Blastema Research Articles

De Novo Transcriptome Sequencing and Analysis of Differential Gene Expression among Various Stages of Tail Regeneration in Hemidactylus flaviviridis.

Across the animal kingdom, lizards are the only amniotes capable of regenerating their lost tail through epimorphosis. Of the many reptiles, the northern house gecko, Hemidactylus flaviviridis, is an excellent model system that is used for understanding the mechanism of epimorphic regeneration. A stage-specific transcriptome profile was generated in the current study following an autotomized tail with the HiSeq2500 platform. The reads obtained from de novo sequencing were filtered and high-quality reads were considered for gene ontology (GO) annotation and pathway analysis. Millions of reads were recorded for each stage upon de novo assembly. Up and down-regulated transcripts were categorized for early blastema (EBL), blastema (BL) and differentiation (DF) stages compared to the normal tail (NT) by differential gene expression analysis. The transcripts from developmentally significant pathways such as FGF, Wnt, Shh and TGF-β/BMP were present during tail regeneration. Additionally, differential expression of transcripts was recorded from biological processes, namely inflammation, cell proliferation, apoptosis and cell migration. Overall, the study reveals the stage-wise transcriptome analysis in conjunction with cellular processes as well as molecular signaling pathways during lizard tail regeneration. The knowledge obtained from the data can be extrapolated to configure regenerative responses in other amniotes, including humans, upon loss of a complex organ.

Stimulation of regenerative blastema formation in lizards as a model to analyze limb regeneration in amniotes.

The hypothesis here presented tries to explain why organ regeneration is present in fish and amphibians (anamniotes) but is absent in reptiles, birds and mammals (amniotes). Anamniotes possess complex life cycles including larvae and metamorphosis stages, the latter representing a physiological form of organ destruction and regeneration coded in their genome that can be reactivated in adults in the form of regeneration. Part of the genome for larvae and metamorphosis phases was likely lost in amniotes with the evolution of direct development, the potentiation of the immune system and the increase in complexity of the nervous system. These events consequently determined incapability for organ regeneration in extant amniotes with the exception of the lizard tail. This likely derives from the evolution of a mechanism of immunosuppression that allows the regeneration of the tail although the complete morphogenetic plane of tail embryogenesis is lost. The lizard model of imperfect but outstanding organ regeneration indicates the possibility to improve organ regeneration also in other amniotes. In fact, the induction of a blastema in the amputated lizard limb has stimulated the formation of short limbs containing cartilaginous bones of the femur, tibia and fibula, and these experiments foster some hope for future attempts to induce limb and digit regeneration also in mammals.

The mammalian blastema and induced regeneration in mice.

Fingertips of humans and toe tips of mice possess the capacity to regenerate following amputation injury. The mouse toe tip has been developed as a regeneration competent model to investigate the regeneration process, and digit amputation at a more proximal level serves as a non‐regenerative wound model to test strategies for enhanced regeneration. The process of toe tip regeneration is divided into a series of overlapping events beginning with an inflammatory response, a bone degeneration response, epidermal closure, migration and proliferation of progenitor stem cells, blastema formation and redifferentiation. These stages are distinct from wound healing of a non‐regenerative amputation that results in truncated skeletal elements covered with scar tissue. BMP signaling has been shown to be essential for toe tip regeneration and BMP treatment is effective in enhancing the regenerative capacity of proximal level amputations. The ability to induce a regeneration response from non‐regenerative amputation wound identifies an unrealized regenerative potential of cells present at traumatic wounds in mammals. To date, we have determined that the regeneration of bone, cartilage, synovial cavity, tendon and ligament can be induced from a non‐regenerative amputation wound with different regimens of targeted growth factor treatments. These studies provide a road map for developing strategies to control regeneration events in mammals and serve as a new direction for the field of regenerative medicine.Support or Funding InformationDARPA (W911NF‐09‐1‐0305)US Army Research Laboratory (W911NF‐09‐1‐0305)Texas A&M UniversityThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Histological analysis after arm tip amputation in the brittle star Ophioplocus januarii (Echinodermata: Ophiuroidea).

Fil: Di Giorgio, Gisele Vanesa. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Nacional Patagonico; Argentina

Childhood pleuropulmonary blastoma: a clinicopathologic study of 16 cases

To study the clinicopathological and immunohistochemical features, histogenesis and prognosis of pleuropulmonary blastoma (PPB) in children. PPB specimens from 16 pediatric cases with an age ranging from 1 year and 7 months to 5 years and 3 months (mean age of 3 years) were retrieved and analyzed by routine histological, immunohistochemical and electron methods. Among 16 patients, there were 2 type I, 7 type II and 7 type III PPB cases. Type I PPB as multilocular cystic structure, consisted of thin fibrous wall lining the respiratory epithelium, subepithelial primitive blastema or immature mesenchymal cells, with or without rhabdomyoblastic differentiation or cartilage; Type II PPB as cystic-solid tumor, comparing with type I, consisted of intracystic components with appearance of anaplastic tumor cells. Type III PPB consisted of completely solid mass, the same as the solid region of type II, had mixed pattern including blastema, undifferentiated spindle-cell proliferations and sarcomas. In addition, anaplastic tumor cells and intra-and extra- cytoplasmic eosinophilic globules were also commonly present. Epithelial components in PPB were benign. Immunohistochemical study showed primitive mesenchymal differentiation of tumors. All cases were positive for vimentin, desmin, myogenin and SMA in tumors with skeletal muscle differentiation, S-100 was positive in tumors with cartilage differentiation. All tumors were negative for synaptophysin, CD99, and CD117. Benign epithelial components were positive for AE1/AE3 and EMA. In 12 cases, electron microscopy revealed few organelles in the primitive mesenchymal cells and rich heterochromatin in mesenchymal cells, the latter also demonstrating cytoplasmic myofilament dysplasia. Nine cases had clinical follow-up ranging from 5 to 48 months, of which 4 patients died. PPB is a rare lung neoplasm of children under the age of 6 years, with distinct pathological morphology. PPB may arise from lung or pleura mesenchymal cells and has a poor clinical outcome.

Clawing Your Way Back: Why Nails Are So Important

The distal tips of mammalian digits can regenerate following amputation, but only when the nail apparatus is intact. Coordinated regrowth of nail and distal phalanx involves nail epithelial cells and undifferentiated mesenchymal cells that form the “blastema,” which subsequently differentiates to reform the distal digit. Takeo and colleagues explored the role of nail epithelial cells in …

Melatonin and Methoxytryptophol have Temporal Effect on Tail Elongation but not Methoxytryptamine: Studies on Tail Regeneration in Hemidactylus flaviviridis

In order to evaluate the time-specific influence of pineal indoles on tail regeneration in lizards, melatonin (M), methoxytryptophol (ML) and methoxytryptamine (MT) were administered intraperitonealy to different groups of lizards at morning 7:00 hrs (m) or in the evening at 17:00 hrs (e). The Mm and MLe groups of lizards showed a delay in the attainment of various arbitrary stages of regeneration like wound healing, pre-blastema, blastema and initiation of growth while the Me and MLm groups of lizards showed hastened attainment. However, MTm and MTe treatments did not bring about any difference compared to the controls. The total length of tail regenerated and percentage replacement at the end of 30 days were significantly less in Mm and MLe groups of lizards. MTm and MTe treatments, however, did not affect the regeneration process. The results indicate that M and ML have opposite time-specific effects on regeneration, while MT has no effect. Apparently, M and ML are part of the photoperiodic and neuro-endocrine transduction mechanisms related to regenerative growth in lizards.

Evaluation of Signaling Molecules in the Post-Autotomy Initiation Phase of Tail Regeneration in the Lizard Hemidactylus flaviviridis

Epimorphic regeneration, as exemplified by lizard tail, involves the formation of regeneration blastema as a pre-requisite for replacement growth. The formation of blastema is preceded by many regressive changes like tissue demolition, histolysis, inflammation, wound closure, de-differentiation, cell migration and proliferation. Induction of signaling molecules would be crucial in the molecular biology of immediate post-autotomy period in providing the trigger for the initiation of regeneration. It is in this behest that the levels of the cAMP, cGMP and NO have been assayed during the first 72 hr post caudal-autotomy in the lizard Hemidactylus flaviviridis . The influence of exaggerated exogenous induction of NO as well as prolonged action of cGMP by the use of PDE5 inhibitor (sidenafil citrate) have also been evaluated in terms of the number of days taken to complete wound healing and form a blastema as well as the length of tail regenerated at the end of 20 days. cAMP-mediated PKA activation and downstream signaling cascades appear to be the principal mechanism as against cGMP-mediated mechanisms. Controlled NO generation appears to be of pivotal significance in minimizing apoptotic cell loss as substantiated by the reduced caspase 3 activity. Exaggerated induction of NO and prolongation of cGMP action appear to promote apoptotic cell loss resulting in retarded regenerative growth. It can be concluded from the present observations that cAMP- and PKA-mediated events occur first and that minimizing cell apoptosis by controlled NO generation is important in the formation of robust regeneration blastema.

Thyroid Hormone Control of Tail Regeneration: Differential in Loco and Systemic Effects and Seasonal Variation

Thyroid hormones have been implicated in the control of vertebrate appendage regeneration. In lizards, thyroid hormones have been reported to induce ependymal outgrowth and also exercise control over adaptive systemic metabolic activities. However, there have been no attempts to correlate the seasonal differences in regenerative performance with thyroid activity. The present study has evaluated the effect of induced thyroid hormone excess or deficiency (by T4 administration or methimazole treatment, respectively) on tail regeneration in H. flaviviridis on a seasonal basis in summer, monsoon and winter months. The experiments revealed a retardative influence of hypothyroidism in tail regeneration in both summer and winter months; however blastema formation occurred in the normal time course in the summer months. Hyperthyroidism induced by daily T4 administration, either systemically or in loco , hastened the formation of blastema and provided an early growth spurt but, ultimately, retarded regenerative growth in the summer months. However, T4 administration daily for the first 15 days and every other day thereafter favored a better regenerative growth. In contrast, during the monsoon months, both daily administration and administration every alternate day, either systemically or in loco , delayed blastema formation as well as retarded linear growth. Neither hypothyroidism nor hyperthyroidism exerted any influence on the sluggish performance characteristic of winter months. It is concluded that thyroid activity and thyroid hormone responsiveness vary on a seasonal basis with maximum activity at higher temperatures and minimal at lower temperatures. It can also be concluded that there is differential sensitivity to thyroid hormone during summer and monsoon seasons.

Elektronenmikroskopische Untersuchungen an Mäuseembryonen über die Differenzierung des Blastems in den Extremitäten zum embryonalen Vorknorpel

Cartilage differentiation in the upper limb bud of the white mouse (NMRI) begins in the humerus anlage on day 12 + 13 h p.c.; cartilage differentiation in the phalanges begins on day 13 + 3 h p.c. Morphologically, differentiation can be characterized as follows: (1) cell densifications with an increase in contact structures between the cells in the blastema centre: (2) development of a two-layered cell densification: a central cartilage zone and a peripheral zone (perichondrium), between precartilage and prospective muscle anlage; numerous mitoses appear in this peripheral zone; (3) appearance of filaments and PG granula in the intercellular space as well as massive appearance of rough endoplasmic reticulum in the cytoplasm and, (4) increased distance between the cells coupled with the loss of specific contact structures and substance increase in the intercellular space.