Victor Túlio Ribeiro-Resende

The mammalian retinal progenitor cells (RPC) exit the cell cycle through signaling of intrinsic and extrinsic factors and give rise to several types of neurons and Müller glia, following an organized spatial–temporal pattern. Extracellular matrix (ECM) plays an important role in retinal development, influencing RPC proliferation and differentiation into pro-gliogenic and/or neurogenic phenotypes. Here, we investigated how four different ECM constituents, fibronectin, vitronectin, collagen type IV and laminin-1 (α1β1γ1), added on coverslips previously treated with 10 µg/mL poly-L-lysine, could impact differentiation of retinal neurospheres generated with epidermal growth factor (EGF) 20 ng/mL and cultivated for four days. Progenitors (activated by muscimol, a GABA_A agonist), neurons (by KCl and/or AMPA, a glutamatergic agonist) and Müller glia (by ATP) show distinct functional responses in terms of calcium imaging due to the pattern of selective receptors and channels expressed during development. A highly heterogeneous cell population was generated when neurospheres were cultivated in different ECM molecules, suggesting the presence of high, medium, and low-responsive cells. As shown, collagen type IV or laminin-1 for 6 days in DMEM F12 had similar responses, revealing that nearly 55% of cells were responsive to KCl, 28–39% to AMPA, 18–28% to ATP and almost none to muscimol (less than 0.5%). On the other hand, in the presence of fibronectin, 56% of retinal neurospheres were induced to respond to KCl, 32% to AMPA, 33% to ATP and 2.8% to muscimol. Finally, neurospheres raised in vitronectin had around 67% of cells responsive to KCl, 41% to AMPA, less than 20% to ATP and 3% to muscimol. As expected, differentiated cells in the presence of fibronectin were immuno-labelled and expressed higher levels of glial fibrillary acidic protein (GFAP), compared to other substrates, while cultures prepared in the presence of vitronectin had increased expression of neuron-specific class III β-tubulin (TUJ-1), a neuronal marker. Altogether, our data suggest that, compared to laminin, a standard substrate, collagen and vitronectin increased the number of functional neurons, while fibronectin induced a two-fold increase in the number of glial cells in the developing cells of the mice retina.

The retina is the sensory tissue responsible for the first stages of visual processing, with a conserved anatomy and functional architecture among vertebrates. To date, retinal eye diseases, such as diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, glaucoma, and others, affect nearly 170 million people worldwide, resulting in vision loss and blindness. To tackle retinal disorders, the developing retina has been explored as a versatile model to study intercellular signaling, as it presents a broad neurochemical repertoire that has been approached in the last decades in terms of signaling and diseases. Retina, dissociated and arranged as typical cultures, as mixed or neuron- and glia-enriched, and/or organized as neurospheres and/or as organoids, are valuable to understand both neuronal and glial compartments, which have contributed to revealing roles and mechanisms between transmitter systems as well as antioxidants, trophic factors, and extracellular matrix proteins. Overall, contributions in understanding neurogenesis, tissue development, differentiation, connectivity, plasticity, and cell death are widely described. A complete access to the genome of several vertebrates, as well as the recent transcriptome at the single cell level at different stages of development, also anticipates future advances in providing cues to target blinding diseases or retinal dysfunctions.

The retina is the sensory tissue responsible for the first stages of visual processing, with a conserved anatomy and functional architecture among vertebrates. To date, retinal eye diseases, such as diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, glaucoma and others, affect nearly 170 million people worldwide, resulting in vision loss and blindness. To tackle retinal disorders, the developing retina has been explored as a versatile model to study intercellular signaling, as it presents a broad neurochemical repertoire. Retina, dissociated and arranged as typical cultures, as mixed or neuron- and glia-enriched, and/or organized as neurospheres or as organoids are valuable to understand both neuronal and glial compartments which have contributed to reveal roles and mechanisms of transmitter systems as well as antioxidants, trophic factors, and extracellular matrix proteins. Overall, contributions in understanding neurogenesis, tissue development, differentiation, connectivity, plasticity, and cell death are widely described. A complete access to the genome of several vertebrates, as well the recent transcriptome at the single cell level at different stages of development also anticipates future advances in providing cues to target blinding diseases or retinal dysfunctions.

The vascular and the nervous systems share similarities in addition to their complex role in providing oxygen and nutrients to all cells. Both are highly branched networks that frequently grow close to one another during development. Vascular patterning and neural wiring share families of guidance cues and receptors. Most recently, this relationship has been investigated in terms of peripheral nervous system (PNS) regeneration, where nerves and blood vessels often run in parallel so endothelial cells guide the formation of the Büngner bands which support axonal regeneration. Here, we characterized the vascular response in regenerative models of the central and peripheral nervous system. After sciatic nerve crush, followed by axon regeneration, there was a significant increase in the blood vessel density 7 days after injury. In addition, the optic nerve crush model was used to evaluate intrinsic regenerative potential activated with a combined treatment that stimulated retinal ganglion cells (RGCs) regrowth. We observed that a 2-fold change in the total number of blood vessels occurred 7 days after optic nerve crush compared to the uncrushed nerve. The difference increased up to a 2.7-fold change 2 weeks after the crush. Interestingly, we did not observe differences in the total number of blood vessels 2 weeks after crush, compared to animals that had received combined treatment for regeneration and controls. Therefore, the vascular characterization showed that the increase in vascular density was not related to the efficiency of both peripheral and central axonal regeneration.

Neocortex development comprises of a complex series of time‐ and space‐specific processes to generate the typical interconnected six‐layered architecture of adult mammals. Axon growth is required for the proper establishment of cortical circuits. Malformations in axonal growth and pathfinding might lead to severe neuropathologies, such as corpus callosum dysgenesis. Cenpj, a microcephaly gene, encodes a scaffold protein that regulates centrosome biogenesis and microtubule stabilization. During corticogenesis, Cenpj regulates progenitor division and neuronal migration. Since microtubule stabilization is crucial for axon extension, we investigated the role of Cenpj in axon growth during cortical development in a mouse model. Through loss‐ and gain‐of‐function assays ex vivo and in utero, we quantified callosal axonal length, branching, and growth cone size compared to controls. We observed that silencing Cenpj results in an increased axonal length. Ex vivo, we assessed the number of branches, the area of growth cones and the stability of microtubules. In silenced Cenpj axons, there were more branches, larger growth cone area, and more stable microtubules. Rescue experiments confirmed that neurons present axonal length comparable to controls. Here we propose that Cenpj regulates axon growth by destabilizing microtubules during cortical development. Finally, our findings suggest that Cenpj might be a novel target for axonal regeneration. image

Like the seasons of the year, all natural things happen in stages, going through adaptations when challenged, and Schwann cells are a great example of that. During maturation, these cells regulate several steps in peripheral nervous system development. The Spring of the cell means the rise and bloom through organized stages defined by time-dependent regulation of factors and microenvironmental influences. Once matured, the Summer of the cell begins: a high energy stage focused on maintaining adult homeostasis. The Schwann cell provides many neuron-glia communications resulting in the maintenance of synapses. In the peripheral nervous system, Schwann cells are pivotal after injuries, balancing degeneration and regeneration, similarly to when Autumn comes. Their ability to acquire a repair phenotype brings the potential to reconnect axons to targets and regain function. Finally, Schwann cells age, not only by growing old, but also by imposed environmental cues, like loss of function induced by pathologies. The Winter of the cell presents as reduced activity, especially regarding their role in repair; this reflects on the regenerative potential of older/less healthy individuals. This review gathers essential information about Schwann cells in different stages, summarizing important participation of this intriguing cell in many functions throughout its lifetime.