INVESTIGATION OF THE EXPRESSION OF THE IMMUNOHISTOCHEMICAL MARKER KI-67 IN THE TRACHEA AND MAIN BRONCHI OF RATS: AN EXPERIMENTAL APPROACH

Rheumatoid arthritis represents a chronic systemic inflammatory disorder of connective tissue characterized by progressive damage primarily affecting peripheral (synovial) joints through symmetrical, progressive, erosive-destructive polyarthritis, with some cases demonstrating characteristic extra-articular manifestations. Objective of the Study. This investigation aims to evaluate morphological alterations in tracheal and bronchial lymphoid structures in outbred white rats subjected to an experimental rheumatoid arthritis model utilizing complete Freund's adjuvant, with particular focus on Ki-67 proliferation marker expression analysis. Materials and Methods. The experimental cohort comprised 30 outbred white rats aged four months (both sexes) with mean body weight 170.5 ± 9.1 g. All laboratory animals originated from a single vivarium source and were maintained under standardized conditions featuring relative humidity (50-60%), ambient temperature (19-22°C), and 12-hour light/dark cycles. The principles of bioethics, approved by the Scientific Council of Bukhara State Medical Institute, are preserved and upheld in full compliance. The methods used for statistical data analysis were t-test, χ²-test, and correlation analysis. The study was conducted in accordance with the research plan of the Bukhara State Medical Institute within the framework of the topic "Early detection and diagnosis of pathological factors affecting the health of the population of the Bukhara region in the post-COVID-19 period, as well as the development of new methods of treatment and prevention (2022-2026)". Results and Discussion. Positively stained cells within designated areas were quantified as percentage ratios relative to total cell counts per microscopic field. Expression levels were categorized as follows: low expression (≤20%), moderate expression (20–60%), and high expression (>60%). Tracheal specimen analysis revealed 1,547 total cells, among which 189 cells demonstrated positive Ki-67 proliferation marker expression indicating proliferative activity. The remaining 1,358 cells showed Ki-67 negativity, suggesting predominant cellular quiescence. The overall positive expression rate of 12.21% indicates low proliferative activity in tracheal hyperplastic lymphoid tissue. Conclusions. Heterogeneous Ki-67 proliferation expression patterns in tracheobronchial tissues of experimental rheumatoid arthritis rats may reflect regional vascular perfusion variations across different tracheal and main bronchial segments.