Adipose-derived stem cells from the brown bear (Ursus arctos) spontaneously undergo chondrogenic and osteogenic differentiation

Abstract

In the den, hibernating brown bears do not develop tissue atrophy or organ damage, despite almost no physical activity. Mesenchymal stem cells could play an important role in tissue repair and regeneration in brown bears. Our objective was to determine if adipose tissue-derived stem cells (ASCs) can be recovered from adipose tissue of wild Scandinavian brown bears and characterize osteogenic, chondrogenic, and adipogenic differentiation in the cells. Following immobilization of 8 wild brown bears 7-10 days after leaving the den in mid-April, adipose tissue biopsies (5-8 ml) were obtained subcutaneously from 7 bears. ASCs were recovered and characterized. Adipose stem cell cultures were established from 6 of 7 bears. Adipose tissue-derived stem cells from yearlings spontaneously formed bone-like nodules surrounded by cartilaginous deposits, suggesting differentiation into osteogenic and chondrogenic lineages. This ability appears to be lost gradually with age. This is the first study to demonstrate stem cell recovery and growth from brown bears, and it is the first report of ASCs spontaneously differentiating into osteocytes and chondrocytes. These findings could have implications for the use of hibernating brown bears as a model to study osteoporosis.