Aging within the Stem Cell niche

Decreased adult stem cell function is thought to play a primary role in organismal aging. Two recent papers in Cell Stem Cell demonstrate the importance of signaling from the stem cell niche in the aging of Drosophila germline stem cells.     

A web of imprinting in stem cells

Imprinted genes are the prototypical epigenetically regulated genes. On the basis of findings in adult lung stem cells, Zacharek et?al. (2011) suggest in this issue of Cell Stem Cell that epigenetic silencing of imprinted genes is a common requirement for maintaining self-renewal in adult stem cell populations.     

Adult neurogenesis: VCAM stems the tide

In this issue of Cell Stem Cell, Kokovay et?al. uncover that VCAM1 expression in neural stem cells regulates adult neurogenesis. Cerebrospinal fluid-borne IL-1β upregulates VCAM1 expression, which in turn regulates the architecture of the stem cell niche, redox homeostasis, and neurogenesis.     

Committing to a hairy fate: epigenetic regulation of hair follicle stem cells

Chromatin modifications are important for embryonic stem cell (ESC) pluripotency, but their functions in adult stem cells are less clear. In this issue of Cell Stem Cell, Lien et?al. (2011) delineate histone methylation patterns in hair follicle stem cells and show that these marks differ from those of ESCs.     

Rearing of ectoparasitoid Diapetimorpha introita on an artificial diet: supplementation with insect cell line-derived factors

We investigated the use of two insect cell lines to improve an artificial diet (DI) for the pupal ectoparasitoid Diapetimorpha introita. DI was supplemented with Grace's culture medium conditioned with IPL-LdFB, a cell line derived from fat body of the gypsy moth, Lymantria dispar (FBCell diet), and with Grace's medium conditioned with Sf9, a cell line derived from ovaries of the fall armyworm, Spodoptera frugiperda (Sf9Cell diet). The diets were also chemically analyzed for nutrients and any deficiencies were filled by the addition of nutrients. One-half ml aliquots of each diet were encapsulated in paraffin domes and newly hatched larvae of D. introita were placed on each diet (one larva/dome) and allowed to develop to the adult stage. Providing fresh diet on day four when the larvae were in the third instar did not improve parasitoid production. Compared with DI, only Sf9Cell had a positive effect on the parasitoid's growth, increasing the size of male parasitoids. The parasitoids, however, took longer to develop to the adult stage than those reared on the natural host. Neither cell line significantly enhanced the average weight of female parasitoids, shortened developmental time, nor increased % cocoons produced and % adult emergence. Providing additional nutrients (amino acids, vitamins, cations and anions, fatty acids and milk/egg protein) to both diets (based on chemical analyses of the cell line-supplemented diets) enhanced the average weight of the females on Sf9Cell and males and females on FBCell. The nutritional additions, however, did not improve the developmental time, pupation and adult emergence.     

Self-renewal in the fly kidney

Tissue stem cells are typically rare and located in niches that prescribe low rates of cell division and survival. In the latest issue of Cell Stem Cell, Singh et al. (2007) demonstrate that, in the adult fly, epithelial cells exist that are neither in niches nor in small numbers, divide at high rates, and are multipotent.     

Insulin induces changes in the subcellular distribution of actin and 5′-nucleotidase

The present study utilized a cultured adult myocardial cell model to examine the arachidonic acid metabolism under different cell-damaging and normoxic conditions. Cell injury was caused by short-time hypoxia, calcium ionophore A 23187-triggered cell-damage under hypoxia and cell disruption by freezing and thawing. The current study demonstrates that under the cell-damaging conditions cultured adult heart myocytes resemble myocardial cells under normoxic conditions in metabolizing arachidonic acid into triacylglycerols and phospholipids as the major route (a), in formation of ETYA-inhibitable indomethacin-resistant lipid metabolites in minor amounts (b) and in being independent of calcium overload in the metabolic pathways of arachidonic acid metabolism (c). The ETYA-inhibitable components were resolved by HPLC. There was no evidence in formation of lipoxygenase products. The results were supported by negative hybridisation experiments of the total mRNA isolated from adult myocardial cells with a cDNA probe of a red-cell-specific lipoxygenase mRNA. We conclude from these observations that cell injury does not result in expression of lipoxygenase activities in heart myocytes.Abbreviations HETE Hydroxyeicosatetraenoic acid - DiHETE Dihydroxyeicosatetraenoic acid - ETYA 5.8.11.14-Eicosatetraynoic acid - TLC Thin-Layer Chromatography - NP-HPLC Normal Phase-High Performance Liquid Chromatography - RBC Red Blood Cell - LOX Lipoxygenase     

TRIM32-dependent transcription in adult neural progenitor cells regulates neuronal differentiation

In the adult mammalian brain, neural stem cells in the subventricular zone continuously generate new neurons for the olfactory bulb. Cell fate commitment in these adult neural stem cells is regulated by cell fate-determining proteins. Here, we show that the cell fate-determinant TRIM32 is upregulated during differentiation of adult neural stem cells into olfactory bulb neurons. We further demonstrate that TRIM32 is necessary for the correct induction of neuronal differentiation in these cells. In the absence of TRIM32, neuroblasts differentiate slower and show gene expression profiles that are characteristic of immature cells. Interestingly, TRIM32 deficiency induces more neural progenitor cell proliferation and less cell death. Both effects accumulate in an overproduction of adult-generated olfactory bulb neurons of TRIM32 knockout mice. These results highlight the function of the cell fate-determinant TRIM32 for a balanced activity of the adult neurogenesis process.     

Body-specific proliferation of adult precursor cells in Xenopus larval epidermis

Cell proliferation was examined in the back and tail epidermis of larval Xenopus laevis using bromodeoxyuridine (BrdU). The BrdU labeling index of the back epidermis increased temporally at stage 59, followed by a rapid decrease to the same level as at stage 51. The temporal increase in cell proliferation of the back epidermis produced a new epidermal layer composed of basal cells. In vitro analysis showed that tri-iodothyronine (T₃) promotes cell proliferation of basal cells but suppresses that of skein cells. Immunohistochemical studies showed that the newly formed basal cell layer functions as adult precursor cells which produce the adult epidermal cells. In contrast to the back epidermis, the labeling index of the tail epidermis decreased from stage 57. However, when the tail skin was transplanted to the back area, cell proliferation in the tail epidermis increased to the same level as that of the normal back epidermis. Cell proliferation of the back epidermis was not suppressed by transplanting the skin to the tail area. These results suggest that some promoting factors are produced in the body region and regulate the number of adult precursor cells, which determine the developmental fate of the larval skin.     

Human and rat adult Schwann cell cultures: fast and efficient enrichment and highly effective non-viral transfection protocol

We present a fast protocol that can be used to obtain highly purified cultures of proliferating adult human and rat Schwann cells accessible for non-viral transfection methods. The use of enriched genetically modified adult Schwann cells is of interest in the context of autologous cell transplantation within nerve transplants for peripheral nerve repair. Cell preparation from pre-degenerated adult peripheral nerves is described, together with the use of melanocyte growth medium plus forskolin, fibroblast growth factor-2 (FGF-2), pituitary extract and heregulin as a selective, serum-free culture medium and a subsequent cell enrichment step (cold jet). Proliferating adult Schwann cells can be efficiently genetically modified using optimized, non-viral electroporation protocols. The protocol results in Schwann cell cultures that are more than 90-95% pure, and transfection efficiencies vary depending on the initial cell constitution from 20 to 40%. The procedure takes up to 21 d, depending on the length of the pre-degeneration period.     

Transdifferentiation: why and how?

Cell therapy is based on the replacement of damaged cells in order to restore injured tissues. The first consideration is that an abundant source of cells is needed; second, these cells should be immunologically compatible with the guest and third, there should be no real threat of these cells undergoing malignant transformation in the future. Given these requirements, already differentiated adult cells or adult stem cells obtained from the body of the patient appear to be the ideal candidates to meet all of these demands. The utilization of somatic cells also avoids numerous ethical and political drawbacks and concerns. Transdifferentiation is the phenomenon by which an adult differentiated cell switches to another differentiated cell. This paper reviews the importance of transdifferentiation, discussing the cells that are suitable for this process and the methods currently employed to induce the change in cell type.     

Development and partial characterization of heliothine cell lines from embryonic and differentiated tissues

The goal of this study was to generate cell lines from a variety of insect tissues that could be useful for developing in vitro assays with tissue-specific properties. In this article, we describe the establishment of new cell cultures from differentiated (primarily neural) and undifferentiated tissues (primarily embryonic) and their initial characterization. Cell lines were established from the following tissues of the budworm, Heliothis virescens, and the bollworm, Helicoverpa zea: larval ventral nerve cords (4 lines), larval midguts (1 line), adult ovaries (1 line), and embryonic tissues (11 lines). Cell lines were primarily characterized by morphological examination and polymerase chain reaction (PCR) (both deoxyribonucleic acid amplification fingerprinting and inter-simple sequence repeats PCR).     

The Capacity of Testicular Cells of the Postnatal Rat to Reorganize into Histotypic Structures

Cell reorganization experiments in vitro were performed with dissociated rat testes at different ages of postnatal development namely, newborn, 8–10, 18–25, 35–40, and 90 days. Only newborn and juvenile rat testicular cells reassociated into testicular-like organization in rotation culture. Puberal and adult rat testicular cells show morphogenetic organization when they were deprived of germ cells by busulphan pretreatment. A factor present in testicular tissue of puberal and adult rats inhibits reorganization. The inhibitor is confined to the spermatic cell fraction in the testis.     

Hematopoietic progenitors express embryonic stem cell and germ layer genes

Cell therapy for tissue regeneration requires cells with high self-renewal potential and with the capacity to differentiate into multiple differentiated cell lineages, like embryonic stem cells (ESCs) and adult somatic cells induced to pluripotency (iPSCs) by genetic manipulation. Here we report that normal adult mammalian bone marrow contains cells, with the cell surface antigen CD34, that naturally express genes characteristic of ESCs and required to generate iPSCs. In addition, these CD34+ cells spontaneously express, without genetic manipulation, genes characteristic of the three embryonic germ layers: ectoderm, mesoderm and endoderm. In addition to the neural lineage genes we previously reported in these CD34+ cells, we found that they express genes of the mesodermal cardiac muscle lineage and of the endodermal pancreatic lineage as well as intestinal lineage genes. Thus, these normal cells in the adult spontaneously exhibit characteristics of embryonic-like stem cells.     

Effects of Puromycin on the Differentiation of the Freshwater Sponge: Ephydatia fluviatilis

Cell reorganization experiments performed with newborn rat gonadal single cell suspensions resulted in organ-like reorganization after 18 h of rotation culture. When, however, testicular cells were incubated in supernatants of newborn rat ovarian cells, testicular organization was suppressed and the architecture of the reorganized gonad was rather feminine. Supernatants of adult rat ovarian cells did not inhibit testicular organization. The possible mechanisms responsible for the failure of the function of H-Y antigen by the presence of ovarian cell supernatants of newborn rats are discussed.     

Glia-like stem cells sustain physiologic neurogenesis in the adult mammalian carotid body

Neurogenesis is known to occur in the specific niches of the adult mammalian brain, but whether germinal centers exist in the neural-crest-derived peripheral nervous system is unknown. We have discovered stem cells in the adult carotid body (CB), an oxygen-sensing organ of the sympathoadrenal lineage that grows in chronic hypoxemia. Production of new neuron-like CB glomus cells depends on a population of stem cells, which form multipotent and self-renewing colonies in vitro. Cell fate mapping experiments indicate that, unexpectedly, CB stem cells are the glia-like sustentacular cells and can be identified using glial markers. Remarkably, stem cell-derived glomus cells have the same complex chemosensory properties as mature in situ glomus cells. They are highly dopaminergic and produce glial cell line-derived neurotrophic factor. Thus, the mammalian CB is a neurogenic center with a recognizable physiological function in adult life. CB stem cells could be potentially useful for antiparkinsonian cell therapy.     

The genetics of cell death: approaches, insights and opportunities in Drosophila

Cell death is ubiquitous in metazoans and involves the action of an evolutionarily conserved process known as programmed cell death or apoptosis. In Drosophila melanogaster, it is now uniquely possible to screen for genes that determine the fate - life or death - of any cell or population of cells during development and in the adult. This review describes these genetic approaches and the key insights into cell-death mechanisms that have been obtained, as well as the outstanding questions that these techniques can help to answer.     

Stem cell grand SLAM

Stem cells in both embryonic and adult tissues are defined by their unique ability to balance self-renewal and differentiation such that mature cells necessary for tissue function can be generated and replaced without depletion of the stem cell pool. In this issue of Cell, report a major step forward for studying the mechanisms and regulation of such stem cell fate decisions in the blood-forming (hematopoietic) system by providing a simple and broadly applicable method to isolate these cells and to visualize them in their normal environment.