Tooth bioengineering from single cell suspensions

Recent advances in bioengineering and biomaterials, along with knowledge deriving from the fields of developmental biology and stem cell research, have rendered feasible functional replacement of full organs. Here, we describe the methodology for bioengineering a tooth, starting from embryonic epithelial and mesenchymal single cell suspensions. In addition, we describe the subsequent steps of processing this minute structure for use in applications such as histological examination, immunofluorescence and in situ hybridisation. This methodology can be used for any minute structure that needs to be used in paraffin blocks.•Detailed methodology for reproducible and reliable results•Extra step to ensure single cell populations•Subsequent minute structure processing for histological analysisPeer reviewe

Microglial subtypes: diversity within the microglial community

Microglia are brain-resident macrophages forming the first active immune barrier in the central nervous system. They fulfill multiple functions across development and adulthood and under disease conditions. Current understanding revolves around microglia acquiring distinct phenotypes upon exposure to extrinsic cues in their environment. However, emerging evidence suggests that microglia display differences in their functions that are not exclusively driven by their milieu, rather by the unique properties these cells possess. This microglial intrinsic heterogeneity has been largely overlooked, favoring the prevailing view that microglia are a single-cell type endowed with spectacular plasticity, allowing them to acquire multiple phenotypes and thereby fulfill their numerous functions in health and disease. Here, we review the evidence that microglia might form a community of cells in which each member (or "subtype") displays intrinsic properties and performs unique functions. Distinctive features and functional implications of several microglial subtypes are considered, across contexts of health and disease. Finally, we suggest that microglial subtype categorization shall be based on function and we propose ways for studying them. Hence, we advocate that plasticity (reaction states) and diversity (subtypes) should both be considered when studying the multitasking microglia.España, Ministerio de Ciencia, Innovación y Universidades FEDER y UE RTI2018-098645-B-10

MANF silencing, immunity induction or autophagy trigger an unusual cell type in metamorphosing Drosophila brain

Glia are abundant cells in the brain of animals ranging from flies to humans. They perform conserved functions not only in neural development and wiring, but also in brain homeostasis. Here we show that by manipulating gene expression in glia, a previously unidentified cell type appears in the Drosophila brain during metamorphosis. More specifically, this cell type appears in three contexts: (1) after the induction of either immunity, or (2) autophagy, or (3) by silencing of neurotrophic factor DmMANF in glial cells. We call these cells MANF immunoreactive Cells (MiCs). MiCs are migratory based on their shape, appearance in brain areas where no cell bodies exist and the nuclear localization of dSTAT. They are labeled with a unique set of molecular markers including the conserved neurotrophic factor DmMANF and the transcription factor Zfh1. They possess the nuclearly localized protein Relish, which is the hallmark of immune response activation. They also express the conserved engulfment receptor Draper, therefore indicating that they are potentially phagocytic. Surprisingly, they do not express any of the common glial and neuronal markers. In addition, ultrastructural studies show that MiCs are extremely rich in lysosomes. Our findings reveal critical molecular and functional components of an unusual cell type in the Drosophila brain. We suggest that MiCs resemble macrophages/hemocytes and vertebrate microglia based on their appearance in the brain upon genetically challenged conditions and the expression of molecular markers. Interestingly, macrophages/hemocytes or microglia-like cells have not been reported in the fly nervous system before.Peer reviewe

Studies on the neurotrophic factor Manf and the pleiotropic factor Lin-28 during Drosophila development

Developmental biology studies how a single cell will give rise to a fully developed, highly ordered and reproducible living organism. In order for this to occur, the fertilized egg needs to grow, divide and differentiate to produce different cell types. Subsequently, these different cell types need to organize into predefined arrays of committed cell groups to produce specialized tissues and organs, which constitute the living multicellular organism. Although the final product seems enormously complex, the multicellular organism is composed of cells that they all have the same set of genes. Cells differentiate by switching on and off the expression of different molecules and they produce and respond to signals which result in cells growing, dividing and dying in a strict spatiotemporal manner. In this work I aimed to address questions on the molecular mechanisms during development by using the fruit fly Drosophila melanogaster as a model system. The first aim of my studies was to characterize and investigate the role of Manf during Drosophila pupation and adulthood. MANF is an evolutionarily conserved neurotrophic factor, which has previously been reported to protect and restore dopaminergic neurons in mammals. In Drosophila embryos DmMANF has been shown to be specifically expressed in glial populations, while DmMANF null mutants die early during development while they exhibit specific and significant reduction of dopaminergic neurites. Our data reveal that in pupae and adults, DmMANF has a much wider expression pattern and it is localized both in glia and neurons. This analysis led to the identification of an unusual phenotype in the Drosophila pupal brain. We showed when Manf is silenced, or either autophagy or immunity is induced in glia, macrophage-like cells appear in areas of the pupal brain that are normally devoid of cell bodies. We identified molecular markers and pathways that are activated in these cells, as well as some of the unique subcellular features they possess. This study brings new and elegant data in several aspects of glial biology with exciting perspectives for studying brain plasticity and repair. The second project was to characterize the expression of Gfrl receptor, the Drosophila homolog of the mammalian GFRα receptor in the Drosophila adult brain. The results showed that although the Gfrl receptor is widely expressed in the fly adult brain, this expression is in surprising contrast to the missing expression of dRet, the Drosophila Ret homolog. This data provide novel insights into further elucidation of the Ret-dependent and Ret-independent -GFRα signaling complexes, as well as to further understand the several aspects of invertebrate brain development and function. The third aim of this study was to investigate the role of the conserved pleiotropic factor Lin28 during Drosophila development. Previous studies have shown that Lin28 is one of the factors sufficient to reprogram human somatic cells into induced pluripotent stem cells. By constructing Lin-28 null mutants, our data reveal that Lin-28 mutant files were viable but sub-fertile, exhibiting oogenesis defects. These results will help us improve our understanding of Lin28 role in stem cell maintenance and differentiation.Kehitysbiologia selittää miten yhdestä solusta voi muodostua kehittynyt ja kompleksinen lisääntymiskykyinen yksilö. Hedelmöittynyt munasolu kasvaa, jakautuu ja erilaistuu organismin eri solutyypeiksi. Solujen tulee järjestäytyä tarkkaan määritellyn suunnitelman mukaan tuottaakseen organismin kudokset, elimet ja siten koko yksilön. Vaikka kehittynyt organismi on hyvin kompleksinen kokonaisuus, jokainen sen soluista sisältää saman geneettisen materiaalin. Solut erilaistuvat hyvinkin erilaisiin tehtäviin geenien ilmentymisen kautta joka on tarkkaan säädelty. Tämän työn tavoitteena oli tutkia molekylaarisia mekanismeja yksilönkehityksen aikana käyttämällä banaanikärpästä (Drosophila) malliorganismina. Työn tavoitteena oli karakterisoida ja tutkia MANF hermokasvutekijän roolia Drosophilan myöhäiskehityksessä. Tuloksemme osoittivat, että MANF proteiini ilmentyy laajasti aikuisen Drosophilan aivoissa. Tutkimuksissa löysimme aivoista uuden makrofaagi-tyyppisen solun joiden solunsisäisiä prosesseja kuvataan väitöskirjassa kattavasti. Nämä solut ilmentävät MANF proteiinia ja ne esiintyvät vain tietyissä olosuhteissa ja sellaisessa osassa kärpäsen aivoa jossa ei yleensä havaita soluja. Tuloksemme täydentävät nykyistä ymmärrystä hermotukisoluista ja mahdollisuutta tutkia aivojen muovautuvuutta. Toisessa osajulkaisussa tutkimme Gfrl reseptorin ilmentymistä Drosophilan aivoissa ja osoitimme, että toisin kuin nisäkkäissä, aikuisen Drosophilan aivoissa Gfrl ilmentyy ilman dRet ilmentymistä. Tutkimme myös evoluutiossa konservoituneen pleiotrooppisen Lin-28 tekijän roolia Drosophilan kehityksessä. Lin-28 on osoitettu olevan yksi niistä tekijöistä jonka avulla erilaistuneita soluja voidaan uudelleen ohjelmoida. Osoitimme, että ilman Lin-28 ilmentymistä Drosophila on elinkykyinen, mutta sen munarauhasen kehitys on viallinen joka johtaa hedelmällisyyden alentumiseen. Tuloksemme täydentävät ymmärrystä Lin-28:n roolista kantasolujen ylläpidosta ja niiden erilaistumisesta

Unilateral zebrafish corneal injury induces bilateral cell plasticity supporting wound closure

The cornea, transparent and outermost structure of camera-type eyes, is prone to environmental challenges, but has remarkable wound healing capabilities which enables to preserve vision. The manner in which cell plasticity impacts wound healing remains to be determined. In this study, we report rapid wound closure after zebrafish corneal epithelium abrasion. Furthermore, by investigating the cellular and molecular events taking place during corneal epithelial closure, we show the induction of a bilateral response to a unilateral wound. Our transcriptomic results, together with our TGF-beta receptor inhibition experiments, demonstrate conclusively the crucial role of TGF-beta signaling in corneal wound healing. Finally, our results on Pax6 expression and bilateral wound healing, demonstrate the decisive impact of epithelial cell plasticity on the pace of healing. Altogether, our study describes terminally differentiated cell competencies in the healing of an injured cornea. These findings will enhance the translation of research on cell plasticity to organ regeneration.Peer reviewe

The Rules of Engagement : Do Microglia Seal the Fate in the Inverse Relation of Glioma and Alzheimer's Disease?

Microglia, the immune cells of the brain, play a major role in the maintenance of brain homeostasis and constantly screen the brain environment to detect any infection or damage. Once activated by a stimulus, microglial cells initiate an immune response followed by the resolution of brain inflammation. A failure or deviation in the housekeeping function of these guardian cells can lead to multiple diseases, including brain cancer and neurodegenerative diseases such as Alzheimer's disease (AD). A small number of studies have investigated the causal relation of both diseases, thereby revealing an inverse relationship where cancer patients have a reduced risk to develop AD and vice versa. In this review, we aim to shed light on the role of microglia in the fate to develop specifically glioma as one type of cancer or AD. We will examine the common and/or opposing genetic predisposition as well as associated pathways of these diseases to unravel a possible involvement of microglia in the occurrence of either disease. Lastly, a set of guidelines will be proposed for future research and diagnostics to clarify and improve the knowledge on the role of microglia in the decision toward one pathology or another.Peer reviewe