Immunophenotyping in Patients With Osteoporosis

Osteoporosis is a disease of bone metabolism. The underlying disturbance of bone homeostasis promotes bone fractures and, in advanced stages, especially spontaneous fractures. The diagnosis of osteoporosis is carried out as part of routine clinical practice. In addition to the patient's medical history and clinical examination, blood tests are also carried out on certain parameters, including the concentrations of vitamin D, calcium and phosphate as well as C-reactive protein. In addition, bone density is measured by dual X-ray absorptiometry (DXA). The results can be used to determine the degree of osteoporosis, which affects the further therapeutic approach.

Therapy is essentially based on fracture prevention through optimization of dietary habits, promotion of physical activity, and adequate vitamin D intake. Pharmacological options mainly do not counteract the pathological bone loss and are usually not tolerable due to serious side effects or are only approved for a limited period of use. Consequently, the development of further options to complement existing methods is required for the diagnosis and treatment of osteoporosis. The modulation of the immune system seems to be promising, since osteoporosis is based on an inflammatory reaction. Thus, various regulatory markers of the innate and acquired immune system, which seem to be relevant in the development of the disease, have already been detected in osteoporosis patients. However, central questions regarding the immune phenotype of affected individuals remain unanswered. For example, it is unclear to what extent certain molecules, mostly growth factors or chemokines, influence the inflammatory processes in the context of osteoporosis. Furthermore, it is controversial whether and, if so, how immune markers influence each other and what effects this has on bone metabolism.In the long term, new insights regarding the properties of disease-associated immunoregulatory markers could revolutionize the diagnostic possibilities for osteoporosis, as affected individuals could be identified early and without additional radiation exposure by simple blood tests. Equally relevant is corresponding information for the improvement of therapy. In the future, the causative immune processes could be treated by regulating the corresponding immunological markers and meaningfully expand existing therapy options.