Effect of aging on bone metabolism: the involvement of complement C1q

Protein profile at newly restored implants compared to contralateral teeth over 12-months: a pilot study

OBJECTIVES

To determine crevicular fluid alterations in protein expression of newly restored implants during their first year of function and associate them with those of contralateral teeth.

MATERIALS AND METHODS

In ten non-smokers, successfully treated for periodontitis, one newly restored implant (baseline-T0) and one corresponding tooth were followed for 12-months (T1). Oral hygiene was monitored during the study. Periodontal clinical indices and crevicular fluid were collected from an implant-site (PICF) and a tooth-site (GCF). Total proteomic profiles of PICF and GCF were investigated using label-free quantitative proteomics.

RESULTS

Clinical recordings remained stable at 12-months on the tooth-/implant-site basis. The comparative analysis of protein enrichment between teeth and implants at T0 revealed 664 human proteins, with 93 found only in teeth and 217 exclusively in implants. Among the 354 overlapping proteins, 46 were upregulated (log2FC > 1) in teeth, while 61 in implants. At T1, 569 human proteins were exclusively identified, with 67 found only in teeth and 193 exclusively in implants. Of the 309 overlapping proteins, 22 were upregulated in teeth, while 48 were in implants. The over-representation enrichment analysis identified "interferon-alpha response" and "allograft rejection" pathways, as significantly regulated categories at T0, with the latter being over-represented at T1.

CONCLUSIONS

Peri-implant tissue maturation was evident during the study. Proteins expressed in crevicular fluid reflected unique patterns between implants and teeth that are worth studying.

CLINICAL RELEVANCE

Different proteomic patterns were observed at the implant-site compared to the contralateral tooth-site towards inflammatory processes that prevail within otherwise clinically healthy peri-implant tissues.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov ID: NCT06379022.

Decoding the immune landscape following hip fracture in elderly patients: unveiling temporal dynamics through single-cell RNA sequencing

BACKGROUND

Hip fractures in the elderly have significant consequences, stemming from the initial trauma and subsequent surgeries. Hidden blood loss and stress due to concealed injury sites could impact the whole osteoimmune microenvironment. This study employs scRNA-seq technique to map immune profiles in elderly hip fracture patients from post-trauma to the recovery period, investigating the dynamic changes of immune inflammation regulation subgroups.

METHODS

We collected peripheral blood samples from four elderly hip fracture patients (two males and two females, all > 75 years of age) at three different time points (24 h post-trauma, 24 h post-operation, and day 7 post-operation) and applied scRNA-seq technique to analyze the cellular heterogeneity and identify differentially expressed genes in peripheral blood individual immune cells from elderly hip fracture patients.

RESULTS

In this study, we analyzed the composition and gene expression profiles of peripheral blood mononuclear cells (PBMCs) from elderly hip fracture patients by scRNA-seq and further identified new CD14 monocyte subpopulations based on marker genes and transcriptional profiles. Distinct gene expression changes were observed in various cell subpopulations at different time points. C-Mono2 monocyte mitochondria-related genes were up-regulated and interferon-related and chemokine-related genes were down-regulated within 24 h post-operation. Further analysis of gene expression profiles at day 7 post-operation showed that C-Mono2 monocytes showed downregulation of inflammation-related genes and osteoblast differentiation-related genes. However, the expression of these genes in cytotoxic T cells, Treg cells, and B cell subsets exhibited a contrasting trend. GZMK+CD8+ cytotoxic T cells showed downregulation of chemokine-related genes, and Treg cells showed upregulation of genes related to the JAK/STAT signaling pathway. Furthermore, we examined interactions among diverse immune cell subsets, pinpointing specific ligand-receptor pairs. These findings imply cross-talk and communication between various cell types in the post-traumatic immune response.

CONCLUSIONS

Our study elucidates the notable alterations in immune cell subpopulations during different stages of hip fracture in elderly patients, both in terms of proportions and differential gene expressions. These changes provide significant clinical implications for tissue repair, infection prevention, and fracture healing in clinic.

The collagen structure of C1q induces wound healing by engaging discoidin domain receptor 2

Background

C1q has been reported to reveal complement-independent roles in immune and non-immune cells. C1q binds to its specific receptors to regulate distinct functions that rely on the environment and cell types. Discoidin domain receptor 2 (DDR2) is activated by collagen and functions in wound healing by controlling matrix metalloproteinase (MMP) expression. Since C1q exhibits a collagen-like structure, we hypothesized that C1q might engage DDR2 to regulate wound healing and extracellular matrix (ECM) remodeling.

Methods

Cell-based assay, proximity ligation assay, ELISA, and surface plasmon analysis were utilized to investigate DDR2 and C1q binding. We also investigate the C1q-mediated in vitro wound healing ability using the human fibrosarcoma cell line, HT1080.

Results

C1q induced the phosphorylation of DDR2, p38 kinase, and ERK1/2. C1q and DDR2 binding improved cell migration and induced MMP2 and MMP9 expression. DDR2-specific shRNA reduced C1q-mediated cell migration for wound healing.

Conclusions

C1q is a new DDR2 ligand that promotes wound healing. These findings have therapeutic implications in wound healing-related diseases.