Regenerative Morphogenesis Research Articles

Walking leg regeneration in the sea spider Nymphon brevirostre Hodge, 1863 (Pycnogonida)

Regeneration is widespread across all animal taxa, but patterns of its distribution and key factors determining regeneration capabilities stay enigmatic. A comparative approach could shed light on the problem, but its efficacy is limited by the fact that data is only available on a few species from derived taxa. Pycnogonida are nested basally within the Chelicerata. They can shed and replace their walking legs and have a high regeneration capacity. In this work, we carried careful observation on leg appendotomy and regeneration processes in a sea spider under laboratory settings. The limb structure and in vivo observation reveal autotomy as the most likely appendotomy mechanism. High regeneration capabilities were ascertained: an anatomically normal but small leg appeared in a single molting cycle and the full functionality regained in 2–3 cycles. Wound closure after appendotomy in N. brevirostre primarily relies on hemolymph coagulation, which apparently differs from both xiphosurans and crustaceans. Regeneration is provided by proliferation in the leg cutpiece. Regenerative morphogenesis resembles the normal ontogenetic morphogenesis of a walking leg, but accelerated. Unlike in most arthropods, in N. brevirostre, regeneration does not necessarily correspond to the molting cycle, inferring a plesiomorphic state.

Exploring the Behavior of Bioelectric Circuits Using Evolution Heuristic Search

Characteristic spatial differences of cellular resting potential across tissues have been shown to act as instructive bioelectric prepatterns regulating embryonic and regenerative morphogenesis, as well as cancer suppression. Indeed, modulation of bioelectric patterns via specific ion channel-targeting drugs, channel misexpression, or optogenetics has been used to control growth and form in vitro, showing promise in regenerative medicine and synthetic bioengineering. Repair of defects, injury, and transformation requires quantitative understanding of bioelectric dynamics within tissues so that these can be modulated toward desired outcomes in organ patterning or the creation of entirely novel synthetic constructs. The major gap in the discovery of interventions for rational control of organ-level outcomes is the inability to predict large-scale bioelectric patterns—their emergence from symmetry breaking (given a set of channels expressed on the tissue) and their change as a function of time under specific bioelectrical interventions. It is thus essential to develop machine learning and other computational tools to help human scientists identify bioelectric states with desirable properties. In this study, we tested the ability of a heuristic search algorithm to explore the parameter space of bioelectrical circuits by adjusting the parameters of simulated cells. We show that while bioelectrical space is not easy to search, it does contain parameter sets that encode rich and interesting patterning behaviors. We demonstrate proof of principle of using a computational search platform to identify circuits with desired properties, as a first step toward the design of machine learning tools for improved bioelectric control of growth and form.

Neurogenesis during optic tectum regeneration in Xenopus laevis

The regenerative neurogenesis of the optic tectum of larval Xenopus laevis has been studied analyzing the proliferative and morphogenetic phases of the regeneration process after removal of one optic lobe. To this end, short-term and long-term pulses were carried out using the thymidine analog BrdU, selectively incorporated into cells during the S phase of the cell cycle. Results indicate that while in early larvae (stage 49/50, according to Nieuwkoop & Faber 1967) regeneration occurs mainly at the expense of the stem cells present in extensive proliferation zones ("matrix areas") of the midbrain, in late larvae (stage 55/56) regeneration occurs at the expense of stem cells present in very limited matrix areas of the brain and of quiescent cells, which re-enter the cell cycle following trauma. Moreover, in early larvae, morphogenesis of the optic tectum is carried out according to a precise spatio-temporal order from rostro-caudal to latero-medial. By contrast, in late larvae, the topographical order of the regenerative morphogenesis of the optic lobe is completely altered. As a consequence, the regenerated optic tectum in early larvae has an apparently normal structure, while the regenerated optic tectum in late larvae lacks stratification.

Regenerative capacity of the planarian Girardia tigrina and the snail Helix lucorum exposed to microgravity during an orbital flight on board the international space station

244 A better understanding of the role of gravity in various processes vitally important for terrestrial organisms is a paradigm of space biology. In particular, regeneration of injured or lost organs and tissues is studied under the conditions of a spaceflight. The available experimental data on regenerative morphogenesis under microgravity are scarce and contradictory. As reported in [1‐3], amputated limbs, tails, retina, and crystalline lens of tritons Pleurodeles waltlii regenerated rapidly under microgravity. Other authors [4] have reported that regeneration of triton stumps under microgravity is noticeably delayed as compared to the terrestrial control (the regenerated bones have atypical lamellar structure). It should be emphasized that, in these experiments conducted on board spacecrafts Bion and Photon, the orbital flight lasted for about 16 days, whereas regeneration was studied a long time after the return to Earth. In another experiment, two Wistar rats that remained under microgravity for two weeks displayed a delayed posttraumatic regeneration: the size of the callus was reduced, and a lower strength of bone fragment consolidation was observed after the surgical fracture of the fibula (diaphysis) made two days before launching of a biosatellite (a terrestrial group of animals served as a control) [5]. Regeneration of the freshwater planarian Girardia tigrina , both whole animals and fragments, as well as regeneration of eye tentacles in the snail Helix lucorum , was studied during the orbital flight of the International Space Station (ISS). G. tigrina is an asexual race: when an animal reaches a certain body size, the hind part of the body is gradually constricted to break away from the fore part. During several days, two new planarians

The renal stem cell system in kidney repair and regeneration

The adult mammalian renal tubular epithelium exists in a relatively quiescent to slowly replicating state, but has great potential for regenerative morphogenesis following severe ischemic or toxic injury. Kidney regeneration and repair occur through three cellular and molecular mechanisms: differentiation of the somatic stem cells, recruitment of circulating stem cells and, more importantly, proliferation/dedifferentiation of mature cells. Dedifferentiation seems to represent a critical step for the recovery of tubular integrity. Dedifferentiation of tubular cells after injury is characterized by the reactivation of a mesenchymal program that is active during nephrogenesis. Epithelial-to-mesenchymal transition (EMT) of renal tubular cells is an extreme manifestation of epithelial cell plasticity. It is now widely recognized as a fundamental process that marks some physiological, such as morphogenesis, as well as pathological events, such as oncogenesis and fibrogenesis. It might be also considered as a key event in the regenerative process of the kidney. Understanding the molecular mechanisms involved in EMT might be useful for designing therapeutic strategies in order to potentiate the innate capacity of the kidney to regenerate.

Cartilage morphogenetic proteins: role in joint development, homoeostasis, and regeneration

Background: Articular cartilage homoeostasis is critical for joint function. The steady state homoeostasis of articular cartilage is a balance between anabolic morphogens such as cartilage derived morphogenetic proteins (CDMPs) and...

Different Regulation of T-Box Genes Tbx4 and Tbx5 during Limb Development and Limb Regeneration

The T-domain transcription factors Tbx4 and Tbx5 have been implicated, by virtue of their limb-type specific expression, in controlling the identity of vertebrate legs and arms, respectively. To study the roles of these genes in developing and regenerating limbs, we cloned Tbx4 and Tbx5 cDNAs from the newt, and generated antisera that recognize Tbx4 or Tbx5 proteins. We show here that, in two urodele amphibians, newts and axolotls, the regulation of Tbx4 and Tbx5 differs from higher vertebrates. At the mRNA and protein level, both Tbx4 and Tbx5 are expressed in developing hindlimbs as well as in developing forelimbs. The coexpression of these genes argues that additional factors are involved in the control of limb type-specific patterns. In addition, newt and axolotl Tbx4 and Tbx5 expression is regulated differently during embryogenesis and regenerative morphogenesis. During regeneration, Tbx5 is exclusively upregulated in the forelimbs, whereas Tbx4 is exclusively upregulated in the hindlimbs. This indicates that, on a molecular level, different regulatory mechanisms control the shaping of identical limb structures and that regeneration is not simply a reiteration of developmental gene programs.

Different Regulation of T-Box Genes Tbx4 and Tbx5 during Limb Development and Limb Regeneration

The T-domain transcription factors Tbx4 and Tbx5 have been implicated, by virtue of their limb-type specific expression, in controlling the identity of vertebrate legs and arms, respectively. To study the roles of these genes in developing and regenerating limbs, we cloned Tbx4 and Tbx5 cDNAs from the newt, and generated antisera that recognize Tbx4 or Tbx5 proteins. We show here that, in two urodele amphibians, newts and axolotls, the regulation of Tbx4 and Tbx5 differs from higher vertebrates. At the mRNA and protein level, both Tbx4 and Tbx5 are expressed in developing hindlimbs as well as in developing forelimbs. The coexpression of these genes argues that additional factors are involved in the control of limb type-specific patterns. In addition, newt and axolotl Tbx4 and Tbx5 expression is regulated differently during embryogenesis and regenerative morphogenesis. During regeneration, Tbx5 is exclusively upregulated in the forelimbs, whereas Tbx4 is exclusively upregulated in the hindlimbs. This indicates that, on a molecular level, different regulatory mechanisms control the shaping of identical limb structures and that regeneration is not simply a reiteration of developmental gene programs.

Tubulogenesis from isolated single cells of adult mammalian kidney: clonal analysis with a recombinant retrovirus.

The adult mammalian kidney tubule epithelium exists in a relatively dormant, slowly replicative state but has a large potential for regenerative morphogenesis following severe ischemic or toxic injury. Under selective serum-free growth conditions, which included epidermal growth factor and retinoic acid, a subpopulation of renal proximal tubule cells isolated from adult rabbit kidney were grown in cell culture. These cells possessed two important characteristics: 1) an ability to differentiate morphogenically into tubule structures when grown in three-dimensional collagen gels and 2) a high capacity for self-renewal, since cell lineage analysis with a recombinant retrovirus demonstrated that in vitro tubulogenesis arose from clonal expansion of a single cell. Thus individual cells in the adult kidney have retained the ability for kidney tubulogenesis in vitro.

Acidic and basic Fibroblast Growth Factor mRNAs are expressed by skeletal muscle satellite cells

We postulated that Fibroblast Growth Factor (FGF) involved in fetal or regenerative morphogenesis of skeletal muscle originated from this tissue. Using a bovine retina cDNA probe encoding acidic FGF, we showed that growing muscles from bovine fetuses express this mRNA, but that this expression is reduced in neonate muscles. Cultures of proliferating satellite cells isolated from adult rat muscles expressed aFGF mRNA strongly but bFGF mRNA weakly; these mRNAs disappeared in cells differentiated into myotubes. 10−7M 12-O-tetradecanoyl phorbol -13-acetate (TPA) increased aFGF mRNA expression in both proliferating and differentiated satellite cells. Contrastingly, proliferating L6 myogenic cells only expressed aFGF mRNA significantly under TPA treatment. Therefore, the satellite cells did seem to be a possible source for FGF, especially aFGF, which might regulate the myogenic process.

Cytogeometrical determination of ciliary pattern formation in the hypotrich ciliate Stylonychia mytilus

Specification of polar and lateral axes has been investigated in several metazoan developmental systems. In order to analyze this phenomenon in unicellular organisms, singlet cells of the ciliate, Stylonychia mytilus, were cut along their longitudinal axis and the regenerative morphogenetic sequence was analyzed. Morphogenesis in right fragments, which folded such that the posterior and anterior ends were juxtaposed and fused, leads to formation of two partially mirror-imaged incomplete ventral ciliary patterns. Regenerative morphogenesis in singlet hypotrich ciliates typically produces only one complete set of ciliary organelles. These data demonstrate that cytoplasmic orientation (cytogeometry) plays a major role in the determination of ciliary pattern and that polar and lateral axes are determined independently in this species.

Utilisation de la régénération intercalaire pour l'étude de la détermination cellulaire au cours de la morphogenèse chez Blabera craniifer (Insecte Dictyoptère)

1. 1. The morphological features of intercalary regenerates and the conditions in which they form have been used for the study of the cellular determination during the regenerative process in insects. 2. 2. Whenever the contacts between hypodermal cells of stump and graft are rapidly established, the association of homologous levels leads to the simple fusion of the abutted surfaces, whereas the association of heterologous levels provokes the formation of an intercalary regenerate. Whenever the establishment of contacts is delayed, stump and graft regenerate for some time independently from one another. 3. 3. One and the same “segment sequence” is repeated within each of the segments (coxa, femur, tibia, and tarsus) of the thoracic appendages. The harmonious succession of these four articles is controlled by an “appendage sequence.” 4. 4. The determinations pertinent to the metameric quality and to the generatrices (the appendix being assimilated to a cylinder) remain unchallenged during regeneration. The polarity of the intercalary regenerate is determined by the one of both section surfaces that is proximal with regard to the other one in the segment sequence ; the segment nature (coxa, femur, tibia, or tarsus) of the intercalary regenerate is determined by the one of both section surfaces that is of proximal nature with regard to the other one. The informations relating to the segment nature and to the polarity of the intercalary regenerate originate, independently from one another, from the differentiated tissues, and may proceed, one from one of the abutted section surfaces, and the other from the other surface. 5. 5. Because of this independent determination of segment nature and segment levels, the principle of the distal quality of regenerates remains unviolated. 6. 6. The functional organization of appendages into sequences is analyzed and a model is proposed, where the determinations result from a balance between an activation of proximal origin and an inhibition of distal origin. An amputation or an association of heterologous levels leads to the suppression of the inhibition first in the segment sequence, thereafter in the appendage sequence. The inhibition is reestablished as soon as the various levels of the segment sequence are laid down, as a whole, in the case of the heterologous associations, and as soon as the various levels of the various segments are laid down, as a whole, in the case of amputations. 7. 7. The mechanism of sequences leads to a genetic conception of regenerative morphogenesis.