PubMed · 15054484
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Leslie G Biesecker. 2004. Phenotype matters.. https://doi.org/10.1038/ng0404-323
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For over five decades, osteochondromas (exostoses) and associated growth retardation have been known to be caused by radiation damage to the growing skeleton. Patients can be divided into three exposure groups. Group I received external beam radiation therapy primarily for the treatment of childhood cancers (typical dose 3,500 cGy), and 6-20% developed osteochondromas and growth retardation within the radiation portal. Group II consists of recently described patients who received total body irradiation in preparation for bone marrow transplant (typical dose: 800-1,200 cGy), and about 20% developed osteochondromas and growth retardation. Group III consists of 206 German children who in the 1940s and early 1950s received intravenous radioactive Peteosthor (Ra-224) to treat bone tuberculosis (estimated typical dose: 1,000-2,000 cGy), and 14% developed osteochondromas and growth retardation, among other benign and malignant sequelae. Combining these three exposure groups, osteochondromas and growth retardation develop in at least 6-20% of children who receive therapeutic radiation to their growing skeletons.
The multiple endocrine neoplasia type 1 (MEN1) gene is a tumor suppressor gene encoding a 610 amino acid nuclear protein, menin. Although mutations of the MEN1 gene are responsible for MEN 1 syndrome, the intracellular functions of menin have not been fully elucidated. Recent data suggest that interactions between menin and menin-interacting proteins have a role in physiological regulation of cell growth, control of the cell cycle and genome stability, and are potentially important in bone development and multipotent mesenchymal stem cell differentiation. Loss of these interactions might also contribute to the development of MEN 1 syndrome.
Matrix metalloproteinases (MMPs), a family of Zn2+-dependent endopeptidases, mediate different physiological processes by digesting components of the extracellular matrix. Nevertheless, overexpression of MMPs is implicated in the pathogenesis of various diseases. Different MMPs and tissue inhibitors of MMPs (TIMPs) are expressed in bone cells, and their biosynthesis is regulated by local and systemic hormones and factors. The levels of enzymatically active MMPs in bone are further controlled by secretion, activation of proenzymes, inhibition by TIMPs, cellular uptake and degradation. Members of the cysteine and serine family of proteinases also coordinate some of the biological activities of MMPs in bone. The functions of MMPs and TIMPs in bone include regulation of processes, such as degradation of collagen and other components of the bone matrix, migration and survival of bone cells, endochondral bone formation and bone resorption. Abnormal expression of MMPs may lead to pathological conditions affecting bone and cartilage. Various pharmacological agents can inhibit MMPs, and some of these inhibitors may be potential therapeutic agents for certain bone diseases. This review briefly describes the regulation and functions of different MMPs and TIMPs in bone, and provides an insight into the role of MMPs in bone development, remodeling and pathology.