Proresolving nanomedicines activate bone regeneration in periodontitis

Abstract

Therapies to reverse tissue damage from osteolytic inflammatory diseases are limited by the inability of current tissue-engineering procedures to restore lost hard and soft tissues. There is a critical need for new therapeutics in regeneration. In addition to scaffolds, cells, and soluble mediators necessary for tissue engineering, control of endogenous inflammation is an absolute requirement for success. Although significant progress has been made in understanding natural resolution of inflammation pathways to limit uncontrolled inflammation in disease, harnessing the biomimetic properties of proresolving lipid mediators has not been demonstrated. Here, we report the use of nano-proresolving medicines (NPRM) containing a novel lipoxin analog (benzo-lipoxin A4, bLXA4) to promote regeneration of hard and soft tissues irreversibly lost to periodontitis in the Hanford miniature pig. In this proof-of-principle experiment, NPRM-bLXA4 dramatically reduced inflammatory cell infiltrate into chronic periodontal disease sites treated surgically and dramatically increased new bone formation and regeneration of the periodontal organ. These findings indicate that NPRM-bLXA4 is a mimetic of endogenous resolving mechanisms with potent bioactions that offers a new therapeutic tissue-engineering approach for the treatment of chronic osteolytic inflammatory diseases.

Keywords: bacteremia; cardiovascular disease; lipoxins; periodontal disease; resolution of inflammation; resolvins.

Conflict of interest statement

The authors declare no potential conflicts of interest with respect to the authorship and/or publication of this article.

© International & American Associations for Dental Research 2014.

Figures

Figure 1.

NPRM-bLXA4 induces bone regeneration. (A) Micro–computed tomography (µCT) images of the 4 treatment conditions: (–) sham surgery, unloaded NPRM, bLXA4 alone, NPRM-bLXA4 (red = new bone; n = 4/group). (B) NPRM-bLXA4 induces greater bone formation (*P < 0.001, analysis of variance). (C) Three-dimensional reconstruction of µCT of surgery alone and NPRM-bLXA4–treated sites to provide visual references for changes induced by lipoxin treatment. Note that bone irregularities are resolved and root notches placed at the time of surgery are covered by new bone in the NPRM-bLXA4–treated specimen.

Figure 2.

Histology confirms bLXA4 regeneration of the periodontal organ. (A) NPRM-bLXA4 induces regeneration of new bone, new connective tissue attachment, and new cementum; evidence for regeneration of the entire periodontal organ (N = notch, CT = connective tissue, B = bone, E = epithelium). (B) NPRM-bLXA4 and bLXA4 alone regenerate periodontium quantified as distance from the bone crest to the root notch created at the time of surgery (*P < 0.05, analysis of variance; n = 4/group).

Figure 3.

NPRM-bLXA4 and bLXA4 alone limit inflammatory cell infiltrate. (A) Histological images captured from hemotoxylin and eosin–stained slides at 400× magnification at the subepithelial connective tissue at 3 mo. (B) Inflammatory cell counts were determined using Image J. (*P < 0.05, analysis of variance; n = 4/group). Three captures were performed for each site, and the averages were used for analysis.

Figure 4.

Regulation of peripheral blood lipid mediator profiles by bLXA4 in periodontal disease. Whole blood was obtained at the indicated intervals post-treatment and serum isolated by centrifugation. Lipid mediator (LM) levels were investigated using LM metabololipidomics (see the Materials and Methods section for details). (Left) Representative multiple reaction–monitoring chromatograms of the identified lipid mediators in the peritoneal exudates. (Right) Accompanying tandem mass spectrometry spectra employed for identification.