Bone marrow remodeling and brain-bone marrow crosstalk in Alzheimer's disease-like neurodegeneration

Alzheimer's disease (AD) is increasingly recognized as a systemic disorder involving not only central neurodegeneration but also alterations in peripheral immune regulation and systemic homeostasis. Among these, the bone marrow represents a critical yet underexplored interface between the brain and systemic homeostasis. In the present study, we investigated whether AD-like neurodegeneration induces functional and structural remodeling of the bone marrow and whether these changes can be modulated through central neural stimulation and treatment with embryonic proteoglycans (PEG). An AD-like model was induced in adult male rats by intracerebroventricular administration of aggregated amyloid-β (Aβ1-42). Bone marrow alterations were assessed using ELISA for insulin-like growth factor-1 (IGF-1) and nerve growth factor (NGF), Western blot analysis of c-Fos and NF-κB, high-performance liquid chromatography for GABA determination, flow cytometry of hematopoietic and niche-associated cell populations, and morphological evaluation using hematoxylin and eosin and Giemsa staining. Additional modulation was performed by sequential electrostimulation of the hypothalamic supraoptic and paraventricular nuclei and by administration of embryonic proteins. Amyloid exposure significantly increased bone marrow IGF-1 levels, c-Fos expression, and NF-κB activation, accompanied by marked remodeling of marrow architecture characterized by reduced adiposity, increased hematopoietic cellularity, megakaryocytic abnormalities, and altered expression of progenitor-, neuronal-, and apoptosis-associated markers. Flow cytometry revealed shifts in specific CD3⁺CD3⁺ T-cell subpopulations and increased apoptotic signaling, indicating dynamic reorganization of the hematopoietic niche. Hypothalamic stimulation and PEG treatment partially normalized these alterations, reducing inflammatory activation and restoring trophic and cellular balance. These findings demonstrate that AD-like neurodegeneration is associated with coordinated bone marrow remodeling and support the existence of a functional brain-bone marrow axis. The reversibility of these changes suggests that the bone marrow represents a biologically active and therapeutically accessible component of systemic responses to neurodegeneration, with potential relevance for future Alzheimer's disease interventions.