The discovery that adult adipose tissue is rich in mesenchymal stem cells (MSCs) capable of differentiating into many lines has led to consider the potential clinical applications for the repair of damaged tissues and for angiogenic therapy. MSCs from adipose tissue (AT) can be obtained easily from the waste product of liposuction. Although the proliferation and differentiation of MSCs have been widely studied, little information is available on the underlying mechanism of apoptosis in MSCs. The aim of this study was to analyze how cell morphology and expression of apoptotic markers are affected by in vitro expansion during adipogenic differentiation of AT-MSCs, which was induced by use of a specific medium (MesenCult Adipogenic Medium). To this purpose, the expression of p53, bax, PDCD4 and PTEN was evaluated by Western blot analysis in control cultures and in cultures treated with adipogenic medium at 7, 14, 21, and 28 days after implant. It was found that all markers tested were significantly down-regulated already after seven days. The same trend was also observed at longer intervals. From these results it can be suggested that MSCs are induced to lose their stem cell characteristics as they start adipocyte differentiation. Concurrently, metabolism and processes of cell survival would be improved. These features should be taken into account for the quality control of MSCs preparations to be used for therapeutic application.