Guided bone regeneration is promoted by the molecular events in the membrane compartment

Abstract

The working hypothesis of guided bone regeneration (GBR) is that the membrane physically excludes non-osteogenic tissues from interfering with bone healing. However, the underlying mechanisms are insufficiently explained. This study aimed to investigate the molecular and structural pattern of bone healing in trabecular bone defects, with and without naturally derived resorbable membrane. Defects were created in rat femurs and treated with the membrane or left empty (sham). After 3d, 6d and 28d, the defect sites and membranes were harvested and analyzed with histology, histomorphometry, quantitative-polymerase chain reaction (qPCR), Western blot (WB) and immunohistochemistry (IHC). Histomorphometry demonstrated that the presence of the membrane promoted bone formation in early and late periods. This was in parallel with upregulation of cell recruitment and coupled bone remodeling genes in the defect. Cells recruited into the membrane expressed signals for bone regeneration (BMP-2, FGF-2, TGF-β1 and VEGF). Whereas the native membrane contained FGF-2 but not BMP-2, an accumulation of FGF-2 and BMP-2 proteins and immunoreactive cells were demonstrated by WB and IHC in the in vivo implanted membrane. The results provide cellular and molecular evidence suggesting a novel role for the membrane during GBR, by acting as a bioactive compartment rather than a passive barrier.

Guided bone regeneration: materials and biological mechanisms revisited

“…Consistent with the aforementioned findings on non‐resorbable, synthetic, PTFE membrane, it has been recently demonstrated that the presence of resorbable, naturally derived, collagen membrane promotes coupled increase in bone formation and bone‐remodeling genes (osteocalcin, calcitonin receptor, cathepsin K, and RANKL) in the underlying rat tibia defect, compared with a similar defect without membrane (Fig. ).…”

“…Interestingly, the latter observation was associated with greater transmembrane vascularization and membrane degradation . Additional support for a role of multinucleated cells during GBR is the observation of these cells particularly in the zone between the lower surface of the membrane and the upper surface of the newly formed bone . At the histological level, these multinucleated osteoclast‐like cells appeared to be in a process of active resorption of the underlying bone, but it was not possible to determine whether these cells were also involved in the process of membrane degradation .…”

Using biomimetically mineralized collagen membranes with different surface stiffness to guide regeneration of bone defects

“…Because the first generation of GBR membranes was used in the clinic, ePTFE membranes have generally shown satisfactory results with respect to both their biocompatibility and the positive maintenance of spaces during healing. However, a second surgical operation is required to remove the ePTFE membrane, which may increase patient morbidity, the economic burden, and infection and may potentially damage the newly regenerated tissues (Ghanaati, ; Ma et al, ; Turri et al, ). To overcome the above drawbacks, bioresorbable barrier membranes as the second generation of GBR membranes have been developed.…”

Barrier membranes: More than the barrier effect?

“…As observed with non‐resorbable PTFE membranes, naturally derived, resorbable, collagen membranes promote an early coupled upregulation of genes related to bone formation (OC) and bone remodelling (the calcitonin receptor (CTR), cathepsin K (CatK) and RANKL)) in the underlying defect compared to the expression of these genes in the untreated sham defect in the rat femur (Turri et al., ; Figure ). Further, the presence of a collagen membrane above the defect appeared to fine‐tune the expression of the pro‐inflammatory cytokine tumour necrosis factor alpha (TNF‐α) during the different phases of GBR, as indicated by the early peak of TNF‐α at day 3 followed by significant downregulation at day 6 and a second peak at day 28 in the defect treated with the collagen membrane (Turri et al., ).…”

“…As observed with non‐resorbable PTFE membranes, naturally derived, resorbable, collagen membranes promote an early coupled upregulation of genes related to bone formation (OC) and bone remodelling (the calcitonin receptor (CTR), cathepsin K (CatK) and RANKL)) in the underlying defect compared to the expression of these genes in the untreated sham defect in the rat femur (Turri et al., ; Figure ). Further, the presence of a collagen membrane above the defect appeared to fine‐tune the expression of the pro‐inflammatory cytokine tumour necrosis factor alpha (TNF‐α) during the different phases of GBR, as indicated by the early peak of TNF‐α at day 3 followed by significant downregulation at day 6 and a second peak at day 28 in the defect treated with the collagen membrane (Turri et al., ). Despite the controversy regarding the role of inflammation and pro‐inflammatory cytokines during bone healing, TNF‐α is crucial for intra‐membranous bone formation (Gerstenfeld et al., ), and the observed early increase in TNF‐α expression in the membrane‐treated defect may positively impact the recruitment of cells, including mesenchymal stem cells (MSCs) (Bocker et al., ; Fu et al., ), and the osteogenic differentiation of these cells (Hess, Ushmorov, Fiedler, Brenner, & Wirth, ).…”