Insufficient alveolar bone thickness increases the risk of periodontal dehiscence and fenestration, especially in orthodontic tooth movement. Abaloparatide (ABL), a synthetic analog of human PTHrP (1-34) and a clinical medication for treating osteoporosis, has recently demonstrated its potential in enhancing craniofacial bone formation. Herein, we show that intraoral submucosal injection of ABL, when combined with mechanical force, promotes in situ alveolar bone thickening. The newly formed bone is primarily located outside the original compact bone, implying its origin from the periosteum. RNA sequencing of the alveolar bone tissue revealed that the focal adhesion (FA) pathway potentially mediates this bioprocess. Local injection of ABL alone enhances cell proliferation, collagen synthesis, and phosphorylation of focal adhesion kinase (FAK) in the alveolar periosteum; when ABL is combined with mechanical force, the FAK expression is upregulated, in line with the accomplishment of the ossification. In vitro, ABL enhances proliferation, migration, and FAK phosphorylation in periosteal stem cells. Furthermore, the pro-osteogenic effects of ABL on alveolar bone are entirely blocked when FAK activity is inhibited by a specific inhibitor. In summary, abaloparatide combined with mechanical force promotes alveolar bone formation via FAK-mediated periosteal osteogenesis. Thus, we have introduced a promising therapeutic approach for drug-induced in situ alveolar bone augmentation, which may prevent or repair the detrimental periodontal dehiscence, holding significant potential in dentistry.
Osteogenesis/drug effects* ; Periosteum/cytology* ; Parathyroid Hormone-Related Protein/administration & dosage* ; Animals ; Focal Adhesion Protein-Tyrosine Kinases/metabolism* ; Alveolar Process/drug effects* ; Cell Proliferation/drug effects* ; Phosphorylation ; Rats ; Male ; Humans ; Focal Adhesion Kinase 1/metabolism* ; Cell Movement/drug effects*

OBJECTIVETo find the optimal proportion of Composite Fructus Psoralea and Fructus Cnidii (CFPC) for inhibiting the bone metastasis of breast cancer by way of exploring its acting mechanism viewing from OPG/RANKL/RANK system.

METHODSThe human bone metastasis of breast cancer model was established by injecting tumor cells of MDA-MB-231BO cell line into the left cardiac ventricle of nude mice. The modeled mice were randomly divided into seven groups: the blank group administered with normal saline by gastrogavage, the positive control group with zoledronic acid via peritoneal injection, and the 5 tested group with CFPC in different proportions of Fructus Psoralea and Fructus Cnidii, i.e., (A, 4:0; B, 3:1; C, 1:1; D, 1:3, and E 0:4), given by gastric infusion. The treatment started from 1 week after modeling and lasted for six weeks. By the end of the experiment, the metastatic foci in bone were imaged by radionuclide tracing method and X-ray photograph, and separated for detecting gene and protein expressions of osteoprotegerin (OPG), receptor activator of nuclear factor-kappaB ligand (RANKL), interleukin-8 (IL-8), parathyroid hormone-related protein (PTHrP), macrophage colony stimulating factor (MCSF) by Real-time PCR and Western blot respectively.

RESULTSInhibition of bone metastasis gene was displayed to some extent in all the tested groups treated with CFPC, showing an increased level of OPG mRNA expression (It was 60.343 +/- 6.274 in the tested group C), and decreased mRNA expressions of IL-8, PTHrP, MCSF, RANKL (218.010 +/- 12.802, 232.399 +/- 14.354, 319.831 +/- 5.322, and 195.701 +/- 4. 862, respectively in the tested group C). The optimal effect was shown in the tested group C, showing significant difference to that in the blank group (P < 0.01). Meanwhile, the OPG in the bone metastatic foci could be up-regulated and protein expressions of RANKL/IL-8/PTHrP/MCSF down-regulated in all the tested groups. The optimal effect was shown in the tested group C, with significant difference from those of the normal saline group.

CONCLUSIONCFPC could inhibit the bone metastasis of breast cancer through activating OPG/RANKL/RANK pathway. Among different proportions of Fructus Psoralea and Fructus Cnidii, 1:1 was the best one.

Animals ; Bone Neoplasms ; metabolism ; pathology ; secondary ; Breast Neoplasms ; metabolism ; pathology ; Cell Line, Tumor ; Coumarins ; administration & dosage ; pharmacology ; Female ; Ficusin ; administration & dosage ; pharmacology ; Interleukin-8 ; metabolism ; Macrophage Colony-Stimulating Factor ; metabolism ; Mice ; Mice, Inbred BALB C ; Mice, Nude ; Neoplasm Metastasis ; Osteoprotegerin ; metabolism ; Parathyroid Hormone-Related Protein ; metabolism ; RANK Ligand ; metabolism ; Receptor Activator of Nuclear Factor-kappa B ; metabolism