymerase chain reaction (RT-PCR), western blotting (WB), immunohistochemistry (IHC), and immunofluorescence (IF) were used to elucidate the mechanism of action of AO toward inflammation and the intestinal barrier in a rat model of IBS-D.

RESULTS

The 15 chemical substances of the highest concentration in AO were identified using GC-MS. AO was effective against IBS-D in the rat model, in terms of increased body weight, diarrhea grade score, levels of interleukin-10 (IL-10), aquaporin 3 (AQP3), and aquaporin 8 (AQP8), and reduced fecal moisture content, levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), 5-HT, VIP, and SP, while also reducing intestinal injury, as observed using hematoxylin-eosin (HE) staining. In addition, the results indicated that AO increased the mRNA and protein expression levels of stem cell factor (SCF) and c-kit and enhanced the levels of zonula occludens-1 (ZO-1) and occludin, as well as decreased the levels of myosin light chain kinase (MLCK) and inhibited the phosphorylation of myosin light chain 2 (p-MLC2).

CONCLUSIONS

AO was found to be efficacious in the rat model of IBS-D. AO inhibited the SCF/c-kit pathway, thereby reducing inflammation and protecting against intestinal barrier damage via the MLCK/MLC2 pathway.

M1 macrophages-derived exosomes miR-34c-5p regulates interstitial cells of Cajal through targeting SCF

Slow transit constipation (STC) is a gastrointestinal disorder characterized by abnormal prolonged colonic transit time, which affects the life quality of many people. The decrease number of interstitial cells of Cajal (ICCs) is involved in the pathogenesis of STC. However, the molecular mechanism of loss of ICCs in STC remains unclear, making it difficult to develop new agents for the disease. In this study, we investigated the mechanism of decreasing ICCs in the pathogenesis of STC. We constructed the STC model rats by using atropine and diphenoxylate. A series of methods were used including immunofluorescence and immunochemistry staining, western blot, qRT-PCR, exosomes extraction and exosomes labeling. The results indicate that ICCs decreased in the STC rats accompanied with the macrophages activation. Further studies suggested that macrophages decreased the cell viability of ICCs by secretion exosomes containing miR-34c-5p. miR-34c5p targeted the 3Ꞌ -UTR of stem cell factor(SCF) mRNA and regulated the expression of SCF negatively. In conclusion, we demonstrated a novel regulatory mechanism of ICCs cell viability in STC. We found that exosome miR-34c-5p mediate macrophage-ICCs cross-talk. M1 macrophages derived exosomes miR-34c-5p decreased ICCs cell viability by directly targeting SCF.

Cell Sheet Comprised of Mesenchymal Stromal Cells Overexpressing Stem Cell Factor Promotes Epicardium Activation and Heart Function Improvement in a Rat Model of Myocardium Infarction

Cell therapy of the post-infarcted myocardium is still far from clinical use. Poor survival of transplanted cells, insufficient regeneration, and replacement of the damaged tissue limit the potential of currently available cell-based techniques. In this study, we generated a multilayered construct from adipose-derived mesenchymal stromal cells (MSCs) modified to secrete stem cell factor, SCF. In a rat model of myocardium infarction, we show that transplantation of SCF producing cell sheet induced activation of the epicardium and promoted the accumulation of c-kit positive cells in ischemic muscle. Morphometry showed the reduction of infarct size (16%) and a left ventricle expansion index (0.12) in the treatment group compared to controls (24-28%; 0.17-0.32). The ratio of viable myocardium was more than 1.5-fold higher, reaching 49% compared to the control (28%) or unmodified cell sheet group (30%). Finally, by day 30 after myocardium infarction, SCF-producing cell sheet transplantation increased left ventricle ejection fraction from 37% in the control sham-operated group to 53%. Our results suggest that, combining the genetic modification of MSCs and their assembly into a multilayered construct, we can provide prolonged pleiotropic effects to the damaged heart, induce endogenous regenerative processes, and improve cardiac function.

Skin wound closure delay in metabolic syndrome correlates with SCF deficiency in keratinocytes

Poor wound closure due to diabetes, aging, stress, obesity, alcoholism, and chronic disease affects millions of people worldwide. Reasons wounds will not close are still unclear, and current therapies are limited. Although stem cell factor (SCF), a cytokine, is known to be important for wound repair, the cellular and molecular mechanisms of SCF in wound closure remain poorly understood. Here, we found that SCF expression in the epidermis is decreased in mouse models of delayed wound closure intended to mimic old age, obesity, and alcoholism. By using SCF conditionally knocked out mice, we demonstrated that keratinocytes' autocrine production of SCF activates a transient c-kit receptor in keratinocytes. Transient activation of the c-kit receptor induces the expression of growth factors and chemokines to promote wound re-epithelialization by increasing migration of skin cells (keratinocytes and fibroblasts) and immune cells (neutrophils) to the wound bed 24-48 h post-wounding. Our results demonstrate that keratinocyte-produced SCF is essential to wound closure due to the increased recruitment of a unique combination of skin cells and immune cells in the early phase after wounding. This discovery is imperative for developing clinical strategies that might improve the body's natural repair mechanisms for treating patients with wound-closure pathologies.

Total glucosides of paeony (TGP) alleviates constipation and intestinal inflammation in mice induced by Sjögren's syndrome

ETHNOPHARMACOLOGICAL RELEVANCE

Sjögren's syndrome (SS) is an autoimmune disease and can cause gastrointestinal disorders such as constipation and intestinal inflammation. As a kind of medicinal material, Paeonia lactiflora Pall has a variety of pharmacological effects, and it is also an indispensable component in many pharmaceutical preparations, which has been widely concerned by the medical and pharmaceutical circles. Total glucosides of paeony (TGP) is a mixture of biologically active compounds extracted from the root of Paeonia lactiflora Pall and has therapeutic effects on a variety of autoimmune diseases.

AIM OF THE STUDY

To investigate the therapeutic effect of TGP on constipation and intestinal inflammation in mice modeled by SS, and to provide a basis for clinical research.

MATERIALS AND METHODS

The SS model was set up by submandibular gland (SMG) immune induction method and then treated with TGP for 24 weeks. The fecal characteristics were observed and the fecal number and moisture content were measured. Colonic pathology was observed by H&E staining. The levels of serum P substance (SP), vasoactive intestinal peptide (VIP), interleukin (IL)-1β, tumor necrosis factor (TNF)-α, nuclear factor (NF)-κB, nitric oxide (NO), and nitric oxide synthase (NOS) were determined by enzyme linked immunosorbent assay (ELISA) and microplate method, respectively. Reverse transcription polymerase chain reaction (RT-PCR) was employed to analyze the mRNA expression of c-kit and stem cell factor (SCF) in colon.

RESULTS

Compared with the model group, the dry and rough condition of the feces was improved, and the fecal gloss, number and moisture content significantly increased after the administration of TGP capsules. Meanwhile, TGP treatment improved colonic pathological damage, inhibited the serum concentrations of NO, NOS, IL-1β, TNF-α, NF-κB and SP, increased serum VIP concentration, and up-regulated mRNA expression of SCF and c-kit in colon.

CONCLUSIONS

TGP could obviously attenuate SS-mediated constipation and intestinal inflammation in mice by acting on some intestinal motility related factors and inflammatory factors.

Absence of glyphosate-induced effects on ovarian folliculogenesis and steroidogenesis

Glyphosate (GLY) is an herbicidal active ingredient and both in vitro and in vivo studies suggest that GLY alters ovarian function. To determine if a chronic GLY exposure model affected steroidogenesis or folliculogenesis in vivo, postnatal day 42 C57BL6 female mice were orally delivered vehicle control (saline) or GLY (2 mg/Kg) from a pipette tip five days per week for either five or ten weeks. Mice were euthanized at the pro-estrus stage of the estrous cycle. GLY exposure did not impact body weight gain, organ weights, or healthy follicle numbers. In addition, GLY exposure did not affect abundance of ovarian mRNA encoding kit ligand (Kitlg), KIT proto-oncogene receptor tyrosine kinase (c-Kit), insulin receptor (Insr), insulin receptor substrate (Irs1 or Irs2) and protein thymoma viral proto-oncogene 1 (AKT) or phosphorylated AKT. Ovarian mRNA or protein abundance of Star, 3β-hydroxysteroid dehydrogenase (Hsd3b1), Cyp11a1 or Cyp19a were also not altered by GLY. Circulating 17β-estradiol and progesterone concentration were unaffected by GLY exposure. In conclusion, chronic GLY exposure for five or ten weeks did not affect the ovarian endpoints examined herein.

Lung Function in African American Children with Asthma Is Associated with Novel Regulatory Variants of the KIT Ligand KITLG/SCF and Gene-By-Air-Pollution Interaction

Baseline lung function, quantified as forced expiratory volume in the first second of exhalation (FEV1), is a standard diagnostic criterion used by clinicians to identify and classify lung diseases. Using whole-genome sequencing data from the National Heart, Lung, and Blood Institute Trans-Omics for Precision Medicine project, we identified a novel genetic association with FEV1 on chromosome 12 in 867 African American children with asthma (P = 1.26 × 10-8, β = 0.302). Conditional analysis within 1 Mb of the tag signal (rs73429450) yielded one major and two other weaker independent signals within this peak. We explored statistical and functional evidence for all variants in linkage disequilibrium with the three independent signals and yielded nine variants as the most likely candidates responsible for the association with FEV1 Hi-C data and expression QTL analysis demonstrated that these variants physically interacted with KITLG (KIT ligand, also known as SCF), and their minor alleles were associated with increased expression of the KITLG gene in nasal epithelial cells. Gene-by-air-pollution interaction analysis found that the candidate variant rs58475486 interacted with past-year ambient sulfur dioxide exposure (P = 0.003, β = 0.32). This study identified a novel protective genetic association with FEV1, possibly mediated through KITLG, in African American children with asthma. This is the first study that has identified a genetic association between lung function and KITLG, which has established a role in orchestrating allergic inflammation in asthma.

A combination of Semen Cuscutae and Fructus Lycii improves testicular cell proliferation and inhibits their apoptosis in rats with spermatogenic dysfunction by regulating the SCF/c-kit--PI3K--Bcl-2 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Semen Cuscutae is the seed of Cuscuta japonica Choisy, and Fructus Lycii is the mature fruit of Lycium barbarum L. (Solanaceae). Semen Cuscutae and Fructus Lycii (SC-FL) are well-known Chinese medicine which have been used to tonify the kidney and replenish the essence for thousands of years. Chinese physicians prefer to prescribe them for treating male infertility. Recent studies have found that SC-FL repair spermatogenic dysfunction, however, the therapeutic mechanism has yet to be clearly elucidated.

AIM OF THE STUDY

This study aimed at evaluating the therapeutic effect of SC-FL in glucosides of Tripterygium wilfordii Hook. f (GTW)-induced dyszoospermia rats and elucidating the underlying molecular mechanism.

MATERIALS AND METHODS

Seventy-eight Sprague-Dauley (SD) rats were randomly divided into five groups: normal control (treated with saline), GTW (treated with saline), GTW + levocarnitine (treated with levocarnitine), GTW + SCFL (treated with SC-FL), and LY (LY294002, the PI3K inhibitor) +SCFL (treated with SC-FL). GTW (40 mg/kg/d) was intragastrically administered for 4 weeks to establish dyszoospermia model. From the start of the study, LY was additionally injected into the tail vein of rats of the LY + SCFL group once a week. After 8 weeks, semen quality and organ coefficient were determined and sex hormone, inhibin B, and epididymal carnitine levels were measured. Testicular tissue and its ultrastructure were observed using H&E (hematoxylin-eosin) staining and electron microscopy. Immunohistochemistry, western blotting, and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were used to determine the protein and mRNA expression of SCF, c-kit, PI3K, p-Akt, Bad, Bcl-2, and Bax in rat testis.

RESULTS

Compared with the GTW group, semen quality, the organ coefficient, follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), and epididymal carnitine levels were significantly improved in the GTW + SCFL group (P < 0.05 or P < 0.01). Histomorphology and testicular ultrastructural evaluation showed that in the GTW + SCFL group, the structure and arrangement of seminiferous tubules were better, the amount of spermatogenic cells increased significantly, the morphology of spermatogenic cells improved, and the mitochondria increased, compared to those in the GTW group. Immunohistochemistry, western blotting, and qRT-PCR results showed that compared with the GTW group, the expression of SCF, c-kit, PI3K, p-Akt, and Bcl-2 in the GTW + SCFL group was increased, while that of Bax and Bad was decreased. The expression of p-Akt and Bcl-2 decreased, while that of Bad and Bax increased in the LY + SCFL group compared with the SCFL group.

CONCLUSION

SC-FL can effectively inhibit spermatogenic cell apoptosis and promote their proliferation, and the mechanism may be related to the regulation of the SCF/c-kit--PI3K--Bcl-2 pathway.

Pigment Intensity in Dogs is Associated with a Copy Number Variant Upstream of KITLG

Dogs exhibit a wide variety of coat color types, and many genes have been identified that control pigment production, appearance, and distribution. Some breeds, such as the Nova Scotia Duck Tolling Retriever (NSDTR), exhibit variation in pheomelanin pigment intensity that is not explained by known genetic variants. A genome-wide association study comparing light red to dark red in the NSDTR identified a significantly associated region on canine chromosome 15 (CFA 15:23 Mb–38 Mb). Coverage analysis of whole genome sequence data from eight dogs identified a 6 kb copy number variant (CNV) 152 kb upstream of KITLG. Genotyping with digital droplet PCR (ddPCR) confirmed a significant association between an increased copy number with the dark-red coat color in NSDTR (p = 6.1 × 10⁻⁷). The copy number of the CNV was also significantly associated with coat color variation in both eumelanin and pheomelanin-based Poodles (p = 1.5 × 10⁻⁸, 4.0 × 10⁻⁹) and across other breeds. Moreover, the copy number correlated with pigment intensity along the hair shaft in both pheomelanin and eumelanin coats. KITLG plays an important role in melanogenesis, and variants upstream of KITLG have been associated with coat color variation in mice as well as hair color in humans consistent with its role in the domestic dog.

Downregulation of hepatic stem cell factor by Vivo-Morpholino treatment inhibits mast cell migration and decreases biliary damage/senescence and liver fibrosis in Mdr2-/- mice

Primary sclerosing cholangitis (PSC) is characterized by increased mast cell (MC) infiltration, biliary damage and hepatic fibrosis. Cholangiocytes secrete stem cell factor (SCF), which is a chemoattractant for c-kit expressed on MCs. We aimed to determine if blocking SCF inhibits MC migration, biliary damage and hepatic fibrosis.

METHODS

FVB/NJ and Mdr2-/- mice were treated with Mismatch or SCF Vivo-Morpholinos. We measured (i) SCF expression and secretion; (ii) hepatic damage; (iii) MC migration/activation and histamine signaling; (iv) ductular reaction and biliary senescence; and (v) hepatic fibrosis. In human PSC patients, SCF expression and secretion were measured. In vitro, cholangiocytes were evaluated for SCF expression and secretion. Biliary proliferation/senescence was measured in cholangiocytes pretreated with 0.1% BSA or the SCF inhibitor, ISK03. Cultured HSCs were stimulated with cholangiocyte supernatant and activation measured. MC migration was determined with cholangiocytes pretreated with BSA or ISK03 loaded into the bottom of Boyden chambers and MCs into top chamber.

RESULTS

Biliary SCF expression and SCF serum levels increase in human PSC. Cholangiocytes, but not hepatocytes, from SCF Mismatch Mdr2-/- mice have increased SCF expression and secretion. Inhibition of SCF in Mdr2-/- mice reduced (i) hepatic damage; (ii) MC migration; (iii) histamine and SCF serum levels; and (iv) ductular reaction/biliary senescence/hepatic fibrosis. In vitro, cholangiocytes express and secrete SCF. Blocking biliary SCF decreased MC migration, biliary proliferation/senescence, and HSC activation.

CONCLUSION

Cholangiocytes secrete increased levels of SCF inducing MC migration, contributing to biliary damage/hepatic fibrosis. Targeting MC infiltration may be an option to ameliorate PSC progression.

[Correlation of single nucleotide polymorphisms rs995030 and rs4474514 of the KITLG gene with male infertility]

OBJECTIVE

To investigate the correlation of the single nucleotide polymorphisms rs995030 and rs4474514 of the tyrosine kinase receptor-specific ligand (KITLG) gene with the risk of male infertility.

METHODS

This study included 360 patients with idiopathic male infertility and 338 healthy fathers as controls, all from the surrounding areas of Nanjing. According to the 5th edition of the WHO Laboratory Manual for the Examination and Processing of Human Semen, we divided the infertility patients into an azoospermia (n = 143), a severe oligozoospermia (n = 159), and an oligozoospermia group (n = 58). We obtained the basic clinical data on all the subjects, collected genomic DNA from the peripheral blood of the patients, determined the genotypes of the KITLG gene rs995030 and rs4474514 by sequence mass-array, and analyzed the correlation between the two-point gene polymorphism and male infertility by logistic regression analysis.

RESULTS

Statistically significant differences were observed between the infertility patients and normal fertile controls in sperm concentration (［13.23 ± 24.52］ vs ［78.74 ± 61.25］ ×10⁶/ml, P < 0.01), the percentage of progressively mobile sperm (［18.71 ± 15.19］% vs ［39.36 ± 9.75］%, P < 0.01), and the level of FSH (［16.09 ± 17.31］ vs ［4.56 ± 2.41］ IU/L, P < 0.01), but not between the genotypes and male infertility, and no correlation was found in subgroup analysis.

CONCLUSIONS

The single nucleotide polymorphisms rs995030 and rs4474514 of the KITLG gene were not significantly correlated with male infertility, which is to be further verified by more studies with samples of larger size and expanded selection range.

Brain expansion promoted by polycomb-mediated anterior enhancement of a neural stem cell proliferation program

During central nervous system (CNS) development, genetic programs establish neural stem cells and drive both stem and daughter cell proliferation. However, the prominent anterior expansion of the CNS implies anterior–posterior (A–P) modulation of these programs. In Drosophila, a set of neural stem cell factors acts along the entire A–P axis to establish neural stem cells. Brain expansion results from enhanced stem and daughter cell proliferation, promoted by a Polycomb Group (PcG)->Homeobox (Hox) homeotic network. But how does PcG->Hox modulate neural-stem-cell–factor activity along the A–P axis? We find that the PcG->Hox network creates an A–P expression gradient of neural stem cell factors, thereby driving a gradient of proliferation. PcG mutants can be rescued by misexpression of the neural stem cell factors or by mutation of one single Hox gene. Hence, brain expansion results from anterior enhancement of core neural-stem-cell–factor expression, mediated by PcG repression of brain Hox expression.

A study in fruit flies shows that the anterior expansion of the central nervous system, to form the brain, is driven by Polycomb-mediated repression of Hox genes, resulting in anterior enhancement of a neural stem cell program.

The central nervous system displays a pronounced anterior expansion that forms the brain. In the fruit fly Drosophila melanogaster, this expansion is driven by enhanced anterior cell proliferation. Recent studies reveal that cell proliferation in the brain is promoted by the Polycomb Group Complex, a key epigenetic complex. During development of the central nervous system, the Polycomb Group Complex acts to exclude Hox homeotic gene expression from the brain, thereby rendering the brain a Hox-free zone. Hox genes act in an antiproliferative manner, which explains the hyperproliferation observed in the brain, as well as the gradient of proliferation along the anterior–posterior axis of the central nervous system. Here, we find that Hox genes act by repressing a common neural stem cell proliferation program in more posterior regions, resulting in an anterior–posterior gradient of “stemness.” Hence, elevated anterior proliferation is promoted by the Polycomb Group Complex acting to keep the brain free of negative Hox input, thereby ensuring elevated expression of neural stem cell factors in the brain. Strikingly, mutants of the Polycomb Group Complex can be rescued by mutation of one single Hox gene, demonstrating that the primary role of the Polycomb Group Complex is indeed Hox repression. This study advances our understanding of how neural stem cell programs operate at different axial levels of the central nervous system and may have implications also for stem cell and organoid biology.

Association between DNA methylation of the KITLG gene and cortisol levels under stress: a replication study

A recent study reported for the first time, that DNA methylation of the KITLG gene mediates the association between childhood trauma and cortisol stress reactivity. Our study aimed to provide the first independent replication of these findings. ESPRIT is a prospective study of community-dwelling participants (age ≥ 65), randomly selected from the electoral rolls of the Montpellier district, in France. Clinical depression was assessed using the Mini-International Neuropsychiatric Interview (MINI, French version 5.00), and the Centre for Epidemiological Studies Depression Scale (CES-D). Experiences of childhood adversity were ascertained via a 25-item questionnaire. Morning, evening, and diurnal salivary cortisol was measured under basal and stress conditions and determined using direct radioimmunoassay analysis. DNA methylation of the KITLG gene was quantified in whole blood using the SEQUENOM MassARRAY EpiTYPER platform. A significant negative association was observed between KITLG DNA methylation and both morning cortisol (β = -1.846 ± 0.666, p = .007) and diurnal cortisol (area under curve [AUC]) (β = -19.429 ± 8.868, p = .031) under a stress condition. However, only the former association was significant after correcting for multiple testing. Further, this association remained after adjusting for age, sex, and depression status. No significant association was observed between childhood trauma and KITLG DNA methylation in this older population. This study provides support for an association between KITLG methylation and stress cortisol levels, suggesting that DNA methylation of this gene may play a role in the longer term regulation of the stress system. Lay summary   The significant negative association between KITLG DNA methylation and morning cortisol, measured under a stressful condition, suggests that individuals with higher KITLG methylation will secrete lower levels of cortisol whilst under stress.

Improved multilineage human hematopoietic reconstitution and function in NSGS mice

Genetic manipulation of NOD/SCID (NS) mice has yielded numerous sub-strains with specific traits useful for the study of human hematopoietic xenografts, each with unique characteristics. Here, we have compared the engraftment and output of umbilical cord blood (UCB) CD34+ cells in four immune-deficient strains: NS, NS with additional IL2RG knockout (NSG), NS with transgenic expression of human myeloid promoting cytokines SCF, GM-CSF, and IL-3 (NSS), and NS with both IL2RG knockout and transgenic cytokine expression (NSGS). Overall engraftment of human hematopoietic cells was highest in the IL2RG knockout strains (NSG and NSGS), while myeloid cell output was notably enhanced in the two strains with transgenic cytokine expression (NSS and NSGS). In further comparisons of NSG and NSGS mice, several additional differences were noted. NSGS mice were found to have a more rapid reconstitution of T cells, improved B cell differentiation, increased levels of NK cells, reduced platelets, and reduced maintenance of primitive CD34+ cells in the bone marrow. NSGS were superior hosts for secondary engraftment and both strains were equally suitable for experiments of graft versus host disease. Increased levels of human cytokines as well as human IgG and IgM were detected in the serum of humanized NSGS mice. Furthermore, immunization of humanized NSGS mice provided evidence of a functional response to repeated antigen exposure, implying a more complete hematopoietic graft was generated in these mice. These results highlight the important role that myeloid cells and myeloid-supportive cytokines play in the formation of a more functional xenograft immune system in humanized mice.

Novel pleiotropic risk loci for melanoma and nevus density implicate multiple biological pathways

The total number of acquired melanocytic nevi on the skin is strongly correlated with melanoma risk. Here we report a meta-analysis of 11 nevus GWAS from Australia, Netherlands, UK, and USA comprising 52,506 individuals. We confirm known loci including MTAP, PLA2G6, and IRF4, and detect novel SNPs in KITLG and a region of 9q32. In a bivariate analysis combining the nevus results with a recent melanoma GWAS meta-analysis (12,874 cases, 23,203 controls), SNPs near GPRC5A, CYP1B1, PPARGC1B, HDAC4, FAM208B, DOCK8, and SYNE2 reached global significance, and other loci, including MIR146A and OBFC1, reached a suggestive level. Overall, we conclude that most nevus genes affect melanoma risk (KITLG an exception), while many melanoma risk loci do not alter nevus count. For example, variants in TERC and OBFC1 affect both traits, but other telomere length maintenance genes seem to affect melanoma risk only. Our findings implicate multiple pathways in nevogenesis.

Preliminary evaluation of neoblast-like stem cell factor and transcript expression profiles in Schistosoma japonicum

Neoblast-like stem cell factors and transcripts are essential for cell proliferation, self-renewal, and differentiation. Recent studies have demonstrated that nanos, sox, and vasa-like transcription factors are associated with neoblast-like stem cells in Schistosoma mansoni and play crucial roles in the regulation of worm development. However, these neoblast-like stem cell factors and transcripts and their expression profiles remain unknown in Schistosoma japonicum. In this study, we identified orthologs of 11 neoblast-like stem cell factors and transcripts in S. japonicum using bioinformatics and confirmed them by PCR. The expression profiles of neoblast-like stem cell factors and transcripts revealed that some of them were highly expressed in certain stages. Sex-based expression analysis revealed that nanos, polo-like kinase, PCNA, cyclin B, and H2A showed significantly higher expression in female worms, whereas ago and bruli showed higher expression in male worms. In addition, we noted that ago, bruli, and pp32 exhibited higher expression in the testes, while nanos, polo-like kinase, cyclin B, H2A, and H2B showed notable higher expression in both isolated ovaries and testes. Our preliminary results are expected to provide important information about the regulatory roles of these stem cell factors in parasite development and sexual maturation.

Kit ligand has a critical role in mouse yolk sac and aorta-gonad-mesonephros hematopoiesis

Few studies report on the in vivo requirement for hematopoietic niche factors in the mammalian embryo. Here, we comprehensively analyze the requirement for Kit ligand (Kitl) in the yolk sac and aorta-gonad-mesonephros (AGM) niche. In-depth analysis of loss-of-function and transgenic reporter mouse models show that Kitl-deficient embryos harbor decreased numbers of yolk sac erythro-myeloid progenitor (EMP) cells, resulting from a proliferation defect following their initial emergence. This EMP defect causes a dramatic decrease in fetal liver erythroid cells prior to the onset of hematopoietic stem cell (HSC)-derived erythropoiesis, and a reduction in tissue-resident macrophages. Pre-HSCs in the AGM require Kitl for survival and maturation, but not proliferation. Although Kitl is expressed widely in all embryonic hematopoietic niches, conditional deletion in endothelial cells recapitulates germline loss-of-function phenotypes in AGM and yolk sac, with phenotypic HSCs but not EMPs remaining dependent on endothelial Kitl upon migration to the fetal liver. In conclusion, our data establish Kitl as a critical regulator in the in vivoAGM and yolk sac endothelial niche.

Expression of transcription factors and stem cell factor precedes hepatocyte differentiation in rat pancreas

Multiple foci of morphologically and functionally differentiated hepatocytes are induced in the pancreas of adult rats subjected to a copper depletion-repletion regimen. Differentiation of hepatocytes in pancreas is preceded by irreversible depletion of over 90% of pancreatic acinar cells. Progressive acinar cell loss during 4-6 weeks of copper deficiency results in the proliferation of oval cells, some of which may serve as the hepatocyte precursor or stem cells. Albumin mRNA is detected in oval cells at 5 and 6 weeks by in situ hybridization at which time no morphologically identifiable hepatocytes are evident in the pancreas. Immunocytochemical analysis demonstrated the presence of stem cell factor (SCF) in proliferating oval cells during 6 weeks of copper depletion, and Northern blot analysis revealed the expression of liver-enriched transcription factors in the rat pancreas during this 4-6-week period of copper deficiency. CCAAT/enhancer binding protein alpha (C/EBP alpha) mRNA was detected first at 4 weeks of copper deficiency. By 5 and 6 weeks of copper deficiency, the expression of mRNAs of C/EBP alpha, beta, and delta, and hepatocyte nuclear factor-3 factor (HNF-3 beta) was markedly enhanced. This enhanced expression of liver-enriched transcription factors and the SCF during oval cell proliferation in the pancreas preceding the expression of albumin mRNA and subsequent differentiation of hepatocyte phenotype further supports the identity of these oval cells as hepatocyte precursors or stem cells.

Oxidized phospholipids stimulate production of stem cell factor via NRF2-dependent mechanisms

Receptor tyrosine kinase c-Kit and its ligand stem cell factor (SCF) regulate resident vascular wall cells and recruit circulating progenitors. We tested whether SCF may be induced by oxidized palmitoyl-arachidonoyl-phosphatidylcholine (OxPAPC) known to accumulate in atherosclerotic vessels. Gene expression analysis demonstrated OxPAPC-induced upregulation of SCF mRNA and protein in different types of endothelial cells (ECs). Elevated levels of SCF mRNA were observed in aortas of ApoE^-/- knockout mice. ECs produced biologically active SCF because conditioned medium from OxPAPC-treated cells stimulated activation (phosphorylation) of c-Kit in naïve ECs. Induction of SCF by OxPAPC was inhibited by knocking down transcription factor NRF2. Inhibition or stimulation of NRF2 by pharmacological or molecular tools induced corresponding changes in SCF expression. Finally, we observed decreased levels of SCF mRNA in aortas of NRF2 knockout mice. We characterize OxPLs as a novel pathology-associated stimulus inducing expression of SCF in endothelial cells. Furthermore, our data point to transcription factor NRF2 as a major mediator of OxPL-induced upregulation of SCF. This mechanism may represent one of the facets of pleiotropic action of NRF2 in vascular wall.

Stem cell factor supports migration in canine mesenchymal stem cells

Adult Mesenchymal Stem Cells (MSC) are cells that can be defined as multipotent cells able to differentiate into diverse lineages, under appropriate conditions. These cells have been widely used in regenerative medicine, both in preclinical and clinical settings. Initially discovered in bone marrow, MSC can now be isolated from a wide spectrum of adult and foetal tissues. Studies to evaluate the therapeutic potential of these cells are based on their ability to arrive to damaged tissues. In this paper we have done a comparative study analyzing proliferation, surface markers and OCT4, SOX9, RUNX2, PPARG genes expression in MSC cells from Bone marrow (BMMSC) and Adipose tissue (ASC). We also analyzed the role of Stem Cell Factor (SCF) on MSC proliferation and on ASCs metalloproteinases MMP-2, MMP-9 secretion. Healthy dogs were used as BMMSC donors, and ASC were collected from omentum during elective ovariohysterectomy surgery. Both cell types were cultured in IMDM medium with or without SCF, 10% Dog Serum (DS), and incubated at 38 °C with 5% CO2. Growth of BMMSCs and ASCs was exponential until 25-30 days. Flow citometry of MSCs revealed positive results for CD90 and negative for CD34, CD45 and MCH-II. Genes were evaluated by RT-PCR and metalloproteinases by zymografy. Our findings indicate morphological and immunological similarities as well as expression of genes from both origins on analyzed cells. Furthermore, SCF did not affect proliferation of MSCs, however it up-regulated MMP-2 and MMP-9 secretion in ASCs. These results suggest that metalloproteinases are possibly essential molecules pivoting migration.

Changes in the interstitial cells of Cajal and neuronal nitric oxide synthase positive neuronal cells with aging in the esophagus of F344 rats

The aging-associated cellular and molecular changes in esophagus have not been established, yet. Thus we evaluated histological structure, interstitial cells of Cajal (ICCs), neuronal nitric oxide synthase (nNOS)-positive cells, and contractility in the esophagus of Fischer 344 rat at different ages (6-, 31-, 74-weeks, and 2-years). The lamina propria thickness and endomysial area were calculated. The immunoreactivity of c-Kit, nNOS and protein gene product (PGP) 9.5 was counted after immunohistochemistry. Expression of c-Kit, stem cell factor (SCF), nNOS and PGP 9.5 mRNA was measured by real-time PCR, and expression of c-Kit and nNOS protein was detected by Western blot. Isovolumetric contractile force measurement and electrical field stimulation (EFS) were conducted. The lamina propria thickness increased (6 week vs 2 year, P = 0.005) and the endomysial area of longitudinal muscle decreased with aging (6 week vs 2 year, P<0.001), while endomysial area of circular muscle did not significantly decrease. The proportions of NOS-immunoreactive cells and c-Kit-immunoreactive areas declined with aging (6 week vs 2 year; P<0.001 and P = 0.004, respectively), but there was no significant change of PGP 9.5-immunopositiviy. The expressions of nNOS, c-Kit and SCF mRNA also reduced with aging (6 week vs 2 year; P = 0.006, P = 0.001 and P = 0.006, respectively), while the change of PGP 9.5 mRNA expression was not significant. Western blot showed the significant decreases of nNOS and c-Kit protein expression with aging (6 week vs 2 year; P = 0.008 and P = 0.012, respectively). The EFS-induced esophageal contractions significantly decreased in 2-yr-old rat compared with 6-wk-old rats, however, L-NG-Nitroarginine methylester did not significantly increase the spontaneous and EFS-induced contractions in the 6-wk- and 2-yr-old rat esophagus. In conclusion, an increase of lamina propria thickness, a decrease of endomysial area, c-Kit, SCF and NOS expression with preserved total enteric neurons, and contractility in aged rat esophagus may explain the aging-associated esophageal dysmotility.

Mesenchymal stem cell-derived factors: Immuno-modulatory effects and therapeutic potential

Stem cell-based therapy is considered to be a new hope in transplantation medicine. Among stem cells, mesenchymal stem cells (MSCs) are, due to their differentiation and immuno-modulatory characteristics, the most commonly used as therapeutic agents in the treatment of immune-mediated diseases. MSCs migrate to the site of inflammation and modulate immune response. The capacity of MSC to alter phenotype and function of immune cells are largely due to the production of soluble factors which expression varies depending on the pathologic condition to which MSCs are exposed. Under inflammatory conditions, MSCs-derived factors suppress both innate and adaptive immunity by attenuating maturation and capacity for antigen presentation of dendritic cells, by inducing polarization of macrophages towards alternative phenotype, by inhibiting activation and proliferation of T and B lymphocytes and by reducing cytotoxicity of NK and NKT cells. In this review, we emphasized current findings regarding immuno-modulatory effects of MSC-derived factors and emphasize their potential in the therapy of immune-mediated diseases. © 2017 BioFactors, 43(5):633-644, 2017.

[Expressions of stem cell factor and hypoxia inducible factor 1 alpha in pancreatic cancer cells and related mechanism]

Objective To study the correlation between the expressions of stem cell factor (SCF) and hypoxia inducible factor 1 alpha (HIF-1α) in pancreatic cancer, and investigate the mechanism by which SCF regulates the expression of HIF-1α. Methods Immunohistochemistry was used to detect the expressions of SCF and HIF-1α in pancreatic cancer specimens and to analyze the correlation between SCF and HIF-1α expressions. Pancreatic cancer PANC-1 cells were treated with different doses of SCF (0, 1, 10, 100 ng/mL) alone or combined with c-KIT inhibitor Gleevec (5 μmol/L). Real-time fluorescent quantitative PCR (qRT-PCR) was performed to detect the level of HIF-1α mRNA, and Western blotting to detect the HIF-1α protein level, the phosphorylation levels of ERK1/2 and AKT. Results SCF and HIF-1α were up-regulated in pancreatic cancer samples and they had an obvious positive correlation. In PANC-1 cells, SCF didn't affect the expression of HIF-1α mRNA, but up-regulated the expression of HIF-1α protein in a dose-dependent manner. Gleevec inhibited the SCF-induced up-regulation of HIF-1α protein, but did not affect the mRNA. And Gleevec blocked the phosphorylation of AKT and ERK1/2. Conclusion SCF/c-KIT can up-regulate the protein expression of HIF-1α by activating AKT and ERK signaling pathways in pancreatic cancer cells.

Decoupling the Functional Pleiotropy of Stem Cell Factor by Tuning c-Kit Signaling

Most secreted growth factors and cytokines are functionally pleiotropic because their receptors are expressed on diverse cell types. While important for normal mammalian physiology, pleiotropy limits the efficacy of cytokines and growth factors as therapeutics. Stem cell factor (SCF) is a growth factor that acts through the c-Kit receptor tyrosine kinase to elicit hematopoietic progenitor expansion but can be toxic when administered in vivo because it concurrently activates mast cells. We engineered a mechanism-based SCF partial agonist that impaired c-Kit dimerization, truncating downstream signaling amplitude. This SCF variant elicited biased activation of hematopoietic progenitors over mast cells in vitro and in vivo. Mouse models of SCF-mediated anaphylaxis, radioprotection, and hematopoietic expansion revealed that this SCF partial agonist retained therapeutic efficacy while exhibiting virtually no anaphylactic off-target effects. The approach of biasing cell activation by tuning signaling thresholds and outputs has applications to many dimeric receptor-ligand systems.

Subfertility and Risk of Testicular Cancer in the EPSAM Case-Control Study

Background/objectives

It has been suggested that subfertility and testicular cancer share genetic and environmental risk factors. We studied both subfertility and the strongest known testicular cancer susceptibility gene, the c-KIT ligand (KITLG), whose pathway is involved in spermatogenesis.

Methods

The EPSAM case-control study is comprised of testicular cancer patients from the Province of Turin, Italy, diagnosed between 1997 and 2008. The present analysis included 245 cases and 436 controls from EPSAM, who were aged 20 years or older at diagnosis/recruitment. The EPSAM questionnaire collected information on factors such as number of children, age at first attempt to conceive, duration of attempt to conceive, use of assisted reproduction techniques, physician-assigned diagnosis of infertility, number of siblings, and self-reported cryptorchidism. Genotyping of the KITLG single nucleotide polymorphism (SNP) rs995030 was performed on the saliva samples of 202 cases and 329 controls.

Results

Testicular cancer was associated with the number of children fathered 5 years before diagnosis (odds ratio (OR) per additional child: 0.78, 95% confidence interval (CI): 0.58–1.04) and sibship size (OR per additional sibling: 0.76, 95% CI: 0.66–0.88). When considering the reproductive history until 1 year before diagnosis, attempting to conceive for at least 12 months or fathering a child using assisted reproduction techniques was not associated with the risk of testicular cancer, nor was age at first attempt to conceive or physician-assigned diagnosis of infertility. The SNP rs995030 was strongly associated with risk of testicular cancer (per allele OR: 1.83; 95%CI: 1.26–2.64), but it did not modify the association between number of children and the risk of testicular cancer.

Conclusion

This study supports the repeatedly reported inverse association between number of children and risk of testicular cancer, but it does not find evidence of an association for other indicators of subfertility.

Total Glucosides of Paeony Promote Intestinal Motility in Slow Transit Constipation Rats through Amelioration of Interstitial Cells of Cajal

Objectives

Using an atropine-diphenoxylate-induced slow transit constipation (STC) model, this study explored the effects of the total glucosides of paeony (TGP) in the treatment of STC and the possible mechanisms.

Study Design

A prospective experimental animal study.

Methods

The constipation model was set up in rats with an oral gavage of atropine-diphenoxylate and then treated with the TGP. The volume and moisture content of the faeces were observed and the intestinal kinetic power was evaluated. Meanwhile, the colorimetric method and enzyme linked immunosorbent assay (ELISA) were employed to determine the changes of nitric oxide (NO), nitric oxide synthase (NOS), vasoative intestinal peptide (VIP) and the P substance (SP) in the serum, respectively. The protein expressions of c-kit and stem cell factor (SCF) were assessed by immunohistochemical analysis and western blot, respectively, and the mRNA level of c-kit was measured by a reverse transcription polymerase chain reaction (RT-PCR).

Results

The TGP attenuated STC responses in terms of an increase in the fecal volume and moisture content, an enhancement of intestinal transit rate and the reduction of NO, NOS and VIP in the serum. In addition, the c-kit, a labeling of interstitial cells of Cajal (ICC) increased at both protein and mRNA levels. SCF, which serves as a ligand of c-kit also increased at protein level.

Conclusion

The analysis of our data indicated that the TGP could obviously attenuate STC through improving the function of ICC and blocking the inhibitory neurotransmitters such as NO, NOS and VIP.

A dynamic niche provides Kit ligand in a stage-specific manner to the earliest thymocyte progenitors

Thymic T cell development is initiated from bone-marrow-derived multi potent thymus-seeding progenitors. During the early stages of thymocyte differentiation, progenitors become T cell restricted. However, the cellular environments supporting these critical initial stages of T cell development within the thymic cortex are not known. Here we use the dependence of early, c-Kit-expressing thymic progenitors on Kit ligand (KitL) to show that CD4(-)CD8(-)c-Kit(+)CD25(-) DN1-stage progenitors associate with, and depend on, the membrane-bound form of KitL (mKitL) provided by a cortex-specific KitL-expressing vascular endothelial cell (VEC) population. In contrast, the subsequent CD4(-)CD8(-)c-Kit(+)CD25(+) DN2-stage progenitors associate selectively with cortical thymic epithelial cells (cTECs) and depend on cTEC-presented mKitL. These results show that the dynamic process of early thymic progenitor differentiation is paralleled by migration-dependent change to the supporting niche, and identify VECs as a thymic niche cell, with mKitL as a critical ligand.

Interleukin-1 beta induces the expression and production of stem cell factor by epithelial cells: crucial involvement of the PI-3K/mTOR pathway and HIF-1 transcription complex

Potential crosslinks between inflammation and leukaemia have been discussed for some time, but experimental evidence to support this dogma is scarce. In particular, it is important to understand the mechanisms responsible for potential upregulation of proto-oncogenic growth factor expressions by inflammatory mediators. Here, we investigated the ability of the highly inflammatory cytokine interleukin-1 beta (IL-1β) to induce the production of stem cell factor (SCF), which is a major hematopoietic growth factor that controls the progression of acute myeloid leukaemia upon malignant transformation of haematopoietic myeloid cells. We found that human IL-1β induced the expression/secretion of SCF in MCF-7 human epithelial breast cancer cells and that this process depended on the hypoxia-inducible factor 1 (HIF-1) transcription complex. We also demonstrated a crucial role of the phosphatidylinositol-3 kinase (PI-3K)/mammalian target of rapamycin (mTOR) pathway in IL-1β-induced HIF-1α accumulation in MCF-7 cells. Importantly, mTOR was also found to play a role in IL-1β-induced SCF production. Furthermore, a tendency for a positive correlation of IL-1β and SCF levels in the plasma of healthy human donors was observed. Altogether, our results demonstrate that IL-1β, which normally bridges innate and adaptive immunity, induces the production of the major haematopoietic/proleukaemic growth factor SCF through the PI-3K/mTOR pathway and the HIF-1 transcription complex. These findings strongly support a cross-talk between inflammation and acute myeloid leukaemia.

Improving the soluble expression and purification of recombinant human stem cell factor (SCF) in endotoxin-free Escherichia coli by disulfide shuffling with persulfide

We here present a new method for the expression and purification of recombinant human stem cell factor (rhSCF(164)) in endotoxin-free ClearColi(®) BL21(DE3) cells harboring codon-optimized Profinity eXact™-tagged hSCF cDNA. Previously, we demonstrated that co-expression with thioredoxin increased the solubility of rhSCF in Escherichia coli BL21(DE3), and addition of l-arginine enhanced chromatography performance by removing the endotoxin-masked surface of rhSCF. Initially, we tried to express rhSCF in an endotoxin-free strain using a thioredoxin co-expression system, which resulted in significantly lower expression, possibly due to the stress imposed by overexpressed thioredoxin or antibiotics susceptibility. Therefore, we developed a new expression system without thioredoxin. External redox coupling was tested using persulfides such as glutathione persulfide or cysteine persulfide for the in vivo-folding of hSCF in the cytoplasm. Persulfides improved the protein solubility by accelerating disulfide-exchange reactions for incorrectdisulfides during folding in E. coli. Furthermore, the persulfides enhanced the expression level, likely due to upregulation of the enzymatic activity of T7 RNA polymerase. The recombinant protein was purified via affinity chromatography followed by cleavage with sodium fluoride, resulting in complete proteolytic removal of the N-terminal tag. The endotoxin-free fusion protein from ClearColi(®) BL21(DE3) could bind to the resin in the standard protocol using sodium phosphate (pH 7.2). Furthermore, purified rhSCF enhanced the proliferation and maturation of the human mast cell line LAD2. Thus, we conclude that use of the protein expression system employing E. coli by disulfide shuffling with persulfide addition could be a very useful method for efficient protein production.

Exploring erythropoiesis of common carp (Cyprinus carpio) using an in vitro colony assay in the presence of recombinant carp kit ligand A and erythropoietin

The use of in vitro colony assays in mammals has contributed to identification of erythroid progenitor cells such as burst-forming unit-erythroid (BFU-E) and colony-forming unit-erythroid (CFU-E) progenitors, and serves to examine functions of erythropoietic growth factors like Erythropoietin (Epo) and Kit ligand. Here, we established an in vitro colony-forming assay capable of investigating erythropoiesis in carp (Cyprinus carpio), cloned and functionally characterized recombinant homologous molecules Epo and Kit ligand A (Kitla), and identified three distinct erythroid progenitor cells in carp. Recombinant carp Epo induced the formation of CFU-E-like and BFU-E-like erythroid colonies, expressing erythroid marker genes, β-globin, epor and gata1. Recombinant carp Kitla alone induced limited colony formation, whereas a combination of Kitla and Epo dramatically enhanced erythroid colony formation and colony cell growth, as well as stimulated the formation of thrombocytic/erythroid colonies expressing not only erythroid markers but also thrombocytic markers, cd41 and c-mpl. Utilizing this colony assay to examine the distribution of distinct erythroid progenitor cells in carp, we demonstrated that carp head and trunk kidney play a primary role in erythropoiesis, while the spleen plays a secondary. Furthermore, we showed that presumably bi-potent thrombocytic/erythroid progenitor cells localize principally in the trunk kidney. Our results indicate that teleost fish possess mechanisms of Epo- and Kitla-dependent erythropoiesis similar to those in other vertebrates, and also help to demonstrate the diversity of erythropoietic sites among vertebrates.

Residues 39-56 of Stem Cell Factor Protein Sequence Are Capable of Stimulating the Expansion of Cord Blood CD34+ Cells

Background

Stem cell factor (SCF) can stimulate hematopoietic stem cell (HSC) expansion; however, the specific structural region(s) of SCF protein that are critical for this function are still unknown. A novel monoclonal antibody (named 23C8) against recombinant human SCF (rhSCF) was previously found to inhibit the ability of rhSCF to enhance HSC expansion, making it possible to identify the relevant active region to HSC.

Methods

Eleven polypeptides were synthesized, which were designed to cover the full-length of rhSCF, with overlaps that are at least 3 amino acids long. ELISA was used to identify the polypeptide(s) that specifically react with the anti-SCF. The effects of the synthetic polypeptides on human HSC expansion, or on the ability of the full-length rhSCF to stimulate cell proliferation, were evaluated ex vivo. Total cell number was monitored using hemocytometer whereas CD34⁺ cell number was calculated based on the proportion determined via flow cytometry on day 6 of culture.

Results

Of all polypeptides analyzed, only one, named P0, corresponding to the SCF protein sequence at residues 39–56, was recognized by 23C8 mAb during ELISA. P0 stimulated the expansion of CD34⁺ cells derived from human umbilical cord blood (UCB). Addition of P0 increased the numbers of total mononucleated cells and CD34⁺ cells, by ~2 fold on day 6. P0 also showed partial competition against full-length rhSCF in the ex vivo cell expansion assay.

Conclusion

Residues 39–56 of rhSCF comprise a critical functional region for its ability to enhance expansion of human UCB CD34⁺ cells. The peptide P0 is a potential candidate for further development as a synthetic substitute for rhSCF in laboratory and clinical applications.

Stress-associated erythropoiesis initiation is regulated by type 1 conventional dendritic cells

Erythropoiesis is an important response to certain types of stress, including hypoxia, hemorrhage, bone marrow suppression, and anemia, that result in inadequate tissue oxygenation. This stress-induced erythropoiesis is distinct from basal red blood cell generation; however, neither the cellular nor the molecular factors that regulate this process are fully understood. Here, we report that type 1 conventional dendritic cells (cDC1s), which are defined by expression of CD8α in the mouse and XCR1 and CLEC9 in humans, are critical for induction of erythropoiesis in response to stress. Specifically, using murine models, we determined that engagement of a stress sensor, CD24, on cDC1s upregulates expression of the Kit ligand stem cell factor on these cells. The increased expression of stem cell factor resulted in Kit-mediated proliferative expansion of early erythroid progenitors and, ultimately, transient reticulocytosis in the circulation. Moreover, this stress response was triggered in part by alarmin recognition and was blunted in CD24 sensor- and CD8α+ DC-deficient animals. The contribution of the cDC1 subset to the initiation of stress erythropoiesis was distinct from the well-recognized role of macrophages in supporting late erythroid maturation. Together, these findings offer insight into the mechanism of stress erythropoiesis and into disorders of erythrocyte generation associated with stress.

The Role of Vascular Endothelial Growth Factor Receptor-1 Signaling in the Recovery from Ischemia

Vascular endothelial growth factor (VEGF) is one of the most potent angiogenesis stimulators. VEGF binds to VEGF receptor 1 (VEGFR1), inducing angiogenesis through the receptor’s tyrosine kinase domain (TK), but the mechanism is not well understood. We investigated the role of VEGFR1 tyrosine kinase signaling in angiogenesis using the ischemic hind limb model. Relative to control mice, blood flow recovery was significantly impaired in mice treated with VEGFA-neutralizing antibody. VEGFR1 tyrosine kinase knockout mice (TK^-/-) had delayed blood flow recovery from ischemia and impaired angiogenesis, and this phenotype was unaffected by treatment with a VEGFR2 inhibitor. Compared to wild type mice (WT), TK^-/- mice had no change in the plasma level of VEGF, but the plasma levels of stromal-derived cell factor 1 (SDF-1) and stem cell factor, as well as the bone marrow (BM) level of pro-matrix metalloproteinase-9 (pro-MMP-9), were significantly reduced. The recruitment of cells expressing VEGFR1 and C-X-C chemokine receptor type 4 (CXCR4) into peripheral blood and ischemic muscles was also suppressed. Furthermore, WT transplanted with TK^-/- BM significantly impaired blood flow recovery more than WT transplanted with WT BM. These results suggest that VEGFR1-TK signaling facilitates angiogenesis by recruiting CXCR4⁺VEGFR1⁺ cells from BM.

The critical and specific transcriptional regulator of the microenvironmental niche for hematopoietic stem and progenitor cells

PURPOSE OF REVIEW

It has been assumed that the special microenvironments known as niches in the marrow play an essential role in maintaining hematopoietic stem and progenitor cells (HSPCs), and the identity of the HSPC niche has been a subject of long-standing debate. Recent studies identified cells, which create microenvironments meeting the criteria for HSPC niches and the critical transcriptional regulators of their development and maintenance.

RECENT FINDINGS

Osterix as well as Ebf2 and Bmi1 are critical but not specific transcriptional regulators of HSPC niche development. The transcription factor Foxc1 is expressed preferentially in a population of adipo-osteogenic progenitors, termed CXCL12-abundant reticular (CAR) cells, which create HSPC niches and are largely equivalent to stem cell factor and Lepr-expressing cells, in developing and adult bone marrow. Foxc1 is essential for CAR cell development and maintenance of bone marrow niches for HSPCs upregulating CXCL12 and SCF expression and inhibition of adipogenic processes in CAR cell progenitors.

SUMMARY

Foxc1 is the first critical and specific transcriptional regulator that is required for development and maintenance of cells creating HSPC niches, including a specialized population of adipo-osteogenic progenitors in bone marrow.

[Effects of electroacupuncture combined with polysaccharide of gastrodia elate blume on expression of nestin and stem cell factor in thalamic ventroposterolateral nucleus in rats with focal cerebral ischemia]

OBJECTIVE

To explore the nerve regeneration mechanism of electroacupuncture (EA) combined with polysaccharide of gastrodia elate blume (PGB) for secondary thalamic damage of focal cerebral ischemia.

METHODS

Forty Sprague-Dawley adult rats were randomly divided into a normal control group, a model group, an EA group, a PGB group and an EA + PGB group, 8 rats in each group. The rat model of right middle cerebral artery occlusion was prepared by suture-occluded method. Two weeks after model establishment, rats in the normal control group and model group received no treatment; rats in the EA group were treated with EA at "Baihui" (GV 20) and left "Zusanli" (ST 36), 30 min per treatment, once a day for 14 successive days; rats in the PGB group were treated with intragastric administration of PGB (100 mg/kg) , once a day for 14 days; rats in the EA + PGB group were treated with EA and PGB treatment, once a day for totally 14 days. The expressions of nestin and stem cell factor (SCF) in thalamic ventroposterolateral nucleus (VPL) were detected by immunohistochemical method.

RESULTS

There were positive cells of nestin in ischemia VPL in the model group, and the number of SCF positive cells was increased compared with that in the normal control group (P<0.05). The number of positive cells of nestin and SCF in ischemia VPL in the EA group, PGB group and the EA + PGB group was increased compared with that in the model group (all P<0.05), and the average gray value of immune positive product was all reduced (all P<0.05). The number of positive cells of nestin and SCF in the EA + PGB group was higher than that in the EA group or the PGB group (all P<0.05).

CONCLUSION

EA combined with PGB can significantly increase the SCF expression in ischemia VPL and promote the proliferation of neural stem cells, which is likely to be one of the nerve regeneration mechanism of acupuncture and medication tor secondary thalamic damage of local cerebral isctemia.

[Effect of electroacupuncture intervention combined with polysaccharide of Gastrodia elata Blume on expression of nestin and stem cell factor around the ischemic locus of frontal lobe cortex in local cerebral ischemia rats]

OBJECTIVE

To observe the effect of electroacupuncture (EA), Polysaccharide of Gastrodia elata Blume (PGB), and EA + PGB on the expression of Nestin and stem cell factor (SCF) in the frontal lobe cortex around the ischemic loci of cerebral ischemia (CI) rats, so as to explore its mechanisms underlying improvement of CI.

METHODS

A total of 40 Sprague-Dawley adult rats were randomly divided into normal control, CI model, EA intervention, PGB intervention and EA + PGB groups (n = 8 in each group). The CI model was prepared by middle cerebral artery occlusion. EA (2 Hz, 2 V) was applied to "Baihui" (GV 20) and left "Zusanli" (ST 36) for 30 min, once daily for 14 days. Rats of the PGB and EA + PGB groups were treated by gastrogavage of PGB at a dose of 100 mg/kg, once daily for 14 successive days. The expression of Nestin and SCF in the frontal lobe around the ischemic loci of the frontal lobe was detected by immunohistochemistry.

RESULTS

Compared with the normal control group, the expression levels of regional cerebral cortical Nestin and SCF proteins were significantly increased in the model group (P < 0.05). After the treatment, the expression levels of Nestin and SCF were significantly further up-regulated in the EA, PGB and EA + PGB groups in comparison with the model group (P < 0.05).

CONCLUSION

EA combined with PGB can significantly up-regulate the expression of Nestin and SCF in the frontal lobe around the ischemic loci in cerebral ischemia rats, which may contribute to their function in improving CI.

Recombinant goldfish thrombopoietin up-regulates expression of genes involved in thrombocyte development and synergizes with kit ligand A to promote progenitor cell proliferation and colony formation

Thrombopoietin (TPO) is the principal regulator of thrombopoiesis and promotes the proliferation, differentiation and maturation of megakaryocytic progenitor cells in mammals. In this study we report on the molecular and functional characterization of goldfish TPO. Quantitative expression analysis of goldfish tpo revealed the highest mRNA levels in heart, followed by spleen, liver, brain, intestine and kidney tissues. Significant decrease of tpo and c-mpl expressions in goldfish primary kidney macrophage (PKM) cultures, as progenitor to macrophage development progressed, indicates that TPO is not involved in monopoiesis. Recombinant goldfish TPO (rgTPO) alone did not induce significant proliferation of progenitor cells, but TPO in cooperation with recombinant goldfish kit ligand A (rgKITLA) supported proliferation of progenitor cells in a dose-dependent manner. In response to rgTPO or a combination of rgTPO and rgKITLA, the mRNA levels of thrombopoietic markers cd41 and c-mpl as well as thrombo/erythropoietic transcription factors gata1 and lmo2 in sorted progenitor cells were up-regulated, while the mRNA levels of granulopoietic markers (cebpα and gcsfr) and the lymphoid transcription factor gata3 were down-regulated. Furthermore, rgTPO and rgKITLA synergistically stimulated thrombocytic colony-formation. Our results demonstrate that goldfish TPO has similar functions to mammalian TPO as a regulator of thrombopoiesis, and suggests a highly conserved molecular mechanism of thrombocyte development throughout evolution of vertebrates.

New NOBOX mutations identified in a large cohort of women with primary ovarian insufficiency decrease KIT-L expression

CONTEXT

Primary ovarian insufficiency (POI) is a major cause of anovulation and infertility in women. This disease affects 1% of women before 40 years, and several genetic causes have been reported.

OBJECTIVE

The aim of the study was to evaluate the prevalence of NOBOX mutations in a new large cohort of women with POI and to characterize these variants and identify a NOBOX novel target gene.

PATIENTS AND METHODS

A total of 213 unrelated patients with POI were screened for NOBOX mutations, and luciferase reporter assays were performed for the mutations identified.

RESULTS

We reported 3 novel and 2 recurrent heterozygous missense NOBOX rare variants found in 12 patients but not in 724 alleles from ethnic-matched individual women with occurrence of menopause at a normal age. Their functional impact had been tested on the classic growth differentiation factor-9 (GDF9) promoter and on KIT-L, a new NOBOX target gene. The p.Gly91Thr, p.Gly111Arg, p.Arg117Trp, p.Lys371Thr, and p.Pro619Leu mutations were deleterious for protein function.

CONCLUSIONS

In our series, 5.6% of the patients with POI displayed heterozygous NOBOX mutations. We demonstrate that KIT-L could be now a direct NOBOX target. These findings replicate the high prevalence of the association between the NOBOX rare variants and POI.

Differential regulation of kit ligand A (kitlga) expression in the zebrafish ovarian follicle cells--evidence for the existence of a cyclic adenosine 3', 5' monophosphate-mediated binary regulatory system during folliculogenesis

Kit ligand (Kitl) is an important paracrine factor involved in the activation of primordial follicles from the quiescent pool and in the maintenance of meiotic arrest before germinal vesicle breakdown (GVBD). It has been reported that follicle-stimulating hormone (FSH) stimulates but luteinizing hormone (LH) suppresses the expression of Kitl in the granulosa cells in mammals. Considering that both gonadotropins signal in the follicle cells mainly by activating cyclic adenosine 3', 5'-monophosphate (cAMP) pathway, we are intrigued by how cAMP differentially regulates Kitl expression. In the present study, we demonstrated that both human chorionic gonadotropin (hCG) and pituitary adenylate cyclase activating polypeptide (PACAP) inhibited insulin-like growth factor I (IGF-I)-induced Akt phosphorylation and kitlga expression in the zebrafish follicle cells. Further experiments showed that cAMP was involved in regulating the expression of kitlga. However, two cAMP-activated effectors, protein kinase A (PKA) and exchange protein directly activated by cAMP (Epac), had converse effects. PKA promoted whereas Epac inhibited the expression of kitlga, as demonstrated by the respective activators. Interestingly, cAMP also appeared to exert differential effects on kitlga expression at different stages of follicle development during folliculogenesis, significantly stimulating kitlga expression at the early growth stage but suppressing it at the full-grown stage before final oocyte maturation, implying a potential mechanism for differential effects of the same pathway at different stages. The inhibitory effect of forskolin (activator of adenylate cyclase) and H89 (inhibitor of PKA) on IGF-I-induced expression of kitlga suggested cross-talk between the cAMP and IGF-I-activated PI3K-Akt pathways. This study, together with our previous findings on IGF-I regulation of kitlga expression, provides important clues to the underlying mechanism that regulates Kit ligand expression during folliculogenesis in the ovary.