Involvement of tissue non-specific alkaline phosphatase in adipogenic program of bone marrow adipose tissue cells

Introduction

Accumulation of bone marrow adipose tissue (MAT) within bone during life interferes with bone health as well as systemic metabolism. We here investigated the implication of tissue non-specific alkaline phosphatase (TNAP) in MAT-derived cell differentiation.

Methods

Bone marrow (BM) samples were obtained from patients undergoing hip surgery and used for bone marrow (BM)-mesenchymal stromal cells (MSC) isolation. BM floating fatty fraction was used for isolation of MAT-cells, while subcutaneous fat from matched donors was used for isolation of peripheral adipose tissue (PAT) cells. Adipogenic differentiation was assessed in absence or presence of the reversible TNAP inhibitor (levamisole hydrochlodride). TNAP expression was estimated by TNAP enzymatic activity assay, and immunofluorescence microscopy combined with mitochondrial staining. Adipogenic marker and Alpl gene expression was analyzed by qPCR. Flow cytometry was applied to investigate functional surface markers.

Results

MAT and PAT cells displayed stronger adipogenic potential associated with their higher CEBPα and PPARγ gene expression than BM-MSC cells. Enzymatic activity, protein and gene expression suggested higher basal expression of TNAP in MAT and PAT cells. Increase of TNAP activity and Alpl mRNA level during adipogenesis was observed at the higher extent in MAT and PAT cells. Inhibition of TNAP activity, coincided with decreased adipogenesis in all three cell types as well as altered expression of CD36 (receptor involved in fatty acid traffic) and CD142 (coagulation factor III).

Conclusions

Results suggest that TNAP might play an important role in adipogenic differentiation, and further investigations will clarify mechanisms of TNAP-regulated adipogenesis in BM cells.

Conflict of Interest

There are no conflicts of interest.

Publication History

Article published online:
04 November 2021