The most popular movie 'Stuart Little' may no longer be a representation of wild imagination alone. It has been proved from experiments that it is technically possible to genetically engineer such mice with the currently available scientific techniques.
It has now been found that human embryonic stem cells claimed to have innumerable health benefits can be made functional inside another experimental animal such as mice. Scientists from California have been successful in incorporating human embryonic stem cells into the brains of fetal mice. Surprisingly, upon development, these mice were found to have working 'human brains' inside their skull.
Such mice produced through specialized genetic techniques are denoted by the term 'Chimeric mice'. The word ' Chimera' is of a Greek origin, which represents an animal with a lion's head, a goat's body and a serpent's tail.
A partial removal of 14-day-old mouse fetuses (no compromise on the placental blood supply) was done followed by injection of human stem cells into lateral ventricles of the fetal brain. Fetal development was then allowed to continue. The human embryonic stem cells were tagged with a marker called ' Green Fluorescent Protein (GFP) ' that enabled researchers to monitor the human stem cells inside the experimental animal.
Nearly 100, 000 human brain cells were introduced into each animal, having no apparent effects on the animal behavior. Despite the successful incorporation, more than 99% of the brain tissue remained original, eliminating ethical concerns regarding development of a human animal model.
The success of the experiment can be attributed to the use of embryonic stem cells rather than mature nerve cells. The embryonic stem cells were found to differentiate into almost all kinds of nerve cells commonly found in the human brain. In addition, synaptic junctions (connection between nerve cells) were well established.
Previous studies had already demonstrated that brain cells from aborted human fetuses could be injected into rodent brains. However, the functionality of these cells however remained unclear.
In order to prevent a breach of ethical regulations, certain guidelines have been established in California regarding chimera research. This has been formulated to prevent the development of human embryos inside experimental animals. Though the above study was conducted before the formulation of these guidelines, an ethical clearance was obtained before initiation of the study.
This novel finding can help scientists better understand the fundamentals of neurological disorders. It would also promote the testing of experimental medicines for the treatment of such diseases. In addition, it could eventually pave way for the development of stem cell based therapies for neurodegenerative disorders such as Parkinson's disease.
The researchers further intend to concentrate on the introduction of healthy human cells into animal models designed to mimic human diseases such as Alzheimer's or Parkinson's. If successful, useful information regarding the origin of the disease and the pathology can be obtained to develop appropriate treatment strategies.