Difference in soft tissue response between immediate and delayed delivery suggests a new mechanism for recombinant human bone morphogenetic protein 2 action in large segmental bone defects

Khaled A. Hussein, Ibrahim E. Zakhary, Ahmed R. Elawady, Hany A. Emam, Mohamed Sharawy, Babak Baban, Sara Akeel, Mohamed Al-Shabrawey, Mohammed E. Elsalanty

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Abstract

The ability of recombinant human bone morphogenetic protein 2 on absorbable collagen sponge (rhBMP2/ACS) to regenerate bone in segmental defect has been well characterized. However, clinical results of rhBMP2/ACS constructs in secondary reconstruction of large mandibular and craniofacial defects have not been consistent. We hypothesized that rhBMP2 delivery triggers an endogenous response in the soft tissues surrounding the defect, in the form of expression of BMP2 and vascular endothelial growth factor (VEGF). Such osteogenic response will occur only after immediate, as opposed to delayed, rhBMP2 delivery, suggesting a new explanation to the difference in bone regeneration between the two settings. A 35-mm segmental bone and periosteum defect was created on one side of the mandible in 16 dogs divided in three groups. Group 1 (Gp1, n=6) ACS was loaded with 8mL of rhBMP2 (0.2mg/mL). In Gp2 (n=5) the same dose of rhBMP2/ACS was delivered into the defect 4 weeks after surgery. In Gp3 (control; n=5) the defect was reconstructed using ACS loaded with 8mL of buffer only (devoid of rhBMP2). Tissues were collected after 12 weeks of reconstruction in all groups. Direct measurement of physical dimensions of regenerates and bone morphometry was performed to evaluate bone regeneration. The mRNA expression of both BMP2 and VEGF in the soft tissue surrounding the defect was evaluated using real-time quantitative PCR. Both BMP2 and VEGF proteins were quantified in immunostained sections. Immunoflurescence colocalization of BMP2 and acetylated low density lipoprotein (AcLDL) was done to detect the source of BMP2. Immediate delivery yielded better bone regeneration. Both BMP2 and VEGF mRNA expression was upregulated only in Gp1 (+7.3, p=0.001; +1.53, p=0.001, respectively). BMP2 protein was significantly higher in the immediate reconstruction group; however, VEGF protein was undetected in the examined sections. Immediate delivery of rhBMP2 seemed to induce endogenous release of BMP2 from the surrounding soft tissues, an effect that was lacking in delayed delivery and may explain the variability of clinical results associated with BMP2 use. Colocalization of BMP2 and endothelial cells (ECs) suggested that ECs could be the source of endogenous BMP2.

Original languageEnglish (US)
Pages (from-to)665-675
Number of pages11
JournalTissue Engineering - Part A
Volume18
Issue number5-6
DOIs
StatePublished - Mar 1 2012

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Vascular Endothelial Growth Factor A
Bone
Bone Regeneration
Tissue
Proteins
Porifera
Bone and Bones
Defects
Collagen
Endothelial cells
Endothelial Cells
Mandibular Reconstruction
Periosteum
Messenger RNA
Mandible
Real-Time Polymerase Chain Reaction
Buffers
recombinant human bone morphogenetic protein-2
Lipoproteins
Dogs

ASJC Scopus subject areas

  • Bioengineering
  • Biochemistry
  • Biomaterials
  • Biomedical Engineering

Cite this

@article{a9057ae7a5984f72a2c737b3812f0460,
title = "Difference in soft tissue response between immediate and delayed delivery suggests a new mechanism for recombinant human bone morphogenetic protein 2 action in large segmental bone defects",
abstract = "The ability of recombinant human bone morphogenetic protein 2 on absorbable collagen sponge (rhBMP2/ACS) to regenerate bone in segmental defect has been well characterized. However, clinical results of rhBMP2/ACS constructs in secondary reconstruction of large mandibular and craniofacial defects have not been consistent. We hypothesized that rhBMP2 delivery triggers an endogenous response in the soft tissues surrounding the defect, in the form of expression of BMP2 and vascular endothelial growth factor (VEGF). Such osteogenic response will occur only after immediate, as opposed to delayed, rhBMP2 delivery, suggesting a new explanation to the difference in bone regeneration between the two settings. A 35-mm segmental bone and periosteum defect was created on one side of the mandible in 16 dogs divided in three groups. Group 1 (Gp1, n=6) ACS was loaded with 8mL of rhBMP2 (0.2mg/mL). In Gp2 (n=5) the same dose of rhBMP2/ACS was delivered into the defect 4 weeks after surgery. In Gp3 (control; n=5) the defect was reconstructed using ACS loaded with 8mL of buffer only (devoid of rhBMP2). Tissues were collected after 12 weeks of reconstruction in all groups. Direct measurement of physical dimensions of regenerates and bone morphometry was performed to evaluate bone regeneration. The mRNA expression of both BMP2 and VEGF in the soft tissue surrounding the defect was evaluated using real-time quantitative PCR. Both BMP2 and VEGF proteins were quantified in immunostained sections. Immunoflurescence colocalization of BMP2 and acetylated low density lipoprotein (AcLDL) was done to detect the source of BMP2. Immediate delivery yielded better bone regeneration. Both BMP2 and VEGF mRNA expression was upregulated only in Gp1 (+7.3, p=0.001; +1.53, p=0.001, respectively). BMP2 protein was significantly higher in the immediate reconstruction group; however, VEGF protein was undetected in the examined sections. Immediate delivery of rhBMP2 seemed to induce endogenous release of BMP2 from the surrounding soft tissues, an effect that was lacking in delayed delivery and may explain the variability of clinical results associated with BMP2 use. Colocalization of BMP2 and endothelial cells (ECs) suggested that ECs could be the source of endogenous BMP2.",
author = "Hussein, {Khaled A.} and Zakhary, {Ibrahim E.} and Elawady, {Ahmed R.} and Emam, {Hany A.} and Mohamed Sharawy and Babak Baban and Sara Akeel and Mohamed Al-Shabrawey and Elsalanty, {Mohammed E.}",
year = "2012",
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doi = "10.1089/ten.tea.2011.0148",
language = "English (US)",
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T1 - Difference in soft tissue response between immediate and delayed delivery suggests a new mechanism for recombinant human bone morphogenetic protein 2 action in large segmental bone defects

AU - Hussein, Khaled A.

AU - Zakhary, Ibrahim E.

AU - Elawady, Ahmed R.

AU - Emam, Hany A.

AU - Sharawy, Mohamed

AU - Baban, Babak

AU - Akeel, Sara

AU - Al-Shabrawey, Mohamed

AU - Elsalanty, Mohammed E.

PY - 2012/3/1

Y1 - 2012/3/1

N2 - The ability of recombinant human bone morphogenetic protein 2 on absorbable collagen sponge (rhBMP2/ACS) to regenerate bone in segmental defect has been well characterized. However, clinical results of rhBMP2/ACS constructs in secondary reconstruction of large mandibular and craniofacial defects have not been consistent. We hypothesized that rhBMP2 delivery triggers an endogenous response in the soft tissues surrounding the defect, in the form of expression of BMP2 and vascular endothelial growth factor (VEGF). Such osteogenic response will occur only after immediate, as opposed to delayed, rhBMP2 delivery, suggesting a new explanation to the difference in bone regeneration between the two settings. A 35-mm segmental bone and periosteum defect was created on one side of the mandible in 16 dogs divided in three groups. Group 1 (Gp1, n=6) ACS was loaded with 8mL of rhBMP2 (0.2mg/mL). In Gp2 (n=5) the same dose of rhBMP2/ACS was delivered into the defect 4 weeks after surgery. In Gp3 (control; n=5) the defect was reconstructed using ACS loaded with 8mL of buffer only (devoid of rhBMP2). Tissues were collected after 12 weeks of reconstruction in all groups. Direct measurement of physical dimensions of regenerates and bone morphometry was performed to evaluate bone regeneration. The mRNA expression of both BMP2 and VEGF in the soft tissue surrounding the defect was evaluated using real-time quantitative PCR. Both BMP2 and VEGF proteins were quantified in immunostained sections. Immunoflurescence colocalization of BMP2 and acetylated low density lipoprotein (AcLDL) was done to detect the source of BMP2. Immediate delivery yielded better bone regeneration. Both BMP2 and VEGF mRNA expression was upregulated only in Gp1 (+7.3, p=0.001; +1.53, p=0.001, respectively). BMP2 protein was significantly higher in the immediate reconstruction group; however, VEGF protein was undetected in the examined sections. Immediate delivery of rhBMP2 seemed to induce endogenous release of BMP2 from the surrounding soft tissues, an effect that was lacking in delayed delivery and may explain the variability of clinical results associated with BMP2 use. Colocalization of BMP2 and endothelial cells (ECs) suggested that ECs could be the source of endogenous BMP2.

AB - The ability of recombinant human bone morphogenetic protein 2 on absorbable collagen sponge (rhBMP2/ACS) to regenerate bone in segmental defect has been well characterized. However, clinical results of rhBMP2/ACS constructs in secondary reconstruction of large mandibular and craniofacial defects have not been consistent. We hypothesized that rhBMP2 delivery triggers an endogenous response in the soft tissues surrounding the defect, in the form of expression of BMP2 and vascular endothelial growth factor (VEGF). Such osteogenic response will occur only after immediate, as opposed to delayed, rhBMP2 delivery, suggesting a new explanation to the difference in bone regeneration between the two settings. A 35-mm segmental bone and periosteum defect was created on one side of the mandible in 16 dogs divided in three groups. Group 1 (Gp1, n=6) ACS was loaded with 8mL of rhBMP2 (0.2mg/mL). In Gp2 (n=5) the same dose of rhBMP2/ACS was delivered into the defect 4 weeks after surgery. In Gp3 (control; n=5) the defect was reconstructed using ACS loaded with 8mL of buffer only (devoid of rhBMP2). Tissues were collected after 12 weeks of reconstruction in all groups. Direct measurement of physical dimensions of regenerates and bone morphometry was performed to evaluate bone regeneration. The mRNA expression of both BMP2 and VEGF in the soft tissue surrounding the defect was evaluated using real-time quantitative PCR. Both BMP2 and VEGF proteins were quantified in immunostained sections. Immunoflurescence colocalization of BMP2 and acetylated low density lipoprotein (AcLDL) was done to detect the source of BMP2. Immediate delivery yielded better bone regeneration. Both BMP2 and VEGF mRNA expression was upregulated only in Gp1 (+7.3, p=0.001; +1.53, p=0.001, respectively). BMP2 protein was significantly higher in the immediate reconstruction group; however, VEGF protein was undetected in the examined sections. Immediate delivery of rhBMP2 seemed to induce endogenous release of BMP2 from the surrounding soft tissues, an effect that was lacking in delayed delivery and may explain the variability of clinical results associated with BMP2 use. Colocalization of BMP2 and endothelial cells (ECs) suggested that ECs could be the source of endogenous BMP2.

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