Macrophage-derived Giant Cells Research Articles

171 Not Just a Matter of Retained Embryonic Spinal Cord: Histopathology of the Filum Terminale in Tethered Cord Syndrome

INTRODUCTION: We present a large consecutive series of patients with tethered cord syndrome who underwent resection of the filum terminale (FT) and the histopathologic findings as analyzed by the neuropathologists. METHODS: FT specimens obtained from a consecutive series of 288 pediatric and adult patients that underwent spinal cord releases performed at a single academic institution from 2013-2021 were analyzed retrospectively (IRB #787945). Hematoxylin and eosin (HE) and immunohistochemistry staining was performed to study the spectrum of cells known to reside in connective tissues. RESULTS: The most common structures included peripheral nerves (97.6%), ependymal cells (70.8%), ganglion cells (38.5%), and neuropil (15.3%). Cases with excess ependymal cells were associated with ependymal canals (5.9%), ependymal cysts (3.1%), and one case with extensive ependymal “proliferation” (0.3%). With regards to the inflammatory cellular findings, eleven specimens (3.8%) contained scattered or accumulated lymphocytes, macrophages, mast cells, macrophage-derived giant cells, and a secondary lymph follicle in one patient. 36 patients (12.5%) had increased vascularity with enlarged capillaries. Nine patients (3.1%) had an associated type of vascular malformation. A group of specimens included dystrophic calcification within the FT (7.6%). CONCLUSIONS: Both vascular and inflammatory changes along with calcifications have been overlooked as possible associated histologic secondary to mechanical stress on the FT. Additionally, vascular anomalies could alter the filum’s mechanical properties due to venous congestion.

ACE overexpression in myeloid cells increases oxidative metabolism and cellular ATP

ACE overexpression in myeloid cells increases oxidative metabolism and cellular ATP

Deletion of the chemokine receptor CCR2 attenuates foreign body reaction to implants in mice

Subcutaneous implantation of synthetic materials and biomedical devices often induces abnormal tissue healing – the foreign body reaction – which impairs their function. Here we investigated the role of the chemokine receptor CCR2 in this reaction to subcutaneous implants in mice. We measured angiogenesis, inflammation and fibrogenesis induced by implantation, for 1, 4, 7 and 14days, of polyether–polyurethane sponges in mice with genetic deletion of CCR2 (KO) and WT mice. Blood flow was determined by dye diffusion and laser Doppler perfusion techniques. Cytokines (VEGF, TNF-α, CCL2, TGF-β1) were measured by ELISA. Histochemical methods were used to assess collagen deposition and macrophage-derived giant cells in the implants. Skin and implant blood flow was lower in CCR2 KO than in WT mice, as were other aspects of neo-vascularization of the implants. Neutrophil accumulation was increased in KO implants but macrophage accumulation was decreased. Implant content of CCL2 was higher in KO implants, but TGF-β1, collagen deposition and the number of foreign body giant cells were lower than in WT implants. Deletion of CCR2 decreased blood flow in normal skin and inhibited neo-vascularization, chronic inflammation and fibrogenesis in subcutaneous implants. The chemokine receptor CCR2 plays an important role in both normal skin and in the reaction elicited by subcutaneous implantation of a foreign body.

ATP receptors and giant cell formation.

We have investigated the role of the purinergic P2X7 receptor in the formation of multinucleated giant cells in human monocyte/macrophage cultures stimulated with either concanavalin A or phytohemagglutinin. Macrophage fusion can be blocked by a P2X7-selective pharmacological antagonist or by a mAb directed against the extracellular P2X7 domain. Furthermore, macrophage cell clones expressing high P2X7 levels spontaneously fuse in culture, whereas macrophage clones lacking P2X7 are unable to fuse. Our findings suggest that the newly identified purinergic P2X7 receptor plays a central role in the complex chain of events leading to generation of macrophage-derived giant cells.

Meltrin-alpha, a fusion protein involved in multinucleated giant cell and osteoclast formation.

The formation of multinucleated cells such as myotubes, macrophage-derived giant cells (MGC), and osteoclasts is the result of cell-cell fusion of mononuclear precursors. Meltrin-alpha, -beta, and -gamma are members of a recently discovered family of proteins that contain disintegrin and metalloprotease domains and are related to fertilin, a protein involved in egg-sperm fusion. Based on this and evidence implicating meltrin-alpha in myoblast formation, we have investigated the possibility that meltrins may also play a role in the formation of MGC and osteoclasts. Using in situ RT-PCR, we have determined that murine mononuclear alveolar macrophages cultured under basal conditions express the transcript for meltrin-beta, but not for meltrin-alpha. However, meltrin-alpha mRNA appeared in mononuclear cells before cell fusion after treatment with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], a potent inducer of giant cell and osteoclast formation. Moreover, addition of meltrin-alpha antisense oligonucleotides to the cultures caused a 50% inhibition of giant cell formation. Similarly, meltrin-alpha antisense oligonucleotides inhibited by 70% the formation of multinucleated osteoclast-like cells expressing tartrate-resistant acid phosphatase (TRAP) in co-cultures of bone marrow cells and osteoblastic cells (2107) in the presence of 1,25(OH)2D3. Mononucleated TRAP-positive cells, induced by 1,25(OH)2D3 in the co-cultures, also expressed meltrin-alpha mRNA, but their number was not changed in the presence of meltrin-alpha antisense oligonucleotide. In contrast to mononuclear macrophages and osteoclast-like cells, murine bone marrow stroma and calvaria derived-cell lines (+/+ LDA.11 and 2107), primary cultures of calvaria cells, and primary cultures of bone marrow cells expressed both meltrin-alpha and -beta mRNA under basal conditions; whereas embryonic fibroblasts (NIH3T3) expressed only the meltrin-beta transcript. Upregulation of meltrin-alpha protein expression during cell fusion in alveolar macrophages and expression in osteoblastic cell lines were confirmed by Western blot analysis. These observations demonstrate that meltrins play a role in MGC and osteoclast formation from mononuclear precursors, as in the case with myotubes.

Immunolocalization of Vimentin in Macrophage-derived Giant Cells. Method for Obtaining Larger Giant Cells.

We studied the ultrastructure of giant cells derived from macrophages that are found on the surface of implanted polymethylmethacrylate intraocular lenses (IOLs) in rabbits and the immunolocalization of vimentin in these cells in order to study the rearrangement of the intermediate filaments in multinucleated cells. In adult Japanese albino rabbits, the crystalline lens was extracted and an IOL was inserted into the residual lens capsule. IOLs were removed after 7 days, and the specimens were processed for ultrastructural observation or for immunostaining for vimentin. Macrophages and multinucleated cell were detected on the surfaces of IOLs by both light and transmission electron microscopy. Nuclei of the large multinucleated cells showed a circular distribution with the center of the cytoplasm occupied by cytoplasmic vacuoles. Vimentin intermediate filaments were observed in the cytoplasm of both macrophages and multinucleated cells. Vimentin in giant cells showed a radial distribution. Results indicate that vimentin intermediate filaments become reorganized after the fusion of macrophages. Experimental implantation of an IOL into the animal eye is a useful method for obtaining larger giant cells derived from macrophages.

Histomorphometry of immature rat testis after heating.

The scrotal testes of albino rats aged 35 and 45 days were immersed in water at constant temperatures of 43 degrees C, 44 degrees C, or 45 degrees C for periods of 15-45 min in a special heating device. At an age of 60 days, the rats were mated in individual cages with two primiparous rats each. At an age of 90 days, they were killed and their testes were histologically processed. Rats with testes that had been subjected to heating when the animals were 45 days old showed both alterations of the seminiferous tubules and a decrease in fertilizing capacity. The effect of heat was greater in animals at 45 than at 35 days of age. In heat-treated testes, tubules contained PAS-positive concretion, sometimes engulfed by macrophage-derived giant cells and multinucleate cells derived from spermatids that failed to separate during spermiogenesis. The decrease in testicular volume observed after heat treatment was due mainly to reduced parenchymal volume. Thermic lability of seminiferous stem cells increases with age until adulthood, and recovery from heat injury declines.

Temporal artery morphology and morphometry in giant cell arteritis

Paraffin sections and more than 7,000 plastic cross-sections of temporal arteries from 27 patients with a clinical diagnosis of polymyalgia rheumatica (PMR), 16 patients with a clinical diagnosis of temporal arteritis (TA) and 18 age- and sex-matched postmortem controls were studied using light microscopy. A new method was developed to permit a morphometric comparison between biopsies and autopsy specimens. Two stages of inflammation were discerned in TA. In atrophic arterial segments there was a focal, foreign-body, giant-cell reaction to the calcified internal elastic membrane (IEM) with a spatially correlated, mononuclear cell infiltration. Isolated giant cells were also found to attack the IEM in these cases. The majority of the biopsies displayed a different picture with a diffuse macrophage attack on media and intima with numerous and apparently macrophage-derived giant cells, which did not attack calcifications. The latter arteries were significantly widened (p less than 0.02), which indicates that this phase is the later one. Non-inflamed segments of PMR vessels displayed a significant, non-reactive media atrophy compared with controls (p less than 0.03) and their IEM calcifications were significantly larger (p less than 0.02). The circumference was smaller in atrophic PMR arteries than in inflamed TA arteries (p less than 0.006), which contradicts post-inflammatory scarring.

Induction of multinucleated giant cell formation from human blood-derived monocytes by phorbol myristate acetate in in vitro culture.

Multinucleated giant cells (MGC) of mononuclear phagocyte origin occur in different tissues in various inflammatory states and pathological conditions. Although MGC are believed to be derived from monocyte-derived macrophages by fusion, their mechanism of formation is not known. In this study, we investigated the role of PMA, a protein kinase C activator, in the induction and formation of MGC from blood monocyte-derived macrophages in in vitro culture. The addition of PMA (1 x 10(-9) to 8 x 10(-8) M) to 3-wk-old cultures of blood-derived monocytes induces cell fusion with a 30% to 80% fusion rate. Moreover, IFN-gamma-treated blood-derived monocyte cultures showed an additional enhancement of fusion rate with the addition of PMA. 1(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride, a protein kinase inhibitor, inhibited the formation of macrophage-derived giant cells when added before phorbol ester and IFN-gamma. These findings suggest that protein kinase C may play an important role in the formation of macrophage-derived MGC.

Cell surface characterization of the human osteoclast: phenotypic relationship to other bone marrow-derived cell types.

Among the differentiated progeny of stem cells transplantable by bone marrow are osteoclasts, the multinucleate cells which are the major agents of bone resorption. Although the osteoclast is well characterized from a structural and functional standpoint, its development and origin are still far from clear. We have used monoclonal antibodies to investigate the interrelationship between osteoclasts and other haemopoietic cells in man. We have analysed the distribution of 19 granulocyte-monocyte antigens in eight reactivity clusters on the non-neoplastic osteoclasts present within nine osteoclastomas (syn. giant cell tumours of bone) and a single example of aneurysmal bone cyst. We found that osteoclasts are antigenically effete, failing to express granulocyte-monocyte, common leucocyte or other haemopoietic determinants; the only monocyte antigens detected on osteoclasts are My-7 and two closely related specificities, MCS.2 and DüHL60.4, which are also expressed by tissues outside the haemopoietic system. Our findings, taken together with recent transplantation studies, cast further doubt on the view that osteoclasts are specialized bone-resorbing macrophage-derived giant cells, and support a hypothesis that they are the end product of fusion of a hitherto unidentified circulating mononuclear cell type, the preosteoclast, which constitutes a cell lineage separate from those originating from the conventional multipotential haemopoietic stem cell, although still of bone marrow origin.