Colony stimulating factor-1 producing endothelial cells and mesenchymal stromal cells maintain monocytes within a perivascular bone marrow niche.

Macrophage colony stimulating factor-1 (CSF-1) plays a critical role in maintaining myeloid lineage cells. However, congenital global deficiency of CSF-1 (Csf1op/op) causes severe musculoskeletal defects that may indirectly affect hematopoiesis. Indeed, we show here that osteolineage-derived Csf1 prevented developmental abnormalities but had no effect on monopoiesis in adulthood. However, ubiquitous deletion of Csf1 conditionally in adulthood decreased monocyte survival, differentiation, and migration, independent of its effects on bone development. Bone histology revealed that monocytes reside near sinusoidal endothelial cells (ECs) and leptin receptor (Lepr)-expressing perivascular mesenchymal stromal cells (MSCs). Targeted deletion of Csf1 from sinusoidal ECs selectively reduced Ly6C- monocytes, whereas combined depletion of Csf1 from ECs and MSCs further decreased Ly6Chi cells. Moreover, EC-derived CSF-1 facilitated recovery of Ly6C- monocytes and protected mice from weight loss following induction of polymicrobial sepsis. Thus, monocytes are supported by distinct cellular sources of CSF-1 within a perivascular BM niche.

Single-cell transcriptomics of LepR-positive skeletal cells reveals heterogeneous stress-dependent stem and progenitor pools.

Leptin receptor (LepR)-positive cells are key components of the bone marrow hematopoietic microenvironment, and highly enrich skeletal stem and progenitor cells that maintain homeostasis of the adult skeleton. However, the heterogeneity and lineage hierarchy within this population has been elusive. Using genetic lineage tracing and single-cell RNA sequencing, we found that Lepr-Cre labels most bone marrow stromal cells and osteogenic lineage cells in adult long bones. Integrated analysis of Lepr-Cre-traced cells under homeostatic and stress conditions revealed dynamic changes of the adipogenic, osteogenic, and periosteal lineages. Importantly, we discovered a Notch3+ bone marrow sub-population that is slow-cycling and closely associated with the vasculatures, as well as key transcriptional networks promoting osteo-chondrogenic differentiation. We also identified a Sca-1+ periosteal sub-population with high clonogenic activity but limited osteo-chondrogenic potential. Together, we mapped the transcriptomic landscape of adult LepR+ stem and progenitor cells and uncovered cellular and molecular mechanisms underlying their maintenance and lineage specification.

Does hypoleptinemia trigger entrapment in anorexia nervosa? Etiological and clinical considerations.

Based on the recent observation that human recombinant leptin (r-Met-hu-leptin; metreleptin) may induce a profound alleviation of the complex symptomatology of patients with anorexia nervosa (AN), we examine the implications for our conceptualisation of this eating disorder. Hypoleptinemia as a core endocrine feature of AN serves as a central and peripheral trigger of tissue-specific adaptations to starvation. In this narrative review, we argue that leptin deficiency may explain many of the puzzling features of this eating disorder. Weight loss can be viewed as a two-step process, with only the second step entailing hypoleptinemia and thereby the entrapment characteristic of AN. We discuss the central and peripheral distribution of leptin receptors and consider possible functional implications of hypoleptinemia. We contrast the slow psychological recovery of patients with AN and of people who experienced starvation upon weight recovery with the rapid onset of improvements upon off-label metreleptin treatment. Characteristics of the sex and age dependent secretion of leptin may contribute to the elevated vulnerability of young females to develop AN.

Generation of LEPR Knockout Rabbits with CRISPR/CAS9 System.

The LEPR gene encodes a leptin hormone receptor, and its mutations are associated with morbid obesity, dysregulation of lipid metabolism, and fertility defects in humans. Spontaneous Lepr mutations have been described in rodents, and Lepr knockout animals have been generated, in particular, using the CRISPR/Cas9 system. Lipid metabolism in rodents significantly differs from that in humans or rabbits, and rabbits are therefore considered as the most relevant model of morbid obesity and lipid metabolism dysregulation in humans. LEPR knockout rabbits have not been reported so far. In this work a LEPR knockout rabbit was generated by introducing a deletion of the region around LEPR exon 10 using the CRISPR/Cas9 system. The body weight of the knockout rabbit was significantly higher than the average body weight of the wild type rabbits. CRISPR/Cas9-mediated generation of LEPR knockout rabbits will allow the development of a model of morbid obesity and endocrine defects due to leptin receptor mutations in humans.

Congenital leptin and leptin receptor deficiencies in nine new families: identification of six novel variants and review of literature.

Early childhood obesity is a real public health problem worldwide. Identifying the etiologies, especially treatable and preventable causes, can direct health professionals toward proper management. Measurement of serum leptin levels is helpful in the diagnosis of congenital leptin and leptin receptor deficiencies which are considered important rare causes of early childhood obesity. The main aim of this study was to investigate the frequency of LEP, LEPR, and MC4R gene variants among a cohort of Egyptian patients with severe early onset obesity. The current cross-sectional study included 30 children who developed obesity during the first year of life with BMI > 2SD (for age and sex). The studied patients were subjected to full medical history taking, anthropometric measurements, serum leptin and insulin assays, and genetic testing of LEP, LEPR and MC4R. Disease causing variants in LEP and LEPR were identified in 10/30 patients with a detection rate of 30%. Eight different homozygous variants (two pathogenic, three likely pathogenic, and three variants of uncertain significant) were identified in the two genes, including six previously unreported LEPR variants. Of them, a new frameshift variant in LEPR gene (c.1045delT, p.S349Lfs*22) was recurrent in two unrelated families and seems to have a founder effect in our population. In conclusion, we reported ten new patients with leptin and leptin receptor deficiencies and identified six novel LEPR variants expanding the mutational spectrum of this rare disorder. Furthermore, the diagnosis of these patients helped us in genetic counseling and patients' managements specially with the availability of drugs for LEP and LEPR deficiencies.

GHRL, LEP, LEPR genes polymorphism and their association with the metabolic syndrome in the Ukrainian population.

Objective. Many conflicting results have been obtained in the study of leptin (LEP) and leptin receptor (LEPR) gene variants that are associated with the obesity and diabetes possibly due to differences in the study populations. The aim of this study was to evaluate changes in the metabolic hormones (leptin, ghrelin, adiponectin, resistin) levels in the blood of obese patients in relation to the GHRL (rs696217), LEP (rs7799039), LEPR (rs1137100, rs1137101, rs1805094) polymorphism in Ukrainian population. Methods. The study involved 53 obesity cases and 48 non-obesity subjects (controls). The GHRL, LEP, and LEPR genes polymorphism (rs696217, rs7799039, rs1137100, rs1137101, rs1805094) was genotyped using a TaqMan real-time polymerase chain reaction method. Blood hormones (leptin, ghrelin, adiponectin, resistin) were determined with commercially available kits using a Multiskan FC analyzer. Results. The study of the effect of genotypes of the GHRL (rs696217), LEP (rs7799039), and LEPR (rs1137100, rs1805094) polymorphisms on the level of metabolic hormones (leptin, ghrelin, adiponectin, resistin) in the blood of obese patients did not show reliably significant results. Thus, the presence of the LEPR genes (rs1137101) polymorphism in the Ukrainian population indicates an increased risk of the metabolic syndrome development regardless of the homozygous or heterozygous genotype (genotypes AA, AG, GG). Conclusions. We established a significant effect of the presence of the A allele and G allele of the LEPR gene polymorphism (rs1137101) on the level of leptin, ghrelin, adiponectin, and resistin in the serum of patients diagnosed with the metabolic syndrome in the Ukrainian population.

Identification of breed-specific genomic variants in Colombian Creole pig breeds by whole-genome sequencing.

Dissecting genetic variation of local breeds is important for the success of conservation. In this research, we investigated the genomic variation of Colombian Creole (CR) pigs, with a focus on the breed-specific variants in the exonic region of 34 genes with reported effects on adaptive and economic traits. Seven individuals of each of the three CR breeds (CM, Casco de Mula; SP, San Pedreño; and ZU, Zungo) were whole-genome sequenced along with 7 Iberian (IB) pigs and 7 pigs of each of the four most used cosmopolitan (CP) breeds (Duroc, Landrace × Large White, and Pietrain). Molecular variability in CR (6,451,218 variants; from 3,919,242, in SP, to 4,648,069, in CM) was comparable to that in CP, but higher than in IB. For the investigated genes, SP pigs displayed less exonic variants (178) than ZU (254), CM (263), IB (200), and the individual CP genetic types (201 to 335). Sequence variation in these genes confirmed the resemblance of CR to IB and indicates that CR pigs, particularly ZU and CM, are not exempt from selective introgression of other breeds. A total of 50 exonic variants were identified as being potentially specific to CR, including a high-impact deletion in the intron between exons 15 and 16 of the leptin receptor gene, which was only found in CM and ZU. The identification of breed-specific variants in genes related to adaptive and economical traits can bolster the understanding of the role of gene-environment interactions on local adaptation and points the way for effective breeding and conservation of CR pigs.

Large-scale isolation of functional dermal papilla cells using novel surface marker LEPTIN Receptor.

Dermal papilla (DP) cells regulate hair follicle epithelial cells and melanocytes by secreting functional factors, playing a key role in hair follicle morphogenesis and hair growth. DP cells can reconstitute new hair follicles and induce hair regeneration, providing a potential therapeutic strategy for treating hair loss. However, current methods for isolating DP cells are either inefficient (physical microdissection) or only applied to genetically labeled mice. We systematically screened for the surface proteins specifically expressed in skin DP using mRNA expression databases. We identified two antibodies against receptors LEPTIN Receptor (LEPR ) and Scavenger Receptor Class A Member 5 (SCARA5) which could specifically label and isolate DP cells by flow cytometry from mice back skin at the growth phase. The sorted LEPR+ cells maintained the DP characteristics after culturing in vitro, expressing DP marker alkaline phosphatase and functional factors including RSPO1/2 and EDN3, the three major DP secretory factors that regulate hair follicle epithelial cells and melanocytes. Furthermore, the low-passage LEPR+ DP cells could reconstitute hair follicles on nude mice using chamber graft assay when combined with epithelial stem cells. The method of isolating functional DP cells we established here lays a solid foundation for developing DP cell-based therapy.

Augmented leptin-induced trefoil factor 3 expression and epidermal growth factor receptor transactivation differentially influences neoplasia progression in the stomach and colorectum of dietary fat-induced obese mice.

Obesity is a risk factor for gastrointestinal malignancies and tumors. However, which factors either protect or predispose the gastrointestinal organs to high-fat diet (HFD)-induced neoplasia remains unclear. Here, we demonstrate that HFD impacts the stomach to a greater extent as compared to the colorectum, resulting in leptin receptor (LepR) signaling-mediated neoplasia in the tissues. HFD activated leptin signaling, which in turn, accelerates the pathogenesis in the gastric mucosa more than that in the colorectum along with ectopic TFF3 expression. Moreover, in the stomach, higher levels of phosphorylated epidermal growth factor receptor (EGFR) in addition to the activation of STAT3 and Akt were observed as compared to the colorectum. The mice with LepR deletion in the gastrointestinal epithelium exhibited a suppressed induction of leptin, TFF3, and phosphorylated EGFR in the stomach, whereas the levels in the colorectum were insignificant. In co-transfected COS-7 cells with LepR and EGFR plasmid DNA, leptin transactivated EGFR to accelerate TFF3 induction along with activation of STAT3, ERK1/2, Akt, and PI3K p85/p55. Furthermore, TFF3 could bind to EGFR but did not transactivate LepR. Leptin-induced TFF3 induction was markedly suppressed by inhibitors of PI3K (LY294002) and EGFR (Erlotinib). Together, these results suggest a novel role of LepR-mediated signaling in transactivating EGFR that leads to TFF3 expression via the PI3K-Akt pathway. Therefore, this study sheds light on the identification of potentially new therapeutic targets for the treatment of pre-cancerous symptoms in stomach and colorectum.

Association of LEPR polymorphisms with egg production and growth performance in female Japanese quails.

This study aimed to screen intron 8 of the leptin receptor (LEPR) gene for polymorphisms in female Japanese quails. Two adjacent novel SNPs (A277G and A304G) were detected using PCR-SSCP and sequencing. These SNPs produced three haplotypes (AA/AA, AG/AG, and GG/GG) that were significantly (p ≤ 0.05) associated with growth and egg production traits. GG/GG haplotype-quails had significantly (p ≤ 0.05) lower egg production, feed intake, growth performance, lipid profile, serum levels of sex hormones (estradiol, progesterone, FSH, LH), and ovarian expressions of survivin, FSHR, and IGF1 than other quails. However, GG/GG quails had significantly (p ≤ 0.05) higher serum levels of LEP and mRNA levels of LEPR, LEP, and caspase 3 in the hypothalamus and ovaries. These higher levels of LEP/LEPR could not only reduce feed intake and body weight gain but also could induce apoptosis of ovarian cells (as indicated by lower survivin and IGF1 and higher caspase3 expression) which could inhibit the development of the follicles and the release of sex hormones with a subsequent decrease in egg production in GG/GG quails. Therefore, with these results, we suggest selecting Japanese quails with AA/AA and AG/AG haplotypes to improve the reproduction and growth performance of this flock.

Leptin Signaling in Obesity and Colorectal Cancer.

Obesity and colorectal cancer (CRC) are among the leading diseases causing deaths in the world, showing a complex multifactorial pathology. Obesity is considered a risk factor in CRC development through inflammation, metabolic, and signaling processes. Leptin is one of the most important adipokines related to obesity and an important proinflammatory marker, mainly expressed in adipose tissue, with many genetic variation profiles, many related influencing factors, and various functions that have been ascribed but not yet fully understood and elucidated, the most important ones being related to energy metabolism, as well as endocrine and immune systems. Aberrant signaling and genetic variations of leptin are correlated with obesity and CRC, with the genetic causality showing both inherited and acquired events, in addition to lifestyle and environmental risk factors; these might also be related to specific pathogenic pathways at different time points. Moreover, mutation gain is a crucial factor enabling the genetic process of CRC. Currently, the inconsistent and insufficient data related to leptin's relationship with obesity and CRC indicate the necessity of further related studies. This review summarizes the current knowledge on leptin genetics and its potential relationship with the main pathogenic pathways of obesity and CRC, in an attempt to understand the molecular mechanisms of these associations, in the context of inconsistent and contradictory data. The understanding of these mechanisms linking obesity and CRC could help to develop novel therapeutic targets and prevention strategies, resulting in a better prognosis and management of these diseases.

A Longitudinal Study of the Association between the LEPR Polymorphism and Treatment Response in Patients with Bipolar Disorder.

Patients with bipolar disorder (BD) exhibit individual variability in the treatment outcome, and genetic background could contribute to BD itself and the treatment outcome. Leptin levels significantly change in BD patients treated with valproate (VPA), but whether LEPR polymorphisms are associated with treatment response is still unknown. This longitudinal study aimed to investigate the associations between LEPR polymorphisms and VPA treatment response in BD patients who were drug naïve at their first diagnosis of BD. The single-nucleotide polymorphisms (SNPs) of LEPR (rs1137101, rs1137100, rs8179183, and rs12145690) were assayed, and the LEPR polymorphism frequencies of alleles and genotypes were not significantly different between the controls (n = 77) and BD patients (n = 130). In addition, after the 12-week course of VPA treatment in BD patients, the LEPR polymorphisms showed significant effects on changes in disease severity. Moreover, considering the effect of the LEPR haplotype, the frequency of the CAGG haplotype in BD patients was higher than that in the controls (9.3 vs. 2.9%, p = 0.016), and the LEPR CAGG haplotype was associated with a better treatment response than the other haplotypes in BD patients receiving VPA treatment. Therefore, LEPR polymorphisms might serve as mediators involved in the therapeutic action of VPA treatment.

The Effect of Polymorphisms of Energy Metabolism Genes on Metabolic Disorders in Overweight Adolescents of Two Ethnicities.

The aim of this cross-sectional observational study is to determine the contribution of polymorphisms of energy metabolism genes into metabolic disorders in Russian and Buryat adolescents with overweight and obesity. The study included 354 Russian and Buryat adolescents aged 13-18 years. Body mass index and serum levels of glucose, insulin, and leptin were measured and insulin resistance index HOMA-IR was calculated. Molecular genetic analysis for the presence of 9 loci of energy metabolism genes LEP, LEPR, POMC, FTO, and MC4R were analyzed. It was found that the risk of metabolic disorders is associated with the presence of polymorphic loci of leptin receptor gene LEPR and melanocortin receptor gene MC4R (LEPR rs1137100+LEPR rs1137101 and LEPR rs1137100+MC4R rs17782313) in Russian adolescents with overweight and obesity and polymorphisms of the gene FTO (FTO rs9939609+rs8050136) associated with fat mass and obesity in Buryat adolescents.

A novel compound heterozygous leptin receptor mutation causes more severe obesity than in Leprdb/db mice.

The leptin receptor (Lepr) pathway is important for food intake regulation, energy expenditure, and body weight. Mutations in leptin and the Lepr have been shown to cause early-onset severe obesity in mice and humans. In studies with C57BL/6NCrl mice, we found a mouse with extreme obesity. To identify a putative spontaneous new form of monogenic obesity, we performed backcross studies with this mouse followed by a quantitative trait locus (QTL) analysis and sequencing of the selected chromosomal QTL region. We thereby identified a novel Lepr mutation (C57BL/6N-LeprL536Hfs*6-1NKB), which is located at chromosome 4, exon 11 within the CRH2-leptin-binding site. Compared with C57BL/6N mice, LeprL536Hfs*6 develop early onset obesity and their body weight exceeds that of Leprdb/db mice at an age of 30 weeks. Similar to Leprdb/db mice, the LeprL536Hfs*6 model is characterized by hyperphagia, obesity, lower energy expenditure and activity, hyperglycemia, and hyperinsulinemia compared with C57BL/6N mice. Crossing Leprdb/wt with LeprL536Hfs*6/wt mice results in compound heterozygous LeprL536Hfs*6/db mice, which develop even higher body weight and fat mass than both homozygous Leprdb/db and LeprL536Hfs*6 mice. Compound heterozygous Lepr deficiency affecting functionally different regions of the Lepr causes more severe obesity than the parental homozygous mutations.

Leptin receptor is a key gene involved in the immunopathogenesis of thyroid-associated ophthalmopathy.

Thyroid-associated ophthalmopathy (TAO), the most common and severe manifestation of Graves' disease (GD), is a disfiguring and potentially blinding autoimmune disease. The high relapse rate (up to 20%) and substantial side effects of glucocorticoid treatment further decrease the life quality of TAO patients. To develop novel therapies, we amid to explore the immunopathogenesis of TAO. To identify the key immune-related genes (IRGs) in TAO, we integrated the IRG expression profiles in thyrocytes from a GD patient set (GD vs healthy control) and a TAO patient set (TAO vs GD). Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), protein-protein interaction (PPI) and receiver operating characteristic (ROC) curve analyses identified the leptin receptor (LEPR) gene as the key IRG in TAO immunopathogenesis. Gene set enrichment analysis (GSEA) suggested enrichment of the antigen presentation pathway in TAO patients with higher LEPR. Increased LEPR expression was validated in TAO orbital tissues, and weighted gene co-expression network analysis (WGCNA) showed that cell adhesion processes were positively correlated with LEPR. Our study revealed that LEPR is a key gene in TAO immunopathogenesis and plays different roles in thyrocytes and orbital tissues. Our findings provide new insights into diagnostic and therapeutic biomarkers for TAO.

Leptin Receptor (LEPR) promotes proliferation, migration, and invasion and inhibits apoptosis in hepatocellular carcinoma by regulating ANXA7.

BACKGROUND: Leptin Receptor (LEPR) has been suggested to have several roles in cancer metastasis. However, the role of LEPR and its underlying mechanisms in lymphatic metastasis of hepatocarcinoma have not yet been studied. METHODS: We performed bioinformatics analysis, qRT-PCR, western blotting, immunohistochemistry, immunofluorescence, enzyme-linked immunosorbent, coimmunoprecipitation assays and a series of functional assays to investigate the roles of LEPR in hepatocellular carcinoma. RESULTS: We discovered that LEPR was highly expressed in liver cancer tissues, and the expression of LEPR in Hca-F cells was higher than that in Hca-P cells. Furthermore, LEPR promotes the proliferation, migration and invasion and inhibits the apoptosis of hepatocarcinoma lymphatic metastatic cells. Further studies indicated that LEPR interacts with ANXA7. Mechanistically, LEPR regulated ERK1/2 and JAK2/STAT3 expression via ANXA7 regulation. CONCLUSIONS: These findings unveiled a previously unappreciated role of LEPR in the regulation of lymphatic metastatic hepatocellular carcinoma, assigning ANXA7-LEPR as a promising therapeutic target for liver cancer treatments.

Association of Single Nucleotide Polymorphism LEP-R c.668A>G (p.Gln223Arg, rs1137101) of leptin receptor gene with endometrial cancer.

BACKGROUND: The aim of this study was to analyze the frequencies of genotypes and alleles of Single Nucleotide Polymorphism (SNP) LEP-R c.668A>G (p.Gln223Arg, rs1137101) of leptin receptor gene and to assess the influence this DNA marker has on endometrial cancer (EC) with respect to total body fat content. METHODS: The study comprised 120 patients treated for endometrial cancer and 90 controls treated for uterine fibroids. In total, 210 patients were included in this research. DNA was isolated from archival post-operative specimens. Polymerase Chain Reaction - Restriction Fragment Length Polymorphism was employed to analyze the SNP. RESULTS: In this paper we have demonstrated that heterozygous genotype AG of SNP LEP-R c.668A>G (p.Gln223Arg, rs1137101) is statistically less frequent in women with endometrial cancer (EC) than in controls: 33 versus 57%, respectively. Similarly, this heterozygous genotype is statistically significantly less frequent in obese (BMI > 30) women with EC than in lean controls (BMI < 25): 30 versus 63%, respectively. CONCLUSIONS: AG polymorphic variant of SNP LEP-R c.668A>G (p.Gln223Arg, rs1137101) in LEP-R may be considered a protective factor in the development of endometrial cancer.

LEP (-2548G>A LEP) and LEPR (223Gln>Arg, 109Lys>Arg) polymorphisms as breast cancer risk factors in the Polish female population.

On a global scale, breast cancer is the most common type of cancer in women, and it is still a growing problem. Therefore, new prognostic or diagnostic markers are required that would facilitate the assessment of patients or provide more efficient therapy, respectively. In these studies, we analyzed the contribution of LEP (2548G>A) and LEPR (109 Lys>Arg and 223Gln>Arg) genes polymorphisms to the risk of breast cancer development. The study involved 209 women aged 59.6 ± 11 years diagnosed with breast cancer and 202 healthy women aged 57.8 ± 8.2 years, who were blood donors. Polymorphism were evaluated by PCR-RFLP reaction followed by the verification of part of the samples by sequencing. The results of the study confirmed obesity as a significant breast cancer development risk factor in Polish women. However, no significant association between the studied polymorphisms and breast cancer risk or severity of the neoplastic disease was found. Interestingly, it was shown that wild type 223Gln>Gln leptin receptor (LEPR) was statistically more common in women with human epidermal growth factor receptor 2 negative (HER2-) than human epidermal groth factor receptor 2 positive (HER2+) breast cancer and wild type form of 2548G>A LEP was more common in women with progesterone receptor positive (PR+) than progesterone receptor negative (PR-) breast cancer. Studied polymorphisms of the LEP and LEPR genes do not increase breast cancer risk in the population of Polish women. However, they can affect PR an HER receptors expression and thus the severity of the disease. Noteworthy, this interesting correlation is being reported for the first time and might constitute an essential contribution to the identification of molecular mechanisms of carcinogenesis.

An Update on the Role of Leptin in the Immuno-Metabolism of Cartilage.

Since its discovery in 1994, leptin has been considered as an adipokine with pleiotropic effects. In this review, we summarize the actual information about the impact of this hormone on cartilage metabolism and pathology. Leptin signalling depends on the interaction with leptin receptor LEPR, being the long isoform of the receptor (LEPRb) the one with more efficient intracellular signalling. Chondrocytes express the long isoform of the leptin receptor and in these cells, leptin signalling, alone or in combination with other molecules, induces the expression of pro-inflammatory molecules and cartilage degenerative enzymes. Leptin has been shown to increase the proliferation and activation of immune cells, increasing the severity of immune degenerative cartilage diseases. Leptin expression in serum and synovial fluid are related to degenerative diseases such as osteoarthritis (OA), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Inhibition of leptin signalling showed to have protective effects in these diseases showing the key role of leptin in cartilage degeneration.

Cytochrome P4501B1 in bone marrow is co-expressed with key markers of mesenchymal stem cells. BMS2 cell line models PAH disruption of bone marrow niche development functions.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants that are metabolized to carcinogenic dihydrodiol epoxides (PAHDE) by cytochrome P450 1B1 (CYP1B1). This metabolism occurs in bone marrow (BM) mesenchymal stem cells (MSC), which sustain hematopoietic stem and progenitor cells (HSPC). In BM, CYP1B1-mediated metabolism of 7, 12-dimethylbenz[a]anthracene (DMBA) suppresses HSPC colony formation within 6 h, whereas benzo(a)pyrene (BP) generates protective cytokines. MSC, enriched from adherent BM cells, yielded the bone marrow stromal, BMS2, cell line. These cells express elevated basal CYP1B1 that scarcely responds to Ah receptor (AhR) inducers. BMS2 cells exhibit extensive transcriptome overlap with leptin receptor positive mesenchymal stem cells (Lepr+ MSC) that control the hematopoietic niche. The overlap includes CYP1B1 and the expression of HSPC regulatory factors (Ebf3, Cxcl12, Kitl, Csf1 and Gas6). MSC are large, adherent fibroblasts that sequester small HSPC and macrophage in the BM niche (Graphic abstract). High basal CYP1B1 expression in BMS2 cells derives from interactions between the Ah-receptor enhancer and proximal promoter SP1 complexes, boosted by autocrine signaling. PAH effects on BMS2 cells model Lepr+MSC niche activity. CYP1B1 metabolizes DMBA to PAHDE, producing p53-mediated mRNA increases, long after the in vivo HSPC suppression. Faster, direct p53 effects, favored by stem cells, remain possible PAHDE targets. However, HSPC regulatory factors remained unresponsive. BP is less toxic in BMS2 cells, but, in BM, CYP1A1 metabolism stimulates macrophage cytokines (Il1b > Tnfa> Ifng) within 6 h. Although absent from BMS2 and Lepr+MSC, their receptors are highly expressed. The impact of this cytokine signaling in MSC remains to be determined.