Impact of Acute and Chronic Stressors on the Morphofunctional Characteristics of Long Bones in Spontaneously Hypertensive Rats: A Histological and Microtomographic Analysis

Background/Objectives: Hypertension is a major contributor to cardiovascular diseases and is often intensified by psychological stress, which can also affect bone metabolism. Although both conditions independently compromise bone health, their combined im-pact—particularly under acute and chronic stress—remains unclear. This study aimed to assess the effects of such stressors on bone structure in spontaneously hypertensive rats (SHR). Methods: Forty male rats, both normotensive and SHR, were randomly as-signed to control, acute stress, or chronic stress groups. Acute stress involves a single 2-hour physical restraint. Chronic stress was induced over 10 days using alternating stressors: agitation, forced swimming, physical restraint, cold exposure, and water dep-rivation. Tibial bones were analyzed by microcomputed tomography (micro-CT), and histology was performed using Hematoxylin & Eosin and Masson’s Trichrome stains. Results: Micro-CT showed an increased trabecular bone volume in normotensive rats under chronic stress, whereas SHR displayed impaired remodeling under both stress types. Histological analysis revealed preserved connective tissue overall but evident changes in growth plate structure among stressed rats. SHR exhibited exacerbated tra-becular formation and cartilage abnormalities, including necrotic zones. Conclusions: Both acute and chronic stress, especially in the context of hypertension, negatively affect bone remodeling and maturation. Despite the absence of overt inflammation, structural bone changes were evident, indicating potential long-term risks. These findings high-light the importance of further studies on stress-hypertension interactions in bone health and the exploration of therapeutic approaches to mitigate skeletal damage under such conditions.