Morphological Characteristics of the Ulna Fracture Zone in Rats Undergoing Therapy With Modified Mesenchymal Stem Cells in Experimental Osteoporosis

Osteoporosis is a progressive systemic disease characterized by a decrease in bone density. This leads to increased bone fragility and a higher likelihood of fractures. New approaches to cellular therapy have been developed for the effective treatment of this pathology, based on the use of modified osteophilic polymers with mesenchymal stem cells (MSCs) for local action on damaged bone areas. The aim of the study was to morphologically assess the effectiveness of modified osteophilic polymer MSCs on reparative osteogenesis processes during the post-traumatic period in animals with a fracture of the ulna and underlying osteoporosis. Material and methods. The experiment involved Wistar rats (females, n=40; 200–300 g, 3 months old). Osteoporosis was simulated by bilateral ovariectomy, and the fracture was simulated through diaphysis osteotomy of the ulna. All rats were randomly distributed into four groups: Group I (control, n=10; buffered solution); Group II (n=10; osteophilic polymer, 1 mg/ml); Group III (n=10; MSC suspension, 1×106); Group IV (n=10; modified osteophilic polymer MSCs, 1×106). The experiment results were evaluated in 1 and 6 months after the fracture. Results. MSCs were applied after exposure to the osteophilic polymer to restore the pool of osteoblast precursors in the fracture area of the ulna in experimental osteoporosis. In all animals, regeneration foci with varying degrees of structural and functional maturation of cellular and intercellular substrates were formed in the fracture area. The most pronounced processes of bone tissue restoration were observed with the use of modified osteophilic polymer MSCs. This is likely associated with the high concentration of modified osteophilic polymer MSCs and their retention in zones of damaged bone regeneration, subsequently stimulating osteogenesis. The paradigm of provisionality, as a universal model manifestating histogenesis and organogenesis, was utilized to gain a more comprehensive biological understanding and interpretation of the observed changes. Conclusion . MSCs applied after exposure to an osteophilic polymer significantly enhance the process of reparative osteogenesis in fractures of long bones in patients with estrogen-induced osteoporosis, thus making this technology promising for combined therapy.