Restoration of Cardiomyogenesis in Aged Mouse Hearts by Voluntary Exercise.

BACKGROUND: The human heart has limited capacity to generate new cardiomyocytes and this capacity declines with age. Because loss of cardiomyocytes may contribute to heart failure, it is crucial to explore stimuli of endogenous cardiac regeneration to favorably shift the balance between loss of cardiomyocytes and the birth of new cardiomyocytes in the aged heart. We have previously shown that cardiomyogenesis can be activated by exercise in the young adult mouse heart. Whether exercise also induces cardiomyogenesis in aged hearts, however, is still unknown. Here, we aim to investigate the effect of exercise on the generation of new cardiomyocytes in the aged heart. METHODS: Aged (20-month-old) mice were subjected to an 8-week voluntary running protocol, and age-matched sedentary animals served as controls. Cardiomyogenesis in aged hearts was assessed on the basis of 15N-thymidine incorporation and multi-isotope imaging mass spectrometry. We analyzed 1793 cardiomyocytes from 5 aged sedentary mice and compared these with 2002 cardiomyocytes from 5 aged exercised mice, followed by advanced histology and imaging to account for ploidy and nucleation status of the cell. RNA sequencing and subsequent bioinformatic analyses were performed to investigate transcriptional changes induced by exercise specifically in aged hearts in comparison with young hearts. RESULTS: Cardiomyogenesis was observed at a significantly higher frequency in exercised compared with sedentary aged hearts on the basis of the detection of mononucleated/diploid 15N-thymidine-labeled cardiomyocytes. No mononucleated/diploid 15N-thymidine-labeled cardiomyocyte was detected in sedentary aged mice. The annual rate of mononucleated/diploid 15N-thymidine-labeled cardiomyocytes in aged exercised mice was 2.3% per year. This compares with our previously reported annual rate of 7.5% in young exercised mice and 1.63% in young sedentary mice. Transcriptional profiling of young and aged exercised murine hearts and their sedentary controls revealed that exercise induces pathways related to circadian rhythm, irrespective of age. One known oscillating transcript, however, that was exclusively upregulated in aged exercised hearts, was isoform 1.4 of regulator of calcineurin, whose regulation and functional role were explored further. CONCLUSIONS: Our data demonstrate that voluntary running in part restores cardiomyogenesis in aged mice and suggest that pathways associated with circadian rhythm may play a role in physiologically stimulated cardiomyogenesis.

Novel Autoimmune IgM Antibody Attenuates Atherosclerosis in IgM Deficient Low-Fat Diet-Fed, but Not Western Diet-Fed Apoe-/- Mice.

OBJECTIVE: Oxidized phospholipids (OxPL), such as the oxidized derivatives of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine, 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphorylcholine, and 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphorylcholine, have been shown to be the principal biologically active components of minimally oxidized LDL (low-density lipoprotein). The role of OxPL in cardiovascular diseases is well recognized, including activation of inflammation within vascular cells. Atherosclerotic Apoe-/- mice fed a high-fat diet develop antibodies to OxPL, and hybridoma B-cell lines producing natural anti-OxPL autoantibodies have been successfully generated and characterized. However, as yet, no studies have been reported demonstrating that treatment with OxPL neutralizing antibodies can be used to prevent or reverse advanced atherosclerosis. Approach and Results: Here, using a screening against 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphorylcholine/1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphorylcholine, we generated a novel IgM autoantibody, 10C12, from the spleens of Apoe-/- mice fed a long-term Western diet, that demonstrated potent OxPL neutralizing activity in vitro and the ability to inhibit macrophage accumulation within arteries of Apoe-/- mice fed a Western diet for 4 weeks. Of interest, 10C12 failed to inhibit atherosclerosis progression in Apoe-/- mice treated between 18 and 26 weeks of Western diet feeding likely due at least in part to high levels of endogenous anti-OxPL antibodies. However, 10C12 treatment caused a 40% decrease in lipid accumulation within aortas of secreted IgM deficient, sIgM-/-Apoe-/-, mice fed a low-fat diet, when the antibody was administrated between 32-40 weeks of age. CONCLUSIONS: Taken together, these results provide direct evidence showing that treatment with a single autoimmune anti-OxPL IgM antibody during advanced disease stages can have an atheroprotective outcome.

Differential expression of mitotic regulators and tumor microenvironment influences the regional growth pattern of solid sarcoma along the cranio-caudal axis.

Soft tissue sarcomas are relatively rare, unusual, anatomically diverse group of malignancies. According to the recent literature and medical bulletins, tumor growth and aggressiveness immensely relies on its anatomical locations. However, it is unclear whether the cranio-caudal anatomical axis of the mammalian body can influence sarcoma development and the underlying molecular mechanisms are not yet deciphered. Here, we investigated the growth pattern of solid sarcoma implanted into the murine cranial and caudal anatomical locations and tried to explore the location specific expression pattern of crucial mammalian mitotic regulators such as Aurora kinase A, Histone H3 and c-Myc in the cranio-caudally originated solid tumors. In addition, the influence of local tumor microenvironment on regional sarcoma growth was also taken into consideration. We found that solid sarcoma developed differentially when implanted into two different anatomical locations and most notably, enhanced tumor growth was observed in case of cranially implanted sarcoma than the caudal sarcoma. Interestingly, Aurora kinase A and c-Myc expression and histone H3 phosphorylation level were comparatively higher in the cranial tumor than the caudal. In addition, variation of tumor stroma in a location specific manner also facilitated tumor growth. Cranial sarcoma microenvironment was well vascularized than the caudal one and consequently, a significantly higher microvessel density count was observed which was parallel with low hypoxic response with sign of local tumor inflammation in this region. Taken together, our findings suggest that differential gradient of mitotic regulators together with varied angiogenic response and local tumor microenvironment largely controls solid sarcoma growth along the cranio-caudal anatomical axis.

Adam10 mediates the choice between principal cells and intercalated cells in the kidney.

A disintegrin and metalloproteinase domain 10 (Adam10), a member of the ADAM family of cell membrane-anchored proteins, has been linked to the regulation of the Notch, EGF, E-cadherin, and other signaling pathways. However, it is unclear what role Adam10 has in the kidney in vivo. In this study, we showed that Adam10 deficiency in ureteric bud (UB) derivatives leads to a decrease in urinary concentrating ability, polyuria, and hydronephrosis in mice. Furthermore, Adam10 deficiency led to a reduction in the percentage of aquaporin 2 (Aqp2)(+) principal cells (PCs) in the collecting ducts that was accompanied by a proportional increase in the percentage of intercalated cells (ICs). This increase was more prominent in type A ICs than in type B ICs. Foxi1, a transcription factor important for the differentiation of ICs, was upregulated in the Adam10 mutants. The observed reduction of Notch activity in Adam10 mutant collecting duct epithelium and the similar reduction of PC/IC ratios in the collecting ducts in mice deficient for mindbomb E3 ubiquitin protein ligase 1, a key regulator of the Notch and Wnt/receptor-like tyrosine kinase signaling pathways, suggest that Adam10 regulates cell fate determination through the activation of Notch signaling, probably through the regulation of Foxi1 expression. However, phenotypic differences between the Adam10 mutants, the Mib1 mutants, and the Foxi1 mutants suggest that the functions of Adam10 in determining the fate of collecting duct cells are more complex than those of a simple upstream factor in a linear pathway involving Notch and Foxi1.

Alteration of hedgehog signaling by chronic exposure to different pesticide formulations and unveiling the regenerative potential of recombinant sonic hedgehog in mouse model of bone marrow aplasia.

Chronic pesticide exposure-induced downregulation of hedgehog signaling and its subsequent degenerative effects on the mammalian hematopoietic system have not been investigated yet. However a number of concurrent studies have pointed out the positive correlation between chronic pesticide exposure induced bone marrow failure and immune suppression. Here, we have given an emphasis on the recapitulation of human marrow aplasia like condition in mice by chronic mixed pesticide exposures and simultaneously unravel the role of individual pesticides in the said event. Unlike the effect of mixed pesticide, individual pesticides differentially alter the hedgehog signaling in the bone marrow primitive hematopoietic compartment (Sca1 + compartment) and stromal compartment. Individually, hexaconazole disrupted hematopoietic as well as stromal hedgehog signaling activation through inhibiting SMO and facilitating PKC δ expression. On contrary, both chlorpyriphos and cypermethrin increased the sequestration and degradation of GLI1 by upregulating SU(FU) and ßTrCP, respectively. However, cypermethrin-mediated inhibition of hedgehog signaling has partly shown to be circumvented by non-canonical activation of GLI1. Finally, we have tested the regenerative response of sonic hedgehog and shown that in vitro supplemented recombinant SHH protein augmented clonogenic stromal progenitors (CFU-F) as well as primitive multipotent hematopoietic clones including CFU-GEMM and CFU-GM of mixed pesticide-induced aplastic marrow. It is an indication of the marrow regeneration. Finally, our findings provide a gripping evidence that downregulated hedgehog signaling contribute to pesticide-mediated bone marrow aplasia but it could be recovered by proper supplementation of recombinant SHH along with hematopoietic base cocktail. Furthermore, SU(FU) and GLI1 can be exploited as future theradiagnostic markers for early marrow aplasia diagnosis.

Pesticide induced alterations in marrow physiology and depletion of stem and stromal progenitor population: an experimental model to study the toxic effects of pesticide.

Long-term exposure of agriculturally used organochloride and organophosphate pesticides have been shown to cause long-lasting hematotoxicity and increased incidence of aplastic anemia in humans. The mechanisms involved in pesticide induced hematotoxicity and the features of toxicity that may play a major role in bone marrow suppression are not known. The aim of the present study was to investigate the hematological consequences of pesticide exposure in swiss albino mice exposed to aqueous mixture of common agriculturally used pesticides for 6 h/day, 5 days/week for 13 weeks. After the end of last exposure, without a recovery period, the strong hematotoxic effect of pesticide was assessed in mice with long-term bone marrow explant culture (LTBMC-Ex) system and cell colony forming assays. Bone marrow explant culture from the pesticide exposed group of mice failed to generate a supportive stromal matrix and did not produce adequate number of hematopoietic cells and found to contain largely the adipogenic precursors. The decreased cell colony numbers in the pesticide exposed group indicated defective maturational and functional status of different marrow cell lineages. As a whole, exposure of mice to the mixture of pesticides reduced the total number of bone marrow cells (granulocytes are the major targets of pesticide toxicity), hematopoietic, and non-hematopoietic progenitor cells and most of the hematological parameters. Replication of primitive stem/progenitor cells in the marrow was decreased following pesticide exposure with G0/G1-phase arrest of most of the cells. The progenitor cells showed decreased percentage of cells in S/G2/M-phase. The increased apoptosis profile of the marrow progenitors (Increased CD95 expression) and primitive stem cells (High Annexin-V positivity on Sca1+ cells) with an elevated intracellular cleaved caspase-3 level on the Sca1+ bone marrow cells provided the base necessary for explaining the deranged bone marrow microenvironmental structure which was evident from scanning electron micrographs. These results clearly indicate a strong, long lasting toxic effect of pesticides on the bone marrow microenvironment and different microenvironmental components which ultimately leads to the formation of a degenerative disease like aplastic anemia.

Phenotypic alteration of limbal niche-associated limbal epithelial stem cell deficiency by ultraviolet-B exposure-induced phototoxicity in mice.

Good vision requires a healthy cornea, and a healthy cornea needs healthy stem cells. Limbal epithelial stem cells (LESCs) are a traditional source of corneal epithelial cells and are recruited for the continuous production of epithelium without seizing throughout an animal's life, which maintains corneal transparency. Like the maintenance of other adult somatic stem cells, the maintenance of LESCs depends on the specific microenvironmental niche in which they reside. The purpose of this study was to determine the microenvironmental damage associated with LESCs fate due to ultraviolet (UV)-B exposure in a mouse model. Structural alteration and deregulation of the stem cell and its neighboring niche components were observed by using clinical, morphological, explant culture study, and flowcytometric analysis, which demonstrated that the limbal microenvironment plays an important role in cornea-related disease development. In UV-exposed mice, overexpression of vascular endothelial growth factor receptor 2 indicated neovascularization, decreased CD38 expression signified the alteration of limbal epithelial superficial cells, and the loss of limbal stem cell marker p63 indicated limbal stem cell deficiency in the limbal vicinity. We concluded that LESC deficiency diseases (LESCDDs) are associated with pathophysiological changes in the LESC niche, with some inhibitory interception such as UV-B irradiation, which results in corneal defects.

Differential remodeling of cadherins and intermediate cytoskeletal filaments influence microenvironment of solid and ascitic sarcoma.

Different forms of sarcoma (solid or ascitic) often pose a critical medical situation for pediatric or adolescent group of patients. To date, predisposed genetic anomalies and related changes in protein expression are thought to be responsible for sarcoma development. However, in spite of genetic abnormality, role of tumor microenvironment is also indispensable for the evolving neoplasm. In our present study, we characterized the deferentially remodeled microenvironment in solid and ascitic tumors by sequential immunohistochemistry and flowcytometric analysis of E-cdaherin, N-cadherin, vimentin, and cytokeratin along with angiogenesis and metastasis. In addition, we considered flowcytometric apoptosis and CD133 positive cancer stem cell analysis. Comparative hemogram was also considered as a part. Our investigation revealed that both types of tumor promoted neovascularization over time with sign of local inflammation. Invasion of neighboring skeletal muscle by solid sarcoma was more frequent than its ascitic counterpart. In contrary, rapid and earlier cadherin switching (E-cadherin to N-cadherin) in ascitic sarcoma made them more aggressive than that of solid sarcoma and helped to early metastasize distant tissue like liver through the hematogenous route. Differential cadherin switching and infidelity of cytokeratin expression in Vimentin positive sarcoma also influenced the behavior of ascitic CD133+ cancer initiating cell pool with respect to CD133+ cells housed in solid sarcoma. Therefore our study concludes that differential cadherin switching program and infidelity of intermediate filaments in part, sharply discriminate the severity and metastatic potentiality of either type of sarcoma accompanying with CD133+ cellular repertoire. Besides, tumor phenotype-based dichotomous cadherin switching program could be exploited as a future drug target to manage decompensated malignant ascitic and solid sarcoma.

Endothelial OCT4 is atheroprotective by preventing metabolic and phenotypic dysfunction.

AIMS: Until recently, the pluripotency factor Octamer (ATGCAAAT)-binding transcriptional factor 4 (OCT4) was believed to be dispensable in adult somatic cells. However, our recent studies provided clear evidence that OCT4 has a critical atheroprotective role in smooth muscle cells. Here, we asked if OCT4 might play a functional role in regulating endothelial cell (EC) phenotypic modulations in atherosclerosis. METHODS AND RESULTS: Specifically, we show that EC-specific Oct4 knockout resulted in increased lipid, LGALS3+ cell accumulation, and altered plaque characteristics consistent with decreased plaque stability. A combination of single-cell RNA sequencing and EC-lineage-tracing studies revealed increased EC activation, endothelial-to-mesenchymal transitions, plaque neovascularization, and mitochondrial dysfunction in the absence of OCT4. Furthermore, we show that the adenosine triphosphate (ATP) transporter, ATP-binding cassette (ABC) transporter G2 (ABCG2), is a direct target of OCT4 in EC and establish for the first time that the OCT4/ABCG2 axis maintains EC metabolic homeostasis by regulating intracellular heme accumulation and related reactive oxygen species production, which, in turn, contributes to atherogenesis. CONCLUSIONS: These results provide the first direct evidence that OCT4 has a protective metabolic function in EC and identifies vascular OCT4 and its signalling axis as a potential target for novel therapeutics.

Calcineurin in the heart: New horizons for an old friend.

Calcineurin, also known as PP2B or PPP3, is a member of the PPP family of protein phosphatases that also includes PP1 and PP2A. Together these three phosphatases carryout the majority of dephosphorylation events in the heart. Calcineurin is distinct in that it is activated by the binding of calcium/calmodulin (Ca2+/CaM) and therefore acts as a node for integrating Ca2+ signals with changes in phosphorylation, two fundamental intracellular signaling cascades. In the heart, calcineurin is primarily thought of in the context of pathological cardiac remodeling, acting through the Nuclear Factor of Activated T-cell (NFAT) family of transcription factors. However, calcineurin activity is also essential for normal heart development and homeostasis in the adult heart. Furthermore, it is clear that NFAT-driven changes in transcription are not the only relevant processes initiated by calcineurin in the setting of pathological remodeling. There is a growing appreciation for the diversity of calcineurin substrates that can impact cardiac function as well as the diversity of mechanisms for targeting calcineurin to specific sub-cellular domains in cardiomyocytes and other cardiac cell types. Here, we will review the basics of calcineurin structure, regulation, and function in the context of cardiac biology. Particular attention will be given to: the development of improved tools to identify and validate new calcineurin substrates; recent studies identifying new calcineurin isoforms with unique properties and targeting mechanisms; and the role of calcineurin in cardiac development and regeneration.

Leukemic stromal hematopoietic microenvironment negatively regulates the normal hematopoiesis in mouse model of leukemia.

BACKGROUND AND OBJECTIVE: Leukemic microenvironment has a major role in the progression of leukemia. Leukemic cells can induce reversible changes in microenvironmental components, especially the stromal function which results in improved growth conditions for maintaining the malignant leukemic cells. This study aimed to investigate the survival advantage of leukemic cells over normal hematopoietic cells in stromal microenvironment in long term. METHODS: The mice were injected intraperitoneally with N-N' ethylnitrosourea (ENU) to induce leukemia; the mice received injection of normal saline were used as control. At 180 days after ENU induction, the mice were killed and the bone marrows were cultured for 19 days. Colony-forming assays were used to analyze the formation of various cell colonies. The expression of Sca-1, CD146, VEGFR2, CD95, pStat3, pStat5, and Bcl-xL in marrow cells were detected by flow cytometry. RESULTS: Long-term leukemic bone marrow culture showed abnormal elongated stromal fibroblasts with almost absence of normal hematopoietic cells. Adherent cell colonies were increased, but CFU-F and other hematopoietic cell colonies were significantly decreased in leukemia group (P<0.001). Primitive progenitor-specific Sca-1 receptor expression was decreased with subsequent increased expression of CD146 and VEGFR-2 in leukemic bone marrow cells. Decreased Fas antigen expression with increased intracellular pStat3, pStat5 and Bcl-xL proteins were observed in leukemic bone marrow cells. CONCLUSIONS: Stromal microenvironment shows altered morphology and decreased maturation in leukemia. Effective progenitor cells are decreased in leukemia with increased leukemia-specific cell population. Leukemic microenvironment plays a role in promoting and maintaining the leukemic cell proliferation and survivability in long term.

Single-cell characterization and metabolic profiling of in vitro cultured human skeletal progenitors with enhanced in vivo bone forming capacity.

Cell populations and their interplay provide the basis of a cell-based regenerative construct. Serum-free preconditioning can overcome the less predictable behavior of serum expanded progenitor cells, but the underlying mechanism and how this is reflected in vivo remains unknown. Herein, the cellular and molecular changes associated with a cellular phenotype shift induced by serum-free preconditioning of human periosteum-derived cells were investigated. Following BMP-2 stimulation, preconditioned cells displayed enhanced in vivo bone forming capacity, associated with an adapted cellular metabolism together with an elevated expression of BMPR2. Single-cell RNA sequencing confirmed the activation of pathways and transcriptional regulators involved in bone development and fracture healing, providing support for the augmentation of specified skeletal progenitor cell populations. The reported findings illustrate the importance of appropriate in vitro conditions for the in vivo outcome. In addition, BMPR2 represents a promising biomarker for the enrichment of skeletal progenitor cells for in vivo bone regeneration.

Aberrant Wnt Signaling Pathway in the Hematopoietic Stem/Progenitor Compartment in Experimental Leukemic Animal.

The evolutionarily conserved Wnt signaling pathway regulates physiological hematopoiesis, a process of formation of blood cells and has been shown to play crucial role in the development of both myeloid and lymphoid malignancies. The Wnt signaling pathway can be broadly divided into canonical and non-canonical pathways. In the present study, we investigated the pathobiology of leukemia by studying the expression profile of Wnt proteins, receptors, key signaling intermediates and endogenous Wnt antagonist involved in canonical and non-canonical pathways in the bone marrow (BM) hematopoietic stem/progenitor cell (HSPC) compartment of experimental leukemic mice. Cell adhesion molecule N-Cadherin and leukemic BM microenvironment with reference to Wnt were also studied. We used ENU, a potent carcinogen, to induce leukemia in wild type Swiss albino mice and malignant transformation was cofirmed by peripheral blood and BM studies. Flow cytometric expression analysis revealed profound up-regulation of canonical Wnt3a/ß-catenin/CyclinD1 signaling axis along with N-Cadherin whereas down-regulation of non-canonical Wnt5a/Ca2+/CaMKII signaling axis in the leukemic HSPC compartment. Subsequent use of anti-Wnt3a antibody in the in vitro clonogenicity assay uncovered that anti-Wnt3a antibody preferentially inhibited the growth and number of the primitive leukemic hematopoietic CFU-GEMM and BFU-E colonies. Stromal cells derived from the leukemic BM also exhibited aberrant Wnt3a and Wnt5a protein expression. Taken together, alteration of canonical and non-canonical Wnt signaling pathways in the HSPC compartment along with classical Wnt protein expression pattern in the leukemic stromal microenvironment resulted in progression of leukemia.

Healing of a Large Long-Bone Defect through Serum-Free In Vitro Priming of Human Periosteum-Derived Cells.

Clinical translation of cell-based strategies for regenerative medicine demands predictable in vivo performance where the use of sera during in vitro preparation inherently limits the efficacy and reproducibility. Here, we present a bioinspired approach by serum-free pre-conditioning of human periosteum-derived cells, followed by their assembly into microaggregates simultaneously primed with bone morphogenetic protein 2 (BMP-2). Pre-conditioning resulted in a more potent progenitor cell population, while aggregation induced osteochondrogenic differentiation, further enhanced by BMP-2 stimulation. Ectopic implantation displayed a cascade of events that closely resembled the natural endochondral process resulting in bone ossicle formation. Assessment in a critical size long-bone defect in immunodeficient mice demonstrated successful bridging of the defect within 4 weeks, with active contribution of the implanted cells. In short, the presented serum-free process represents a biomimetic strategy, resulting in a cartilage tissue intermediate that, upon implantation, robustly leads to the healing of a large long-bone defect.

Pesticide induced marrow toxicity and effects on marrow cell population and on hematopoietic stroma.

Long term inhalation of toxic pesticides used for the domestic and industrial purposes have been shown to cause moderate to severe hematotoxicity and increased incidence of several marrow degenerative diseases, specifically hypoplastic bone marrow failure condition in humans. The progression of pesticide induced hematotoxicity and the exact underlying mechanisms of toxicity that play major role in limiting normal hematopoiesis are not quite well explained. In this present study, we have developed an animal model of hypoplastic bone marrow failure following pesticide exposure to show the deleterious effects of toxic pesticides on mouse hematopoietic system. Here we have presented the results of studying long-term marrow explant culture, IL-2, IL-3 and IL-5 receptors expression profile, fibroblast colony forming unit (CFU-F), hematopoietic progenitor cell colony formation and caspase-3 expression by the bone marrow cells. We have also identified the expression levels of several extracellular apoptosis markers (CD95/Fas) and intracellular apoptosis inducer proteins (pASK1, pJNK, caspase-3 and cleaved caspase-3) in the bone marrow cells of pesticide exposed mice. The long-term marrow explant culture demonstrated the impairment in proliferation of the stromal cells/stromal fibroblasts in culture. Decreased IL-2, IL-3 and IL-5 receptors expression profile essentially hinted at the suppressed cytokine activity in the pesticide exposed marrow. CFU-F analysis showed the defect in functional maturation of the stromal fibroblasts. The decreased hematopoietic progenitor cell colony formation indicated the toxicity induced inhibition of cellular proliferation and functional maturation of hematopoietic stem/progenitor cells in pesticide exposed marrow. We have detected a sharp increase in the expression levels of both the extracellular Fas-antigen and intracellular apoptosis inducer proteins in the bone marrow cells of pesticide exposed mice that explained well, the apoptosis pathway involved following marrow toxicity. The decreased proliferation and functional maturation of marrow stromal cells and hematopoietic progenitors with subsequent increase in marrow cellular apoptosis following pesticide toxicity provided the base necessary for explaining the increased incidence of hypoplastic bone marrow failure in humans exposed to moderate to high concentrations of pesticides.

Altered canonical hedgehog-gli signalling axis in pesticide-induced bone marrow aplasia mouse model.

The mechanistic interplay between pesticide exposure and development of marrow aplasia is not yet well established but there are indices that chronic pesticide exposure in some instances causes marrow aplasia like haematopoietic degenerative condition in human beings. Canonical Hedgehog (Hh) signalling has multiple roles in a wide range of developmental processes, including haematopoiesis. The present study was designed to explore the status of four important components of the canonical Hedgehog signalling cascade, the Sonic Hedgehog (Shh), Ptch1, Smo, and Gli1, in a mouse model of chronic pesticide-induced bone marrow aplasia. We used 5 % aqueous mixture of pesticides (chlorpyriphos, prophenophos, cypermethrin, alpha-methrin, and hexaconazole) for inhalation and dermal exposure of 6 hours per day and 5 days a week up to 90 days. Murine bone marrow aplasia related to chronic pesticide treatment was confirmed primarily by haemogram, bone marrow cellularity, short term bone marrow explant culture for cellular kinetics, bone marrow smear, and fl ow cytometric Lin-Sca-1+C-kit+ extracellular receptor expression pattern. Later, components of hedgehog signalling were analysed in the bone marrow of both control and pesticide-treated aplastic groups of animals. The results depicted pancytopenic feature of peripheral blood, developmental anomaly of neutrophils, depression of primitive stem and progenitor population along with Shh, Ptch1, Smo and Gli1 expression in aplasia group. This investigation suggests that pesticide-induced downregulation of two critically important proteins--Ptch1 and Gli1--inside the haematopoietic stem and progenitor cell population impairs haematopoietic homeostasis and regeneration mechanism in vivo concurrent with bone marrow aplasia.

Effects of inorganic arsenic on bone marrow hematopoietic cells: an emphasis on apoptosis and Sca-1/c-Kit positive population.

Apoptosis, proliferation and differentiation are balanced molecular processes which may alter their pattern during environmental insults. Arsenic is an environmental pollutant, ranks 20(th) in abundance in the earth crust, 14(th) in sea water and 12(th) in the human body. Millions of people worldwide are chronically exposed to arsenic often due to naturally occurring arsenic in ground water. Hematopoietic stem cells within the bone marrow are the source of all haematopoietic cell lineages and are essential for tissue development throughout the life. In this experimental study, we have evaluated the impact of arsenic, on blood and blood forming cells by the changes in their cellular morphology, immune functional capacity, alteration of bone marrow CD34 positive stem/progenitors and changes in the phenotype of Sca-1, c-Kit dual positive primitive stem cell population. The study revealed that arsenic has a significant effect on bone marrow and hematopoietic stem cells, their immune capacity and upregulation of death process, all indicative of impairment in differentiation suggesting presence of deregulation in their precursors by arsenic toxicity.

The bone marrow stem stromal imbalance--a key feature of disease progression in case of myelodysplastic mouse model.

Myelodysplastic syndromes (MDSs) represent a spectrum of disorders that are generally thought to arise from a defective hematopoietic stem cell leading to clonal, dysregulated hematopoiesis. Although it is generally agreed that the marrow microenvironment plays a role in the biology of MDS, it is unclear whether this represents an intrinsically abnormal stromal compartment derived from the MDS clone. Hematopoiesis requires cooperation between progenitors and a variety of functionally and phenotypically different cell types that form the bone marrow stroma. Stromal abnormalities suspected to contribute to the pathology of bone marrow disorder with impaired hematopoiesis. Several studies on human MDS bone marrow microenvironment revealed functional alteration and increased cellular apoptosis thus contribute to the pathology of the disease progression. In this present study, we have investigated alterations in the hematopoietic microenvironment and underlying mechanisms involved in the disease progression of MDS animal model. We presented the results of bone marrow single cell culture study, Long-term bone marrow adherent culture study (LTBMC) and their functional efficacy, flowcytometric characterization of stem (Scal+c-kit+) and stromal (Scal+CD44+) progenitor cell population and expression level of extracellular apoptosis marker (Annexin v) in the bone marrow cells of MDS animal model. Bone marrow single cell culture study of MDS animal showed impairment in the normal cellular generation, proliferation and presence of apoptic cells. Long-term liquid Bone marrow stromal cell colony formation assay from MDS bone marrow cells showed significant difference in the colony formation and their maintenance than the control groups of animals. Immune functional capacity of the bone marrow stromal cells through cell mediated immune (CMI) parameter study denoted defects in the stromal microenvironment. Decreased expression of bone marrow long-term primitive hematopoietic population and stromal progenitor population depicted bone marrow abnormality in case of MDS animal model, which bears significant correlation with high expression level of apoptosis marker in the bone marrow cells. From the above experimental study we tried to highlight the abnormal bone marrow microenvironment and alteration in the bone marrow cell surface marker expression, which could be the probable mechanism of evolution and disease progression in case of MDS animal model.

Phenotypic alteration of bone marrow HSC and microenvironmental association in experimentally induced leukemia.

Leukemia is a heterogeneous disorder of bone marrow (BM) failure syndrome where normal hematopoiesis gets altered due to transformation of either the normal hematopoietic cell or the hematopoietic microenvironment or both. Scientists have tried for decades to understand leukemia development in the context of therapeutic strategies. The existence of "leukemic stem cells" and their possible role in leukemogenesis have only recently been identified and it has changed the perspective with regard to new approaches for treating the disease. However the relationship between leukemic stem cells (LSCs) and leukemogenesis requires further investigation. In this present study, we have experimentally induced leukemia in mice by means of N-N' Ethylnitrosourea (ENU) to investigate the alterations in normal bone marrow cellular phenotype and associated changes in the stromal hematopoietic microenvironment under the event of leukemic disease progression. We have identified a significant decrease in the normal HSC phenotype in terms of Sca1 and c-kit receptor expression and subsequent sharp increase in certain leukemic cell specific receptor expression like CD123, CXCR4 and CD44 in the leukemic bone marrow. The decreased HSC receptor (Sca1 and c-kit) expression profile with concurrent increase in the expression of leukemic cell specific receptors (CD123, CXCR4, CD44) by the bone marrow cells of leukemic mice may account for the possible transformation of the normal hematopoietic cells that is necessary for the disease initiation and progression. Some of these receptors like CXCR4 and CD44 are also known to play an important role in maintaining leukemic cells and their complex crosstalk with the surrounding stromal microenvironment. Thus up-regulation in CXCR4 and CD44 receptor expression essentially pointed towards the stroma dependent surveillance of the leukemic bone marrow cells in leukemia. Leukemic bone marrow cells documented a rapid generation of stromal feeder layer in culture. The rapid stroma generation further supported the fact that leukemic stromal microenvironment gets altered in possible ways to support leukemic cell generation and fueling leukemogenesis. The study presented here, has tried to hint at exploring new therapeutic strategies by not only identifying the expression profile of cell surface receptors unique to cells involved in leukemic progression but also targeting the specific components of the stromal microenvironment that would facilitate therapeutic management of the disease.

Primitive Sca-1 Positive Bone Marrow HSC in Mouse Model of Aplastic Anemia: A Comparative Study through Flowcytometric Analysis and Scanning Electron Microscopy.

Self-renewing Hematopoietic Stem Cells (HSCs) are responsible for reconstitution of all blood cell lineages. Sca-1 is the "stem cell antigen" marker used to identify the primitive murine HSC population, the expression of which decreases upon differentiation to other mature cell types. Sca-1(+) HSCs maintain the bone marrow stem cell pool throughout the life. Aplastic anemia is a disease considered to involve primary stem cell deficiency and is characterized by severe pancytopenia and a decline in healthy blood cell generation system. Studies conducted in our laboratory revealed that the primitive Sca-1(+) BM-HSCs (bone marrow hematopoietic stem cell) are significantly affected in experimental Aplastic animals pretreated with chemotherapeutic drugs (Busulfan and Cyclophosphamide) and there is increased Caspase-3 activity with consecutive high Annexin-V positivity leading to premature apoptosis in the bone marrow hematopoietic stem cell population in Aplastic condition. The Sca-1(bright), that is, "more primitive" BM-HSC population was more affected than the "less primitive" BM-HSC Sca-1(dim ) population. The decreased cell population and the receptor expression were directly associated with an empty and deranged marrow microenvironment, which is evident from scanning electron microscopy (SEM). The above experimental evidences hint toward the manipulation of receptor expression for the benefit of cytotherapy by primitive stem cell population in Aplastic anemia cases.