Lipoaspirate fluid proteome: A preliminary investigation by LC-MS top-down/bottom-up integrated platform of a high potential biofluid in regenerative medicine.

The lipoaspirate fluid (LAF) has recently emerged as a potentially valuable source in regenerative medicine. In particular, our group recently demonstrated that it is able to exert osteoinductive properties in vitro. This original observation stimulated the investigation of the proteomic component of LAF, by means of LC-ESI-LTQ-Orbitrap-MS top-down/bottom-up integrated approach, which represents the object of the present study. Top-down analyses required the optimization of sample pretreatment procedures to enable the correct investigation of the intact proteome. Bottom-up analyses have been directly applied to untreated samples after monodimensional SDS-PAGE separation. The analysis of the acid-soluble fraction of LAF by top-down approach allowed demonstrating the presence of albumin and haemoglobin fragments (i.e. VV- and LVV-hemorphin-7), thymosins β4 and β10 peptides, ubiquitin and acyl-CoA binding protein; adipogenesis regulatory factor, perilipin-1 fragments, and S100A6, along with their PTMs. Part of the bottom-up proteomic profile was reproducibly found in both tested samples. The bottom-up approach allowed demonstrating the presence of proteins, listed among the components of adipose tissue, and/or are comprised within the ASCs intracellular content and secreted proteome. Our data provide a first glance on the LAF molecular profile, which is consistent with its tissue environment. LAF appeared to contain bioactive proteins, peptides and paracrine factors, suggesting its potential translational exploitation.