Novel therapeutic platforms, which are based on biological therapies, are required to overcome extensive skeletal tissue loss or degeneration and to replace the currently used synthetic prostheses. Complex clinical challenges,such as intervertebral disc degeneration, osteoporotic vertebral fractures, tendon and ligament injuries, non-union fractures, and osteoarthritis, pose a great challenge both to health systems and to clinicians. We have been investigating the use of adult mesenchymal stem cells (MSCs) for skeletal tissue regeneration for the last twenty years. Our studies have shown that MSCs were able to regenerate tissues in a wide variety of skeletal injury models including complex limb, skull, and jaw fractures, and even tendon tears. In recent years we have been establishing new stem cell-based therapies for spinal disorders. Specifically, we have developed the use of MSCs for spine fusion that could replace the common surgical procedure, which requires metal implants. In addition, we are aiming at using MSCs for the treatment of lower back pain, which results from intervertebral disc degeneration, a medical problem that has no remedy to date. Furthermore, we are investigating the use of MSCs for the treatment of osteoporosis-related vertebral bone fractures. Toward this goal, we are investigating a systemic approach, in which the cells are injected into the blood circulation,as well as a direct approach, injecting the cells into the fractured vertebrae. Importantly, in order to quantitatively analyze tissue regeneration and monitor the effect of stem cell implantation, state-of-the-art molecular and micro-imaging technologies are needed. We have pioneered the application of optical, magnetic resonance and x-ray based micro CT imaging in the field of skeletal tissue engineering. These are noninvasive imaging techniques that allow real-time, accurate analysis of tissue regeneration and stem cell tracking in the living subject.