From where comes the osteoclast?

A RANKL-based Osteoclast Culture Assay of Mouse Bone Marrow to Investigate the Role of mTORC1 in Osteoclast Formation

Osteoclasts are unique bone-resorbing cells that differentiate from the monocyte/macrophage lineage of bone marrow. Dysfunction of osteoclasts may result in a series of bone metabolic diseases, including osteoporosis. To develop pharmaceutical targets for the prevention of pathological bone mass loss, the mechanisms by which osteoclasts differentiate from precursors must be understood. The ability to isolate and culture a large number of osteoclasts in vitro is critical in order to determine the role of specific genes in osteoclast differentiation. Inactivation of the mammalian/mechanistic target of rapamycin complex 1 (TORC1) in osteoclasts can decrease osteoclast number and increase bone mass; however, the underlying mechanisms require further study. In the present study, a RANKL-based protocol to isolate and culture osteoclasts from mouse bone marrow and to study the influence of mTORC1 inactivation on osteoclast formation is described. This protocol successfully resulted in a large number of giant osteoclasts, typically within one week. Deletion of Raptor impaired osteoclast formation and decreased the activity of secretory tartrate-resistant acid phosphatase, indicating that mTORC1 is critical for osteoclast formation.

Osteoclast derivation from mouse bone marrow

Osteoclasts are highly specialized cells that are derived from the monocyte/macrophage lineage of the bone marrow. Their unique ability to resorb both the organic and inorganic matrices of bone means that they play a key role in regulating skeletal remodeling. Together, osteoblasts and osteoclasts are responsible for the dynamic coupling process that involves both bone resorption and bone formation acting together to maintain the normal skeleton during health and disease. As the principal bone-resorbing cell in the body, changes in osteoclast differentiation or function can result in profound effects in the body. Diseases associated with altered osteoclast function can range in severity from lethal neonatal disease due to failure to form a marrow space for hematopoiesis, to more commonly observed pathologies such as osteoporosis, in which excessive osteoclastic bone resorption predisposes to fracture formation. An ability to isolate osteoclasts in high numbers in vitro has allowed for significant advances in the understanding of the bone remodeling cycle and has paved the way for the discovery of novel therapeutic strategies that combat these diseases. Here, we describe a protocol to isolate and cultivate osteoclasts from mouse bone marrow that will yield large numbers of osteoclasts.

Osteoclast-type giant cell neoplasms of the parotid gland

The parotid gland is added to the list of parenchymal organs, notably the pancreas, in which osteoclast-like cells appear as constituent cells in their neoplasms. The cells' role in the neoplasms is a reactive one or, more rarely, as an integral element in an osteoclast-type giant cell neoplasm or so-called osteoclastoma. Distinctive in histological appearance, the osteoclast-type giant cell neoplasm is a malignant lesion that, to date, has been described only in the pancreas and parotid glands. This report presents examples of each type of giant cell lesion in the parotid gland.

S-100 protein localization in minor salivary gland tumours: an aid to diagnosis

The clinician is almost entirely dependent on the histopathologist to accurately diagnose minor salivary gland tumours, but in some cases the histological interpretation of the specimen is very difficult. Recently it has been demonstrated using immunohistochemical techniques that S-100 protein is present in some salivary gland tissues and its localization has been used as an aid in the differentiation of major salivary gland tumours. To assess its value in the diagnosis of minor salivary gland tumours it was localized in sections from 15 such tumours using both a standard peroxidase-antiperoxidase (PAP) and a newly developed immunogold-silver staining sequence (IGSS) technique. Strong staining for S-100 protein was seen in the nuclei and cytoplasm of the cellular areas and also in the cells in the chondroid and myxoid areas of pleomorphic adenomas. Generally the staining was more intense and widespread with the IGSS method. No staining was observed in any of the other tumour types. We conclude that S-100 protein localization is a valuable aid in the differentiation of minor salivary gland tumours. Furthermore, the IGSS method enables more sensitive 'reading' of the staining reaction.

Nature of mononuclear cells positive for acid phosphatase activity in bone marrow of patients with renal osteodystrophy

Fifty two of 63 patients with renal osteodystrophy had one or more mononuclear cells positive for acid phosphatase in the marrow. These cells are also tartrate resistant and non-specific esterase negative, and are believed to be precursors to osteoclasts and other acid phosphatase positive cells resorbing bone on the trabecular surface.

Role of vitamin D in the immune system

Classically, the only roles attributed to vitamin D have been regulation of intestinal calcium absorption and maintenance of skeletal homeostasis. This review examines the new evidence describing a regulatory role for vitamin D (1,25-dihydroxyvitamin D) in immune cell functions along with research that has linked immune cell functions with skeletal homeostasis. The possible significance of this evidence with respect to the parturient dairy cow is discussed.