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Kinoshita M, Yamada S, Sasaki J, Suzuki S, Kajikawa T, Iwayama T, Fujihara C, Imazato S, Murakami S. Mice Lacking PLAP-1/Asporin Show Alteration of Periodontal Ligament Structures and Acceleration of Bone Loss in Periodontitis. Int J Mol Sci 2023; 24:15989. [PMID: 37958972 PMCID: PMC10649079 DOI: 10.3390/ijms242115989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 10/24/2023] [Accepted: 11/03/2023] [Indexed: 11/15/2023] Open
Abstract
Periodontal ligament-associated protein 1 (PLAP-1), also known as Asporin, is an extracellular matrix protein expressed in the periodontal ligament and plays a crucial role in periodontal tissue homeostasis. Our previous research demonstrated that PLAP-1 may inhibit TLR2/4-mediated inflammatory responses, thereby exerting a protective function against periodontitis. However, the precise roles of PLAP-1 in the periodontal ligament (PDL) and its relationship to periodontitis have not been fully explored. In this study, we employed PLAP-1 knockout mice to investigate its roles and contributions to PDL tissue and function in a ligature-induced periodontitis model. Mandibular bone samples were collected from 10-week-old male C57BL/6 (WT) and PLAP-1 knockout (KO) mice. These samples were analyzed through micro-computed tomography (μCT) scanning, hematoxylin and eosin (HE) staining, picrosirius red staining, and fluorescence immunostaining using antibodies targeting extracellular matrix proteins. Additionally, the structure of the PDL collagen fibrils was examined using transmission electron microscopy (TEM). We also conducted tooth extraction and ligature-induced periodontitis models using both wild-type and PLAP-1 KO mice. PLAP-1 KO mice did not exhibit any changes in alveolar bone resorption up to the age of 10 weeks, but they did display an enlarged PDL space, as confirmed by μCT and histological analyses. Fluorescence immunostaining revealed increased expression of extracellular matrix proteins, including Col3, BGN, and DCN, in the PDL tissues of PLAP-1 KO mice. TEM analysis demonstrated an increase in collagen diameter within the PDL of PLAP-1 KO mice. In line with these findings, the maximum stress required for tooth extraction was significantly lower in PLAP-1 KO mice in the tooth extraction model compared to WT mice (13.89 N ± 1.34 and 16.51 N ± 1.31, respectively). In the ligature-induced periodontitis model, PLAP-1 knockout resulted in highly severe alveolar bone resorption, with a higher number of collagen fiber bundle tears and significantly more osteoclasts in the periodontium. Our results demonstrate that mice lacking PLAP-1/Asporin show alteration of periodontal ligament structures and acceleration of bone loss in periodontitis. This underscores the significant role of PLAP-1 in maintaining collagen fibrils in the PDL and suggests the potential of PLAP-1 as a therapeutic target for periodontal diseases.
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Affiliation(s)
- Masaki Kinoshita
- Department of Periodontology and Regenerative Dentistry, Osaka University Graduate School of Dentistry, Suita 565-0871, Osaka, Japan; (M.K.); (T.I.); (C.F.); (S.M.)
| | - Satoru Yamada
- Department of Periodontology and Endodontolgy, Tohoku University Graduate School of Dentistry, Sendai 980-8575, Miyagi, Japan; (S.S.); (T.K.)
| | - Junichi Sasaki
- Department of Dental Biomaterials, Osaka University Graduate School of Dentistry, Suita 565-0871, Osaka, Japan; (J.S.); (S.I.)
| | - Shigeki Suzuki
- Department of Periodontology and Endodontolgy, Tohoku University Graduate School of Dentistry, Sendai 980-8575, Miyagi, Japan; (S.S.); (T.K.)
| | - Tetsuhiro Kajikawa
- Department of Periodontology and Endodontolgy, Tohoku University Graduate School of Dentistry, Sendai 980-8575, Miyagi, Japan; (S.S.); (T.K.)
| | - Tomoaki Iwayama
- Department of Periodontology and Regenerative Dentistry, Osaka University Graduate School of Dentistry, Suita 565-0871, Osaka, Japan; (M.K.); (T.I.); (C.F.); (S.M.)
| | - Chiharu Fujihara
- Department of Periodontology and Regenerative Dentistry, Osaka University Graduate School of Dentistry, Suita 565-0871, Osaka, Japan; (M.K.); (T.I.); (C.F.); (S.M.)
| | - Satoshi Imazato
- Department of Dental Biomaterials, Osaka University Graduate School of Dentistry, Suita 565-0871, Osaka, Japan; (J.S.); (S.I.)
| | - Shinya Murakami
- Department of Periodontology and Regenerative Dentistry, Osaka University Graduate School of Dentistry, Suita 565-0871, Osaka, Japan; (M.K.); (T.I.); (C.F.); (S.M.)
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Abstract
Proteoglycans consist of a protein core with one or more covalently attached glycosaminoglycan (GAG) side chains and have multiple roles in the initiation and progression of atherosclerosis. Here we discuss the potential and known functions of a group of small leucine-rich repeat proteoglycans (SLRPs) in atherosclerosis. We focus on five SLRPs, decorin, biglycan, lumican, fibromodulin and PRELP, because these have been detected in atherosclerotic plaques or demonstrated to have a role in animal models of atherosclerosis. Decorin and biglycan are modified post-translationally by substitution with chondroitin/dermatan sulphate GAGs, whereas lumican, fibromodulin and PRELP have keratan sulphate side chains, and the core proteins have leucine-rich repeat (LRR) motifs that are characteristic of the LRR superfamily. The chondroitin/dermatan sulphate GAG side chains have been implicated in lipid retention in atherosclerosis. The core proteins are discussed here in the context of (i) interactions with collagens and their implications in tissue integrity, fibrosis and wound repair and (ii) interactions with growth factors, cytokines, pathogen-associated molecular patterns and cell surface receptors that impact normal physiology and disease processes such as inflammation, innate immune responses and wound healing (i.e. processes that are all important in plaque development and progression). Thus, studies of these SLRPs in the context of wound healing are providing clues about their functions in early stages of atherosclerosis to plaque vulnerability and cardiovascular disease at later stages. Understanding of signal transduction pathways regulated by the core protein interactions is leading to novel roles and therapeutic potential for these proteins in wound repair and atherosclerosis.
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Affiliation(s)
| | - J Borén
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden
| | - S Chakravarti
- Departments of Medicine, Ophthalmology and Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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