This suggests that adult regeneration may be an acquired trait in axolotls that might be inducible in mammals if the required genetic pathways are mapped. 6 The axolotl’s nearest relatives, anuran frogs and reptiles, lose the ability to reform tissues after metamorphosis or show limited tail regeneration.

Axolotls can replace a wide variety of tissues and complex structures including muscle, cartilage, skin, spinal cord, brain, heart, jaw, and limbs. Organ segregation, made possible by embryonic microsurgeries wherein halves of 2 differently colored embryos were joined, indicate that the spleen is the definitive site of adult hematopoiesis.Īmong vertebrates, urodele amphibians, such as the axolotl ( Ambystoma mexicanum), display a unique and extensive ability for adult regeneration. Donor-derived hematopoiesis occurred for >2 years in recipients generating stable hematopoietic chimeras. As in zebrafish, use of the white axolotl mutant allows direct visualization of homing, engraftment, and hematopoiesis in real time. The liver and spleen are both active sites of hematopoiesis in adult axolotls and contain transplantable HSCs capable of long-term multilineage blood reconstitution. We also established a fluorescence-activated cell sorter enrichment technique for major blood lineages and colony-forming unit assays for hematopoietic progenitors. We used white and cytomegalovirus:green fluorescent protein + transgenic white axolotl strains to map sites of hematopoiesis and develop hematopoietic cell transplant methodology. However, a lack of knowledge of axolotl hematopoiesis hinders the use of this animal for the study of hematopoietic cells in scar-free wound healing and tissue regeneration. Among vertebrates, none display such an extensive ability for adult regeneration as urodele amphibians, including 1 of the more popular models: the axolotl. Unfortunately for mammals, wound repair typically results in scarring and nonfunctional reparation. These ” c/ c chimeric” axolotls provide a useful and unique way to investigate early embryonic heart development in cardiac mutant Mexican axolotls.Hematopoietic stem cell (HSC)-derived cells are involved in wound healing responses throughout the body. Examination of the mutant hearts with electron microscopy and comfocal microscopy after immunofluorescent staining for tropomyosin showed identical images to those described previously in naturally-occurring c/ c mutant axolotls (i.e., lacking organized sarcomeric myofibrils). The mutant phenotypes were confirmed by the absence of beating hearts and death at stage 41 in 100% of the embryos. The chimeric axolotl is composed of a normal head and heart region (+/+), permitting survival and a mutant body containing mutant gonads ( c/ c) that permits the production of c/ c mutant offspring: 100% c/ c offspring were obtained by mating c/ c chimeras ( c/ c× c/ c). The general approach was to transect tailbud embryos and join the anterior and posterior halves of two different individuals. In the present study, we created chimeric axolotls by using microsurgical techniques. To date, there has been no way to analyze the genotypes of embryos from heterozygous spawnings (+/ c×+/ c) until stage 35 when the normal (+/ c or +/+) embryos first begin to have beating hearts mutant ( c/ c) embryos fail to develop normal heartbeats.

In cardiac mutant axolotls ( c/ c) the hearts do not beat, apparently because of an absence of organized myofibrils. The Mexican axolotl ( Ambystoma mexicanum) provides an excellent model for studying heart development since it carries a cardiac lethal mutation in gene c that results in failure of contraction of mutant embryonic myocardium.

Chimera axolotl