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Dominant negative Bmp5 mutation reveals key role of BMPs in skeletal response to mechanical stimulation.

Ho AM, Marker PC, Peng H, Quintero AJ, Kingsley DM, Huard J - BMC Dev. Biol. (2008)

Bottom Line: Clinical studies have noted that the size and the strength of bone increase with weight bearing and muscular activity and decrease with bed rest and disuse.Genetic analysis shows that the mutation occurs at a site encoding the proteolytic processing sequence of the BMP5 protein and blocks proper processing of BMP5.Anatomic studies reveal that this mutation affects the formation of multiple skeletal features including several muscle-induced skeletal sites in vivo.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Developmental Biology and Howard Hughes Medical Institute, Beckman Center B300, Stanford University School of Medicine, Stanford, California 94305, USA. andrewho@pitt.edu

ABSTRACT

Background: Over a hundred years ago, Wolff originally observed that bone growth and remodeling are exquisitely sensitive to mechanical forces acting on the skeleton. Clinical studies have noted that the size and the strength of bone increase with weight bearing and muscular activity and decrease with bed rest and disuse. Although the processes of mechanotransduction and functional response of bone to mechanical strain have been extensively studied, the molecular signaling mechanisms that mediate the response of bone cells to mechanical stimulation remain unclear.

Results: Here, we identify a novel germline mutation at the mouse Bone morphogenetic protein 5 (Bmp5) locus. Genetic analysis shows that the mutation occurs at a site encoding the proteolytic processing sequence of the BMP5 protein and blocks proper processing of BMP5. Anatomic studies reveal that this mutation affects the formation of multiple skeletal features including several muscle-induced skeletal sites in vivo. Biomechanical studies of osteoblasts from these anatomic sites show that the mutation inhibits the proper response of bone cells to mechanical stimulation.

Conclusion: The results from these genetic, biochemical, and biomechanical studies suggest that BMPs are required not only for skeletal patterning during embryonic development, but also for bone response and remodeling to mechanical stimulation at specific anatomic sites in the skeleton.

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Altered response to mechanical stimulation in deltoid tuberosity osteoblast cells of Bmp5clv/Bmp5clv mutants. Cultured cells from the indicated sites were subjected to 0- or 24-h cyclic mechanical strain and visualized afterwards by indirect immunofluorescence using antibodies against collagen 1 (osteoblast) or vimentin (fibroblast). After subjection to 24-h strain, most osteoblasts from the deltoid tuberosity of wild-type (wt) mice become spindle-shaped and reorient perpendicular to the strain axis (arrow). In contrast, Bmp5clv deltoid tuberosity osteoblasts display a random orientation after mechanical strain. Femur trochanter osteoblasts from wild-type or Bmp5clv mice both realign after mechanical strain. Deltoid muscle fibroblasts from wild-type or Bmp5clv mice also respond appropriately to mechanical strain.
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Figure 4: Altered response to mechanical stimulation in deltoid tuberosity osteoblast cells of Bmp5clv/Bmp5clv mutants. Cultured cells from the indicated sites were subjected to 0- or 24-h cyclic mechanical strain and visualized afterwards by indirect immunofluorescence using antibodies against collagen 1 (osteoblast) or vimentin (fibroblast). After subjection to 24-h strain, most osteoblasts from the deltoid tuberosity of wild-type (wt) mice become spindle-shaped and reorient perpendicular to the strain axis (arrow). In contrast, Bmp5clv deltoid tuberosity osteoblasts display a random orientation after mechanical strain. Femur trochanter osteoblasts from wild-type or Bmp5clv mice both realign after mechanical strain. Deltoid muscle fibroblasts from wild-type or Bmp5clv mice also respond appropriately to mechanical strain.

Mentions: The loss of a prominent muscle-induced skeletal feature in Bmp5clv mice suggests that Bmp signaling plays a key role in bone cells' response to mechanical activity. To test this hypothesis, we isolated osteoblasts from the deltoid tuberosity of 10-month-old wild-type and Bmp5clv mice and subjected the cells to 24 hours of cyclic uniform radial strain in culture. The stretch regimen we applied (10-second maximum 15% elongation, then 10-second relaxation, frequency 0.05 Hz or 3 cycles/minute) is similar to the mechanical stimulation known to induce cellular responses in cultured osteoblasts [18,19]. After 24-hour cyclic strain, control osteoblasts became spindle-shaped, showed elongation of cellular processes, and were largely oriented perpendicular to the radial strain field (Fig. 4 and Table 1). In contrast, osteoblasts from the deltoid tuberosity of the Bmp5clv mice displayed no significant changes in morphology or orientation after mechanical strain (Fig. 4 and Table 1), suggesting that the defect in BMP signaling blocked normal response of bone cells to mechanical stimulation.


Dominant negative Bmp5 mutation reveals key role of BMPs in skeletal response to mechanical stimulation.

Ho AM, Marker PC, Peng H, Quintero AJ, Kingsley DM, Huard J - BMC Dev. Biol. (2008)

Altered response to mechanical stimulation in deltoid tuberosity osteoblast cells of Bmp5clv/Bmp5clv mutants. Cultured cells from the indicated sites were subjected to 0- or 24-h cyclic mechanical strain and visualized afterwards by indirect immunofluorescence using antibodies against collagen 1 (osteoblast) or vimentin (fibroblast). After subjection to 24-h strain, most osteoblasts from the deltoid tuberosity of wild-type (wt) mice become spindle-shaped and reorient perpendicular to the strain axis (arrow). In contrast, Bmp5clv deltoid tuberosity osteoblasts display a random orientation after mechanical strain. Femur trochanter osteoblasts from wild-type or Bmp5clv mice both realign after mechanical strain. Deltoid muscle fibroblasts from wild-type or Bmp5clv mice also respond appropriately to mechanical strain.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2335095&req=5

Figure 4: Altered response to mechanical stimulation in deltoid tuberosity osteoblast cells of Bmp5clv/Bmp5clv mutants. Cultured cells from the indicated sites were subjected to 0- or 24-h cyclic mechanical strain and visualized afterwards by indirect immunofluorescence using antibodies against collagen 1 (osteoblast) or vimentin (fibroblast). After subjection to 24-h strain, most osteoblasts from the deltoid tuberosity of wild-type (wt) mice become spindle-shaped and reorient perpendicular to the strain axis (arrow). In contrast, Bmp5clv deltoid tuberosity osteoblasts display a random orientation after mechanical strain. Femur trochanter osteoblasts from wild-type or Bmp5clv mice both realign after mechanical strain. Deltoid muscle fibroblasts from wild-type or Bmp5clv mice also respond appropriately to mechanical strain.
Mentions: The loss of a prominent muscle-induced skeletal feature in Bmp5clv mice suggests that Bmp signaling plays a key role in bone cells' response to mechanical activity. To test this hypothesis, we isolated osteoblasts from the deltoid tuberosity of 10-month-old wild-type and Bmp5clv mice and subjected the cells to 24 hours of cyclic uniform radial strain in culture. The stretch regimen we applied (10-second maximum 15% elongation, then 10-second relaxation, frequency 0.05 Hz or 3 cycles/minute) is similar to the mechanical stimulation known to induce cellular responses in cultured osteoblasts [18,19]. After 24-hour cyclic strain, control osteoblasts became spindle-shaped, showed elongation of cellular processes, and were largely oriented perpendicular to the radial strain field (Fig. 4 and Table 1). In contrast, osteoblasts from the deltoid tuberosity of the Bmp5clv mice displayed no significant changes in morphology or orientation after mechanical strain (Fig. 4 and Table 1), suggesting that the defect in BMP signaling blocked normal response of bone cells to mechanical stimulation.

Bottom Line: Clinical studies have noted that the size and the strength of bone increase with weight bearing and muscular activity and decrease with bed rest and disuse.Genetic analysis shows that the mutation occurs at a site encoding the proteolytic processing sequence of the BMP5 protein and blocks proper processing of BMP5.Anatomic studies reveal that this mutation affects the formation of multiple skeletal features including several muscle-induced skeletal sites in vivo.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Developmental Biology and Howard Hughes Medical Institute, Beckman Center B300, Stanford University School of Medicine, Stanford, California 94305, USA. andrewho@pitt.edu

ABSTRACT

Background: Over a hundred years ago, Wolff originally observed that bone growth and remodeling are exquisitely sensitive to mechanical forces acting on the skeleton. Clinical studies have noted that the size and the strength of bone increase with weight bearing and muscular activity and decrease with bed rest and disuse. Although the processes of mechanotransduction and functional response of bone to mechanical strain have been extensively studied, the molecular signaling mechanisms that mediate the response of bone cells to mechanical stimulation remain unclear.

Results: Here, we identify a novel germline mutation at the mouse Bone morphogenetic protein 5 (Bmp5) locus. Genetic analysis shows that the mutation occurs at a site encoding the proteolytic processing sequence of the BMP5 protein and blocks proper processing of BMP5. Anatomic studies reveal that this mutation affects the formation of multiple skeletal features including several muscle-induced skeletal sites in vivo. Biomechanical studies of osteoblasts from these anatomic sites show that the mutation inhibits the proper response of bone cells to mechanical stimulation.

Conclusion: The results from these genetic, biochemical, and biomechanical studies suggest that BMPs are required not only for skeletal patterning during embryonic development, but also for bone response and remodeling to mechanical stimulation at specific anatomic sites in the skeleton.

Show MeSH
Related in: MedlinePlus