Simulations demonstrate a simple network to be sufficient to control branch point selection, smooth muscle and vasculature formation during lung branching morphogenesis

Proper lung functioning requires not only a correct structure of the conducting airway tree, but also the simultaneous development of smooth muscles and vasculature. Lung branching morphogenesis is strongly stereotyped and involves the recursive use of only three modes of branching. We have previously shown that the experimentally described interactions between Fibroblast growth factor (FGF)10, Sonic hedgehog (SHH) and Patched (Ptc) can give rise to a Turing mechanism that not only reproduces the experimentally observed wildtype branching pattern but also, in part counterintuitive, patterns in mutant mice. Here we show that, even though many proteins affect smooth muscle formation and the expression of Vegfa, an inducer of blood vessel formation, it is sufficient to add FGF9 to the FGF10/SHH/Ptc module to successfully predict simultaneously the emergence of smooth muscles in the clefts between growing lung buds, and Vegfa expression in the distal sub-epithelial mesenchyme. Our model reproduces the phenotype of both wildtype and relevant mutant mice, as well as the results of most culture conditions described in the literature.Comment: Initially published at Biology Ope

A mammalian Wnt5a-Ror2-Vangl2 axis controls the cytoskeleton and confers cellular properties required for alveologenesis.

Alveolar formation increases the surface area for gas-exchange and is key to the physiological function of the lung. Alveolar epithelial cells, myofibroblasts and endothelial cells undergo coordinated morphogenesis to generate epithelial folds (secondary septa) to form alveoli. A mechanistic understanding of alveologenesis remains incomplete. We found that the planar cell polarity (PCP) pathway is required in alveolar epithelial cells and myofibroblasts for alveologenesis in mammals. Our studies uncovered a Wnt5a-Ror2-Vangl2 cascade that endows cellular properties and novel mechanisms of alveologenesis. This includes PDGF secretion from alveolar type I and type II cells, cell shape changes of type I cells and migration of myofibroblasts. All these cellular properties are conferred by changes in the cytoskeleton and represent a new facet of PCP function. These results extend our current model of PCP signaling from polarizing a field of epithelial cells to conferring new properties at subcellular levels to regulate collective cell behavior

Three dimensional oral mucosa models: development and applications

Animal experimentation has been extensively and for a long time applied in several research fields, but since 2011 it has been substantially limited by the Commission of the European Parliament to ensure people/animals safety and reduce research costs. To respond to these directives, many attempts have been focused on the development and validation of new in vitro 3D systems, bypassing the traditional 2D cell cultures. In this regard, diverse approaches to tissue-engineered bone and oral mucosa have been developed. Despite the promising premises and the cutting-edge results, the used 3D in vitro bone-oral mucosal models still lack interaction between the mucosal and the bone components. Therefore, this project aimed to create 3D models, entirely made with primary human cells (keratinocytes, fibroblasts, and osteoblasts), able to mimic the natural structure and interaction of bone and oral mucosa. In the present work, the regulatory role of the mesenchymal tissue onto epithelia was evaluated. The main results showed that that during the differentiation hMSC produce and secrete factors that induce the keratinization and the expression of the marker of differentiation CK10; in particular in the middle stage of differentiation (OB14). The proteomic analysis revealed that this effect can be ascribable to KGF secretion. This finding may impact the design of new implantable devices able to induce, alone, the epithelial growth and keratinization to improve implant graft avoiding epithelial graft linked to the morbidity of another zone. Moreover, we also showed that OM might have a pro-innervation effect, at least during the last stages of keratinocytes stratification. Finally, we obtained and characterized an innervated mucoperiosteal model that could open new in vitro frontiers for oral biomaterials validation as well as improve knowledge regarding the mesenchymal stem cells roles onto oral mucosa development

Development, Evolution, and Teeth: How We Came to Explain The Morphological Evolution of the Mammalian Dentition

abstract: This dissertation begins to lay out a small slice of the history of morphological research, and how it has changed, from the late 19th through the close of the 20th century. Investigators using different methods, addressing different questions, holding different assumptions, and coming from different research fields have pursued morphological research programs, i.e. research programs that explore the process of changing form. Subsequently, the way in which investigators have pursued and understood morphology has witnessed significant changes from the 19th century to modern day research. In order to trace this shifting history of morphology, I have selected a particular organ, teeth, and traced a tendril of research on the dentition beginning in the late 19th century and ending at the year 2000. But even focusing on teeth would be impossible; the scope of research on this organ is far too vast. Instead, I narrow this dissertation to investigation of research on a particular problem: explaining mammalian tooth morphology. How researchers have investigated mammalian tooth morphology and what counts as an explanation changed dramatically during this period.Dissertation/ThesisDoctoral Dissertation Biology 201

Chitin-based Materials in Tissue Engineering: Applications in Soft Tissue and Epithelial Organ

Chitin-based materials and their derivatives are receiving increased attention in tissue engineering because of their unique and appealing biological properties. In this review, we summarize the biomedical potential of chitin-based materials, specifically focusing on chitosan, in tissue engineering approaches for epithelial and soft tissues. Both types of tissues play an important role in supporting anatomical structures and physiological functions. Because of the attractive features of chitin-based materials, many characteristics beneficial to tissue regeneration including the preservation of cellular phenotype, binding and enhancement of bioactive factors, control of gene expression, and synthesis and deposition of tissue-specific extracellular matrix are well-regulated by chitin-based scaffolds. These scaffolds can be used in repairing body surface linings, reconstructing tissue structures, regenerating connective tissue, and supporting nerve and vascular growth and connection. The novel use of these scaffolds in promoting the regeneration of various tissues originating from the epithelium and soft tissue demonstrates that these chitin-based materials have versatile properties and functionality and serve as promising substrates for a great number of future applications

Recent strategies for tooth regeneration: a narrative review

Complete dental regeneration through tissue engineering could be the treatment of the future, as an alternative to the current prosthetic ways of replacing a missing tooth, thus avoiding the disadvantages of the latter. For such an emergence of tissue engineering, a perfect knowledge of the embryological mechanisms of dental development is required, as well as the stem cells involved. This narrative review will describe the current state of knowledge regarding tooth regeneration, focusing on the scientific advances made in this field and the tools used. However, there are limitations that will be described and analyzed in order to understand the challenges that must be overcome in this field before achieving the full functional outcome and large-scale clinical application of tissue-engineered dental regeneration in humans.A regeneração dentária completa através da engenharia de tecidos poderia ser o tratamento do futuro, como alternativa aos atuais meios protéticos de substituição de um dente em falta, evitando assim as desvantagens deste último. Para uma tal emergência de engenharia de tecidos, é necessário um conhecimento perfeito dos mecanismos embriológicos do desenvolvimento dentário, bem como das células estaminais envolvidas. Esta narrativa descreverá o estado atual dos conhecimentos relativos à regeneração dentária completa, focando-se nos avanços científicos feitos neste campo e nas ferramentas utilizadas. No entanto, existem limitações que serão descritas e discutidas a fim de compreender os desafios que devem ser ultrapassados neste campo antes de ser possível alcançar o resultado funcional completo e a aplicação clínica em larga escala da regeneração dentária tecidual em humanos

The Notch-mediated circuitry in the evolution and generation of new cell lineages: the tooth model

The Notch pathway is an ancient, evolutionary conserved intercellular signaling mechanism that is involved in cell fate specification and proper embryonic development. The Jagged2 gene, which encodes a ligand for the Notch family of receptors, is expressed from the earliest stages of odontogenesis in epithelial cells that will later generate the enamel-producing ameloblasts. Homozygous Jagged2 mutant mice exhibit abnormal tooth morphology and impaired enamel deposition. Enamel composition and structure in mammals are tightly linked to the enamel organ that represents an evolutionary unit formed by distinct dental epithelial cell types. The physical cooperativity between Notch ligands and receptors suggests that Jagged2 deletion could alter the expression profile of Notch receptors, thus modifying the whole Notch signaling cascade in cells within the enamel organ. Indeed, both Notch1 and Notch2 expression are severely disturbed in the enamel organ of Jagged2 mutant teeth. It appears that the deregulation of the Notch signaling cascade reverts the evolutionary path generating dental structures more reminiscent of the enameloid of fishes rather than of mammalian enamel. Loss of interactions between Notch and Jagged proteins may initiate the suppression of complementary dental epithelial cell fates acquired during evolution. We propose that the increased number of Notch homologues in metazoa enabled incipient sister cell types to form and maintain distinctive cell fates within organs and tissues along evolution