Evaluating Animal Models for Improved Hemodialysis Vascular Access: A Focus on Arteriovenous Fistula

Introduction

With the aging of the population and the changes in lifestyle worldwide, the incidence of chronic kidney disease (CKD) and related medical expenses are rising year by year, posing a significant threat to public health systems [1]. In 2020, there were 159.8 million CKD patients in China [2]. As CKD progresses to end-stage renal disease (ESRD), the kidneys’ excretory, secretory, and synthetic functions become severely compromised, leading to severe clinical symptoms that can affect multiple systems. Renal replacement therapy is the primary treatment for ESRD, which includes kidney transplantation, hemodialysis, and peritoneal dialysis. Kidney transplantation is the preferred option, but in practice, hemodialysis (HD) remains the most commonly used form of renal replacement therapy [3].

To maintain HD, a well-functioning access between the artery and vein is required to provide adequate blood flow for the multiple weekly hemodialysis sessions. There exist 3 types of vascular access: autogenous arteriovenous fistula (AVF), arteriovenous graft (AVG), and central vein catheter (CVC) [4]. AVF has a better primary patency rate and is recommended as the preferred vascular access for long-term HD by the Kidney Disease Outcomes Quality Initiative and the National Kidney Foundation. However, its primary patency rate remains between 60% and 65% [5]. Currently, various dialysis guidelines and expert consensus assume that the elements of AVF access dysfunction include stenosis, thrombosis, access steal syndrome, aneurysm, and infection, among other complications, and the incidence of complications is increasing from year to year [4]. Stenosis is the main cause of AVF access dysfunction. Repeated punctures during and after AVF surgery cause to endothelial trauma, leading to oxidative stress reactions [6,7]. At the same time, the venous outflow segment is affected by hemodynamic changes, causing endothelial damage that triggers the release of pro-inflammatory cytokines and a cascade of reactions, which in turn induce the migration and proliferation of vascular smooth muscle cells, resulting in abnormal hyperplasia of the neointima, and obstruction of venous outward expansion and remodeling, ultimately contributing to fistula stenosis and inability to provide sufficient blood flow for multiple weekly hemodialysis sessions [6,8].

When AVF access develops functional stenosis, percutaneous transluminal angioplasty (PTA) tends to be used as the first-line therapy, while about half of HD patients experience restenosis within 6 months after PTA treatment [9]. At present, research on the prevention and treatment of AVF stenosis has not yet found a better solution. Therefore, studying the factors related to AVF stenosis and improving its patency rate is an indispensable clinical issue for patients undergoing long-term HD and for medical staff [5].

Nowadays, research concerning the pathogenesis, diagnostic, therapeutic methods, and preventive measures for AVF stenosis mainly relies on animal experiments, yet no clear and effective medical interventions to prevent the maturation of AVF function have been identified [6]. Moving forward, animal experiments will continue to be utilized to confront this tremendous challenge. In experimental research, the selection of experimental animals is a critical step, which requires the consideration of multiple factors. The choice of experimental animals depends on specific research objectives to precisely simulate clinical scenarios and enhance the accuracy of translating research findings into clinical applications [10,11]. For studies focusing on factors related to AVF stenosis, experimental animals are often used to create models of renal failure with AVF. This approach aims to mimic clinical diseases and investigate their pathogenesis, as well as novel diagnostic, therapeutic methods, and preventive measures. The goal is to extend the lifespan of vascular access and improve the quality of life for patients with ESRD. In this review, we aim to assess the role of animal models in studies on autologous AVF for HD.

Clinical Arteriovenous Fistula

Firstly, we should acknowledge the establishment of human AVF models with the aim of conducting the animal experiments with autologous arteriovenous fistulas, which can better reflect the pathogenesis, diagnosis methods, treatment approaches and preventive measures for human autologous arteriovenous fistula stenosis.

Selection of Vascular Accesses

According to the recommendations of the National Kidney Foundation (NKF), AVF is the preferred vascular access for long-term hemodialysis [5]. When patients are medically suitable for the use of the 3 types of vascular accesses, the order of selection should be as follows: first, upper-limb autogenous arteriovenous fistula; then, upper-limb arteriovenous graft (AVG); and, followed by trunk or lower-limb AVF and AVG [12]. Central venous catheters are typically used as temporary vascular accesses for hemodialysis.

Human Autologous Arteriovenous Fistula

Patients should receive surgical education and undergo assessments of various indicators before undergoing autogenous arteriovenous fistula (AVF) surgery [4]. AVF, postoperatively, demand meticulous care to estimate the patency and maturity of the fistula. Similarly, there should also be a sufficiently long venous outflow segment available for cannulation during hemodialysis after the AVF has matured [5]. The upper limb is physiologically superior to the lower limb for AVF creation and is also the most common location for fistula creation in clinical practice, which aligns with the principles of vascular selection for AVF creation. Taking the upper-limb vessels as an example, the commonly chosen vessels for human AVF include: wrist AVF (radial artery-cephalic vein), forearm transposition AVF (radial artery-basilic vein transposition, brachial artery-basilic vein transposition, brachial artery-cephalic vein transposition), and elbow AVF (brachial artery-cephalic vein, brachial artery-antecubital vein, brachial artery-basilic vein) [12]. The anastomosis methods for AVF chiefly embrace end-to-side (Figure 1A), side-to-side (Figure 1B), and end-to-end anastomosis (Figure 1C), with end-to-side anastomosis being the most commonly used in clinical practice [13]. Proper postoperative maintenance becomes essential to promote AVF maturation and extend the lifespan of the vascular access.

Animal Experimentation Research

CURRENT SITUATION OF ANIMAL EXPERIMENTAL RESEARCH:

At the biological level, animals share a high degree of similarity with humans, which makes them susceptible to many health issues that are consistent with those of humans. Leveraging this similarity, researchers study animal diseases to explore human diseases [14]. However, with the advancement of science and technology, there is increasing public demand for alternative research to animal experimentation, driven by considerations of animal experimentation regulations, medical ethics, and animal rights. The US Food and Drug Administration (FDA) has stated that researchers should only use experimental animals when necessary. This decision has spurred the development of animal alternatives, such as organoids, tissue chips, and computer models [15]. Although non-animal models have made significant breakthroughs, capable of replicating complex human physiology to improve experimental accuracy, reduce costs, and fill gaps in research on rare diseases and biotherapies [16], animal experiments remain the primary method for studying complex human physiological functions. No complete alternatives to animals have yet been developed. Animals hold an irreplaceable position in the biomedical field, such as in the study of drug absorption, distribution, and excretion, vaccine development, immune system diseases, and metabolic diseases. Non-human primates, with their high similarity to the human nervous system, are indispensable for research on neurological diseases. Furthermore, in the ongoing exploration of COVID-19, animal experiments have been crucial for studying transmission routes, treatment methods, and testing the safety and efficacy of vaccines in animals, which non-animal models cannot achieve. Various animals, including snow leopards, pigs, and rodents, have been used in COVID-19 research, further emphasizing the irreplaceability of animal experimentation [10,11].

ETHICS OF ANIMAL EXPERIMENTAL RESEARCH:

With adverse medical incidents such as the sulfanilamide elixir event in the United States and the thalidomide tragedy in Europe, and combined with science, philosophy, humanitarianism, and the protection of animal rights, as well as the irreplaceable role of animal research in disease investigation and treatment development, there has been a significant adjustment in the regulations governing animal experimentation [17]. The text focuses on the protection of animal welfare and the optimization of scientific research, establishing relevant principles for animal experiments: (1) The Animal Welfare Protection Principle, which emphasizes the importance of animal welfare. Attention should be paid to the living conditions and basic needs of animals, ensuring that they are free from unnecessary pain and suffering, and maintaining the basic dignity of animal life in animal research. (2) The “3R” Principle, standing for reduction, refinement, and replacement, is an essential ethical guideline in animal research, which requires that the number of animals used should be minimized, experimental techniques and methods should be refined, and the development and application of non-animal experimental alternatives should be encouraged to gradually replace some animal experiments while ensuring the quality of research [10,18]. (3) The Institutional Review and Regulation Principle, according to the Public Health Service Act of 1985 in the United States, all institutions conducting animal research and trials are required to establish an Institutional Animal Care and Use Committee (IACUC), which is responsible for reviewing animal research projects to ensure that the use of animals complies with ethical and legal requirements [17]. It guarantees the humane and accountable conduct of animal research, thereby regulating animal research practices at an institutional level to prevent the misuse of animals. It proves the best available science that the current ethical framework for animal research and testing is based on the combination of animal models and auxiliary methods. Consequently, it is essential to develop and optimize animal experimental techniques and auxiliary methods while recognizing their limitations. Regulatory agencies should make sure that the research is humane and standardized [17,18].

PURPOSE AND REQUIREMENTS OF ANIMAL EXPERIMENTAL RESEARCH:

Since ancient times, scientists have relied on animal models in many critical scientific experiments to simulate human diseases, thereby solving clinical issues. Given the significant anatomical and physiological similarities between animals and humans, the construction of animal models with clear characteristics that are highly similar to clinical conditions is essential to improve the efficiency of disease pathophysiology research and the validity of clinical treatment, and then practically address clinical problems [19]. Autogenous arteriovenous fistula is the preferred vascular access for hemodialysis patients, and maintaining the patency of AVF has significant clinical importance. At present, there are few effective methods to prevent the poor maturation of AVF. Experts are dedicated to investigating its pathogenesis to find therapeutic targets [20]. To understand the pathophysiological mechanisms, diagnostic and therapeutic methods, and preventive measures of AVF dysfunction, researchers use experimental animals to create AVF models that closely simulate human AVF conditions [21]. The present article reviews animal models suitable for creating AVF in current scientific research and their respective research characteristics. Commonly used large animals include pigs, sheep, and dogs, and small animals such as mice, rats, and rabbits. Large animals, due to their high similarity in vascular structure to humans, can better reflect human AVF conditions [21].

When conducting animal experiments, it is necessary to comply with the ethics of animal experimental research and obtain approval from the relevant agencies for the use and protection of animals. Animal care and breeding should be in accordance with the “Policy on Humane Care and Use of Public Health Services for Experimental Animals” and follow the 3R principle [18]. During the experiments, animals should be provided with adequate and humane care to minimize their suffering. Rigorous experimental design and data analysis, standardize the experimental operation processes, reduce variability among experimental animals, and follow the principles of randomness, balance, and reproducibility, to improve the accuracy of the experiment at the animal level and ensure the scientific and validity of the experimental results When designing animal experiments, we must be rigorous and reasonable, and the experimental operations on animals must be standardized. In animal experiments, we should adhere to the principles of randomness, balance, and repeatability. This helps to reduce experimental errors and ensures the scientific validity and reliability of the experimental results [13,11,18].

Animal Arteriovenous Fistula Models

Large Animal Arteriovenous Fistula Model

LARGE ANIMAL ARTERIOVENOUS FISTULA MODEL:

Research has found that large animals are more similar to humans in terms of vascular size, anatomical structure, and physiological functions than smaller animals, which gives them an advantage in the study of AVF, allowing for better simulation of human conditions [22]. Consequently, this increases the likelihood of AVF maturation and provides higher blood flow rates. They are more suitable for studies on hemodynamic shear stress, in vivo evaluation of new synthetic vascular grafts, and the study of hemodialysis devices.

PIG ARTERIOVENOUS FISTULA MODEL: Among large animal models, pigs, as non-primates, are the most commonly used experimental models due to their vascular structure, which is similar to humans in terms of size and histological composition. Furthermore, in pig models, AVF stenosis mainly occurs at the anastomotic site and the venous outflow segment, characterized by the proliferation of smooth muscle cells and intimal thickening. These pathological changes closely resemble those observed in human AVF stenosis. Therefore, measures to prevent and treat AVF stenosis based on pig model experiments can more accurately predict their clinical efficacy [21,23–26].

In healthy pigs, the commonly used vessels for creating AVF include the common carotid artery and external jugular vein, femoral artery and femoral vein, abdominal aorta and inferior vena cava, and external iliac artery and external iliac vein. The frequently employed anastomosis methods are end-to-end, side-to-side, and end-to-side anastomosis. To simulate vascular access-related lesions in clinical environment, particularly those affected by renal failure [27], researchers have further investigated the CKD pig AVF model. The CKD models that have been published contain subtotal nephrectomy (removal of one entire kidney and partial resection of the other kidney) and renal artery embolization (embolization of the proximal renal artery on one side and the distal renal artery on the other side (Figure 2B) [28–30]. Postoperatively, renal function was assessed based on serum urea nitrogen and creatinine levels, while vascular diameter and blood flow velocity were monitored by ultrasound. In the experiments, commonly used pig types involved standard-sized pigs and mini pigs, with the choice of sex depending on the experimental requirements. Mini pigs are preferred for their neck vessel dimensions (arteries 2–4 mm, veins 4–6 mm), which closely resemble the size of human arm vessels, allowing for better simulation of human AVF. However, they are more expensive than standard-sized pigs [21]. The maturation time for pig AVF after surgery is approximately 4 weeks (Table 1), with a high rate of maturation and patency. According to different experimental purposes and requirements, appropriate vascular access and anastomosis methods should be selected to ensure the success of the operation and the accuracy of the experimental results.

Currently, the pig AVF model is frequently used to investigate the pathophysiological mechanisms following AVF vascular injury, changes in hemodynamics, arteriovenous grafts [31], vascular stents [21], the effects of radiotherapy on AVF intimal hyperplasia [32], the reduction of thrombosis in endothelial damage targeted by dual antiplatelet therapy [33], and the recent research results, such as the early diagnosis of AVF using MRI and the therapeutic effects of nanomedicine delivery systems on AVF stenosis (Table 1) [29,34]. The pig model is selected to study AVF not only because its vascular histological changes are similar to those of humans, but also because these research results provide an important reference for subsequent AVF-related studies in terms of animal model selection, experimental design, and result analysis, which helps to promote the standardization and in-depth development of AVF research.

SHEEP ARTERIOVENOUS FISTULA MODEL: Sheep, as large animals, have vascular structures and sizes that are similar to humans. The vascular anatomy of the sheep’s forelimbs is similar to that of the human forearm, with superficial veins that provide a sufficiently long venous outflow segment for puncture during dialysis [22]. After the creation of AVF, the sheep model is closer to the human forearm AVF, offering advantages over the pig AVF model with deep blood vessels.

In healthy sheep, the commonly used vessels for creating an AVF include the external jugular vein and common carotid artery [35], the superficial femoral vein and femoral artery [36], the basilic vein and brachial artery, or the cephalic vein and brachial artery (Table 1). There are also 3 types of anastomotic methods: end-to-end, side-to-side, and end-to-side anastomoses. Unlike in humans, to date, no sheep AVF model has been developed to simulate renal failure for research purposes. Approximately 5 weeks after surgery, the AVF matures (Table 1), and the maturity rate is about 75% [22]. Postoperatively, ultrasound was used to evaluate the AVF’s blood flow velocity, vessel diameter, patency rates, and other parameters, and it was found that the survival rate was not affected. Sheep aged 1–2 years were often selected, and males or females were selected according to the experimental requirements [37–40].

Sheep can be an ideal model for studying human AVF due to their similar vascular structure and size to humans. The sheep AVF model is not only used to investigate the pathophysiological mechanisms of human AVF stenosis and complications of AVFs, but also involves research fields such as vascular anastomosis technology, the use of U-clips, hemodialysis equipment, and vascular stents. Additionally, the sheep model has also been employed to explore new therapies such as photochemical therapy to promote AVF maturation [39] and non-invasive AVF blood flow control devices during hemodialysis [40], which highlights the potential of the sheep model in researching methods to promote AVF maturation and control its blood flow (Table 1). In the future, researchers may develop a sheep AVF model that simulates the environment of kidney failure to more accurately simulate the physiological state of human kidney failure patients, so as to further study the series of responses of AVF in kidney failure patients and provide more insights and solutions for the treatment and care of human AVF to improve the quality of life and prognosis of dialysis patients.

CANINE ARTERIOVENOUS FISTULA MODEL: As a large animal model, dogs have vascular dimensions and AVF blood flow that are slightly smaller than those of humans. However, due to genetic diversity, different breeds may produce inconsistent experimental results, which could affect the consistency of the experiments. Therefore, canine AVF models are generally not the preferred animal models. Despite this limitation, the pathological characteristics of AVF-induced stenosis in canine models are highly similar to those observed in human AVFs. This similarity makes them an important experimental basis for studying vascular access complications and developing new treatment strategies [41,42].

In healthy dogs, the vessels used to establish an arteriovenous fistula (AVF) include the external jugular vein and the common carotid artery, the brachial artery or the humeral artery and the cephalic vein, and the femoral artery and the femoral vein or the femoral artery and the lateral saphenous vein (Table 1) [41–43]. These vessels can be connected using 3 types of anastomosis: end-to-end, end-to-side, and side-to-side. Postoperatively, the patency of the fistula can be monitored through palpation, ultrasound, and angiography. Approximately 4–5 weeks later, the vascular access matures (Table 1), allowing for percutaneous venous puncture and catheterization to simulate clinical hemodialysis [44]. Studies have found that autogenous biological conduits (biotubes) exhibit good vascular access patency rates. Canine AVF stenosis occurs later than pigs and sheep, but for dogs requiring hemodialysis (HD), autogenous arteriovenous fistulas remain the optimal choice for vascular access [42,44], which is similar to humans. The most commonly used breed in experiments is the Beagle, with a weight range of 10–20 kg, and the sex is selected based on experimental requirements.

Canine AVF models primarily focus on the study of graft vascular pathways, particularly investigating the maturation barriers of arteriovenous grafts (AVG), dysfunction, intimal hyperplasia, the effects of blood flow dynamics on endothelial cells, endothelization of metal scaffolds, and the application of autologous tissue collagen conduits (biotubes) (Table 1) [41–46]. These studies bring hope for renal failure patients who are not suitable for autogenous arteriovenous fistulas. With the advancement of biomaterials and tissue engineering technologies, such as biotubes technology, the application prospects of canine AVF models in autologous tissue-engineered vascular research are promising.

SMALL ANIMAL ARTERIOVENOUS FISTULA MODEL:

Small animal models offer several advantages, including low cost, short reproductive cycles, and strong genetic manipulability. These features enable more effective study and assessment of the mechanisms of disease onset and progression. Additionally, their broad applicability and reduced space requirements for experiments make them widely used in biomedical research. They provide strong support for both basic and applied research.

MOUSE ARTERIOVENOUS FISTULA MODEL:

The mouse arteriovenous fistula model has emerged as one of the most frequently utilized and valuable experimental models in contemporary biomedical research, attributed to its cost-effectiveness, rapid breeding, and robust genetic manipulability.

In healthy mice, when creating an arteriovenous fistula (AVF) model to simulate clinical conditions of renal dysfunction, common methods to induce chronic kidney disease (CKD) include: (1) Subtotal nephrectomy, which requires 2 surgeries. Initially, about 2/3 of the left kidney is removed. One week later, the right kidney is excised (Figure 2A1, 2A2) [47]. (2) Nephrectomy, where the right kidney is removed in a single surgery, and the upper pole renal artery of the left kidney is ligated with nylon suture [48]. (3) Adenine diet induction, which involves feeding mice a diet containing 0.2% adenine to induce CKD (Figure 2B) [49]. For mice undergoing nephrectomy-induced CKD, a protein diet is administered postoperatively to decrease mortality. CKD is diagnosed by monitoring serum urea nitrogen and creatinine levels. The AVF model is created 1 week after the induction of CKD. Commonly used vessels include the common carotid artery and internal jugular vein [47], as well as the aorta or abdominal aorta and the inferior vena cava (Table 1). The method of arteriovenous anastomosis can be either the aortic-inferior vena cava puncture technique or surgical anastomosis [50]. According to the needs of the experiments, the appropriate arteriovenous anastomosis method is selected. After the fistula is created, blood flow and fistula diameter are evaluated using imaging techniques such as ultrasound and magnetic resonance imaging. The AVF maturation time is generally 2–4 weeks (Table 1) [51,52]. Experiments typically use 8-week-old male C57BL/6 mice with matched body weights, and a sufficient number of mice are involved in the experimental design to ensure the reliability and statistical power of the results. The appropriate method for establishing the AVF model is chosen based on the specific needs of the experiment.

The mouse AVF model is widely used to investigate the pathogenesis of AVF stenosis, hemodynamic changes in AVF, signal pathways and genes related to intimal hyperplasia [53,54], as well as drugs to prevent and treat intimal hyperplasia in vascular access. In addition, the mouse model is employed in the field of drug delivery and post-stenosis treatment methods, such as nanomedicine delivery systems [55,56] and percutaneous transluminal angioplasty (Table 1) [57]. These models not only contribute to a deeper understanding of the pathophysiological mechanisms of AVF stenosis but also provide a platform for developing new treatment approaches. For instance, they facilitate the screening and testing of new drugs, exploration of gene therapy strategies related to intimal hyperplasia, evaluation of the efficacy of minimally invasive therapeutic techniques, and in-depth research of the molecular mechanisms of AVF stenosis, offering new targets for clinical treatment.

RAT ARTERIOVENOUS FISTULA MODEL: Rats are frequently used as small animals in animal AVF models. Similar to mouse AVF models, they are also utilized to simulate clinical CKD. Common methods to induce CKD include: (1) Subtotal nephrectomy, which involves surgically removing part of the kidney tissue, and (2) Adenine diet induction, where rats are fed a diet containing 0.2% adenine to induce CKD. Other less commonly used methods involve drug-induced kidney damage, renal artery embolism, and ureteral ligation techniques [52,58–60]. When creating AVF models, in addition to the vascular access commonly used in mice, the femoral artery and femoral vein in rats are often used as vascular access (Table 1) [61,62]. The anastomosis methods include end-to-end, end-to-side, and side-to-side. The stenosis characteristics of the rat AVF model are similar to those of the mouse, and the methods for diagnosing CKD and monitoring AVF blood flow and fistula diameter are also the same as in mice. Generally, Wistar rats aged 6–8 weeks or Sprague-Dawley (SD) rats are used, and male or female rats are selected according to experimental needs for the creation of the arteriovenous fistula model.

The rat AVF model, owing to its physiological similarities to humans and ease of manipulation, is important in the study of vascular access diseases. These models are helpful for investigating the pathogenesis of AVF stenosis, hemodynamic changes, drug-eluting stent placement, drug delivery, and the hemostatic effects of hydrogel coatings at puncture sites during hemodialysis, as well as other therapeutic approaches (Table 1). However, repeated venous punctures during hemodialysis can cause endothelial cell damage, leading to abnormal proliferation of the neointima and ultimately resulting in AVF failure. It is anticipated that future research in large animal models will simulate multiple hemodialysis sessions of AVF under clinical CKD conditions. Building on the research of hydrogel-coated needles, the development of new-material hemodialysis needles that can deliver specific drugs to repair endothelial cells is expected. This would help prevent AVF failure caused by stenosis at the puncture site [52,58–62]. Furthermore, like the mouse AVF model, the rat AVF model is expected to play a greater role in the development of new drugs, gene therapy, evaluation of minimally invasive treatment techniques, and personalized medicine, providing more experimental data and a theoretical basis for research on vascular access diseases.

RABBIT ARTERIOVENOUS FISTULA MODEL: Rabbits are an option in animal AVF models. Although their susceptibility to carotid artery dilation due to increased blood flow is relatively high [63], leading to a lower application rate in AVF research, they still have value in simulating clinical CKD. Common approaches for establishing rabbit CKD models include the oral administration of standard granular rabbit food containing adenine for 5–6 weeks (Figure 2C), and regular blood draws from the ear vein to monitor serum urea nitrogen and creatinine levels for CKD diagnosis [64]. Frequently used vascular access routes for creating rabbit AVF include the common carotid artery to the external jugular vein, the femoral artery to the femoral vein, and the abdominal aorta to the inferior vena cava (Table 1) [65–67]. Anastomosis methods include end-to-end, end-to-side, and side-to-side anastomosis, with the appropriate method chosen based on the experimental needs. After surgery, high-frequency ultrasound is used to monitor changes in hemodynamics and vascular morphology, and the general maturation time is 4–6 weeks (Table 1). Commonly used breeds include New Zealand white rabbits, domestic rabbits, lop-eared rabbits, and Japanese rabbits, with both males and females being suitable. The breeding environment should be maintained at a constant temperature and humidity. The rabbit AVF model exhibits minimal inter-individual differences in kidney function and has a low mortality rate, which reduces the number of experimental animals required and thereby lowers experimental costs [68–70].

Although the rabbit AVF model is inferior to the mouse and rat models, it still has unique advantages in specific research fields. Presently, the rabbit AVF model is applied to examine changes in AVF hemodynamics, mechanisms of intimal hyperplasia, and the effects of therapeutic methods such as hyperbaric oxygen therapy that inhibits intimal hyperplasia (Table 1). In the future, the rabbit AVF model is expected to play a greater role in the prevention and treatment of AVF stenosis and its complications, particularly in studies requiring larger vessels or specific physiological responses. Additionally, the low mortality rate and minimal inter-individual differences of the rabbit model provide high cost-effectiveness and reproducibility, making it a valuable experimental tool [63–70].

Conclusions

AVF is an important vascular access for hemodialysis in patients with ESRD, and its long-term functional stability is crucial for patients’ quality of life. Despite the fact that animal experiments have been primarily used in recent years to explore the pathogenesis, diagnosis and treatment methods, and preventive measures of AVF stenosis, the results have been unsatisfactory.

In terms of animal experiments, it is essential to have rigorous experimental design plans, be familiar with the animal AVF surgical procedures, and enhance surgical skills to minimize experimental data errors. Although there are intrinsic differences between experimental animals and humans in physiology and pathology, their experimental data cannot fully represent human disease conditions. However, animal models play an irreplaceable role in exploring disease mechanisms, testing the efficacy and safety of new drugs and vaccines, and other areas.

From the perspective of animal model selection, large animals have vascular structures that are more similar to humans, being able to simulate percutaneous venous puncture for hemodialysis. However, in current AVF research, they do not simulate the internal environment of renal failure. Small animals can simulate AVF in human CKD in experiments, but due to differences in physiological structure from humans, experimental results need to be repeated multiple times to improve accuracy. Additionally, experimental designs should be rigorous to minimize errors.

Future Directions

In general, selecting an appropriate animal model of AVF, conducting a thorough assessment before surgery, improving its surgical methods, intraoperative placement of drug membranes, postoperative phototherapy or topical medication, and the utilization of the new-type venous puncture needle for hemodialysis, have important clinical significance for the treatment of AVF dysfunction. Although current animal models have limitations, optimizing and standardizing these models, combined with advanced computational models and bioengineering technologies, the complex pathological process of AVF can be further analyzed, and the research of innovative treatment methods can be promoted. This can thereby prolong the long-term function of AVF and improve the survival rate and quality of life of patients with ESRD. Future research should continue to explore animal models that more closely mimic human pathophysiological characteristics and utilize these models to evaluate novel therapeutic strategies.