Abstract
Alzheimer's disease is a chronic progressive neurodegenerative disorder that impairs the meningeal lymphatics, glymphatic system, and compartmental fluid exchange, leading to a decline in cognitive function. Due to the lack of non-pharmacological and physiological treatments, cranial osteopathic manipulation (COM) poses a potential minimally invasive therapeutic choice. To understand the treatment and related effects objectively, we have established a technique to quantify the force applied during COM on an animal model of AD for the first time. Our results indicate that quantified COM can be applied to rodents to study behavioral and biochemical phenotype changes.
Keywords
Introduction
Alzheimer's disease (AD) is a chronic progressive neurodegenerative disorder that affects over seven million Americans.1,2 Reduced fluid dynamics and reduction in cerebral vasculature pulsation are pathogenic mechanisms that impair cerebral fluid exchange, causing a buildup of metabolic waste3,4; this paves a foundation for neuroinflammation, resulting in AD.4,5 Most available treatments do not often target these impacted mechanisms.6–8 However, the role of lymphatic vessels in waste clearance presents the capability to increase clearance of macromolecules, like amyloid-β (Aβ).9–12 Since there lacks pharmacological and non-pharmacological methods to alter impaired fluid dynamics, we propose using cranial osteopathic manipulation (COM). COM is a clinically practiced, minimally invasive treatment that offers the means to modulate fluid circulation 13 and has shown promise in other neurological studies.13–17 However, mechanistic and efficacy preclinical data is limited; this necessitates further research. Hence, to standardize this treatment, we employed a nanosensor glove to quantify force applied to rat models while assessing their spatial and biochemical outcomes after treatment.
Methods
Animals
Experiments and housing were approved by the Institutional Animal Care and Use Committee (IACUC) of Virginia Tech (Protocol ID#15-099 and ID#19-045). Two cohorts of rats from both sexes were used: (1) twelve 3-month-old wild-type rats (Yg) were purchased from Charles River laboratories, and (2) eleven 18-month-old transgenic (Tg) Fischer 344 (F344) rats were purchased from Rat Resource and Research Center at the University of Missouri. Tg-rats express two Swedish point mutations in the amyloid precursor protein-encoding gene (K595N & M596L) and exon9 deletion in the presenilin-1-gene. Rats were randomly divided into untreated (UT) and COM-treated groups. Rats were pair-housed and provided standard food and water ad libitum with a 12-h light-dark cycle. Methods described were conducted following relevant guidelines and regulations.
COM treatment
COM treatment was performed daily for seven days by a board-certified osteopathic physician. Rats were anesthetized with 1.5–3% isoflurane throughout treatment. UT rats remained anesthetized for the average duration of treatment to nullify the influence of isoflurane in behavioral testing. Pressure applied intends to improve cranial rhythmic impulse (CRI), impact the CSF-ISF fluid compartment fluctuation, and improve cranial bone and dural membrane mobility. FingerTPS (Medical Tactile, Inc.) nanosensor gloves were used to record force and treatment duration.
Morris water maze assay (MWM)
MWM was performed for eight days and experimenters were not blinded to groups. Day zero, rats were introduced to the MWM tub (5 feet diameter, two feet high walls) for acclimatization. AnyMaze (AnyMaze 5.1, Stoelting Co. IL), a video tracking software, was used to capture performance. The tub was divided digitally into four quadrants, and a platform (∼5-in diameter) was placed in the northwest (NW) quadrant. Water was kept at room temperature, and the level was one to two cm below the platform. Visual cues were attached to the maze in the NW, northeast (NE), and southeast (SE) zones. For learning trials (days one through four), rats were trained in each of the quadrants (NW, NE, SE, and southwest (SW)) with the water transparent and the platform visible. Before each trial, rats were placed on the platform for 15 s (s) and then given 60 s to reach the platform from one of the four quadrants. Rats that could not reach the platform within 60 s were gently guided to it. Upon completion, rats were gently wiped dry and placed under a heating lamp for two minutes. On testing days (five through eight), water was made opaque and raised to cover the platform. Two probe trials were performed from two different starting locations (e.g., Trial one: SE-zone, Trial two: NW-zone). 18 Day eight, the platform was removed, and rats completed one trial, starting in the SE-zone.
Western blot (WB)
Prefrontal cortex, hippocampus, and cerebellum tissue samples were collected from UT and COM rat brains. Samples were lysed using RIPA buffer with a protease inhibitor cocktail (ThermoFisher Cat# 89900 and 78440). Protein concentration was determined using Bradford assay. For WBs, equal amounts (30 µg, unless stated otherwise) of protein samples from each group were electrophoresed on 10% SDS-PAGE gel under reducing conditions by beta-mercaptoethanol followed by transfer to PVDF (pore size 0.2 µm) membranes. Blots were blocked with 5% nonfat dry milk in Tris buffered saline with 0.075% Tween20. Blots were probed with monoclonal antibody recognizing the N-terminal (Abcam, cat#ab201060) of Aβ1−42 peptide was used with antibodies recognizing AQP4 (DIF8E, cell signaling), LYVE1 (rabbit, ThermoFisher), and GAD67 (mouse IgG2a, Millipore). Membranes were washed with 1X PBS and probed with goat anti-rabbit/chicken/mouse IgG secondary antibody (GeneTex). Chemiluminescence (Pierce, Rockford, IL) signals were detected by Fluorchem M (Protein Simple, San Jose, CA) scanner.
Proteomics
Hippocampus samples from six Tg-UT and five Tg-COM rats were homogenized in RIPA buffer containing protease and phosphatase inhibitors (ThermoFisher, Cat# 78440). Samples were precipitated using methanol and then resolubilized in S-Trap loading buffer. Samples containing 100 μg protein were all brought to equal volume. Cysteine disulfide bonds were reduced using dithiothreitol (DTT), free sulfhydryl groups alkylated with iodoacetamide (IAA), and unreacted IAA quenched with an excess of DTT. Protein was again precipitated using methanol, and the precipitate was loaded onto S-Traps. Samples were digested using PierceTM Trypsin Protease, MS grade (ThermoFisher Scientific). Peptides were recovered from S-Traps by centrifugation. The samples were analyzed in duplicate (2 × 5 μg) using LC-MS/MS. LC-MS/MS was performed utilizing a Lumos Fusion Orbitrap (ThermoFisher Scientific).
Statistical analysis
Analysis was performed using GraphPad Prism. Normality of MWM and WB data sets were assessed with the Shapiro-Wilk Test. Data that did not pass normality were analyzed using a non-parametric test or transformed. Repeated-measures two-way ANOVA or mixed-effect model with Geisser-Greenhouse correction and a Tukey’s multiple comparison test were used to assess longitudinal behavioral data. The remaining behavioral and WB data sets were analyzed with an unpaired parametric t-test. Welch's correction was used when data for the unpaired parametric t-test did not pass the F-test. Proteomics data was analyzed using Proteome Discoverer 2.5 (ThermoFisher Scientific). Untargeted and relative differences in protein abundances were identified with a False Discovery rate (q-values) less than 0.01. Mascot scores with values less than 100 or blank were removed.
Results
Quantification of COM treatment
COM was performed with FingerTPS, as shown in Figure 1(a) and (b). Force applied to the rat's skull during treatment and duration were recorded when treating Yg-COM rats, as shown in Figure 1(c) and (d). COM duration was an average of 3.12 ± 0.08 min across seven treatment days. On day four, the average force was 1.95 ± 0.16 N.

The different components and use of FingerTPS pressure sensing device and preliminary data obtained using this device. (a) FingerTPS setup: i) Wrist mount and cable. (a) FingerTPS setup: i) Wrist mount and cable to sensor interface, ii) Custom-made fingertip sensors, iii) Bluetooth dongle, iv) FingerTPS electronics, v) reference sensor. (b) Image of practitioner wearing FingerTPS on stabilizing (first finger) and treatment (third) finger while treating a young adult rat. Histograms represent the duration of COM treatment from the young rat cohort preliminary data set (c) for each animal and average force applied by the treatment and stabilizing fingers on day six, when acquisition was most accurate (d (N = six, Yg-COM) SEM reported). Clinical notes for both cohorts (Supplemental Material 1) and Tg-rat FingerTPS dataset (Supplemental Material 2 A) can be found in the Supplemental Material.
COM alters learning-related phenotypes
MWM results showed a significant reduction in escape latency when placed in the NW zone in Yg-rats (Figure 2(a)). For Yg-COM rats, comparing days one to three (60.0 ± 0.00 s versus 5.83 ± 2.71 s, p < 0.001) and one to four (60.0 ± 0.00 s versus 14.0 ± 6.65 s, p = 0.024) showed a significant decrease over time. A similar significant decrease was observed with the Yg-UT rats for days one to two (45.7 ± 6.63 s versus 16.2 ± 4.43 s, p = 0.016) and one to four (45.7 ± 6.63 s versus 5.50 ± 2.35 s, p = 0.014). By day three, Yg-COM rats had a significantly quicker escape latency than Yg-UT rats (5.83 ± 2.71 s versus 17.2 ± 3.98 s, p = 0.044). Three parameters from day eight (Figure 2(b)) showed significance. Yg-COM rats had significantly fewer platform visits (3.50 ± 0.67 versus 6.17 ± 0.91, p = 0.040) and time moving towards (13.3 ± 0.46 s versus 15.4 ± 0.35 s, p = 0.004) and away from the platform zone (9.05 ± 0.69 s versus 11.5 ± 0.59 s, p = 0.040).

Wild type three-month-old (Yg) and TG-F344 18-month-old (Tg) Morris water maze manual and anymaze recording results. Yg-rat comparisons of (a) escape latency from the i) NW-zone for learning days and (b) significant performance parameters from platform-less day eight. No significant differences were found during testing day analysis. (N = 12, six males and six females per treatment group). Tg-rat comparison of (c) escape latency from the i) NE and ii) SE zones. Behavioral parameters significantly differ between Tg-COM and Tg-UT rats during testing days and day eight. (N = 11, six Tg-COM, and five Tg-UT). (APA p-value style: 0.12(ns), 0.033(*), 0.002(**), 0.001(***)), SEM reported.
In the Tg-cohort, a significant difference was observed within the Tg-UT rat escape latency for days one and four when placed in the NE-zone (38.7 ± 8.94 s versus 9.83 ± 3.59 s, p = 0.032). Significance was also found in SE-zone days one and three (47.8 ± 8.25 s versus 10.2 ± 3.58 s, p = 0.024), and one and four (47.8 ± 8.25 s versus 17.5 ± 5.86 s, p = 0.035) for Tg-UT (Figure 2(c)). No significance for testing days was found between either group. Most of the day five parameters (Figure 2(d)), like time moving towards the NW-zone, show that Tg-UT rats’ results are significantly greater than Tg-COM rats (17.4 ± 1.70 s versus 6.32 ± 0.784 s, p < 0.001). However, the average speed in the NW zone is significantly greater for Tg-COM rats. Days five (Tg-COM:48.0 ± 22.6° versus Tg-UT:-49.7 ± 31.3°, p = 0.034) and six (Tg-COM:35.2 ± 23.8° versus Tg-UT:-39.3 ± 4.52°, p = 0.034) show Tg-COM rats had a significantly more positive deviation for signed initial heading errors to the platform zone. On day eight, latency to last entry to the platform zone is significantly greater for the Tg-COM rats (37.8 ± 5.63 s versus 12.2 ± 5.67 s, p = 0.026) and significantly lesser for path efficiency (0.024 ± 0.005 versus 0.068 ± 0.015, p = 0.036).
COM alters the expression of proteins associated with CNS fluid circulation
Based on previous reports,13–15 we chose to study the quantitative expression of proteins involved in CNS fluid circulation and cognitive function using WBs; proteins include Aβ1−42, AQP4, LYVE-1, and GAD67. Among the Yg-rats, no significant differences were found between the groups (Figure 3(a)). However, within the Tg-COM rats (Figure 3(b)), GAD67 expression in the cerebellum (1.24 ± 0.118 versus 0.923 ± 0.0838, p = 0.049) and LYVE-1 expression in the PFC (0.442 ± 0.0234 versus 0.319 ± 0.0159, p = 0.002) was significantly greater than the Tg-UT rats; also, LYVE-1 was significantly lower in the hippocampus of Tg-COM rats (0.208 ± 0.0255 versus 0.281 ± 0.0153, p = 0.30).

Western blot analysis of wild-type three-month-old (Yg) and TG-F344 18-month-old (Tg) coupled with proteomic analysis of TG-F344 18-month-old rat hippocampus. (a) Histograms of relative signal density, and unpaired t-test analysis for the expression of Aβ1-42, AQP4, LYVE-1, and GAD67 in Yg and (b) Tg-cohorts. (APA p-value style: 0.12(ns), 0.033(*), 0.002(**), 0.001(***)), SEM reported. Representative western blot images are displayed. Whole blot images are provided in the supplementary section. (c) Volcano plot shows differential expression proteins in COM-treated rats compared to the UT group. The analysis identified that COM significantly up (blue) and down (red) regulated the expression of 45 proteins, including 34 Alzheimer's Disease-related proteins. False Discovery rate (q-values) set to less than 0.01. Whole western blot annotated images (Supplemental Material 2B and 2C) and Tg-rat transcriptomics results (Supplemental Material 2D) can be found in the Supplemental Material.
A proteomic assay was performed using hippocampal tissue to identify COM-induced changes; 86 differentially expressed proteins were identified with 33 proteins upregulated and 53 downregulated (Figure 3(c)). 34 proteins were associated with neurological disorders and diseases, including Serine-threonine kinase P21-activated kinase-3 (PAK3).
Discussion
We established a novel technique to quantify COM-treatment force. Results from the Yg-cohort indicate that COM does not adversely affect spatial learning and memory. Yg-UT and Yg-COM rats exhibited similar trends throughout all testing days, with a decreasing escape latency. Explorative activity was observed with Yg-COM rats on day eight. They spent less time moving towards and away from the platform zone. Repetitiveness could have given them security in escape, and once removed, the rats opted to explore other areas. 19 Opposite behaviors are seen in the Yg-UT rats, who spent more time investigating the platform zone, indicating they have learned the platform's location. In the Tg-cohort, Tg-UT rats presented more goal-oriented behaviors than Tg-COM rats. In contrast Tg-COM rats exhibited more explorative behaviors, hence them having a significantly greater latency to last entry to the platform zone and lower path efficiency. We can conclude that Tg-COM rats, similar to Yg-COM rats, have slightly more interest in exploring before committing to escape during testing days and upon platform removal (day eight).
Immunoassay results for the Yg-rats lacked significance in the expression of Aβ1−42, AQP4, LYVE-1, and GAD67 between the groups. For Tg-rats, there was no significant difference between UT and COM groups for Aβ expression. Together, these findings suggest that the frequency or strength of treatment was insufficient to see a difference. The fabric, sensor stiffness, and inability for tactile sensation limits the physician's fine motor skills while administering treatment.18,20 Additionally, Yg-rats are less likely to have Aβ1−42 aggregation due to age, so differences in expression are expected to be minimal in the F344 rat model. 21 These are possible reasons why our preceding study reported a reduction in Aβ1−42 expression in 18-month-old F344 male rats. 13 The Tg-rats were genetically modified to express a large concentration of Aβ (cerebral:∼60 μg/wet g of brain in aged animals). 21 Absence of significant Aβ reduction in Tg-COM rats suggests lack of treatment response as the pathology is evolving from multiple genetic mutations, which is probably beyond the capability of COM treatment intervention. However, Tg-rats’ significant differences with LYVE-1 and GAD67 show that treatment was sufficient to change proteins associated with meningeal clearance and neurotransmission.11,22 The hippocampal-proteomic analysis also identified proteins like PAK3, which regulate neuronal synaptic morphology, functionality, and outgrowth. 23 PAK3 is reduced or dysregulated in the AD brain, so upregulation in Tg-COM rats implies that COM has neuroprotective effects through protein modulation.23,24
Though not directly studied, Aβ reduction and increases in expression of proteins associated with neuroactivity and clearance indicate that COM can alter cerebral fluid systems to improve cognition. Improved clearance, via meningeal-lymphatic and glymphatic systems, of Aβ enhances the circulation of cerebrospinal and interstitial fluid.25,26 Cerebral blood flow also improves upon a decrease in accumulation, allowing for restored angiogenesis.27,28 Collectively, all systems having better functionality improves cognition in the AD brain. Considering results from this study, COM has more evidence as an efficacious therapeutic. For the future, we propose using a larger cohort to validate findings and investigate sex differences.
Limitations
The lack of experimenter blinding during behavioral assessments may have introduced unintentional observer bias. Additionally, the use of isoflurane anesthesia could serve as a potential confounding factor, as anesthetics can independently alter central nervous system fluid dynamics.
Supplemental Material
sj-docx-1-alr-10.1177_25424823251393742 - Supplemental material for A preliminary study on the effect of quantified cranial osteopathic manipulation on wild-type and transgenic rat models of Alzheimer's disease
Supplemental material, sj-docx-1-alr-10.1177_25424823251393742 for A preliminary study on the effect of quantified cranial osteopathic manipulation on wild-type and transgenic rat models of Alzheimer's disease by De’Yana Hines, Hope Tobey, Patrick Dugan, Seth Boehringer, Richard Helm, Ramu Anandakrishnan, Stephen Werre, Pamela VandeVord and Blaise M Costa in Journal of Alzheimer's Disease Reports
Footnotes
Acknowledgements
Work was funded by grant# 1915733 American Osteopathic Association (AOA) and grant# 1R15 AT010789-01A1 National Institute of Health (NIH) to Blaise Costa. The authors acknowledge Costa lab research assistants and animal house staff for their help with the MWM assay. We also thank Dr. Susan Murphy for critically reading the manuscript and providing constructive feedback.
Ethical considerations
All experimental procedures were conducted in accordance with Virginia Tech's Institutional Animal Care and Use Committee (IACUC) of (Protocol ID# 15-099 and ID#19-045).
Consent to participate
Not applicable
Consent for publication
Not applicable
Author contribution(s)
Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the American Osteopathic Association, National Center for Complementary and Integrative Health, (grant number 1915733, 1R15 AT010789-01A1).
Declaration of conflicting interests
The authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: BMC is founder and CEO of Clab LLC.
Data availability statement
All data associated with the results presented in this manuscript are provided in the figures and supplemental files. Additional and raw data can be obtained from the corresponding author with a reasonable request.
Supplemental material
Supplemental material for this article is available online.
References
Supplementary Material
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