Neonatal bone marrow interstitial fluid supports expansion and osteogenic ability of human bone marrow mesenchymal stromal cells.

The bone marrow microenvironment is critical for the maintenance and functionality of stem/progenitor cells, which are essential for bone development and regeneration. However, the composition and potential use of bone marrow interstitial fluid have not been well explored. In this study, we report the role of neonatal bovine bone marrow interstitial fluid (NBIF) in enhancing the bone regeneration capacity of human bone marrow mesenchymal stem cells (hBMSCs). Unlike adult bovine bone marrow interstitial fluid (ABIF), NBIF-fed hBMSCs exhibit enhanced self-renewal and osteogenic potential and bone marrow homing ability, along with transcriptome changes as compared to hBMSCs cultured in standard fetal bovine serum (FBS) supplemented medium. Mass spectrometry analysis reveals that multiple secreted factors associated with tissue repair and bone development are enriched in NBIF compared to FBS and ABIF. The combined use of NBIF-enriched Nerve Growth Factor (NGF), Lactoferrin (LTF), and High Mobility Group Protein B1 (HMGB1), together with Insulin-Like Growth Factor 1(IGF1) for culturing hBMSCs in the presence of FBS can enhance osteogenic potential and bone marrow homing ability, mimicking NBIF's effects. These findings highlight the role of interstitial fluid in the bone marrow microenvironment and its potential to optimize stem cell-based therapies.