Abstract: Compositions and methods are provided for culturing in vitro potentially regenerative cells (PRCs) from which functional tissue-organs are regenerated. In one aspect of the invention, a tissue culture medium is provided which comprises at least 50% of water and a sterol compound that is dissolved in a fatty acid-containing oil at a concentration at least 0.1% by weight based on the weight of the oil and added to the water. The culture medium can be used to culture PRCs that are isolated from the body of a mammal to generate functional tissue-organs in vitro with substantially the same physiological structure and function as the corresponding ones existing in vivo and in situ. The cultured PRCs, tissues, and tissue-organs can serve as valuable models for scientific investigation in life sciences, nutraceutical discovery, drug screening, pharmacokinetic studies, medical devices and tissue/organ transplantation.