Ectopic expression of delta FBJ murine osteosarcoma viral oncogene homolog B mediates transdifferentiation of adipose-like spheroids into osteo-like microtissues

Tissue Eng Part A. 2008 Aug;14(8):1377-94. doi: 10.1089/ten.tea.2007.0185.


Differentiation and transdifferentiation strategies have a large role in the manipulation of cells in replacing dysfunctional cells and tissues. We developed adipose-like microtissues using gravity-enforced self-assembly of monodispersed human primary preadipocytes to determine their transdifferentiation capacity to form bone-like tissues. Using lentivirus-derived particles to induce ectopic bone morphogenetic protein (BMP)-2 and delta FBJ murine osteosarcoma viral oncogene homolog B (DeltaFosB) gene expression, we demonstrated a time-dependent induction of osteoblast-specific genes and properties such as calcium deposits, bone-like extracellular matrix (ECM), and matrix mineralization. DeltaFosB was able to trigger partial Pref-1-mediated de-differentiation of adipocytes, which also retained their adipocytic cell phenotype. Osteoblast-specific structures could be co-localized in the ECM of lipid-containing cells analyzed using immunofluorescence and transmission electron microscopy when BMP-2 and DeltaFosB were co-expressed, suggesting that differentiated adipocytes are able to transdifferentiate into osteoblasts via a transient hybrid adipocyte-preadipocyte-osteoblast cell phenotype. Microtissues transgenic for BMP-2 and DeltaFosB expression were able to reproduce bone matrix, which occurs to a lesser extent in conventional two-dimensional (2D) cultures but is known to play a decisive role in the development and function of bone in vivo. This demonstrates that ECM-inclusive studies are essential for future characterization assays. Therefore, 3D cultures provide a superior ex vivo system for the improved characterization of phenotypical and functional alterations resulting from interventions directed toward differentiation processes. Precise control of transdifferentiation of adipocytes into osteoblasts in a 3D culture mimicking in vivo tissue conditions as closely as possible will foster important advances in regenerative medicine and tissue engineering.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipocytes / cytology*
  • Adipocytes / ultrastructure
  • Animals
  • Bone Morphogenetic Protein 2
  • Bone Morphogenetic Proteins / metabolism
  • Calcification, Physiologic
  • Calcium / metabolism
  • Calcium-Binding Proteins
  • Cell Transdifferentiation*
  • Fluorescent Antibody Technique
  • Gene Expression Profiling
  • Humans
  • Intercellular Signaling Peptides and Proteins / metabolism
  • Lipid Metabolism
  • Membrane Proteins / metabolism
  • Mice
  • Microscopy, Confocal
  • Osteoblasts / cytology*
  • Proto-Oncogene Proteins c-fos / metabolism*
  • Spheroids, Cellular / cytology*
  • Spheroids, Cellular / ultrastructure
  • Time Factors
  • Transforming Growth Factor beta / metabolism


  • BMP2 protein, human
  • Bmp2 protein, mouse
  • Bone Morphogenetic Protein 2
  • Bone Morphogenetic Proteins
  • Calcium-Binding Proteins
  • DLK1 protein, human
  • FOSB protein, human
  • Fosb protein, mouse
  • Intercellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Proto-Oncogene Proteins c-fos
  • Transforming Growth Factor beta
  • Calcium