Secretome analysis of in vitro aged human mesenchymal stem cells reveals IGFBP7 as a putative factor for promoting osteogenesis

Aging is a complex biological process, which involves multiple mechanisms with different levels of regulation. Senescent cells are known to secrete senescence-associated proteins, which exert negative influences on surrounding cells. Mesenchymal stem cells (MSCs), the common progenitors for bone, cartilage and adipose tissue (which are especially affected tissues in aging), are known to secrete a broad spectrum of biologically active proteins with both paracrine and autocrine functions in many biological processes. In this report, we have studied the secreted factors (secretome) from human MSCs (hMSCs) and hMSCs-derived adipocytes which were induced to accumulate prelamin A, the immature form of the nuclear lamina protein called Lamin A, known to induce premature aging syndromes in humans and in murine models. Proteomic analysis from two different techniques, antibody arrays and LS-MS, showed that prelamin A accumulation in hMSCs promotes the differential secretion of factors previously identified as secreted by hMSCs undergoing osteogenesis. Moreover, this secretome was able to modulate osteogenesis of normal hMSCs in vitro. Finally, we found that one of the overexpressed secreted factors of this human aging in vitro stem cell model, IGFBP-7, is an osteogenic factor, essential for the viability of hMSCs during osteogenesis.