Gravity: An Essential Factor in Skeletal Health and Bone Homeostasis

Gravity contributes significantly to bone integrity and bone health. If gravity is absent or reduced, resulting in massive loss of bone density and structural impairment, like astronauts, who lose much of their bone mass and structure, when they are in space. Human bones are highly responsive to mechanical loading, which is controlled mainly by gravitational forces. This review aimed to show the physiological, cellular, and molecular mechanisms through which gravity influences bone remodeling. It focuses attention on how mechanical loading and weight-bearing activities contribute to maintaining bone mass and the prevention of osteoporosis. The role of osteocytes as mechanosensors, the impact of microgravity on gene expression, and epigenetic modifications linked to skeletal deterioration are also discussed. This narrative review addresses some of the implications of prolonged weightlessness, potential measures for bone loss in space, and opportunities for insights into osteoporosis prevention and treatment on Earth. This narrative review was conducted by examining peer-reviewed literature from databases including PubMed and Google Scholar, using keywords such as 'gravity,' 'bone health,' 'osteoporosis,' and 'epigenetics.' Relevant studies were selected based on their contribution to understanding the physiological impact of gravity on skeletal integrity. It provides recommendations for emerging research into artificial gravity, whole-body vibration therapy, and medicines designed to preserve skeletal health. The contribution of gravity in bone physiology to preventing and treating bone disease is critical for developing strategies to prevent bone deterioration in both space travelers and persons with long-term sedentary lifestyles and conditions of musculoskeletal disorders. Understanding the role of microgravity experiments can contribute to understanding techniques for the prevention and treatment of osteoporosis on Earth.

Gravity, bone remodeling, microgravity, osteocytes, osteoporosis, mechanotransduction, skeletal adaptation, artificial gravity, bone loss, epigenetics.