title: Cell Cotransplantation Strategies for Vascularized Craniofacial Bone Tissue Engineering: A Systematic Review and Meta-Analysis of Preclinical In Vivo Studies.
abstract: The regenerative potential of tissue-engineered bone constructs may be enhanced by in vitro coculture and in vivo cotransplantation of vasculogenic and osteogenic (progenitor) cells. The objective of this study was to systematically review the literature to answer the focused question: In animal models, does cotransplantation of osteogenic and vasculogenic cells enhance bone regeneration in craniofacial defects, compared with solely osteogenic cell-seeded constructs? Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, electronic databases were searched for controlled animal studies reporting cotransplantation of endothelial cells (ECs) with mesenchymal stem cells (MSCs) or osteoblasts in craniofacial critical size defect (CSD) models. Twenty-two studies were included comparing outcomes of MSC/scaffold versus MSC+EC/scaffold (co)transplantation in calvarial (n = 15) or alveolar (n = 7) CSDs of small (rodents, rabbits) and large animal (minipigs, dogs) models. On average, studies presented with an unclear to high risk of bias. MSCs were derived from autologous, allogeneic, xenogeneic, or human (bone marrow, adipose tissue, periosteum) sources; in six studies, ECs were derived from MSCs by endothelial differentiation. In most studies, MSCs and ECs were cocultured in vitro (2-17 days) before implantation. Coculture enhanced MSC osteogenic differentiation and an optimal MSC:EC seeding ratio of 1:1 was identified. Alloplastic copolymer or composite scaffolds were most often used for in vivo implantation. Random effects meta-analyses were performed for histomorphometric and radiographic new bone formation (%NBF) and vessel formation in rodents' calvarial CSDs. A statistically significant benefit in favor of cotransplantation versus MSC-only transplantation for radiographic %NBF was observed in rat calvarial CSDs (weighted mean difference 7.80% [95% confidence interval: 1.39-14.21]); results for histomorphometric %NBF and vessel formation were inconclusive. Overall, heterogeneity in the meta-analyses was high (I2> 80%). In summary, craniofacial bone regeneration is enhanced by cotransplantation of vasculogenic and osteogenic cells. Although the direction of treatment outcome is in favor of cotransplantation strategies, the magnitude of treatment effect does not seem to be of relevance, unless proven otherwise in clinical studies.
authors.affiliation: 1 Department of Clinical Dentistry, Centre for Clinical Dental Research, University of Bergen , Bergen, Norway .|2 Department of Periodontology, Faculty of Odontology, Malmö University , Malmö, Sweden .
authors.forename: Siddharth
authors.initials: S
authors.lastname: Shanbhag
authors.affiliation: 3 Department of Orthodontics and Dentofacial Orthopedics, School of Dental Medicine, University of Bern , Bern, Switzerland .
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Pandis
authors.affiliation: 1 Department of Clinical Dentistry, Centre for Clinical Dental Research, University of Bergen , Bergen, Norway .
authors.forename: Kamal
authors.initials: K
authors.lastname: Mustafa
authors.affiliation: 4 Stereology and Electron Microscopy Laboratory, Department of Clinical Medicine, Aarhus University , Aarhus, Denmark .
authors.forename: Jens R
authors.initials: JR
authors.lastname: Nyengaard
authors.affiliation: 2 Department of Periodontology, Faculty of Odontology, Malmö University , Malmö, Sweden .
authors.forename: Andreas
authors.initials: A
authors.lastname: Stavropoulos
mesh_terms: D000818:Animals; D042783:Endothelial Cells / Q000166:cytology; D005145:Face / Q000098:blood supply*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology; D023421:Models, Animal; D011785:Quality Assurance, Health Care; D012886:Skull / Q000098:blood supply*; D023822:Tissue Engineering / Q000379:methods*
keywords: bone tissue engineering; coculture; endothelial cells; mesenchymal stem cells; meta-analysis; vascularization