High-Temperature Sintering of Xenogeneic Bone Substitutes Leads to Increased Multinucleated Giant Cell Formation: In Vivo and Preliminary Clinical Results
The present preclinical and clinical study assessed the inflammatory response to a high-temperature–treated xenogeneic material (Bego-Oss) and the effects of this material on the occurrence of multinucleated giant cells, implantation bed vascularization, and regenerative potential. After evaluation of the material characteristics via scanning electron microscopy, subcutaneous implantation in CD-1 mice was used to assess the inflammatory response to the material for up to 60 days. The clinical aspects of this study involved the use of human bone specimens 6 months after sinus augmentation. Established histologic and histomorphometric analysis methods were applied. After implantation, the material was well integrated into both species without any adverse reactions. Material-induced multinucleated giant cells were observed in both species and were associated with enhanced vascularization. These results revealed the high heat treatment led to an increase in the inflammatory tissue response to the biomaterial, and a combined increase in multinucleated giant cell formation. Further clarification of the differentiation of the multinucleated giant cells toward so-called osteoclast-like cells or foreign-body giant cells is needed to relate these cells to the physicochemical composition of the material.
Figure 1. Images of the ultrastructure of the xenogenic bone substitute material Bego-Oss taken with a scanning electron microscope (red asterisks indicate bone matrix; green arrows, breaking edges; blue arrows, macropores; red arrows, microparticles; yellow arrows, micropores). (1) Magnification ×21; scale bar = 1 mm. (b) Magnification = ×600. Figure 2. Tissue reactions to the bovine-based bone substitute material within the subcutaneous tissue of CD-1 mice. (a) Tissue reaction on day 3 after implantation. The bone substitute granules (Bego-Oss [BGO]) were embedded within a network of fibrin and collagen fibers (asterisk) that also contained low numbers of mononuclear cells (black arrows). Vessels (red arrows) were detectable only within the neighboring connective tissue (CT) of the implantation beds (hematoxylin and eosin [H&E] staining; magnification ×200, scale bar = 100 μm). (b) The embedding of bone substitute granules (BGO) within the connective/granulation tissue (CT) that was moderately vascularized (red arrows indicate vessels) on day 10 after implantation. At this time point, multinucleated giant cells (arrow heads) were found within the implantation beds in addition to mononuclear cells (black arrows; H&E staining; magnification ×200, scale bar = 100 μm). (c–e) Tissue embedding of the xenogenic bone substitute granules (BGO) on days 15, 30, and 60 after implantation. The intergranular tissue (CT) was still permeated by a moderate number of vessels (red arrows) on day 15 after implantation, while a pattern of greater vascularization was detectable at the later study time points (red arrows in d and e). At the surfaces, multinucleated granules (arrow heads) and mononuclear cells (black arrows) were observable at all study time points (Azan stainings; magnification ×200, scale bars = 100 μm). Figure 3. Representative pictures of the material-adherent multinucleated giant cells and their tartrate-resistant acid phosphatase (TRAP)–positive and TRAP-negative subforms within the implantation beds of the xenogenic bone substitutes (BGO) on day 15 after implantation within the subcutaneous connective tissue (CT) of CD-1 mice (red arrow heads indicate TRAP-positive multinucleated giant cells; black arrow heads, TRAP-negative multinucleated giant cells; black arrows, mononuclear cells; red arrows, vessels; TRAP stainings; a: magnification ×200; b: magnification ×400, scale bars = 100 μm).
Figure 4. Histomorphometrical results of the preclinical portion of the study in CD-1 mice. (a) Vessel density. (b) Percentage vascularization. (c) Numbers of material-induced multinucleated giant cells (MNGCs) and their tartrate-resistant acid phosphatase (TRAP)–positive and TRAP-negative subtypes (TRAP[+] MNGCs and TRAP[−] MNGCs) (*/**/*** = interindividual significances, •/••/••• = intraindividual significances). Figure 5. Representative histologic images of the tissue reactions and the integration behavior of the bone substitute material Bego-Oss within the bone cores after the sinus augmentation procedure. (a) The Bego-Oss granules (BGO) were often completely embedded within the newly formed bone tissue (BT). The surrounding connective tissue (CT) contained high numbers of vessels (red arrows; Sirius staining, magnification ×100, scale bar = 100 μm). (b) At the surfaces of the BGO that were covered by CT, multinucleated giant cells (black arrow heads) were found in addition to mononuclear cells (black arrows). The neighboring CT contained high numbers of granulocytes (blue arrows) and vessels (red arrows; hematoxylin and eosin staining, magnification ×400, scale bar = 10 μm). (c) The multinucleated giant cells located at the surfaces of the BGO exhibited the most frequent signs of tartrate-resistant acid phosphatase (TRAP) expression (red arrowheads), and few of these cells were TRAP-negative (blue arrowheads; TRAP staining, magnification ×200, scale bar = 100 μm). Figure 6. Histomorphometric results of the clinical portion of the study. (a) Tissue distribution. (b) Numbers of material-induced multinucleated giant cells (MNGCs) and their tartrate-resistant acid phosphatase (TRAP)–positive and TRAP-negative subtypes (TRAP[+] MNGCs and TRAP[−] MNGCs).
Contributor Notes