Periodontal ligament‑associated protein‑1 delays rat periodontal bone defect repair by regulating osteogenic differentiation of bone marrow stromal cells and osteoclast activation

Abstract

The aim of the present study was to assess the roles of periodontal ligament‑associated protein‑1 (PLAP‑1) in the osteogenic differentiation of rat bone marrow stromal cells (rBMSCs) and in osteoclast activation during the repair of rat periodontal bone defects. Male, 6‑week‑old, Wistar rats treated with periodontal bone defects were randomly assigned to 3 groups: The PLAP‑1‑transfected rBMSC group (PLAP‑1 group), the empty vector‑transfected rBMSC group (vector group) and the normal rBMSC group (control group). Specimens were obtained at 2, 4 and 6 weeks post‑surgery. Histological observation and micro‑computed tomography were applied to evaluate the repair effect. The bone defect areas of the mandible were dissected for western blotting and reverse transcription-quantitative polymerase chain reaction (RT‑qPCR). Osteogenesis‑associated proteins, including alkaline phosphatase (ALP), bone sialoprotein (BSP), runt-related transcription factor 2 (Runx2), Osterix (Osx) and osteocalcin (OC), as indicators of rBMSC‑induced osteogenesis, were examined by RT-qPCR and western blotting. Osteoclasts were identified and quantified using tartrate‑resistant acid phosphatase staining. Meanwhile, the receptor activator of nuclear factor κΒ ligand (RANKL)/οsteoprotegerin (OPG) ratio was quantified to assess osteoclast activation by western blotting. Τhe repair effect of the PLAP‑1 group was significantly worse than that of the vector and control groups. In the PLAP‑1 group, newly formed and mineralized bones were significantly less in quantity than that in the other two groups (P<0.05), and the expression of osteogenic proteins (ALP, BSP, Runx2, Osx and OC) was also reduced (P<0.01). However, there was no significant difference between the vector and control groups. The RANKL/OPG ratio was upregulated in the PLAP‑1 group due to decreased OPG protein expression and a simultaneous increase in RANKL protein expression (P<0.01), and more osteoclasts were activated in the PLAP‑1 group (P<0.01). In conclusion, the present study found that PLAP‑1 delays rat periodontal bone defect repair by inhibiting osteogenic differentiation and promoting osteoclast activation, mainly dependent on the upregulation of the RANKL/OPG ratio.

ASPN Synergizes with HAPLN1 to Inhibit the Osteogenic Differentiation of Bone Marrow Mesenchymal Stromal Cells and Extracellular Matrix Mineralization of Osteoblasts

“…also reported that ASPN treatment inhibited ALP intensity and activity and decreased the expression levels of osteogenesis‐related COL1A1, thereby inhibiting the cytodifferentiation and mineralization of periodontal ligament cells 39 . Another study reported that ASPN overexpression decreased OCN expression in rat periodontal bone defects 40 . The just‐mentioned documentations further increased the credibility of our results.…”

“…39 Another study reported that ASPN overexpression decreased OCN expression in rat periodontal bone defects. 40 The just-mentioned documentations further increased the credibility of our results. Meanwhile, a decrease in HAPLN1 expression was accompanied by an increase in COL1A1 expression in damaged cartilage, 41 which indirectly supports our finding in this study that COL1A1 expression was upregulated after HAPLN1 knockdown in BMSCs of OVX mice.…”

Core Matrisome Protein Signature During Periodontal Ligament Maturation From Pre-occlusal Eruption to Occlusal Function

“…This mechanical property is called thixotropy and has been attributed to proteoglycans in skin (Finlay, 1978). Asporin regulates PDL fibroblasts (Kajikawa et al, 2014) via BMP-2 and PDL osteoclasts via receptor activator of nuclear factor κB ligand (RANKL) and osteoprotegerin (OPG) (Yu et al, 2018) as well as negative regulation of TGF-β (Kizawa et al, 2005) and bone morphogenetic protein 2 (BMP-2) (Yamada et al, 2008) and enhancement of fibroblast growth factor 2 (FGF-2) (Awata et al, 2015). Asporin's regulation of osteogenic growth factors is in line with our results showing localization near the alveolar bone side of the PDL and in the bone itself.…”

“…Proteoglycans contribute to maintaining the structure of the tissue and the ECM and protect the integrity in the face of heavy loading, for example in intervertebral disks (Roughley, 2006), in tendons (Screen et al, 2006), and in the PDL (Kurylo et al, 2016). Beyond their mechanical function, they also modulate growth factors (Zhang et al, 1995;Häkkinen et al, 2000;Kizawa et al, 2005;Yamada et al, 2008;Awata et al, 2015;Yu et al, 2018) and regulate ECM composition and structure (Matheson et al, 2005;Chen and Birk, 2013;Kurylo et al, 2016). Gylcoproteins are proteins with covalently attached N-linked glycans.…”

Periodontal ligament‐associated protein‐1 gets involved in experimental periodontitis

“…Periodontal ligament‐associated protein 1 (PLAP‐1/asporin) is an extracellular matrix protein preferentially expressed in periodontal ligament (PDL) and an important regulator of osteogenic differentiation of periodontal ligament cells . PLAP‐1 is involved in the homeostasis of periodontal tissues and protects the periodontal ligament from excessive osteogenesis .…”