The dynamic changes of circulating OCN+ cells versus insulinlike growth factor-I during primary healing of orthognathic surgeries

Increase in bone metabolic markers and circulating osteoblast-lineage cells after orthognathic surgery

Increased mineralisation rate and bone formation after surgery or fracture is the regional acceleratory phenomenon (RAP), and its systemic impact is the systemic acceleratory phenomenon (SAP). The proportion of circulating osteoblast lineage cells, including osteocalcin-positive (OCN⁺) cells, in the peripheral blood is markedly higher during pubertal growth and in patients with bone fractures. This study aimed to elucidate the dynamic changes in bone metabolic activity after orthognathic surgery by longitudinal prospective observation. Peripheral venous blood samples were collected from patients who had undergone orthognathic surgery, and serum bone metabolic markers and the proportion of OCN⁺ cells were measured. Orthognathic surgery induces systemic dynamic changes in bone metabolic activity by targeting steps in the bone healing process and related proteins, such as surgical stress/inflammation (C-reactive protein), bone resorption (type I collagen C-telopeptide), and bone formation (alkaline phosphatase and bone-specific alkaline phosphatase). During the early post-operative period, the population of OCN⁺ cells significantly increased. Confocal microscopy revealed that OCN proteins were localised in the cytoplasm in Triton X-100-treated OCN⁺ cells. Furthermore, OCN, ALP, and COL1A1 gene expression was detected in OCN⁺ cells, suggesting the contribution of the local maturation of bone marrow-derived OCN⁺ cells at the site of bone healing.

MicroRNA‑223 promotes osteoblast differentiation of MC3T3‑E1 cells by targeting histone deacetylase 2

MicroRNAs (miRNAs) have emerged as pivotal regulators in various physiological and pathological processes at the post‑transcriptional level, and may serve important roles in osteogenic differentiation. However, their roles and functions are not fully understood. In the present study, miR‑223‑5p was identified as a modulator of osteoblastic differentiation in MC3T3‑E1 cells. Reverse transcription‑quantitative polymerase chain reaction and western blotting demonstrated that miR‑223‑5p was significantly upregulated in MC3T3‑E1 cells following the induction of osteoblast differentiation. Overexpression of miR‑223‑5p promoted osteogenic differentiation both in vitro and vivo. Expression of histone deacetylase 2 (HDAC2), which acts as a negative regulator of osteogenesis, was regulated by miR‑223‑5p. Collectively, the results of the present study revealed a novel miR‑223‑5p/HDAC2 axis that regulates osteoblast differentiation, and may serve as a potential target for enhancing bone formation in vivo.

Orthognathic surgery induces genomewide changes longitudinally in DNA methylation in saliva

OBJECTIVE

Orthognathic surgery dramatically changes morphology of the maxillofacial deformity and improves the malocclusion morphologically and functionally. We investigated the influence of orthognathic surgery on genomewide DNA methylation in saliva.

METHODS

Saliva was obtained from nine patients undergoing orthognathic surgery and two healthy reference individuals before and 3 months after orthognathic surgery. Genomewide DNA methylation profiling of saliva (341,482 CpG dinucleotides) was conducted using Infinium HumanMethylation450 BeadChips.

RESULTS

Comparison between pre- and postsurgery saliva samples revealed significant changes in DNA methylation patterns at 2,381 CpG sites (p < 0.01) with suggestive significance. The differentially methylated probe sets were significantly associated with the cancer pathway (p = 2.8 × 10^-7 ; a false discovery rate q-value = 3.7 × 10^-4 ) and PI3K-Akt signalling pathway (p = 2.4 × 10^-5 ; a false discovery rate q-value = 3.1 × 10^-2 ).

CONCLUSION

Pathway enrichment analysis of genes with suggestive significance demonstrated that altered DNA methylation in saliva of patients undergoing orthognathic surgery, possibly as a response to surgical stress or bone injury. Further studies with a large sample size and long-term observation are needed to validate the phenomena identified in this study.

T Lymphocytes Influence the Mineralization Process of Bone

Bone is a unique organ able to regenerate itself after injuries. This regeneration requires the local interplay between different biological systems such as inflammation and matrix formation. Structural reconstitution is initiated by an inflammatory response orchestrated by the host immune system. However, the individual role of T cells and B cells in regeneration and their relationship to bone tissue reconstitution remain unknown. Comparing bone and fracture healing in animals with and without mature T and B cells revealed the essential role of these immune cells in determining the tissue mineralization and thus the bone quality. Bone without mature T and B cells is stiffer when compared to wild-type bone thus lacking the elasticity that helps to absorb forces, thus preventing fractures. In-depth analysis showed dysregulations in collagen deposition and osteoblast distribution upon lack of mature T and B cells. These changes in matrix deposition have been correlated with T cells rather than B cells within this study. This work presents, for the first time, a direct link between immune cells and matrix formation during bone healing after fracture. It illustrates specifically the role of T cells in the collagen organization process and the lack thereof in the absence of T cells.