Osteoconductive properties of upside-down bilayer collagen membranes in rat calvarial defects

Abstract

Background Bilayer collagen membranes are routinely used in guided bone/tissue regeneration to serve as osteoconductive scaffolds and prevent the invasion of soft tissues. It is recommended to place the membranes with their dense layer towards the soft tissue and their porous layer towards the bony defect area. However, evidence supporting this recommendation is lacking. This study aimed to determine whether the alignment of bilayer collagen membranes has an effect on bone regeneration. Methods In two groups of ten male Sprague-Dawley rats each, a 5-mm calvarial defect was created. Thereafter, the defect was randomly covered with a bilayer, resorbable, pure type I and III collagen membrane placed either regularly or upside-down (i.e., dense layer towards bone defect). After 4 weeks of healing, micro-computed tomography (μCT), histology, and histomorphometry of the inner cylindrical region of interest (4.5 mm in diameter) were performed to assess new bone formation and the consolidation of the collagen membrane in the defect area. Results Quantitative μCT showed similar bone volume (median 8.0 mm3, interquartile range 7.0–10.0 vs. 6.2 mm3, 4.3–9.4, p = 0.06) and trabecular thickness (0.21 mm, 0.19–0.23 vs. 0.18 mm, 0.17–0.20, p = 0.03) between upside-down and regular placement, both leading to an almost complete bony coverage. Histomorphometry showed comparable new bone areas between the upside-down and regularly placed membranes, 3.9 mm2 (2.7–5.4) vs. 3.8 mm2 (2.2–4.0, p = 0.31), respectively. Both treatment groups revealed the same regeneration patterns and spatial distribution of bone with and without collagen fibers, as well as residual collagen fibers. Conclusions Our data support the osteoconductive properties of collagen membranes and suggest that bone regeneration is facilitated regardless of membrane layer alignment.

Ectopic Bone Tissue Engineering in Mice Using Human Gingiva or Bone Marrow-Derived Stromal/Progenitor Cells in Scaffold-Hydrogel Constructs

“…However, in several instances the mineralized areas revealed the presence of embedded cells, including transplanted BMSC and GPC; in one instance of 2D-BMSC, organized bone-like tissue with embedded osteocytes was observed. A similar pattern of atypical mineralization has previously been reported in rat calvarial defects treated with collagen membranes ( Kuchler et al, 2018 ; Feher et al, 2021 ). It has been hypothesized that the collagen fibres underwent mineralization via cell-independent mechanisms and thereby served as “scaffolds” for subsequent bone formation ( Nudelman et al, 2013 ) and may explain the observations herein.…”

Osteoconductive Properties of a Volume-Stable Collagen Matrix in Rat Calvaria Defects: A Pilot Study

“…Yet, we have positive controls as this research is part of a larger series of experiments testing the osteoconductive properties of collagen membranes [25,26]. We have observed an almost complete defect coverage when using a native collagen membrane (Bio-Gide, Geistlich, Wolhusen, Switzerland) as a positive control in rat calvaria defects [25,26]. This control is valid for the surgical technique and also the osteogenic capacity of the calvaria defects.…”

“…Another limitation is that no negative controls have been performed. Yet, we have positive controls as this research is part of a larger series of experiments testing the osteoconductive properties of collagen membranes [25,26]. We have observed an almost complete defect coverage when using a native collagen membrane (Bio-Gide, Geistlich, Wolhusen, Switzerland) as a positive control in rat calvaria defects [25,26].…”

“…It is thus legitimate to conclude that the VSCM behaves differently when compared to the native collagen membrane used for guided bone augmentation. Considering that the studies have a different research question, the data were reported elsewhere [25,26]. Another appropriate control would be a native non-crosslinked VSCM to understand how the stiffness of the biomaterial affects its chondrogenic properties.…”

“…The VSCM data are part of a larger study to evaluate the osteoconductive properties of collagen-based biomaterials but with a different hypothesis. It is thus legitimate to consider our data observed with a collagen membrane (Bio-Gide, Geistlich, Wolhusen, Switzerland) as a positive control considering the osteogenic properties of the rat calvaria defect [25,26].…”