Mechanical loading stimulates BMP7, but not BMP2, production by osteocytes

Area of Science:

• Biomedical Engineering
• Cell Biology
• Orthopedics

Background:

• Bone mechanical adaptation is a cellular process regulated by osteocytes responding to mechanical loads.
• Osteocytes produce signaling molecules influencing bone remodeling, with Bone Morphogenetic Proteins (BMPs) being potential candidates.
• The role of mechanically stimulated osteocytes in BMP production for bone adaptation remains unclear.

Purpose of the Study:

• To determine if osteocytes produce BMPs in response to mechanical loading.
• To investigate the involvement of the vitamin D receptor (VDR) in the mechanical response of BMP7 production.

Main Methods:

• In vitro study using human and VDR(-/-) mouse primary bone cells.
• Cells were subjected to pulsating fluid flow (PFF) for 1 hour, followed by postincubation.
• Quantification of BMP2 and BMP7 gene and protein expression.

Main Results:

• Pulsating fluid flow (PFF) did not alter BMP2 gene expression in human bone cells.
• PFF upregulated BMP7 gene expression (4.4-5.6 fold) and protein expression (2.4 fold) in human bone cells.
• PFF did not stimulate BMP7 gene expression in VDR(-/-) mouse bone cells, suggesting VDR involvement.

Conclusions:

• Mechanical loading upregulates BMP7, but not BMP2, gene and protein expression in osteocytes in vitro.
• The vitamin D receptor (VDR) likely mediates the response of BMP7 to mechanical loading.
• These findings contribute to understanding the mechanisms of bone mechanical adaptation.