Muscle and bone interact via physical forces and secreted osteokines and myokines. Physical forces are generated through gravity, locomotion, exercise, and external devices. Cells sense mechanical strain via adhesion molecules and translate it into biochemical responses, modulating the basic mechanisms of cellular biology such as lineage commitment, tissue formation, and maturation. This may result in the initiation of bone formation, muscle hypertrophy, and the enhanced production of extracellular matrix constituents, adhesion molecules, and cytoskeletal elements. Bone and muscle mass, resistance to strain, and the stiffness of matrix, cells, and tissues are enhanced, influencing fracture resistance and muscle power. This propagates a dynamic and continuous reciprocity of physicochemical interaction. Secreted growth and differentiation factors are important effectors of mutual interaction. The acute effects of exercise induce the secretion of exosomes with cargo molecules that are capable of mediating the endocrine effects between muscle, bone, and the organism. Long-term changes induce adaptations of the respective tissue secretome that maintain adequate homeostatic conditions. Lessons from unloading, microgravity, and disuse teach us that gratuitous tissue is removed or reorganized while immobility and inflammation trigger muscle and bone marrow fatty infiltration and propagate degenerative diseases such as sarcopenia and osteoporosis. Ongoing research will certainly find new therapeutic targets for prevention and treatment.

Background.: Sarcomas arising in the heart or the great vessels are rare entities. The prognosis of the patients is dismal. Methods.: Between January 1993 and September 2006, of 1,429 patients registered to the Sarcoma Center, 14 had a primary sarcoma of the heart or large vessels. Results.: Tumors were located in the left ventricle (n = 3), left/right atrium (n = 2/3), pulmonary artery (n = 2), and ventricular septum, aorta, pericardium, and inferior vena cava (n = 1 each). The most frequently encountered histologic subtypes were leiomyosarcoma and angiosarcoma. Six patients presented with distant metastases to the lungs (n = 5), lymph nodes (n = 2), and liver (n = 1). Eight patients had localized disease. Six of them underwent resection with curative intent. Of those, two developed local recurrence within 2 and 10 months from surgery. Eleven patients received palliative chemotherapy, seven of those as initial treatment. Eight patients attained a response to treatment, two had disease stabilization for 6 and 12 months. After a median follow-up of 14.5 months (range, 2–156), three patients were alive with no evidence of disease 11, 52, and 156 months after diagnosis. Two patients were alive with disease and nine patients had died. Conclusions.: Patients with primary sarcomas of the heart and the large vessels were of a young age, and more than half of them presented with advanced disease. Given the promising response to chemotherapy, an optimized treatment approach including neoadjuvant chemo-/radiotherapy in patients with locally advanced disease should be pursued.

Avascular necrosis (AVN) of the femoral head is a debilitating disease of multifactorial genesis, predominately affects young patients, and often leads to the development of secondary osteoarthritis. The evolving field of regenerative medicine offers promising treatment strategies using cells, biomaterial scaffolds, and bioactive factors, which might improve clinical outcome. Early stages of AVN with preserved structural integrity of the subchondral plate are accessible to retrograde surgical procedures, such as core decompression to reduce the intraosseous pressure and to induce bone remodeling. The additive application of concentrated bone marrow aspirates, ex vivo expanded mesenchymal stem cells, and osteogenic or angiogenic growth factors (or both) holds great potential to improve bone regeneration. In contrast, advanced stages of AVN with collapsed subchondral bone require an osteochondral reconstruction to preserve the physiological joint function. Analogously to strategies for osteochondral reconstruction in the knee, anterograde surgical techniques, such as osteochondral transplantation (mosaicplasty), matrix-based autologous chondrocyte implantation, or the use of acellular scaffolds alone, might preserve joint function and reduce the need for hip replacement. This review summarizes recent experimental accomplishments and initial clinical findings in the field of regenerative medicine which apply cells, growth factors, and matrices to address the clinical problem of AVN.