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Current Directions in Biomedical Engineering

Joint Journal of the German Society for Biomedical Engineering in VDE and the Austrian and Swiss Societies for Biomedical Engineering

Editor-in-Chief: Dössel, Olaf

Editorial Board: Augat, Peter / Buzug, Thorsten M. / Haueisen, Jens / Jockenhoevel, Stefan / Knaup-Gregori, Petra / Kraft, Marc / Lenarz, Thomas / Leonhardt, Steffen / Malberg, Hagen / Penzel, Thomas / Plank, Gernot / Radermacher, Klaus M. / Schkommodau, Erik / Stieglitz, Thomas / Urban, Gerald A.

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A macrophage model of osseointegration

Herbert P. Jennissen
  • Corresponding author
  • Institut für Physiologische Chemie, Universität Duisburg-Essen, Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany
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Published Online: 2016-09-30 | DOI: https://doi.org/10.1515/cdbme-2016-0015

Abstract

The mechanisms of peri-implant de novo bone formation and contact osteogenesis are still largely unknown. In 1984 Donath et al. showed that macrophages were the first cells to colonize a titanium implant. Recently it was shown that that there are inflammatory (M1) and healing macrophages (M2), the latter of which can secrete BMP 2. In the context of data from a gap healing experiment a macrophage model of osseointegration is suggested.

Keywords: BMP-2; histiocytes; M1 macrophages; M2 macrophages; peri-implant bone healing; VEGF

1 Introduction

Peri-implant healing by de novo bone formation (increase in bone volume) involves two principal pathways, namely contact osteogenesis and distance osteogenesis as originally reported by Osborn 1979 [1]. In contact osteogenesis (osteoconduction), predominant in trabecular bone, bone forms first on the implant surface by recruitment and migration of osteogenic cells so the implant surface, followed by bone formation in apposition to the implant surface [2]. In distance osteogenesis, predominant in cortical bone, autochtonous new bone is formed on the surface of old bone, instead of on the implant, and approximates the implant surface from the periphery [2]. An important factor influencing contact osteogenesis appears to be the hydrophilicity and microtopography of an implant surface (for reviews see Ref. [3], [4]). The histology of the first stages of peri-implant healing on a titanium plasma sprayed surface (TPS) was reported in 1984 by Donath et al. [5]. However, how de novo bone formation occurs on an inert metallic surface such as titanium is unclear. Here a model is proposed for nanostructured, hyperhydrophilic titanium surfaces (see [6]).

2 Material and methods

Methods for the preparation of hyperhydrophilic titanium plasma sprayed surfaces are described in Ref. [6]. The methods involved in gap healing experiments in vivo have been described for osteoinductive TPS-surfaces (BMP-2) in sheep [7] and for nanostructured hyperhydrophilic TPS surfaces preliminarily in minipigs [8]. The hyperhydrophilic nanostructured TPS-implant surfaces were conserved in the dry state by an exsiccation layer of salt [9]. They were implanted in this dry state being wetted intra operationem with blood. The de novo bone formation is defined as the ratio between the area (mm2) of new bone and the total defined area (reference region of interest) in percent. Bone ongrowth i.e. bone implant contact (BIC) via histological slide (1D) is defined as the ratio between the length (mm) of the bone-implant contact and the total defined unit length (reference, region of interest) in percent.

3 Results

As has been shown by others [4] and in Ref. [9], [10] ultra- and hyperhydrophilic titanium surfaces can lead to an increase in bone volume (osteoinduction) and bone ongrowth i.e. BIC (osteoconduction). This is illustrated in Table 1.

Table 1:

Bone volume increase and bone ongrowth increase on nanostructured surface in minipig femur (see [8]).

Titanium TPS surfaces are originally super- or hyperhydrophobic. A wettability shift by acid etching makes the surfaces hyperhydrophilic. In experiments on nanostructured hyperhydrophilic TPS surfaces (Table 1) 4 weeks after implantation in minipigs [8] osteoid volume increases two-fold corresponding to induced de novo bone. Bone ongrowth (i.e. BIC) after 8 weeks increases nearly by two orders of magnitude and osteoid ongrowth (BIC) after 12 weeks nearly 20-fold.

The question is, how can these increases in peri-implant bone volume and bone implant contact be explained?

4 Discussion

4.1 Macrophages are the first cells to colonize a titanium implant

In 1984 Donath et al. [5] first described mononuclear histiocytes, today known as stationary form of connective tissue macrophages [11], on the surface of TPS coated titanium cylinders 3 days after implantation in the rat femur (Figure 1). Between 5 and 56 postoperative days foreign body giant cells (multinucleate macrophages) on the implant surface were observed. Two populations could be distinguished cytoplasm-rich “acid-phosphatase-positive giant cells” and smaller “acid-phophatase-negative giant cells” [5]. In contrast osteoclasts and osteoblastswere observed on bone spicules and trabeculae [5] but not on the Ti-implant. The above results are in agreement with the recent conclusion that specific osteal macrophages (“osteomacs”) exist in bone and that osteal macrophages and osteoclast precursor cells are cytologically different after having diverged from a common progenitor cell [12]. Thus the observations of Donath et al. strongly indicate the importance of macrophages for peri-implant endosseous healing.

Multinucleated giant cells (arrows) on titanium plasma sprayed (TPS) implant surface (Ti). Two types giant cells were first reported as (i) acid-phosphatase positive and (ii) acid phosphates negative cells. The former correspond to osteoclasts and the latter may be derived from wound-healing osteal macrophages (from: Donath et al. [5]).
Figure 1:

Multinucleated giant cells (arrows) on titanium plasma sprayed (TPS) implant surface (Ti). Two types giant cells were first reported as (i) acid-phosphatase positive and (ii) acid phosphates negative cells. The former correspond to osteoclasts and the latter may be derived from wound-healing osteal macrophages (from: Donath et al. [5]).

Peri-implant healing by de novo bone formation involves two principal pathways, namely contact osteogenesis and distance osteogenesis as originally reported by Osborn 1979 [1]. Of prime importance for bone bonding to the biomaterial surface is a structure called “cement line” an initial secretion of non-collagenous proteins followed by mineral nucleation and crystal growth [2], [13].

Of key importance appear to be the physico-chemical properties of the hyperhydrophilic CSA-TPS implant surface as previously described [6], [14]. Together with the high wettability expressed in imaginary contact angles of ΘAR = 10.9i°/13.5i°, and an extremely high wetting and spreading rate on hyperhydrophilic surfaces appear optimal for the immediate deposition of a fibrin matrix [2] together with blood platelets [15]. Platelet-rich plasma contains a variety of growth factors supporting bone repair [15], which may also play an important initial role on the first day. However, very soon afterwards macrophages move in [5]. Recently the connective tissue macrophages of the bone, i.e. histiocytes, discovered on the third postoperative day on implants together with the fused form of macrophages (i.e. foreign body giant cells) on the fifth day by Donath et al. [5] (Figure 1), have become of prime interest. Bone tissue specific macrophages have beentermed “osteal macrophages” [12], which can secrete a large number of cytokines, chemokines and growth factors [16].

4.2 M2-macrophages synthesize BMP-2

An important discovery was the polarization of macrophages into two phenotypes i.e. destructive inflammatory M1 and reparative wound healing M2 macrophages [17]. Crucial growth factors of such reparative macrophages for bone growth are VEGF [18] and surprisingly also of BMP-2 [19], [20]. Therefore the findings of oseoconductivity can be interpreted on this pathophysiological and biochemical basis. BMP-2 in concentrations of 50–300 pg/ml can be secreted into the cell culture medium by macrophage cell lines such as J774A.1 and RAW264.1 cells [19], [20]. In sum these findings can be interpreted as a new pathophysiological and biochemical basis of osteoconductivity.

4.3 Nanostructures on implant surface stimulate synthesis of BMP-2

Recently Sun et al. [20] reported that TiO2 nanotube layers stimulate RAW 264.7 macrophages to secrete BMP-2 in contrast to smooth surfaces. A nanostructure with tubes of 30 nm in diameter begins to stimulate BMP-2 secretion versus a smooth surface. BMP-2 secretion by RAW 264.7 macrophages then increases two-fold up to 300 pg/ml as the diameter is increased to 120 nm. Since the hyperhydropilic TPS surfaces (e.g. in Table 1) are nanostructured [7], it is conceivable that the osteal macrophages are optimally stimulated by the nanostructured TPS surface to secrete BMP-2, explaining the osteoinductive and osteoconductive properties of this surface (Table 1). In contrast the super hydrophobic TPS controls, which lack high wettability, high wetting and spreading rates as well as the macrophage stimulating nanostructure, show practically neither osteoinductivity nor osteoconductivity. Given these results, hyperhydrophilic nanostructured implants may display a great potential in a variety of orthopedic and trauma surgery applications.

4.4 Macrophage model of osseointegration

A novel model of surface contact osteogenesis can be proposed on the above observations. The new insights indicate that the osteoconductive efficiency of hyperhydrophilic micro- and nanostructured surfaces can be tested in vitro [20]. The putative mononuclear osteal macrophages arriving on day 3 on the implant surface as histiocytes [5] (Figure 2A) differentiate further into M2 wound healing macrophages putatively secreting BMP-2 (Figure 2B) for recruiting osteoblasts to the implant surface by chemotaxis. Donath et al. [5] in addition clearly describe multinuclear giant cells on day 5 (Figure 1). Thus the “cytoplasm-rich acid-phosphatase-positive and smaller acid-phophatase-negative giant cells [5], are in agreement with osteal macrophages and osteoclast precursor cells having diverged from a common progenitor cell [12]. Recently it was shown that interleukin 4 converts mononuclear macrophages into multinuclear giant cells [21] (Figure 2C). At present it is unclear, how BMP-2 in concentrations of 50–300 pg/ml stimulate bone growth, when the affinity of BMP-2 receptors on bone precursor cells and osteoblasts is two to three orders of magnitude lower [22], [23]. However, this might be explained by a juxtacrine secretion model [24] or other unconventional secretory processes [25].

Model of the development of macrophage types M1, M2 and osteoclasts in bone and peri-implant bone healing. Uncommitted macrophages differntiate into M1 and M2 macrophages and into osteoclasts. Wound-healing M2 macrophages secrete BMP-2 and VEGF. Nanostructures on the biomaterial enhance BMP-2 secretion.
Figure 2:

Model of the development of macrophage types M1, M2 and osteoclasts in bone and peri-implant bone healing. Uncommitted macrophages differntiate into M1 and M2 macrophages and into osteoclasts. Wound-healing M2 macrophages secrete BMP-2 and VEGF. Nanostructures on the biomaterial enhance BMP-2 secretion.

In the model (Figure 2) it is proposed that MGCs not only secrete BMP-2 for recruiting osteoblasts to the implant surface by chemotaxis (Figure 2), but also VEGF for angiogenesis initiating osteoinduction. BMP-2 secretion is stimulated further by nanostructures offering an innovative approach to synthesizing bioactive implant surfaces. A stimulation of VEGF secretion by nanostructures has however, not yet been shown.

Author’s Statement

Research funding: The author state no funding involved. Conflict of interest: Authors state no conflict of interest. Material and Methods: Informed consent: Informed consent is not applicable. Ethical approval: The conducted research is not related to either human or animal use.

References

  • [1]

    Osborn JF. [Biomaterials and their application to implantation] Biowerkstoffe und ihre Anwendung bei Implantaten. SSO. Schweiz. Monatsschr. Zahnheilkd. 1979;89:1138–9. Google Scholar

  • [2]

    Davies JE. Understanding peri-implant endosseous healing. J Dent Educ. 2003;67:932–49. Google Scholar

  • [3]

    Jennissen HP. Ultra-hydrophilic transition metals as histophilic biomaterials. Macromol Symp. 2005;225:43–69. Google Scholar

  • [4]

    Schwarz F, Wieland M, Schwartz Z, Zhao G, Rupp F, Geis-Gerstorfer J, et al. Potential of chemically modified hydrophilic surface characteristics to support tissue integration of titanium dental implants. J Biomed Mater Res B Appl Biomater. 2009;88:544–57. Google Scholar

  • [5]

    Donath K, Kirsch A, Osborn JF. Zelluläre Dynamik um enossale Titanimplantate. Fortschr Zahnärztl Implantol. 1984;1:55–8. Google Scholar

  • [6]

    Jennissen HP. Hyperhydrophilic rough surfaces and imaginary contact angles. Materialwiss Werkstofftech. (Mater Sci Eng Technol). 2012;43:743–50. Google Scholar

  • [7]

    Chatzinikolaidou M, Lichtinger TK, Müller RT, Jennissen HP. Peri-implant reactivity and osteoinductive potential of immobilized rhBMP-2 on titanium carriers. Acta Biomater. 2010;6:4405–21. Google Scholar

  • [8]

    Lüers S, Lehmann L, Laub M, Schwarz M, Obertacke U, Jennissen HP. The inverse lotus effect as a means of increasing osseointegration of titanium implants in a gap model. Bionanomaterials (formerly: Biomaterialien). 2011;12:34. Google Scholar

  • [9]

    Jennissen HP. Stabilizing ultra-hydrophilic surfaces by an exsiccation layer of salts and implications of the hofmeister effect. Materialwiss Werkstofftech. (Mater Sci Eng Technol). 2010;41:1035–9. Google Scholar

  • [10]

    Becker J, Kirsch A, Schwarz F, Chatzinikolaidou M, Rothamel D. Lekovic V, et al. Bone apposition to titanium implants biocoated with recombinant human bone morphogenetic protein-2 (rhBMP-2). A Pilot Study in dogs. Clin Oral Investig. 2006;10:217–4. Google Scholar

  • [11]

    Galli SJ, Borregaard N, Wynn TA. Phenotypic and functional plasticity of cells of innate immunity: macrophages, mast cells and neutrophils. Nat Immunol. 2011;12:1035–44. Google Scholar

  • [12]

    Alexander KA, Chang MK, Maylin ER, Kohler T, Muller R, Wu AC, et al. Osteal macrophages promote in vivo intramembranous bone healing in a mouse tibial injury model. J. Bone Miner Res. 2011;26:1517–32. Google Scholar

  • [13]

    Davies JE. Bone bonding at natural and biomaterial surfaces. Biomaterials. 2007;28:5058–67. Google Scholar

  • [14]

    Lattner D, Jennissen HP. Preparation and properties of ultra-hydrophilic surfaces on titanium and steel. Materialwiss Werkstofftech. (Mater Sci Eng Technol). 2009;40:109–16. Google Scholar

  • [15]

    El-Sharkawy H, Kantarci A, Deady J, Hasturk H, Liu H, Alshahat M, et al. Platelet-rich plasma: growth factors and pro- and anti-inflammatory properties. J Periodontol. 2007;78:661–9. Google Scholar

  • [16]

    Arango DG, Descoteaux A. Macrophage cytokines: involvement in immunity and infectious diseases. Front Immunol. 2014;5:491. Google Scholar

  • [17]

    Mills CD. Anatomy of a discovery: m1 and m2 macrophages. Front Immunol. 2015;6:212. Google Scholar

  • [18]

    Dohle E, Bischoff I, Bose T, Marsano A, Banfi A, Unger RE, et al. Macrophage-mediated angiogenic activation of outgrowth endothelial cells in co-culture with primary osteoblasts. Eur Cell Mater. 2014;27:149–64. Google Scholar

  • [19]

    Champagne CM, Takebe J, Offenbacher S, Cooper LF. Macrophage cell lines produce osteoinductive signals that include bone morphogenetic protein-2. Bone. 2002;30:26–31. Google Scholar

  • [20]

    Sun SJ, Yu WQ, Zhang YL, Jiang XQ, Zhang FQ. Effects of TiO2 nanotube layers on RAW 264.7 macrophage behaviour and bone morphogenetic protein-2 expression. Cell Prolif. 2013;46:685–94. Google Scholar

  • [21]

    Binder F, Hayakawa M, Choo MK, Sano Y, Park JM. Interleukin-4-induced beta-catenin regulates the conversion of macrophages to multinucleated giant cells. Mol Immunol. 2013;54:157–63. Google Scholar

  • [22]

    Wiemann M, Rumpf HM, Bingmann D, Jennissen HP. The binding of rhBMP-2 to the receptors of viable MC3T3 cells and the question of cooperativity. Materialwiss Werkstofftech. (Mat Sci Engineer Technol). 2001;32:931–6. Google Scholar

  • [23]

    Laub M, Chatzinikolaidou M, Jennissen HP. Aspects of BMP-2 binding to receptors and collagen: influence of cell senescence on receptor binding and absence of high-affinity stoichiometric binding to collagen. Materialwiss Werkstofftech. (Mat Sci Engineer Technol). 2007;38:1020–6. Google Scholar

  • [24]

    Jennissen HP. Accelerated and improved osteointegration of implants biocoated with bone morphogenetic protein 2 (BMP-2). Annals N Y Acad Sci. 2002;961:139–42. Google Scholar

  • [25]

    La VG, Zeitler M, Steringer JP, Muller HM, Nickel W. The startling properties of fibroblast growth factor 2: how to exit mammalian cells without a signal peptide at hand. J Biol Chem. 2015;290:27015–20. Google Scholar

About the article

Corresponding author: Prof. Dr. Herbert P. Jennissen, Institut für Physiologische Chemie, Universität Duisburg-Essen, Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany


Published Online: 2016-09-30

Published in Print: 2016-09-01


Citation Information: Current Directions in Biomedical Engineering, Volume 2, Issue 1, Pages 53–56, ISSN (Online) 2364-5504, DOI: https://doi.org/10.1515/cdbme-2016-0015.

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©2016 Herbert P. Jennissen, licensee De Gruyter.. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. BY-NC-ND 4.0

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