Role of IL-34 and its receptors in inflammatory diseases

Longitudinal associations between serum IL-34 with severity and prognosis in community-acquired pneumonia patients

BACKGROUND

Interleukin-34 (IL-34) is a hematopoietic cytokine and a ligand of colony-stimulating factor 1 receptor (CSF-1R). Numerous studies have demonstrated that IL-34 is involved in several inflammatory diseases. Nevertheless, the role of IL-34 is obscure in community-acquired pneumonia (CAP) patients. This research aimed to assess the associations of serum IL-34 with severity and prognosis in CAP patients through a longitudinal study.

METHODS

CAP patients and healthy volunteers were recruited. Peripheral blood samples were collected. Serum IL-34 and inflammatory cytokines were tested by enzyme linked immunosorbent assay (ELISA). Demographic characteristics and clinical information were acquired through electronic medical records.

RESULTS

Serum IL-34 was elevated in CAP patients compared with healthy volunteers. The content of serum IL-34 was gradually upregulated with increased CAP severity scores. Mixed logistic and linear regression models suggested that serum IL-34 elevation was associated with increased PSI and SMART-COP scores. Correlative analysis found that serum IL-34 was positively correlated with inflammatory cytokines among CAP patients. A longitudinal study indicated that higher serum IL-34 at admission elevated the risks of mechanical ventilation and death during hospitalization. Serum IL-34 had a higher predictive capacity for death than CAP severity scores.

CONCLUSION

There are prominently positive dose-response associations between serum IL-34 at admission with the severity and poor prognosis, suggesting that IL-34 is implicated in the occurrence and development of CAP. Serum IL-34 may serve as a biomarker to forecast disease progression and poor prognosis in CAP patients.

A Lower IL-34 Expression Is Associated with Non-Healing Diabetic Foot Ulcers

BACKGROUND

The non-healing of diabetic foot ulcers (DFU) is a major cause of high disability, morbidity, and mortality. Thus, new therapeutic targets and methods to help healing in patients with DFUs are major research hotspots.

OBJECTIVE

This study examined the molecular differences between healing and non-healing DFUs to identify genes associated with DFU healing.

METHODS

Differentially expressed genes (DEGs) were identified by bioinformatics. Samples were collected from patients with healing (n=10) and non-healing (n=10) DFUs from September 2021 to September 2022. Interleukin (IL)-34 expression was measured by ELISA and qRT-PCT. The fibroblasts from healing and non-healing DFU were divided according to their gene signatures and subdivided based on their gene expression profile differences.

RESULTS

A comparison of fibroblast subpopulation characteristics revealed that the proportion of subpopulation 4 was significantly higher in non-healing DFUs than in healing DFUs. Subpopulation 4 had 254 upregulated genes and 2402 downregulated genes in the non-healing compared with the healing DFUs. The DEGs were involved in several biological functions, including cytokine activity, receptor-ligand activity, signaling receptor activator activity, and receptor regulator activity. IL-34 was downregulated in non-healing compared with healing DFUs, suggesting a possible role of IL-34 in DFU healing. In the clinical specimens, IL-34 was significantly downregulated in non-healing DFUs, consistent with the bioinformatics results.

CONCLUSION

IL-34 expression is downregulated in non-healing DFU. IL-34 appears to be involved in DFU healing, but the exact causal relationship remains to be explored.