Expression and role of HIF-1α and HIF-2α in tissue regeneration: a study of hypoxia in house gecko tail regeneration

Abstract

The house gecko (Hemidactylus platyurus) has evolved the ability to autotomize its tail when threatened. The lost part is then regrown via epimorphic regeneration in a process that requires high energy and oxygen levels. Oxygen demand is therefore likely to outstrip supply and this can result in relative hypoxia in the tissues of the regenerating tail. The hypoxic state is stabilized by the Hypoxia Inducible Factor-1α (HIF-1α) and HIF-2α proteins. We induced tail autotomy in 30 mal H. platyurus Correspondence to: Mohamad Sadikin, 69 adults using a standard procedure and then collected samples of the regenerated tail tissue on days 1, 3,5,8,10,13,17,21,25, and 30 post autotomy. For each sample, mRNA expression was analyzed by qPCR, proteins were analyzed using Western Blot tests and immunohistochemistry, and the histological structure was analyzed using Hematoxylin and Eosin staining. On day 1, HIF-1α mRNA expression increased and the tissue was dominated by leucocyte and erythrocyte cells. HIF-1α mRNA expression peaked on day 3, at which time some cells were actively proliferating, migrating, and differentiating. At the same time as HIF-1α expression decreased, HIF-2α mRNA expression increased, as did overall cellular activity. HIF-2α expression increased more gradually but was present over a longer period of time than HIF-1α. We hypothesize that HIF-1α helps to initially stimulate the tissue regeneration process while HIF-2α functionally takes over the role of HIF-1α after HIF-1α succumbs to the oxygen conditions, but we suspect that both HIF-1α and HIF-2α play a role in overcoming the tissue's hypoxic state.

Parallels between wound healing, epimorphic regeneration and solid tumors

“…Specifically, the early blastema during newt and axolotl limb regeneration is avascular (Mescher, 1996;Peadon and Singer, 1966), while neovascularization in axolotl occurs later in blastema formation and relies on VEGF signaling (Ritenour and Dickie, 2017). Using qPCR at different time points of the regenerating gecko tail, it was shown that HIF1α mRNA is upregulated early, highlighting the initial hypoxic state during blastema formation (Novianti et al, 2019). Additionally, slice cultures of the regenerating mouse digit-tip blastema revealed that dynamic changes in oxygen may contribute to bone regenerationnamely, that initial hypoxic events in the blastema followed by increasing oxygen concentrations from vascularization may promote bone mineralization (Sammarco et al, 2014).…”

From Cell Death to Regeneration: Rebuilding After Injury

“…There is an interesting link between apoptosis and reactive oxygen species (ROS). ROS are detected early in regeneration and are necessary for regeneration in multiple species ( Love et al, 2013 ; Ferreira et al, 2018 ; Novianti et al, 2019 ). Perhaps not coincidentally, ROS are important for apoptosis-dependent regeneration.…”

Preliminary Study of Common House Gecko (Cosymbotus platyurus) Density in Java Island

“…Geckos (family Gekkonidae) have skin characteristics that look soft even though they remain scaly, are active at night (nocturnal) and can sever the tip of their tail (autotomy) as a form of self-defense and avoid predators (Barton, 2007;Leo et al, 2020;Novianti et al, 2019;Rakhmiyati and Jaâ, 2018) Cosymbotus platyurus is a species of common house gecko that is commonly found in Indonesia. This species has a wide range of distribution including India, Southeast Asia, to Australia.…”