Key Event Title
|Level of Biological Organization|
Key Event Components
|fin regeneration||blastemal cell||decreased|
Key Event Overview
AOPs Including This Key Event
|AOP Name||Role of event in AOP|
|GR Agonism Leading to Impaired Fin Regeneration||KeyEvent|
|teleost fish||teleost fish||NCBI|
|All life stages|
Key Event Description
Fin regeneration is a naturally occurring process in fish (Fu et al., 2013). Fin regeneration is a complex process involving coordinated cellular processes such as cellular signaling, differentiation, and migration (Wehner & Weidinger, 2015). Commonly known signaling pathways such as activin signaling, notch signaling and wnt signaling all play a role in the process of fin regeneration (Wehner & Weidinger, 2015). Poss et al (2003) outline fin regeneration as follows:
- Damaged vertebrate organs heal through either repair or regeneration
- Repair: characterized by heavy inflammation, fibrosis and formation of a collagen-rich connective tissue scar, believed to be permanent.
- Regeneration: damaged or lost structure is perfectly or nearly perfectly replaced
- Blastlema – a mass of proliferative, pluripotent, progenitor cells
- Within 1-3 h, thin epidermal layer covers wound – can occur in dissected or explanted fin regenerates
- 12-18 h, epidermis accumulates through cell migration – β-catenin is an early molecular marker of fin regeneration – presumed to function in helping to mediate cell migration.
- Formation of the blastlema is a hallmark of epimorphic regeneration – proliferative mass of mesenchymal cells that gives rise to the new structures
- Switch from blastlema formation to proliferative outgrowth occurs around 4 d post-amputation (at 25 C). -regenerate consists of mature blastlema (distal) and proximally positioned differentiating tissue – consisting of at least two cell types – scleroblasts (bone forming) and fibroblast-like cells.
- Wfgf expression is markedly higher during outgrowth phase than during blastlema formation
- Wnt3a is not detected during blastlema formation, but is up-regulated in distal portion of epidermis during regenerative outgrowth.
- Distal blastema is composed of slow- or non-proliferative cells – mxsb positive
- Proximal blastemal is rapidly proliferative
- Immediately proximal to the PB is the patterning zone (PZ) or differentiation zone, consists of scleroblasts and differentiating mesenchymal cells. Sonic hedgehog (shh) aligns with the border between PB and PZ (DZ)
- Shh is thought to be responsible for scleroblast alignment and proliferation
Many, if not all the genes required for regeneration will also be required during embryonic development - this suggests contaminant mixtures that prevent fin regeneration would likely be developmentally toxic as well.
How It Is Measured or Detected
- A consistent method of fin measurement was found by measuring the length of the top fin ray, bottom fin ray, and middle fin ray, as well as the total area of the fin.
- Ellis et al. (2008) have used a fin index where Fin Index = 100 x (Fin Length/Total Length).
Domain of Applicability
Ellis T, Hoyle I, Oidtmann B, Turnbull JF, Jacklin TE, Knowles TG. 2009. Further development of the “Fin Index” method for quantifying fin erosion in rainbow trout. Aquaculture 289: 283-288. doi:10.1016/j.aquaculture.2009.01.022
Fu C, Cao ZD, Fu SJ. 2013. The effects of caudal fin loss and regeneration on the swimming performance of three cyprinid fish species with different swimming capactities. The Journal of Experimental Biology 216:3164-3174. doi:10.1242/jeb.084244
Poss KD, Shen J, Keating MT, Nechiporuk A. 2003. Tales of Regeneration in Zebrafish. Developmental Dynamics 226:202-210. DOI 10.1002/dvdy.10220
Wehner D, Weidinger G. 2015. Signaling networks organizing regenerative growth of the zebrafish fin. Trends in Genetics 31 (6):336-343. http://dx.doi.org/10.1016/j.tig.2015.03.012