Directly auto-transplanted mesenchymal stem cells induce bone formation in a ceramic bone substitute in an ectopic sheep model.
Bottom Line: Up-regulation was detected using immunohistology methods and RT-PCR.Dense vascularization was demonstrated by CD31 immunohistology staining in all three groups.Hence BMP-2 stimulation might become dispensable in the future, thus providing an attractive, clinically feasible approach to bone tissue engineering.
Affiliation: Department of Plastic and Hand Surgery, University Hospital of Erlangen, Friedrich-Alexander-University of Erlangen-Nürnberg, Erlangen, Germany.Show MeSH
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Mentions: To identify the most suitable cell type for bone tissue engineering purposes, different groups (expanded versus directly auto-transplanted MSC, groups 8–10) were investigated. Cells were either expanded over five passages following plastic adherence or only purified with Ficoll gradient centrifugation without interim plastic adherence selection. In both groups cells were DiI labelled prior to implantation and implanted subcutaneously with or without BMP-2. Based on the clinical application and because expanded MSC have been evaluated in combination with BMP-2 previously we decided to perform only the directly auto-transplanted MSC in combination with the BMP-2. In all three groups bone formation was observed after standard histology haematoxylin and eosin and immunohistology COL1 staining (Fig. 7A–F, A–C haematoxylin and eosin, D–F COL1 staining, A/D expanded MSC, B/E directly auto-transplanted MSC, C/F directly auto-transplanted MSC in combination with BMP-2). Formation of new bone parts was in particular taking place adjacent to the β-TCP/HA granules. Newly formed bone parts commenced to interconnect the granules into one continuous bony block. Sizes of areas with newly formed bone were analysed semi-automatically: no significant difference between the three groups could be detected. No significant differences between groups with directly auto-transplanted and expanded MSC were detected, neither did combination with BMP-2 induce a significant higher amount of bone formation (Fig. 7G). The expression of bone-specific genes was demonstrated in groups 8–10 as shown by RT-PCR analysis (Fig. 8A–C). Osteocalcin and osteopontin were up-regulated in groups 8–10 in comparison to β-TCP/HA granules with fibrin matrix without growth factors or cells (Fig. 8D). DiI-labelled MSC were found particularly close to β-TCP/HA granules contributing to the new formation of bone (Fig. 9A–C, A expanded MSC, B directly auto-transplanted MSC, C directly auto-transplanted MSC in combination with BMP-2). In the explants with directly auto-transplanted MSC a higher section of the DiI-labelled cells was found in the connective tissue parts of the constructs compared to the explants with expanded MSC or directly auto-transplanted MSC with BMP-2. The constructs in all groups were well vascularized as shown by CD31 immunohistochemistry (Fig. 9D–F, A expanded MSC, B directly auto-transplanted MSC, C directly auto-transplanted MSC in combination with BMP-2). There seemed to be no difference with regards to the used cell type.
Affiliation: Department of Plastic and Hand Surgery, University Hospital of Erlangen, Friedrich-Alexander-University of Erlangen-Nürnberg, Erlangen, Germany.