Estradiol increases hematopoietic stem and progenitor cells independent of its actions on bone

Influence of donor-recipient sex on engraftment of normal and leukemia stem cells in xenotransplantation

Immunodeficient mouse models are widely used for the assessment of human normal and leukemic stem cells. Despite the advancements over the years, reproducibility, as well as the differences in the engraftment of human cells in recipient mice remains to be fully resolved. Here, we used various immunodeficient mouse models to characterize the effect of donor-recipient sex on the engraftment of the human leukemic and healthy cells. Donor human cells and recipient immunodeficient mice demonstrate sex-specific engraftment levels with significant differences observed in the lineage output of normal CD34+ hematopoietic stem and progenitor cells upon xenotransplantation. Intriguingly, human female donor cells display heightened sensitivity to the recipient mice's gender, influencing their proliferation and resulting in significantly increased engraftment in female recipient mice. Our study underscores the intricate interplay taking place between donor and recipient characteristics, shedding light on important considerations for future studies, particularly in the context of pre-clinical research.

Estrogen-Responsive Gene MAST4 Regulates Myeloma Bone Disease

Our previous data showed that young female multiple myeloma (MM) patients had a low frequency of osteolytic lesions. Based on this clinical observation, we found that estrogen cell signaling played a regulatory role in MM bone disease (MMBD), and the estrogen-responsive gene microtubule-associated serine/threonine kinase family member 4 (MAST4) was a critical factor. The presence of estrogen in cell cultures promoted MAST4 expression in MM cells, while knocking down estrogen receptor 1 (ESR1) inhibited MAST4 expression. Chromatin immunoprecipitation assay suggested a binding site of ESR1 on the MAST4 promoter. Bisphosphonates, such as zoledronic acid (ZOL), which was widely used in MMBD control, could stimulate MAST4 expression in MM cells by promoting ESR1 expression. MAST4 interacted with phosphatase and tensin homolog (PTEN), therefore regulating the PI3K-Akt-mTOR pathway and the expression of downstream cytokines, such as CCL2/3/4. MAST4 knockdown (MAST4-KD) or ESR1 knockdown (ESR1-KD) MM cells had repressed PTEN activity, elevated PI3K-Akt-mTOR activity, and increased CCL2/3/4 expressions. Coculture of MAST4-KD or ESR1-KD MM cells with pre-osteoclasts (pre-OCs) stimulated OC formation in vitro, whereas neutralizing antibodies of CCL2/3/4 attenuated such stimulation. In mouse models, mice inoculated with MAST4-KD or ESR1-KD MM cells had severer MMBD than control knockdown (CTR-KD). The correlations between MAST4 and ESR1 expressions in MMBD, as well as related cell signaling pathways, were confirmed in analyses using gene expression profiles (GEPs) of patients' MM cells. The negative correlation of MAST4 expression and occurrence of MMBD was further validated by patients' immunohistochemical tissue array. Overall, our data suggested that estrogen cell signaling negatively regulated MMBD through MAST4. © 2022 American Society for Bone and Mineral Research (ASBMR).

The Hematopoietic Stem/Progenitor Cell Response to Hemorrhage, Injury, and Sepsis: A Review of Pathophysiology

ABSTRACT

Hematopoietic stem/progenitor cells (HSPC) have both unique and common responses following hemorrhage, injury, and sepsis. HSPCs from different lineages have a distinctive response to these "stress" signals. Inflammation, via the production of inflammatory factors, including cytokines, hormones, and interferons, has been demonstrated to impact the differentiation and function of HSPCs. In response to injury, hemorrhagic shock, and sepsis, cellular phenotypic changes and altered function occur, demonstrating the rapid response and potential adaptability of bone marrow hematopoietic cells. In this review, we summarize the pathophysiology of emergency myelopoiesis and the role of myeloid-derived suppressor cells, impaired erythropoiesis, as well as the mobilization of HSPCs from the bone marrow. Finally, we discuss potential therapeutic options to optimize HSPC function after severe trauma or infection.

Natural estrogens enhance the engraftment of human hematopoietic stem and progenitor cells in immunodeficient mice

Hematopoietic Stem and Progenitor Cells are crucial in the maintenance of lifelong production of all blood cells. These Stem Cells are highly regulated to maintain homeostasis through a delicate balance between quiescence, self-renewal and differentiation. However, this balance is altered during the hematopoietic recovery after Hematopoietic Stem and Progenitor Cell Transplantation. Transplantation efficacy can be limited by inadequate Hematopoietic Stem Cells number, poor homing, low level of engraftment, or limited self-renewal. As recent evidences indicate that estrogens are involved in regulating the hematopoiesis, we sought to examine whether natural estrogens (estrone or E1, estradiol or E2, estriol or E3 and estetrol or E4) modulate human Hematopoietic Stem and Progenitor Cells. Our results show that human Hematopoietic Stem and Progenitor Cell subsets express estrogen receptors, and whose signaling is activated by E2 and E4 on these cells. Additionally, these natural estrogens cause different effects on human Progenitors in vitro. We found that both E2 and E4 expand human Hematopoietic Stem and Progenitor Cells. However, E4 was the best tolerated estrogen and promoted cell cycle of human Hematopoietic Progenitors. Furthermore, we identified that E2 and, more significantly, E4 doubled human hematopoietic engraftment in immunodeficient mice without altering other Hematopoietic Stem and Progenitor Cells properties. Finally, the impact of E4 on promoting human hematopoietic engraftment in immunodeficient mice might be mediated through the regulation of mesenchymal stromal cells in the bone marrow niche. Together, our data demonstrate that E4 is well tolerated and enhances human reconstitution in immunodeficient mice, directly by modulating human Hematopoietic Progenitor properties and indirectly by interacting with the bone marrow niche. This application might have particular relevance to ameliorate the hematopoietic recovery after myeloablative conditioning, especially when limiting numbers of Hematopoietic Stem and Progenitor Cells are available.

Race/ethnicity and underlying disease influences hematopoietic stem/progenitor cell mobilization response: A single center experience

BACKGROUND

Whether race/ethnicity plays a role in hematopoietic stem/progenitor cells (HSPC) mobilization in autologous donors has not been studied. We hypothesize that donor characteristic including race/ethnicity, age, sex, body mass index, and diagnostic groups influences HSPC mobilization. Diagnostic groups include healthy allogeneic donors, autologous multiple myeloma (MM) and non-MM donors.

STUDY DESIGN AND METHODS

Here, we conducted a single-center retrospective study in 64 autologous patients and 48 allogeneic donors. Autologous donors were patients diagnosed with MM or non-MM. All donors were grouped as African American (AA), White (W), or "Other"(O).

RESULTS

Multivariate analysis demonstrated diagnostic group differences for CD34+ cell yields between race/ethnicity. Specifically, non-MM patients had the lowest CD34+ cell yields in AA and O, but not in W. For pre-apheresis peripheral blood (PB) CD34+ cell numbers, race/ethnicity had a significant effect both in bivariate and multivariate analyses. Non-MM patients had the lowest, and AA patients had the highest PB CD34+ cells. The results support the view that past therapies used in MM are likely more conducive of recovery of HSPC.

CONCLUSIONS

Our study shows that race/ethnicity and diagnostic group differences influenced CD34+ cell mobilization response across donor types. Interestingly, autologous MM donors with the aid of plerixafor displayed comparable CD34 yields to allogeneic donors. Even though both MM and non-MM donors received plerixafor, non-MM donors had significantly lower CD34 yields among AA and O donors but not in W donors. Larger studies would be required to validate the role of diagnostic groups and race/ethnicity interactions.

Estrogens as regulator of hematopoietic stem cell, immune cells and bone biology

Hematopoietic stem cells provide continuous supply of all the immune cells, through proliferation and differentiation decisions. These decisions are controlled by local bone marrow environment as well as by long-range signals for example endocrine system. Sex dependent differential immunological responses have been described under homeostasis and disease conditions. Females show higher longevity than male counterpart that seems to depend on major female sex hormone, estrogen. There are four estrogens - Estrone (E1), estradiol (E2), Estriol (E3) and Estetrol (E4) that spatially and temporarily present during different female reproductive phases. In this review, we discussed recent updates describing the effects of estrogen on HSC, immune cells and in bone biology. Estradiol (E2) being a major/abundant estrogen is extensively investigated, while effects of other estrogens E1, E3 and E4 are started to unravel recently. Furthermore, clinical effect of estrogen as hormone therapy is discussed in HSC and immune cells perspectives. The data presented in this review is compiled by searches of PubMed, database of American Cancer Society (ACS). We have included article from September 1994 to March 2020 as covering all article in chronological order is not fissile so we included relevant article with substantial information in this specific area of research by using the search term (alone or in combination) estrogen, hematopoietic stem cell, immune cells, gender difference, estrone, estriol, estetrol, therapeutic application, pregnancy, effect on bone.

Sexual dimorphism in aging hematopoiesis: an earlier decline of hematopoietic stem and progenitor cells in male than female mice

Adult hematopoietic stem and progenitor cells (HSPCs) reside in the bone marrow (BM) ensuring homeostasis of blood production and immune response throughout life. Sex differences in immunocompetence and mortality are well-documented in humans. However, whether HSPCs behave dimorphically between sexes during aging remains unknown. Here, we show that a significant expansion of BM-derived HSPCs occurs in the middle age of female but in the old age of male mice. We then show that a decline of HSPCs in male mice, as indicated by the expression levels of select hematopoietic genes, occurs much earlier in the aging process than that in female mice. Sex-mismatched heterochronic BM transplantations indicate that the middle-aged female BM microenvironment plays a pivotal role in sustaining hematopoietic gene expression during aging. Furthermore, a higher concentration of the pituitary sex hormone follicle-stimulating hormone (FSH) in the serum and a concomitant higher expression of its receptor on HSPCs in the middle-aged and old female mice than age-matched male mice, suggests that FSH may contribute to the sexual dimorphism in aging hematopoiesis. Our study reveals that HSPCs in the BM niches are possibly regulated in a sex-specific manner and influenced differently by sex hormones during aging hematopoiesis.

Advances in preclinical hematopoietic stem cell models and possible implications for improving therapeutic transplantation

Hematopoietic stem cell transplantation (HSCT) is a treatment for many malignant, congenital, and acquired hematologic diseases. Some outstanding challenges in the HSCT field include the paucity of immunologically‐matched donors, our inability to effectively expand hematopoeitic stem cells (HSCs) ex vivo, and the high infection risk during engraftment. Scientists are striving to develop protocols to generate, expand, and maintain HSCs ex vivo, however these are not yet ready for clinical application. Given these problems, advancing our understanding of HSC specification, regulation, and differentiation in preclinical models is essential to improve the therapeutic utility of HSCT. In this review, we link biomedical researchers and transplantation clinicians by discussing the potential therapeutic implications of recent fundamental HSC research in model organisms. We consider deficiencies in current HSCT practice, such as problems achieving adequate cell dose for successful and rapid engraftment, immense inflammatory cascade activation after myeloablation, and graft‐vs‐host disease. Furthermore, we discuss recent advances in the field of HSC biology and transplantation made in preclinical models of zebrafish, mouse, and nonhuman primates that could inform emerging practice for clinical application.

Estrogen Receptors Alpha and Beta in Acute Myeloid Leukemia

Estrogen receptor (ER) signaling has been widely studied in a variety of solid tumors, where the differential expression of ERα and ERβ subtypes can impact prognosis. ER signaling has only recently emerged as a target of interest in acute myeloid leukemia (AML), an aggressive hematological malignancy with sub-optimal therapeutic options and poor clinical outcomes. In a variety of tumors, ERα activation has proliferative effects, while ERβ targeting results in cell senescence or death. Aberrant ER expression and hypermethylation have been characterized in AML, making ER targeting in this disease of great interest. This review describes the expression patterns of ERα and ERβ in AML and discusses the differing signaling pathways associated with each of these receptors. Furthermore, we assess how these signaling pathways can be targeted by various selective estrogen receptor modulators to induce AML cell death. We also provide insight into ER targeting in AML and discuss pending questions that require further study.

Comparative Evaluation of Hormones and Hormone-Like Molecule in Lineage Specification of Human Induced Pluripotent Stem Cells

Background and Objectives

Proficient differentiation of human pluripotent stem cells (hPSCs) into specific lineages is required for applications in regenerative medicine. A growing amount of evidences had implicated hormones and hormone-like molecules as critical regulators of proliferation and lineage specification during in vivo development. Therefore, a deeper understanding of the hormones and hormone-like molecules involved in cell fate decisions is critical for efficient and controlled differentiation of hPSCs into specific lineages. Thus, we functionally and quantitatively compared the effects of diverse hormones (estradiol 17-β (E2), progesterone (P4), and dexamethasone (DM)) and a hormone-like molecule (retinoic acid (RA)) on the regulation of hematopoietic and neural lineage specification.

Methods and Results

We used 10 nM E2, 3 µM P4, 10 nM DM, and 10 nM RA based on their functional in vivo developmental potential. The sex hormone E2 enhanced functional activity of hematopoietic progenitors compared to P4 and DM, whereas RA impaired hematopoietic differentiation. In addition, E2 increased CD34⁺CD45⁺ cells with progenitor functions, even in the CD43^- population, a well-known hemogenic marker. RA exhibited lineage-biased potential, preferentially committing hPSCs toward the neural lineage while restricting the hematopoietic fate decision.

Conclusions

Our findings reveal unique cell fate potentials of E2 and RA treatment and provide valuable differentiation information that is essential for hPSC applications.

The Roles of Cholesterol and Its Metabolites in Normal and Malignant Hematopoiesis

Hematopoiesis is sustained throughout life by hematopoietic stem cells (HSCs) that are capable of self-renewal and differentiation into hematopoietic progenitor cells (HPCs). There is accumulating evidence that cholesterol homeostasis is an important factor in the regulation of hematopoiesis. Increased cholesterol levels are known to promote proliferation and mobilization of HSCs, while hypercholesterolemia is associated with expansion of myeloid cells in the peripheral blood and links hematopoiesis with cardiovascular disease. Cholesterol is a precursor to steroid hormones, oxysterols, and bile acids. Among steroid hormones, 17β-estradiol (E2) induces HSC division and E2-estrogen receptor α (ERα) signaling causes sexual dimorphism of HSC division rate. Oxysterols are oxygenated derivatives of cholesterol and key substrates for bile acid synthesis and are considered to be bioactive lipids, and recent studies have begun to reveal their important roles in the hematopoietic and immune systems. 27-Hydroxycholesterol (27HC) acts as an endogenous selective estrogen receptor modulator and induces ERα-dependent HSC mobilization and extramedullary hematopoiesis. 7α,25-dihydroxycholesterol (7α,25HC) acts as a ligand for Epstein-Barr virus-induced gene 2 (EBI2) and directs migration of B cells in the spleen during the adaptive immune response. Bile acids serve as chemical chaperones and alleviate endoplasmic reticulum stress in HSCs. Cholesterol metabolism is dysregulated in hematologic malignancies, and statins, which inhibit de novo cholesterol synthesis, have cytotoxic effects in malignant hematopoietic cells. In this review, recent advances in our understanding of the roles of cholesterol and its metabolites as signaling molecules in the regulation of hematopoiesis and hematologic malignancies are summarized.

Dynamics of Bone Marrow VSELs and HSCs in Response to Treatment with Gonadotropin and Steroid Hormones, during Pregnancy and Evidence to Support Their Asymmetric/Symmetric Cell Divisions

Gender plays an important role in the incidence of hematological malignancies and recently hematopoietic stem cells (HSCs) were found to proliferate more in females that gets further augmented during pregnancy. It was suggested that since basal numbers of HSCs remain the same in both sexes, possibly HSCs in females undergo increased self-renewal and apoptosis. Then how is self-renewal of stem cells regulated in males? More important, do HSCs undergo asymmetric cell divisions (ACD) or a more primitive population of pluripotent, very small embryonic-like stem cells (VSELs) undergo ACD to self-renew and specify into HSCs? Lot more clarity is required on the bone marrow stem cells biology. Present study was undertaken to evaluate whether similar dimorphism reported for HSCs also exists among VSELs. Bone marrow VSELs and HSCs were studied in bilaterally ovariectomized and castrated mice by flow cytometry after treating with gonadotropin (FSH) and sex steroid (estrogen & progesterone) hormones and during pregnancy. Differential expression of pluripotent (Oct-4A, Sox2, Nanog) and differentiation (Oct-4, Sca1, c-Kit, Ikaros) specific transcripts was studied. Basal BrdU uptake was more in both VSELs (p < 0.01) and HSCs (p < 0.05) in female bone marrow. FSH exerted a more profound effect compared to estradiol in both the sexes. Flow cytometry results showed ten-fold increase in spleen VSELs by mid-gestation associated with approximately two-fold increase in HSCs. These results point to a novel yet unreported role of spleen VSELs during pregnancy. Furthermore, VSELs underwent ACD to self-renew and give rise to slightly bigger HSCs based on unequal expression of NUMB, CD45 and OCT-4.

Influence of diet and metabolism on hematopoietic stem cells and leukemia development following ionizing radiation exposure

PURPOSE

The review aims to discuss the prominence of dietary and metabolic regulators in maintaining hematopoietic stem cell (HSC) function, long-term self-renewal, and differentiation.

RESULTS

Most adult stem cells are preserved in a quiescent, nonmotile state in vivo which acts as a "protective state" for stem cells to reduce endogenous stress provoked by DNA replication and cellular respiration as well as exogenous environmental stress. The dynamic balance between quiescence, self-renewal and differentiation is critical for supporting a functional blood system throughout life of an organism. Stress-conditions, for example ionizing radiation exposure can trigger the blood forming HSCs to proliferate and migrate through extramedullary tissues to expand the number of HSCs and increase hematopoiesis. In addition, a wealth of investigation validated that deregulation of this balance plays a critical pathogenic role in various different hematopoietic diseases including the leukemia development.

CONCLUSION

The review summarizes the current knowledge on how alterations in dietary and metabolic factors could alter the risk of leukemia development following ionizing radiation exposure by inhibiting or even reversing the leukemic progression. Understanding the influence of diet, metabolism, and epigenetics on radiation-induced leukemogenesis may lead to the development of practical interventions to reduce the risk in exposed populations.

Estradiol Modulates Local Gut Injury Induced by Intestinal Ischemia-Reperfusion in Male Rats

Intestinal ischemia and reperfusion (I/R) triggers a systemic inflammatory response characterized by leukocyte mobilization from the bone marrow, release of cytokines to the circulation, and increased microvascular permeability, leading to high mortality. Females have shown attenuated inflammatory response to trauma when compared with males, indicating a role for female sex hormones in this process. Here, we have evaluated the effect of estradiol on the local gut injury induced by I/R in male rats. I/R was induced by the clamping of the superior mesenteric artery for 45 min, followed by 2 h of reperfusion. A group received 17β-estradiol (280 μg/kg, i.v., single dose) at 30 min of ischemia. Morphometric analysis of the gut showed I/R induced a reduction of villous height that was prevented by estradiol. White blood cells, notably granulocytes, were mobilized from the circulation to the intestine by I/R, which was also prevented by estradiol treatment. Groups had the intestine wrapped in a plastic bag to collect intestinal fluid, where leukocytes count, TNF-α, and IL-10 levels were increased by I/R. Serum chemokines (CINC-1, MIP-1α, MIP-2), ICAM-1 expression in the mesenteric tissue, and neutrophils spontaneous migration measured in vitro were also increased after I/R. Estradiol treatment reduced leukocytes numbers and TNF-α on intestinal fluid, serum chemokine release and also downregulated MIP-1α, MIP-2 gene expression, and spontaneous in vitro neutrophil migration. In conclusion, estradiol blunts intestinal injury induced by I/R by modulating chemokines release and leukocyte trafficking.

Estrogen receptor α- (ERα), but not ERβ-signaling, is crucially involved in mechanostimulation of bone fracture healing by whole-body vibration

Mechanostimulation by low-magnitude high frequency vibration (LMHFV) has been shown to provoke anabolic effects on the intact skeleton in both mice and humans. However, experimental studies revealed that, during bone fracture healing, the effect of whole-body vibration is profoundly influenced by the estrogen status. LMHFV significantly improved fracture healing in ovariectomized (OVX) mice being estrogen deficient, whereas bone regeneration was significantly reduced in non-OVX, estrogen-competent mice. Furthermore, estrogen receptors α (ERα) and β (ERβ) were differentially expressed in the fracture callus after whole-body vibration, depending on the estrogen status. Based on these data, we hypothesized that ERs may mediate vibration-induced effects on fracture healing. To prove this hypothesis, we investigated the effects of LMHFV on bone healing in mice lacking ERα or ERβ. To study the influence of the ER ligand estrogen, both non-OVX and OVX mice were used. All mice received a femur osteotomy stabilized by an external fixator. Half of the mice were sham-operated or subjected to OVX 4 weeks before osteotomy. Half of each group received LMHFV with 0.3 g and 45 Hz for 20 min per day, 5 days per week. After 21 days, fracture healing was evaluated by biomechanical testing, μCT analysis, histomorphometry and immunohistochemistry. Absence of ERα or ERβ did not affect fracture healing in sham-treated mice. Wildtype (WT) and ERβ-knockout mice similarly displayed impaired bone regeneration after OVX, whereas ERα-knockout mice did not. Confirming previous data, in WT mice, LMHFV negatively affected bone repair in non-OVX mice, whereas OVX-induced compromised healing was significantly improved by vibration. In contrast, vibrated ERα-knockout mice did not display significant differences in fracture healing compared to non-vibrated animals, both in non-OVX and OVX mice. Fracture healing in ERβ-knockout mice was similarly affected by LMHFV as in WT mice. These results suggest that ERα-signaling may be crucial for vibration-induced effects on fracture healing, whereas ERβ-signaling may play a minor role.

Oestrogen, progesterone and stem cells: the discordant trio in endometriosis?

Oestrogen–progesterone signalling is highly versatile and critical for the maintenance of healthy endometrium in humans. The genomic and nongenomic signalling cascades initiated by these hormones in differentiated cells of endometrium have been the primary focus of research since 1920s. However, last decade of research has shown a significant role of stem cells in the maintenance of a healthy endometrium and the modulatory effects of hormones on these cells. Endometriosis, the growth of endometrium outside the uterus, is very common in infertile patients and the elusiveness in understanding of disease pathology causes hindrance in selection of treatment approaches to enhance fertility. In endometriosis, the stem cells are dysfunctional as it can confer progesterone resistance to their progenies resulting in disharmony of hormonal orchestration of endometrial homeostasis. The bidirectional communication between stem cell signalling pathways and oestrogen–progesterone signalling is found to be disrupted in endometriosis though it is not clear which precedes the other. In this paper, we review the intricate connection between hormones, stem cells and the cross-talks in their signalling cascades in normal endometrium and discuss how this is deregulated in endometriosis. Re-examination of the oestrogen–progesterone dependency of endometrium with a focus on stem cells is imperative to delineate infertility associated with endometriosis and thereby aid in designing better treatment modalities.

Improved hematopoietic differentiation of human pluripotent stem cells via estrogen receptor signaling pathway

Background

Aside from its importance in reproduction, estrogen (E2) is known to regulate the proliferation and differentiation of hematopoietic stem cells in rodents. However, the regulatory role of E2 in human hematopoietic system has not been investigated. The purpose of this study is to investigate the effect of E2 on hematopoietic differentiation using human pluripotent stem cells (hPSCs).

Results

E2 improved hematopoietic differentiation of hPSCs via estrogen receptor alpha (ER-α)-dependent pathway. During hematopoietic differentiation of hPSCs, ER-α is persistently maintained and hematopoietic phenotypes (CD34 and CD45) were exclusively detected in ER-α positive cells. Interestingly, continuous E2 signaling is required to promote hematopoietic output from hPSCs. Supplementation of E2 or an ER-α selective agonist significantly increased the number of hemangioblasts and hematopoietic progenitors, and subsequent erythropoiesis, whereas ER-β selective agonist did not. Furthermore, ICI 182,780 (ER antagonist) completely abrogated the E2-induced hematopoietic augmentation. Not only from hPSCs but also from human umbilical cord bloods, does E2 signaling potentiate hematopoietic development, suggesting universal function of E2 on hematopoiesis.

Conclusions

Our study identifies E2 as positive regulator of human hematopoiesis and suggests that endocrine factors such as E2 influence the behavior of hematopoietic stem cells in various physiological conditions.

Electronic supplementary material

The online version of this article (doi:10.1186/s13578-016-0111-9) contains supplementary material, which is available to authorized users.

VEGF-A/VEGFR Inhibition Restores Hematopoietic Homeostasis in the Bone Marrow and Attenuates Tumor Growth

Antiangiogenesis-based cancer therapies, specifically those targeting the VEGF-A/VEGFR2 pathway, have been approved for subsets of solid tumors. However, these therapies result in an increase in hematologic adverse events. We surmised that both the bone marrow vasculature and VEGF receptor-positive hematopoietic cells could be impacted by VEGF pathway-targeted therapies. We used a mouse model of spontaneous breast cancer to decipher the mechanism by which VEGF pathway inhibition alters hematopoiesis. Tumor-bearing animals, while exhibiting increased angiogenesis at the primary tumor site, showed signs of shrinkage in the sinusoidal bone marrow vasculature accompanied by an increase in the hematopoietic stem cell-containing Lin-cKit(+)Sca1(+) (LKS) progenitor population. Therapeutic intervention by targeting VEGF-A, VEGFR2, and VEGFR3 inhibited tumor growth, consistent with observed alterations in the primary tumor vascular bed. These treatments also displayed systemic effects, including reversal of the tumor-induced shrinkage of sinusoidal vessels and altered population balance of hematopoietic stem cells in the bone marrow, manifested by the restoration of sinusoidal vessel morphology and hematopoietic homeostasis. These data indicate that tumor cells exert an aberrant systemic effect on the bone marrow microenvironment and VEGF-A/VEGFR targeting restores bone marrow function.

Estrogen deficiency heterogeneously affects tissue specific stem cells in mice

Postmenopausal disorders are frequently observed in various organs, but their relationship with estrogen deficiency and mechanisms remain unclear. As tissue-specific stem cells have been found to express estrogen receptors, we examined the hypothesis that estrogen deficiency impairs stem cells, which consequently contributes to postmenopausal disorders. Six-week-old C57BL/6 female mice were ovariectomized, following which they received 17β-estradiol replacement or vehicle (control). Sham-operated mice were used as healthy controls. All mice were killed for evaluation 2 months after treatments. Compared with the healthy control, ovariectomy significantly decreased uterine weight, which was partially recovered by 17β-estradiol replacement. Ovariectomy significantly increased the numbers of c-kit-positive hematopoietic stem/progenitor cells in bone marrow, but impaired their capacity to grow mixed cell-type colonies in vitro. Estrogen replacement further increased the numbers of c-kit-positive hematopoietic stem/progenitor cells in bone marrow, without significantly affecting colony growth in vitro. The number of CD105-positive mesenchymal stem cells in bone marrow also significantly decreased after ovariectomy, but completely recovered following estrogen replacement. Otherwise, neither ovariectomy nor estrogen replacement changed the number of Pax7-positive satellite cells, which are a skeletal muscle-type stem cell. Estrogen deficiency heterogeneously affected tissue-specific stem cells, suggesting a likely and direct relationship with postmenopausal disorders.

Estrogen signaling selectively induces apoptosis of hematopoietic progenitors and myeloid neoplasms without harming steady-state hematopoiesis

Estrogens are potent regulators of mature hematopoietic cells; however, their effects on primitive and malignant hematopoietic cells remain unclear. Using genetic and pharmacological approaches, we observed differential expression and function of estrogen receptors (ERs) in hematopoietic stem cell (HSC) and progenitor subsets. ERα activation with the selective ER modulator (SERM) tamoxifen induced apoptosis in short-term HSCs and multipotent progenitors. In contrast, tamoxifen induced proliferation of quiescent long-term HSCs, altered the expression of self-renewal genes, and compromised hematopoietic reconstitution after myelotoxic stress, which was reversible. In mice, tamoxifen treatment blocked development of JAK2(V617F)-induced myeloproliferative neoplasm in vivo, induced apoptosis of human JAK2(V617F+) HSPCs in a xenograft model, and sensitized MLL-AF9(+) leukemias to chemotherapy. Apoptosis was selectively observed in mutant cells, and tamoxifen treatment only had a minor impact on steady-state hematopoiesis in disease-free animals. Together, these results uncover specific regulation of hematopoietic progenitors by estrogens and potential antileukemic properties of SERMs.

Hormonal regulation of hematopoietic stem cells and their niche: a focus on estrogen

Self-renewal and differentiation are hallmarks of stem cells and controlled by various intrinsic and extrinsic factors. Increasing evidence indicates that estrogen (E2), the primary female sex hormone, is involved in regulating the proliferation and lineage commitment of adult and pluripotent stem cells as well as modulating the stem cell niche. Thus, a detailed understanding of the role of E2 in behavior of stem cells may help to improve their therapeutic potential. Recently, it has been reported that E2 promotes cell cycle activity of hematopoietic stem and progenitor cells and induces them to megakaryocyte-erythroid progenitors during pregnancy. This study paves the way towards a previously unexplored endocrine mechanism that controls stem cell behavior. In this review, we will focus on the scientific findings regarding the regulatory effects of E2 on the hematopoietic system including its microenvironment.

Estrogen receptors regulate innate immune cells and signaling pathways

Humans show strong sex differences in immunity to infection and autoimmunity, suggesting sex hormones modulate immune responses. Indeed, receptors for estrogens (ER) regulate cells and pathways in the innate and adaptive immune system, as well as immune cell development. ERs are ligand-dependent transcription factors that mediate long-range chromatin interactions and form complexes at gene regulatory elements, thus promoting epigenetic changes and transcription. ERs also participate in membrane-initiated steroid signaling to generate rapid responses. Estradiol and ER activity show profound dose- and context-dependent effects on innate immune signaling pathways and myeloid cell development. While estradiol most often promotes the production of type I interferon, innate pathways leading to pro-inflammatory cytokine production may be enhanced or dampened by ER activity. Regulation of innate immune cells and signaling by ERs may contribute to the reported sex differences in innate immune pathways. Here we review the recent literature and highlight several molecular mechanisms by which ERs regulate the development or functional responses of innate immune cells.

Regulation of hematopoietic progenitors by estrogens as a basis for new antileukemic strategies

We recently reported that estrogens regulate survival, proliferation, and self-renewal of hematopoietic stem cells and progenitors via estrogen receptor-α activation. Through its proapoptotic effect on malignant progenitors, tamoxifen treatment blocks the development of JAK2 (V617F) -induced myeloproliferative neoplasms in mice and sensitizes MLL-AF9-induced leukemias to chemotherapy, without detrimental effects on normal hematopoiesis.

Girl power: estrogen promotes HSC self-renewal

Although some hematopoietic cell types are known to respond to sex hormones, hematopoietic stem cells (HSCs) are generally thought to function similarly in both sexes. Recently in Nature, Nakada et al. (2014) show that HSCs respond to higher levels of estrogen in females, resulting in enhanced self-renewal and increased erythropoiesis.

Sexual dimorphism in immunity: improving our understanding of vaccine immune responses in men

Weaker immune responses are often observed in males compared to females. Since female hormones have proinflammatory properties and androgens have potent immunomodulatory effects, this sexual dimorphism in the immune response seems to be hormone dependent. Despite our current knowledge about the effect of sex hormones on immune cells, definition of the factors driving the sex differences in immunoclinical outcomes, such as the diminished response to infection and vaccination observed in men or the higher rates of autoimmunity observed in females, remains elusive. Recently, systems approaches to immune function have started to suggest a way toward establishing this connection. Such studies promise to improve our understanding of the mechanisms underlying the sexual dimorphism observed in the human immune system.

Breast cancer stem cells: Multiple capacities in tumor metastasis

Breast cancer is the leading cause of cancer death among women worldwide. Accumulating evidence indicates that the local recurrent and/or distant metastatic tumors, the major causes of lethality in the clinic, are related to the aggressive phenotype of a small fraction of cancer cells loosely termed as cancer stem cells (CSCs), tumor initiating cells (TICs), or cancer metastasis-initiating cells (CMICs). Breast cancer stem cells (BCSCs) are shown to exhibit unique growth abilities including self-renewal, differentiation potential, and resistance to most anti-cancer agents including chemo- and/or radiotherapy, all of which are believed to contribute to the development and overall aggressiveness of the recurrent or metastatic lesions. It is in the urgent need not only to further define the nature of heterogeneity in each tumor but also to characterize the precise mechanisms governing tumor-host cross-talk which is assumed to be initiated by BCSCs. In this review, we will focus on recently identified key factors, including the BCSCs among circulating tumor cells, interaction of BCSCs with the host, epithelial mesenchymal transition (EMT), tumor microenvironment, the intrinsic resistance due to HER2 expression, potential biomarkers of BCSCs and cancer cell immune signaling. We believe that new evidence coming from both bench and clinical research will help to develop more effective approaches to control or significantly reduce the aggressiveness of metastatic tumors.

The relationship between inflammatory biomarkers and telomere length in an occupational prospective cohort study

Background

Chronic inflammation from recurring trauma is an underlying pathophysiological basis of numerous diseases. Furthermore, it may result in cell death, scarring, fibrosis, and loss of tissue function. In states of inflammation, subsequent increases in oxidative stress and cellular division may lead to the accelerated erosion of telomeres, crucial genomic structures which protect chromosomes from decay. However, the association between plasma inflammatory marker concentrations and telomere length has been inconsistent in previous studies.

Objective

The purpose of this study was to determine the longitudinal association between telomere length and plasma inflammatory biomarker concentrations including: CRP, SAA, sICAM-1, sVCAM-1, VEGF, TNF-α, IL-1β, IL-2, IL-6, IL-8, and IL-10.

Methods

The longitudinal study population consisted of 87 subjects. The follow-up period was approximately 2 years. Plasma inflammatory biomarker concentrations were assessed using highly sensitive electrochemiluminescent assays. Leukocyte relative telomere length was assessed using Real-Time qPCR. Linear mixed effects regression models were used to analyze the association between repeated-measurements of relative telomere length as the outcome and each inflammatory biomarker concentration as continuous exposures separately. The analyses controlled for major potential confounders and white blood cell differentials.

Results

At any follow-up time, each incremental ng/mL increase in plasma CRP concentration was associated with a decrease in telomere length of −2.6×10⁻² (95%CI: −4.3×10⁻², −8.2×10⁻³, p = 0.004) units. Similarly, the estimate for the negative linear association between SAA and telomere length was −2.6×10⁻² (95%CI:−4.5×10⁻², −6.1×10⁻³, p = 0.011). No statistically significant associations were observed between telomere length and plasma concentrations of pro-inflammatory interleukins, TNF-α, and VEGF.

Conclusions

Findings from this study suggest that increased systemic inflammation, consistent with vascular injury, is associated with decreased leukocyte telomere length.