314 ADIPOSE- AND BONE MARROW-DERIVED MESENCHYMAL STEM CELLS PRESENT LARGE SIMILARITIES IN TRANSCRIPTOME PRIOR TO AND DURING ADIPOGENIC AND OSTEOGENIC DIFFERENTIATION

Abstract

Previous data support adipose-derived stem cells as an alternative to bone marrow as a source of adult stem cells for therapeutic purposes. The aim of the present study was to directly compare the transcriptome of adipose-derived (ADSC) and bone marrow-derived (BMSC) mesenchymal stem cells prior to differentiation and during in vitro osteogenic and adipogenic differentiation. The ADSC and BMSC were harvested from 3 adult pigs and differentiated in vitro into adipocytes and osteocytes for up to 4 weeks. Prior to differentiation and at differentiation day 2, 7, and 21, cells were harvested and RNA extracted for transcriptomics analysis by a 13 263 oligo 70-mers array (Sus scrofa AROS V1.0 with extension; Operon). Data were normalized by Lowess and statistical analysis was run using ANOVA with Benjamini-Hochberg false discovery rate (FDR) correction. Data mining was carried out using Ingenuity Pathway Analysis and David. Using an FDR of <0.05 for overall tissue effect and a post-hoc correction of P < 0.001, we observed 65 differentially expressed genes (DEG) between ADSC and BMSC before starting differentiation (0.66% of unique genes in the array). Functional analysis uncovered significant enrichment of extracellular matrix genes with direct roles in cell adhesion, migration, movement, and morphology. When the interaction cell type × differentiation × time was assessed, we observed >2 000 DEG with an FDR <0.05. This large number was mostly due to time effects. When pair-wise comparisons between cell types for each time point during the same differentiation were performed (post-hoc P < 0.001), we observed a strikingly low number of DEG. The number of DEG was lower between cell types in osteogenic (<100 DEG) compared with adipogenic (<200 DEG) differentiation. We observed significant enrichment (FDR-corrected P-value cut-off <0.05) of functions related to metabolism, antigen presentation, angiogenesis, and cell cycle in both differentiation conditions. We also observed an overall greater induction of the enriched functions in ADSC and a decrease in BMSC during adipogenic differentiation and the opposite during osteogenic differentiation except for metabolism, which appeared to be larger in ADSC in all cases. Among the significant enriched functions of DEG between the 2 differentiations, we observed enrichment of genes involved in metabolism, cell death, cell-to-cell signalling, and antigen presentation in ADSC during adipogenic compared with osteogenic differentiation. In BMSC we observed enrichment of functions related to cell death, antigen presentation, and lipid metabolism in osteogenic v. adipogenic differentiation. Overall data uncovered a high similarity at the transcriptional level between ADSC and BMSC both prior to differentiation and during differentiation. Those data support ADSC being particularly similar to BMSC.