This study presents a protocol for thread-embedding acupuncture therapy in Alzheimer’s disease-like rats.
Thread-embedding therapy (TEAT) is a treatment that prevents and manages diseases by inserting a biodegradable suture into an acupoint, providing long-lasting stimulation. TEAT is a simple approach that avoids the discomfort of regular acupuncture and provides sustained therapeutic effects. This article discusses the potential impact of TEAT on the learning and memory abilities of rats with Alzheimer's disease-like symptoms. Since chemically induced neuronal degeneration and cognitive impairments in rats does not entirely reflect the true pathological changes observed in Alzheimer's disease. Consequently, our research group has designated these manifestations as Alzheimer's disease-like symptoms. A protocol has been established to outline the selection of acupoints, the operation process, and necessary precautions for the head and lower back. The experiment was conducted on three groups: a control group, a model group, and a TEAT group, each containing 6 rats. To induce Alzheimer's disease-like symptoms, rats were intraperitoneally injected with D-galactose for 7 weeks (49 days). The rats in the TEAT group received acupoint catgut embedding treatment. Following the intervention period, a Morris Water Maze (MWM) was conducted to evaluate the rats' learning and memory. Subsequently, the rats were sacrificed, and their brain tissue was examined. A histological examination was performed to understand the effects of TEAT on the pathology of rats exhibiting symptoms of Alzheimer's disease. This study suggests that TEAT may improve learning and memory in rats with Alzheimer's disease-like symptoms, indicating a potentially promising new treatment approach for this neurodegenerative condition.
Thread-embedding acupuncture (TEA) involves embedding catgut or absorbable sutures into acupoints using a special needle. This technique has a prolonged effect until the sutures are absorbed and degraded. It provides continuous and sustained stimulation to the acupoints for a week or longer1, achieving a comparable outcome without the necessity for daily repetitive procedures2. This reduces the number of patients seeking medical treatment, thus conserving medical resources to some extent. In recent years, TEAT has been increasingly used in various medical fields in China, including internal medicine, external medicine, dermatology, facial features, gynecology, and pediatrics3. Studies have shown that it is effective in producing long-term and reliable effects for certain chronic and complex diseases, such as epilepsy4 and facial nerve paralysis5. It has the advantages of minimal trauma and simple operation6. Additionally, the treatment costs of TEAT have been reported to be lower than those of electroacupuncture (EA)7. Therefore, TEAT is increasingly valued in clinical and scientific research.
Alzheimer’s disease (AD) is a neurodegenerative condition that progresses over time. Its pathophysiological process begins to accumulate approximately 20 years before clinical symptoms appear, but its mechanism is still not fully understood8. Given the limited availability of effective drugs for AD, research is increasingly focusing on the prodromal and preclinical stages of the disease9. Prevention is a crucial strategy for addressing the development and progression of AD9,10. In recent years, traditional Chinese medicine (TCM) has made significant progress, and it is expected to offer new possibilities for preventing and treating AD11,12. As a subtype of acupuncture, TEAT is preferred over other therapies due to its wide treatment range, minimal trauma, simple operation, low treatment frequency, and long-lasting efficacy6. Emerging literature suggests that TEAT may benefit individuals with obesity13,14, diabetes15, insomnia16, postmenopausal osteoporosis17, and depression18, all of which are risk factors for AD. It also improves senescence in aging rats by regulating mitophagy2, improves spatial learning and memory impairment, alleviates pathological damage of the hippocampus, and inhibits inflammation response in vascular dementia (VD) rats19. It appeared attractive to figure out whether TEAT could also act on pathological processes during AD.
The current research lacks uniformity and standardization in several critical elements of TEAT operation, including the embedding method, embedding tool, thread, and embedding interval period. This lack of standardization affects the evaluation of the therapy’s effect and the exploration of related mechanisms and restricts external promotion and communication. Prior research20,21 has demonstrated that intraperitoneal administration of D-galactose (D-gal) can induce Alzheimer’s disease-like pathological changes in rats, including neuronal degeneration and cognitive impairments. Furthermore, electroacupuncture at the Baihui(GV20) and Shenshu(BL23) has been shown to effectively ameliorate cognitive decline, mitigate neuroinflammation, and reduce neuronal damage. This study takes Alzheimer’s disease-like model rats as an example to introduce the selection of acupoints and the operation process and precautions of TEAT under this model. It discusses the critical operational elements of TEAT in experimental research to provide a reference for future studies.
All experiments were carried out following the National Institutes of Health Guide for the Care and Use of Laboratory Animals and were approved by the Hubei Provincial Center for Disease Control and Prevention Laboratory Animal Management and Use Committee. A total of 18 3-month-old female Sprague-Dawley (SD) rats weighing 220-250 g were used for the test. All rats were maintained on a 12 h light/dark cycle at 23 ± 1 °C and 40%-50% humidity, with free access to food and water. Following a one-week acclimatization period, during which the rats were allowed to habituate to the laboratory conditions, the experiments were initiated.
1. Model development
2. Preparation for TEAT
3. Thread-embedding operation for Baihui (GV 20)
4. Thread-embedding operation for Shenshu (BL 23)
5. Post-operative care
6. Behavioral testing and histological examination
This article introduces the specific operation method of TEAT in Alzheimer's disease-like rats. It discusses the critical operational elements of TEAT in experimental research to provide a reference for future studies.
TEAT improves learning in Alzheimer's disease-like rats
As illustrated in the flowchart (Figure 5), during the adaptive training period, it was observed that rats in each group were observing the surrounding environment while swimming. The analysis of swimming speed (Figure 6) showed no significant difference among the groups, indicating consistent baseline levels of movement speed and visual perception. Any observed differences in experimental results were not due to variations in movement ability or visual perception.
The rats underwent 5 days of platform search training. In Figure 7A, it can be observed that the movement trajectories of each group of rats differed in the early and late stages of training. On day 2, most of the escape-driven rat groups swam randomly. However, on day 5, the rats in the control group swam with direction, while the model group rats swam randomly along the pool wall. The TEAT group rats' movement became denser in the target quadrant. The experiment measured escape latency, with shorter latency indicating stronger abilities. Figure 7B shows that the model group exhibited reduced learning and memory abilities compared to the control group. However, the TEAT group showed a significant improvement in spatial reference memory impairment in rats with AD-like pathology.
TEAT improves spatial memory in Alzheimer's disease-like rats
In the probe trial, the location where the animal spends time indicates spatial bias27. Rats use four primary methods to search for platforms: edge-based, random-based, trend-based, and linear-based28. The results indicate that each group of rats employed different search strategies (Figure 8A). The control group primarily used linear and directional search strategies, suggesting a strong memory and ability to recall the platform's location. In contrast, the rats in the model group exhibited an edge-like main search strategy, indicating a significant decline in their memory ability. They did not learn to find the platform or remember its location. The rats in the TEAT group showed a trend-based search strategy. The trajectory density was highest in the quadrant where the original platform was located, as well as in the adjacent quadrants. This indicates a memory improvement compared to the model group.
Figure 8B and Figure 8C show the results of the duration of stay in the quadrant of the original platform and the number of times the rats crossed the platform. The model group rats exhibited a significant reduction in their stay time in the original platform quadrant and the number of times they crossed the platform compared to the control group (p <0.01). Compared to the model group, the TEAT group rats exhibited a significant increase in their stay time in the original platform quadrant and the number of times they crossed the platform (p <0.01). These results suggest that TEAT can improve spatial learning and memory impairment in rats with AD-like pathology.
TEAT ameliorates hippocampal aging in rats (Figure 9). Compared to the control group, rats in the model group exhibited severe pathological changes, including a significant reduction in the number of pyramidal cells and their irregular arrangement. In addition, nuclear condensation, neuronal degeneration, and other abnormalities were observed. However, following TEAT treatment, the number of hippocampal pyramidal cells in rats increased and were more organized. Although some nuclei exhibited condensation, the overall cell morphology appeared more normal. Cells were more densely distributed and ordered, cytoplasmic staining was more consistent, and the edema surrounding the cells was significantly reduced. Notably, normal pyramidal cells were observed.
Figure 1: Flow diagram of the experiment. After 1 week of adaption (week 0), the study allocated 18 rats into three groups: Control, Model, and TEAT. During weeks 1 to 7, the control group received saline injections, while the model and TEAT groups were administered D-galactose. The TEAT group additionally underwent thread-embedding acupuncture therapy on weeks 2, 4, and 6. All rats were subjected to the Morris water maze test in week 8, followed by euthanasia. Abbreviations: Adapt = adaptation, Con = Control group, Mod = Model group, TEAT = Thread-embedding Acupuncture Therapy group, D-gal = D-galactose, MWM = the Morris water maze test. Please click here to view a larger version of this figure.
Figure 2: The location of the acupoint. (A) The acupoint Baihui (GV 20) in rats. It is located at the right midpoint of the parietal bone. (B) The acupoint Shenshu (BL 23) in rats. It is located 5 mm lateral to the second lumbar vertebra. Abbreviations: GV = Governor Vessel, a concept in Traditional Chinese Medicine (TCM) that refers to the main meridian running along the midline of the body's posterior aspect, BL = Bladder, stands for the Bladder Meridian, which in TCM corresponds to the Foot-Taiyang meridian, one of the six yang meridians, running along the back of the body and legs. Please click here to view a larger version of this figure.
Figure 3: Detailed thread-embedding operation of Baihui (GV 20). (A) The needle is inserted horizontally at a 15° angle to the skin surface, 0.1 cm below the Baihui (GV 20) acupoint, with the skin pinched to facilitate the procedure. (B) Once the needle tip reaches a position 0.1 cm above the Baihui (GV 20) acupoint, the needle core is pushed while retracting the needle tube to fully implant the 0.2 cm absorbable surgical suture into the subcutaneous tissue at the acupoint. Abbreviations: GV = Governor Vessel, a concept in Traditional Chinese Medicine (TCM) that refers to the main meridian running along the midline of the body's posterior aspect. Please click here to view a larger version of this figure.
Figure 4: Detailed thread-embedding operation of Shenshu (BL 23). (A) The needle is rapidly inserted perpendicularly into the acupoint to a depth of 0.25 cm below the Shenshu (BL 23). (B) Once the needle tip has reached a depth of 0.5 cm beneath the skin surface, the needle is redirected towards the center of the acupoint, creating a 45°angle with the skin, and then obliquely inserted to a depth of 0.5 cm. (C) While the needle shaft is advanced, the tube is retracted, ensuring the complete implantation of a 0.5 cm segment of absorbable surgical suture into the muscle tissue at the Shenshu (BL 23) acupoint. Abbreviations: BL = Bladder, stands for the Bladder Meridian, which in TCM corresponds to the Foot-Taiyang meridian, one of the six yang meridians, running along the back of the body and legs. Please click here to view a larger version of this figure.
Figure 5: The flow chart of the WMW test. The adaption training prior to the experiment is denoted as Day 0, during which the rats' motor capabilities are observed and the swimming velocity is statistically analyzed. This is followed by a five-day place navigation phase (Days 1 to 5), where the latency to escape (escape latency) is compared and analyzed among the different groups. On Day 6, a spatial probe trial is conducted to assess the time spent in the target quadrant (target quadrant dwell time) and the number of platform crossings. Please click here to view a larger version of this figure.
Figure 6: Comparison of swimming speed (m/s) among groups. This figure delineates the mean swimming velocities (in meters per second) of rats across various experimental groups, each comprising six animals (n=6). The error bars show standard deviation. No inter-group differences were obtained, as indicated by ns (p > 0.05). The statistical analysis was executed using SPSS software, with all data adhering to a normal distribution. Please click here to view a larger version of this figure.
Figure 7: The results of WMW's place navigation. (A) This panel presents the representative motion trajectory diagrams, illustrating the navigational paths of rats within each experimental group during the place navigation trials. (B) The escape latency, measured in seconds (s), is compared across the groups, with each group consisting of six rats (n=6). Statistical analysis was performed using two-way repeated measures ANOVA to assess the within-subjects' effects over the course of the navigation trials and the between-subjects differences among the groups. Data are compliant with normal distribution assumptions and are depicted as the group mean ± standard deviation. Significant differences are indicated by asterisks (*p < 0.05, **p < 0.01) compared to the control group and by hashtags (#p < 0.05, ##p < 0.01) compared to the model group. Please click here to view a larger version of this figure.
Figure 8: The results of WMW's probe trail. (A) The panel displays representative motion trajectory diagrams that capture the spatial exploration behaviors of rats in the probe trial within each experimental group. (B) This graph compares the dwell time (in seconds, s) within the target quadrant among the groups, reflecting the rats' memory retention of the platform location. (C) The graph illustrates the frequency (freq) with which rats crossed the platform area, indicating their spatial memory performance. Each group comprised six rats (n=6), and the data were statistically analyzed using one-way ANOVA to assess differences across the groups. The data adhere to a normal distribution and are presented as the mean ± standard deviation. Significant differences are indicated by asterisks (**p < 0.01) compared to the control group and by hashtags (#p < 0.05, ##p < 0.01) compared to the model group. **p < 0.01 vs. control group, #p < 0.05 vs. model group, ##p < 0.01 vs. model group. Please click here to view a larger version of this figure.
Figure 9: Hematoxylin and Eosin Staining Assessment of Hippocampal CA1 Region in Rat Groups at 200x magnification. (A) Control group exhibits typical neuronal structure with well-preserved pyramidal cells. (B) Model group displays pronounced pathological alterations, characterized by a marked decrease in the density of pyramidal cells, darkly stained degenerated neurons, and disordered arrangement. (C) TEAT group demonstrates enhanced hippocampal architecture, with an increased number of pyramidal cells that are more orderly and possess a more normative morphology. Despite occasional nuclear condensation, the cells are more densely packed, exhibit uniform cytoplasmic staining, and show a significant reduction in pericellular edema. The presence of normative pyramidal cells is notably observed. Scale bar = 50 µm. Please click here to view a larger version of this figure.
Intervention time
The etiology of AD is complex, and its pathogenesis remains uncertain. Currently, there is no effective treatment for the disease, and its course is irreversible. Therefore, the academic community has reached a consensus on the importance of focusing on the prevention and treatment of AD. The prevention and treatment strategies for AD emphasize early intervention, following the TCM concept of treating conditions before they occur, emphasizing treatment before its onset, transmission, and recurrence. The accumulated research in humans29,30 and rodents31,32 has shown that early acupuncture and moxibustion intervention can achieve significant results without apparent side effects, making it a promising potential method for preventing and treating AD. Therefore, this study administered treatment during the modeling process. TEAT was implemented at the beginning of the D-gal intraperitoneal injection.
Acupoint selection
AD is a severe neurodegenerative disease that primarily affects the brain regions responsible for memory, language, reasoning, and social behavior. The brain (Nao) is considered the sea of marrow (Sui) in TCM. The marrow (Sui) is made of essence (Jing), a substance unique in TCM that is believed to be the body's essential constitutional strength, vitality, and resistance. Essence (Jing) is mainly stored in the kidneys (Shen). If the kidney essence (Shen Jing) is weak, the brain (Nao) may lack nourishment, and cognitive impairment may occur. Therefore, TCM suggests tonifying the kidneys and benefiting the essence (Jing) can help improve brain function. The brain can be directly influenced by certain meridians, such as the Governor vessel (GV) and the bladder meridian of foot Taiyang (BL), as they enter the brain. The combination of the Governor vessel (GV) and the bladder meridian of foot Taiyang (BL) used for preventing and treating AD is highly utilized33,34. Baihui (GV 20) is an acupoint located at the vertex of the head and is part of the Governor vessel. According to literature, in studies using acupuncture and moxibustion for the prevention and treatment of AD, Baihui (GV 20) has the highest frequency of occurrence and is considered a critical point in the formula35. The Shenshu (BL 23) is an acupoint on the bladder meridian of foot Taiyang. It is located 1.5 cun lateral to the lower border of the spinous process of the second lumbar vertebra. As the kidney back transporting-Shu point, it can strengthen all aspects of the kidneys, including kidney yin, yang, essence (Jing), and qi. Acupuncture and moxibustion at Baihui (GV 20) and Shenshu (BL 23) may improve cognitive function and alleviate AD symptoms in various ways36,37.
Interval time
The operating standards of TEAT38 dictate that the treatment interval and course of treatment should be determined based on the disease's condition and the selected operating site, with an interval of 1 week to 1 month. The course of treatment can range from 1 to 5 times. This suggestion can also be followed in experimental animal research. Based on the reviewed literature39, treatment is generally administered once a week or every 2 weeks, with most cases involving 4-8 consecutive treatments. The experiment lasted 49 days, during which the threads were buried on the 14th, 28th, and 42nd days.
Tool and methods
Various thread-embedding tools are used in current experimental animal research. These include No. 740 or No. 941 disposable thread-embedding needles, self-reinvented needles, and No. 12 lumbar puncture needle42. The self-reinvented needles use No. 5-7 syringes as the tube and an appropriate filiform needle for the needle core. The needle tip has been pre-smoothed in advance. For example, in a study using SD rats weighing 250 ± 20 g (month age not specified in the text), choose the No.7 syringe and the 0.30 x 0.40 mm filiform needle43,44. However, the self-reinvented needles must be strictly disinfected, making them unable to be used widely. If the needle tip is too large or sharp, it can damage blood vessels and nerves, increasing the likelihood of bruising45. Lumbar puncture needles, which have a large diameter and sharp tips, are more likely to damage blood vessels and nerves. The disposable embedding needle is the most used in clinical practice39. It is more convenient to use and safer to operate compared to self-reinvented needles and lumbar puncture needles, making it ideal for TEAT. Additionally, the goal of the experiment is to improve human health. Therefore, animal studies should reflect the clinical situation. Hence, it is advisable to use disposable thread-embedding needles as thread-embedding tools.
Catgut was the primary thread material used in TEAT, but due to tissue rejection and animal-derived ingredients, it has been replaced by biosynthetic absorbable surgical sutures. Sutures are available in various sizes and should be matched to the needle, such as No.7 for 4-0 or 3-0 sutures. In animal research, 3-041, 4-046, and 5-047 are mainly used. Most sutures are 1-2 cm long. However, rodents have much smaller bodies than humans, so there is a lack of appropriate size for their body size. Therefore, researchers must cut sutures into 0.2-0.5 cm segments to make them suitable for rodents. Therefore, it is recommended that sutures be rinsed with clean and sterile distilled water or saline after cutting and before soaking for later use or immediate application to reduce the risk of infection46.
Some studies have proposed detailed requirements for the embedding method, such as rapidly inserting needles into the acupoint from about 0.5 cm below the acupoint towards the acupoint48. This is important because rodents are small. In addition to having abundant muscle tissue in their lower limbs, their subcutaneous tissue and muscle layers in the head, back, and abdomen is relatively weak. Therefore, the issue of TEAT's insertion points and insertion angle in animal research needs to be emphasized here. When performing TEAT on the lower limbs of rodents, direct needling at the acupoints is feasible. As for the body, it is recommended to insert the needle below the acupoints (the distance can be flexibly adjusted according to the length of the thread body) using oblique needling (<45°) or flat needling (<15°) to avoid damage to the internal organs.
Potential of TEAT for the prevention and treatment of Alzheimer's disease
Recently, research on TEAT is emerging, although its effects and mechanisms remain elusive. As mentioned above, TEAT can improve AD-related risk factors such as obesity13,14, diabetes15, insomnia16, postmenopausal osteoporosis17, and depression18. It has a beneficial effect on learning and memory impairment in VD rats19. TEAT regulates lipid metabolism through the PPAR pathway to ameliorate tissue injury in exercise-induced fatigued rats49 and exerts anti-inflammatory and analgesic effects in intermittent cold stress-induced mice through the TRPV1 pathway50. In the present study, we demonstrated that thread-embedding treatment on AD-like rats could alleviate learning and memory impairments by ameliorating spatial memory loss and reducing degenerated cells in hippocampal CA1 regions. However, due to the current research's lack of uniformity and standardization in several critical elements of TEAT operation, including the embedding method, embedding tool, thread, and embedding interval period, this article mainly discusses the critical operational elements of TEAT in experimental research. This research was only a preliminary exploration of the effect of TEAT on AD, which required much more complement and improvement in clarifying the exact molecular and interaction between them. Nevertheless, it offered a new trial for the inevitable AD process, which may somehow relieve the heavy burden on the public health care system.
The authors have nothing to disclose.
This work was supported with funds from the National Natural Science Foundation of China (NSFC) Nos. 82374564 (to YJD) and Nos. 82074566 (to YJD) and from Sun Guojie Inheritance Base for TCM Acupuncture-Moxibustion of World Federation of Acupuncture-Moxibustion Societies in Wuhan, China (World Federation of Acupuncture-Moxibustion Societies [2019] No. 26) (to YJD) and the National Famous TCM Inheritance Studio construction project of the National Administration of Traditional Chinese Medicine, China (the National Administration of Traditional Chinese Medicine [2022] No. 5) (to YJD).
0.9% saline, 4% paraformaldehyde, Hematoxylin, Eosin Y (water-soluble), absolute ethanol, 0.01M PBS powder, xylene, hydrochloric acid, embedded paraffin, neutral gum | sinopharm (www.sinopharm.com) | ||
5-0 absorbable surgical suture | bodamedical (www.bodamedical.com) | ||
70% alcohol, iodophor, cotton ball | Used for disinfection. | ||
chloral hydrate | sigma | C8383 | |
coverslips, glass slides | Guangzhou Wuqiang Experimental Equipment Co., Ltd | ||
Dehydrator | Wuhan Junjie JT-12J Computerized Biological Tissue Dehydrator | ||
DELUXE THERMOSTAT HEAT MAT | Zhenhua Instruments | For maintaining the body temperature of rats. | |
D-galactose | sigma | G0750 | |
electric men's beard trimmer | Used for shaving rats. | ||
Electronic scale for small animals (ZK-DST) | Henan Zhike Information Technology Co., Ltd | ||
erythromycin ointment | frontpharm | ||
glass dish | Used to place cut absorbable sutures. | ||
High-Pressure Steam Sterilization Pot (YM100Z) | Shanghai Sanshen medical equipment factory | For sterilization of surgical instruments. | |
Ice Maker (CMB40) | Shanghai Sheyan Instrument Co., Ltd. | ||
Microscope (BX-53) | OLYMPUS | ||
milk powder | Used for the MWM test. | ||
Morris Water Maze Video Tracking System & Data Analysis Software (Version: Watermaze 2.0) | Chengdu Taimeng Technology Co., Ltd | ||
No.6 thread-embedding needle | bodamedical (www.bodamedical.com) | ||
ophthalmic scissors, trays, tweezers | |||
Pathology Microtome (RM 2016) | LEICA, Germany | ||
pentobarbital | Germany | P11011 | |
permanent marker | Used to mark the acupoint. | ||
Slicing knives (R35) | Feathers, Japanese | ||
soap | Used to wash hands. | ||
sterile gloves |