The role of Wnt3 in early Hydra head regeneration

CHARA OSVALDO; BRUSCH LUTZ; GALLIOT BRIGITTE; DEUTSCH ANDREAS

Kraków

Conferencia; 8th European Conference on Mathematical and Theoretical Biology (ECMTB); 2011

European Society for Mathematical and Theoretical Biology (ESMTB)

Several organisms including planaria, fish, insects and salamanders respond to injuryand amputation by regenerating the lost body part. A general open questionis: How does the remaining tissue ?measure? the degree of injury and mount a regenerationresponse of adequate magnitude? This question is studied in the freshwater polyp Hydra. The Hydra body column can be viewed as a hollow bilayeredtissue cylinder with head and foot on opposite ends referred to as apical and basal,respectively. The tissue consists of the following cell types: ectodermal and endodermalcells (in the epithelial lineage), interstitial stem cells, progenitors, neurons,nematocytes and gland cells (in the interstitial lineage). Previous experiments ofcutting Hydra into two halves showed secretion of Wnt3 molecules by cells undergoingapoptosis near the amputation plane of the basal half [1].We model this immediate Wnt3 response and the following response of the differentcell types by a system of coupled partial differential equations. We assumethatWnt3 is produced by apoptotic cells near the amputation plane, diffuses deeperinto the tissue and subsequently undergoes a lytic degradation. We model the celldynamics considering cell differentiation, self-renewal, apoptosis (triggered by amputation),basal loss of cells due to migration toward the extremities along withincreases in cell proliferation and cell migration in response to the concentrationand spatial gradient of Wnt3, respectively.We implemented the model in a simulation program coded in C++. Modeldependentfitting simulations to the experimental data [1] demonstrated that thesemechanisms could be responsible for the measured cell dynamics, corroborating animportant role of Wnt3 within the injury response that ultimately determines thefate of the regeneration process in Hydra.References[1] Chera S, Ghila L, Dobretz K, Wenger Y, Bauer C, Buzgariu W, Martinou JC, Galliot B.2009. Apoptotic cells provide an unexpected source of Wnt3 signaling to drive hydra headregeneration. Dev Cell. 17(2):279-89.