Worm regeneration: research done in the regrowth of cells in mammals :

'To better understand how this regeneration happens, researchers at the Stowers Institute for Medical Research removed the heads from planarians and watched as the creatures regrew the missing body part, including tubular structures of the excretory system. Among other findings, they learned that interfering with the expression of one gene kept the tubules and pores from branching off a precursor structure and from re-forming. This suggests the gene plays a critical role in regeneration. Studying similar genes in mammals could shed light on how we maintain our kidneys — and might grow new ones.'http://www.livescience.com/24791-worm-regeneration-research-nsf-ria.html