Effect of microgravity on bone Tissue: Mechanisms of osteodegeneration and advanced treatment modalities

Preeminent human existence in space raises concerns about bone health due to the effect of microgravity on bone tissue degeneration. Space experiments pose logistical challenges, but ground-based research using microgravity simulation provides information about bone loss mechanisms. This review compiles and evaluates data from astronaut, animal, and cellular experiments, emphasizing microgravity-induced skeletal deconditioning. These findings contribute to creating treatment approaches for preventing bone loss risks in space and potentially on Earth. Astronauts experience notable bone loss, up to 1 %-2 % per month in a gravity-less environment, predominantly influencing weight-bearing bones. These necessitate finding efficient treatment approaches for preventing bone loss risks in space and potentially on Earth. There is a significant need to investigate microgravity's impact on various bone compartments and skeletal recovery processes. The current review explores the stages of bone remodeling and the fundamental causes of bone loss in microgravity, including effects on osteoblasts, osteocytes, osteoclasts, hematopoietic stem cells, and bone marrow stromal cells, as well as the impact on calcium levels. The article also explores various treatment options, including general management, recent therapies, supportive therapies, and emerging therapies such as BP-NELL-PEG, melatonin, calcitonin, and molecular therapies, highlighting their therapeutic potential against microgravity-induced bone loss.