Cathepsin G promotes arteriovenous fistula maturation by positively regulating the MMP2/MMP9 pathway

BACKGROUND

Arteriovenous fistula (AVF) is currently the preferred vascular access for hemodialysis patients. However, the low maturation rate of AVF severely affects its use in patients. A more comprehensive understanding and study of the mechanisms of AVF maturation is urgently needed.

METHODS AND RESULTS

In this study, we downloaded the publicly available datasets (GSE119296 and GSE220796) from the Gene Expression Omnibus (GEO) and merged them for subsequent analysis. We screened 84 differentially expressed genes (DEGs) and performed the functional enrichment analysis. Next, we integrated the results obtained from the degree algorithm provided by the Cytohubba plug-in, Molecular complex detection (MCODE) plug-in, weighted gene correlation network analysis (WGCNA), and Least absolute shrinkage and selection operator (LASSO) logistic regression. This integration allowed us to identify CTSG as a hub gene associated with AVF maturation. Through the literature search and Pearson's correlation analysis, the genes matrix metalloproteinase 2 (MMP2) and MMP9 were identified as potential downstream effectors of CTSG. We then collected three immature clinical AVF vein samples and three mature samples and validated the expression of CTSG using immunohistochemistry (IHC) and double-immunofluorescence staining. The IHC results demonstrated a significant decrease in CTSG expression levels in the immature AVF vein samples compared to the mature samples. The results of double-immunofluorescence staining revealed that CTSG was expressed in both the intima and media of AVF veins. Moreover, the expression of CTSG in vascular smooth muscle cells (VSMCs) was significantly higher in the mature samples compared to the immature samples. The results of Masson's trichrome and collagen I IHC staining demonstrated a higher extent of collagen deposition in the media of immature AVF veins compared to the mature. By constructing an in vitro CTSG overexpression model in VSMCs, we found that CTSG upregulated the expression of MMP2 and MMP9 while downregulating the expression of collagen I and collagen III. Furthermore, CTSG was found to inhibit VSMC migration.

CONCLUSIONS

CTSG may promote AVF maturation by stimulating the secretion of MMP2 and MMP9 from VSMCs and reducing the extent of medial fibrosis in AVF veins by inhibiting the secretion of collagen I and collagen III.

Contemporary Strategies to Promote Dialysis Access Fistula Maturation

Background: The inability of a newly created arteriovenous fistula to support hemodialysis due to non-maturation results in increased complications secondary to catheter dependence. Methods: In view of the highly variable approaches by providers with heterogenous backgrounds (general surgery, vascular surgery, interventional radiology and interventional nephrology, urology, transplant surgery, etc.) we sought to describe a collection of algorithms that have functioned well in our hands to manage this challenging clinical problem and guide trainees and practicing clinicians alike.Results: Physical examination along with selective duplex ultrasound and fistulogram can identify most pathologies underlying non-maturation.Conclusion: Both endovascular and open techniques can be employed to optimize maturation rates in this complex population.

Surgical rejoining of small arm veins to enhance dialysis fistula maturation

Non-maturation of arteriovenous fistulas is a frequent problem after dialysis access creation, especially in the forearm. The presence of accessory veins may play an important role in the non-maturing fistula. Several surgical and endovascular techniques are described to deal with this problem. We describe a new surgical technique in which we perform a rejoining of the arm veins to create a single large run-off vessel with greater diameter and flow for haemodialysis.

Non-matured arteriovenous fistulae for haemodialysis: diagnosis, endovascular and surgical treatment

Non-maturation is a feature of autologous vascular access. The autologous arteriovenous fistula needs time to mature and for the vein to enlarge to a size where it can be needled for dialysis. A fistula that fails early is one that either never develops adequately to support dialysis or fails within the first three months of its use. Two variables are required for fistula maturation. Firstly, the fistula should have adequate blood flow to support dialysis and secondly, it should have enough size to allow for successful repetitive cannulation. Three main reasons for maturation failure are: arterial and venous problems and the presence of accessory veins. Early diagnostics and intervention for fistula maturation minimizes catheter use and its associated complications. The identification of immature fistulae is relatively simple. Physical examination has been highlighted to be a valuable tool in assessing fistula. Any fistula that fails to mature adequately and demonstrates abnormal physical findings should be studied aggressively. Ultrasonography can successfully identify candidates who fail to meet the recently developed criteria for immature fistulae. In recent years, digital subtraction angiography and contrast-enhanced magnetic resonance angiography has been introduced for assessment of dysfunctional haemodialysis conduits, including immature fistulae. A great majority of non-matured fistulae can be successfully salvaged using percutaneous techniques. In addition to endovascular techniques, surgical intervention can also be an option. This paper reviews the process of fistula maturation and presents information regarding how to obtain a mature fistula.