Inherent variations in the cellular events at the site of amputation orchestrate scar‐free wound healing in the tail and scarred wound healing in the limb of lizardHemidactylus flaviviridis

Abstract

Lizards are unique in having both-regeneration competent (tail) as well as non-regenerating appendages (limbs) in adults. They therefore present an appropriate model for comparing processes underlying regenerative repair and nonregenerative healing after amputation. In the current study, we use northern house gecko Hemidactylus flaviviridis to compare major cellular and molecular events following amputation of the limb and of the tail. Although the early response to injury in both cases comprises apoptosis, proliferation, and angiogenesis, the temporal distribution of these processes in each remained obscure. In this regard, observations were made on the anatomy and gene expression levels of key regulators of these processes during the healing phase of the tail and limb separately. It was revealed that cell proliferation markers like fibroblast growth factors were upregulated early in the healing tail, coinciding with the growing epithelium. The amputated limb, in contrast, showed weak expression of proliferation markers, limited only to fibroblasts in the later stage of healing. Additionally, apoptotic activity in the tail was limited to the very early phase of healing, as opposed to that in the limb, wherein high expression of caspase-3 was observed throughout the healing process. Early rise in VEGF-α expression reflected an early onset of angiogenesis in the tail, while it was seen to occur at a later stage in case of the limb. Moreover, the expression pattern of transforming growth factor beta members points toward a pro-fibrotic response being induced very early in the amputated limb. Collectively, these results explain why regenerating appendages are able to heal without scars and if we are to induce scar-free healing in nonregenerating limbs, what interventions can be envisaged. This is crucial to the field of regenerative medicine since it is the initial stages of repair following amputation, which decide whether the appendage will be restored or only covered with a scab.

Supercritical Carbon Dioxide-decellularized Porcine Acellular Dermal Matrix combined with Autologous Adipose-derived Stem Cells: Its Role in Accelerated Diabetic Wound Healing

“…VEGF is an important regulator of pathophysiological angiogenesis and vascular development in wound healing [57]. VEGF expression was found elevated in the early phase of wound healing then followed with a decrease in the late phase [58][59][60]. In the study of Li et al, VEGF expression was significantly weak during 4-8 weeks of wound healing stage [58].…”

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

“…Transcripts of the major pathways governing these processes such as FGF, Shh, Wnt and TGF were also present during the transcriptome analysis. These signaling pathways control all the cellular and molecular processes required for successful regeneration in zebrafish, [ 23 , 24 , 25 ], axolotl [ 14 , 26 ], A. carolinensis [ 17 , 26 ] and H. flaviviridis [ 4 , 7 , 8 ].…”

“…The total RNA was isolated from 50 mg tail tissue using the TRIzol reagent, as reported previously by Ranadive et al (2018) [ 4 ]. The quality and quantity of the isolated RNA were estimated using Qubit Fluorimeter 3.0 and Agilent Tapestation 2200.…”

“…Moreover, the histological features of reptiles and mammals are highly comparable, making the former an appealing group for studying tissue and organ regeneration [ 1 ]. Despite their limitations, lizards can regrow lost parts, similar to their vertebrate counterparts, such as fish and amphibians [ 2 , 3 , 4 ]. In contrast to the metamerically segmented original tail, lizards replace their lost appendage (tail) with an unsegmented tail [ 5 ].…”

“…By 4 days post-autotomy (dpa), a flat early blastema is formed covering the stump. The initiation of blastema is accompanied by histolysis of stump tissues such as bone and muscle, from which dedifferentiated cells arise and aggregate directly beneath the early blastema [ 4 ]. These cells re-enter the cell cycle and give rise to the blastema, a mass of mesenchyme-derived cells thought to be substantially, if not entirely, formed from 6 dpa dedifferentiation of previously differentiated cells.…”