Immunolocalization indicates that both original and regenerated lizard tail tissues contain populations of long retaining cells, putative stem/progenitor cells

Abstract

The regeneration of the tail in lizards is likely sustained by stem/progenitor cells located in the stump after amputation of the tail. This microscopic and ultrastructural study shows the localization of 5-bromo-deoxy-uridine (5BrdU)-long retaining labeled cells in different tissues of the tail stump. These putative stem/progenitor cells are sparsely detected in the epidermis of scales, adipose tissue, intermuscle connective septa, myosatellite cells, and perichondrion of the vertebrae. Most of 5BrdU-labeled cells are present in the bone marrow of vertebrae as hemocytoblasts and reticulate cells, whereas more numerous myelocytes and polychromatophilic erythroblasts show a variable level of nuclear labeling. 5BrdU and tritiated-thymidine labeled and unlabeled hemopoietic cells are seen in circulating vessels and in the blastema where their maturation is completed. This observation indicates that the entire differentiation span of both white and red blood cells, at least during tail regeneration, lasts longer than 4 weeks. Labeled polychromatophilic erythroblasts and heterophilic and basophilic myelocytes are present in the synusoidal vessels of the regenerating tail. This study indicates that extravasating blood cells involved in immunity make large part of the forming blastema cell population, but are replaced by mesenchymal cells of different origin. The presence of long retaining labeled cells in tissues of the tail stump is likely connected to the production of blastema mesenchymal cells. Although no direct cell-lineage study has been done, histological, immunocytochemical, and autoradiographic studies have indicated that it is from these tissues that proliferating cells appear mainly localized after tail amputation and blastema formation.

Review: Biological and Molecular Differences between Tail Regeneration and Limb Scarring in Lizard: An Inspiring Model Addressing Limb Regeneration in Amniotes

“…After tail or limb loss, the extravasating blood cells form a superficial clot in 3–6 hr postinjury, and underneath the clot the damaged tissues of the stump accumulate on their surface numerous free cells while the epidermis from the borders of the tail or limb gives rise to migrating keratinocytes that gradually insinuate underneath the clot over the following 4–7 days (Alibardi and Sala, ; Alibardi and Toni, ; McLean and Vickaryous, ). The cells of the blastema originate from different tissues in both tail and limb that possess a variable number of 5BrdU long‐retaining cells, putative stem cells, including blood cells from the bone marrow (Quattrini, ; Simpson, ; Cox, '69; Alibardi and Sala, ; Alibardi, , , , ; Gilbert et al., 2015). The activation of c‐myc and telomerase is among the initial proteins involved in the stimulation of formation of a blastema (Alibardi , d, ).…”

Immunodetection of FGF1-2 and FGFR1-2 Indicates that these Proteins Disappear in the Wound Epidermis and Blastema of the Scarring Limb in Lizard

“…Histologically it showed a thick wound (regenerating) epidermis with a thin corneous layer that covered underneath a loose connective tissue here termed a regenerating blastema for analogy with the blastema of the regenerating tail details in. 6,7,17 However, differently from the tail blastema, the limb blastema is generally destined to form a scarring outgrowth in the following days, and it grows to about 1mm before turning into a scaled outgrowth. Among the proximal tissues included in the limb stump at 16 days after the amputation, some fragmented and repairing muscles were present, and the sectioned femur showed a compact lamellar bone in the diaphysis while its proximal, untouched epiphysis showed in the cavity of the secondary ossification center the presence of some cartilaginous cells (Figure 1).…”

“…18,20 FGF immune labeling tends to disappear later on when the proliferation in the limb decreases and only few tissues such a muscle and cartilageare still repairing. 6,7,17,20 Cell proliferation and FGF immune labeling is also abolished in scarring tails after cauterization, an intervention that drives the tail to form a scar instead of regenerates into a new tail. [6][7][8]10 The importance of FGFs and FGFRs for lizard regeneration confirms previous observations, 10 and the numerous data available for anamniotes such as amphibians and fish, two groups of vertebrates where tissue and organ regeneration is even higher than in lizards.…”

“…17 The experiments were conducted following the Italian guidelines for animal care and handling (art. 5, DL 116/92).…”

Current Understanding on Tail Regeneration in Green Anoles (Anolis carolinensis)

“…With the extension of blastema, new blood vessel and spinal cord are regenerated within it. Mature hemopoietic cells, which provide immunity and replaced by mesenchymal cells later, are found in the blastema by 5-bromodeoxyuridine (5-BrdU) and tritiated thymidine (3H-T) labelling [29]. Together with necessary blood vessel and spinal cord, formation and rearrangement of muscles form a new tail [2].…”