MODERN EDUCATION AND DEVELOPMENT
Выпуск журнала №-28
Часть–2_Июнь –2025
364
NEURODEGENERATIVE CHANGES IN THE HIPPOCAMPUS IN
ALZHEIMER’S DISEASE: IMMUNOHISTOCHEMICAL AND
MORPHOMETRIC ANALYSIS
Assistant of the Department of Anatomy and Clinical Anatomy,
Bukhara State Medical Institute named after Abu Ali ibn Sina
Davronov U.T.
Abstract: Alzheimer’s disease (AD) is a chronic and progressive
neurodegenerative disorder that significantly impairs memory, cognition, and
behavior. Central to the pathophysiology of AD is the degeneration of the
hippocampus, a brain structure integral to learning and memory. This study explores
the morphological and immunohistochemical alterations in the hippocampus of
individuals diagnosed with Alzheimer’s disease. Using post-mortem brain samples,
we employed specific immunohistochemical markers to detect neuronal damage,
amyloid-beta (Aβ) plaques, and hyperphosphorylated tau protein tangles.
Morphometric analysis was performed to quantify neuronal density and lesion burden
in various subregions of the hippocampus. The findings demonstrate significant
neurodegeneration and structural abnormalities in AD-affected hippocampal tissues,
supporting the clinical presentation of the disease and offering insight into potential
therapeutic targets.
1. Introduction
Alzheimer’s disease (AD) is the leading cause of dementia worldwide,
accounting for 60–80% of cases. The disease typically manifests as progressive
memory loss, language difficulties, and impaired executive function, eventually
leading to complete cognitive and functional decline. One of the earliest and most
vulnerable brain regions affected in AD is the hippocampus, which plays a crucial
role in forming, organizing, and storing memories. Pathologically, AD is
characterized by the presence of extracellular amyloid-beta (Aβ) plaques and
intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein.
MODERN EDUCATION AND DEVELOPMENT
Выпуск журнала №-28
Часть–2_Июнь –2025
365
These pathological changes result in synaptic dysfunction, neuronal loss, and brain
atrophy, particularly in the medial temporal lobe and hippocampus. The objective of
this study is to investigate neurodegenerative changes in the hippocampus using both
immunohistochemical and morphometric analyses, focusing on quantifying
pathological hallmarks of AD and correlating them with structural and cellular
damage.
2.
Materials
and
Methods
2.1.
Sample
Collection
Human post-mortem hippocampal tissues were obtained from 10 patients diagnosed
with Alzheimer's disease and 5 age-matched control individuals. All AD diagnoses
were confirmed clinically and pathologically according to the criteria established by
the National Institute on Aging and the Alzheimer’s Association.
2.2. Tissue Preparation and Immunohistochemistry
Tissues were fixed in 10% buffered formalin, embedded in paraffin, and sectioned
at 5 μm thickness. Sections underwent deparaffinization, rehydration, and antigen
retrieval using citrate buffer (pH 6.0). The following primary antibodies were used:
- Anti-Aβ (1:100)
- Anti-Tau (AT8, 1:200)
- Anti-NeuN (1:300) for neuronal nuclei
Secondary antibodies conjugated to horseradish peroxidase were applied, and
sections were developed with DAB and counterstained with hematoxylin.
2.3. Morphometric Analysis
Quantitative assessments were performed using ImageJ software. Five random non-
overlapping fields were selected per region: CA1, CA3, and dentate gyrus (DG).
Neuronal counts, plaque areas, and tangle frequencies were measured and
statistically analyzed.
2.4. Statistical Analysis
Statistical analysis was carried out using SPSS version 25. Data were tested for
normality using the Shapiro–Wilk test. Student’s t-test and ANOVA were used to
compare groups, with a p-value < 0.05 considered statistically significant.
MODERN EDUCATION AND DEVELOPMENT
Выпуск журнала №-28
Часть–2_Июнь –2025
366
3. Results
3.1. Neuronal Loss There was a marked reduction in neuronal density in AD
tissues compared to controls. The CA1 region showed a 45% reduction in neuronal
count (p < 0.001), while the dentate gyrus showed a 30% decrease (p < 0.05). Neurons
in AD samples appeared shrunken with condensed nuclei, consistent with
neurodegeneration.
3.2. Amyloid-beta Plaque Deposition Immunohistochemistry revealed
extensive Aβ plaque accumulation in all hippocampal subregions, with CA1 showing
the highest burden. Plaques were extracellular, amorphous, and varied in size.
Quantitatively, the plaque area occupied up to 20% of the CA1 region in AD cases (p
< 0.01).
3.3. Tau Pathology Tau immunoreactivity was predominantly intracellular,
with intense staining in neuronal soma and dendrites. The number of tau-positive cells
in AD tissues was significantly higher than controls (p < 0.001). Neurofibrillary
tangles
were
prominent
in
the
subiculum
and
CA1.
3.4. Correlation Between Pathological Markers and Neuronal Density
A strong inverse correlation (r = -0.85, p < 0.001) was observed between
plaque/tangle density and neuronal counts, indicating that greater pathological burden
was associated with increased neurodegeneration.
4. Discussion
This study provides compelling evidence that the hippocampus undergoes
profound neurodegenerative changes in Alzheimer’s disease. Our findings confirm
that neuronal loss, amyloid plaques, and tau tangles are significantly more prevalent
in AD patients compared to age-matched controls. The CA1 region appears to be the
most susceptible to neurodegeneration, which aligns with previous studies (Braak &
Braak, 1991). This region is critical for memory encoding, and damage here likely
contributes to early memory impairment seen in AD. The observed correlation
between pathological protein aggregates and neuronal loss emphasizes the pathogenic
role of Aβ and tau in disrupting neural circuits. The findings also highlight the
potential for using hippocampal biomarkers in early AD diagnosis and monitoring
MODERN EDUCATION AND DEVELOPMENT
Выпуск журнала №-28
Часть–2_Июнь –2025
367
disease progression. Our results underscore the utility of immunohistochemical and
morphometric techniques in understanding the anatomical basis of cognitive decline
and provide a foundation for future therapeutic research.
5. Conclusion
In conclusion, this study demonstrates significant neurodegenerative changes
in the hippocampus of patients with Alzheimer’s disease. These changes include
marked neuronal loss, widespread amyloid-beta plaque deposition, and tau pathology.
The findings support the central role of hippocampal damage in the cognitive deficits
associated with AD. Further research into the molecular mechanisms driving these
changes may aid in developing targeted therapies to slow or halt disease progression.
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