Human osteogenic sarcoma: fine structure of the osteoblastic type

Histograms of computed tomography values in differential diagnosis of benign and malignant osteogenic lesions

BACKGROUND

The use of histogram analysis of computed tomography (CT) values is a potential method for differentiating between benign osteoblastic lesions (BOLs) and malignant osteoblastic lesions (MOLs).

PURPOSE

To explore the diagnostic efficacy of histogram analysis in accurately distinguishing between BOLs and MOLs based on CT values.

MATERIAL AND METHODS

A total of 25 BOLs and 25 MOLs, which were confirmed through pathology or imaging follow-up, were included in this study. FireVoxel software was used to process the lesions and obtain various histogram parameters, including mean value, standard deviation, variance, coefficient of variation, skewness, kurtosis, entropy value, and percentiles ranging from 1st to 99th. Statistical tests, such as two independent-sample t-tests and the Mann-Whitney U test with Bonferroni correction, were employed to compare the differences in histogram parameters between BOLs and MOLs. A receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic efficacy of each parameter.

RESULTS

Significant differences were observed in several histogram parameters between BOLs and MOLs, including the mean value, coefficient of variation, skewness, and various percentiles. Notably, the 25th percentile demonstrated the highest diagnostic efficacy, as indicated by the largest area under the curve in the ROC curve analysis.

CONCLUSION

Histogram analysis of CT values provides valuable diagnostic information for accurately differentiating between BOLs and MOLs. Among the different parameters, the 25th percentile parameter proves to be the most effective in this discrimination process.

The microenvironment-specific transformation of adult stem cells models malignant triton tumors

Here, we demonstrated the differentiation potential of murine muscle-derived stem/progenitor cells (MDSPCs) toward myogenic, neuronal, and glial lineages. MDSPCs, following transplantation into a critical-sized sciatic nerve defect in mice, showed full regeneration with complete functional recovery of the injured peripheral nerve at 6 weeks post-implantation. However, several weeks after regeneration of the sciatic nerve, neoplastic growths were observed. The resulting tumors were malignant peripheral nerve sheath tumors (MPNSTs) with rhabdomyoblastic differentiation, expressing myogenic, neurogenic, and glial markers, common markers of human malignant triton tumors (MTTs). No signs of tumorigenesis were observed 17 weeks post-implantation of MDSPCs into the gastrocnemius muscles of dystrophic/mdx mice, or 1 year following subcutaneous or intravenous injection. While MDSPCs were not oncogenic in nature, the neoplasias were composed almost entirely of donor cells. Furthermore, cells isolated from the tumors were serially transplantable, generating tumors when reimplanted into mice. However, this transformation could be abrogated by differentiation of the cells toward the neurogenic lineage prior to implantation. These results establish that MDSPCs participated in the regeneration of the injured peripheral nerve but transformed in a microenvironment- and time-dependent manner, when they likely received concomitant neurogenic and myogenic differentiation signals. This microenvironment-specific transformation provides a useful mouse model for human MTTs and potentially some insight into the origins of this disease.

Risk factors in the development of stem cell therapy

Stem cell therapy holds the promise to treat degenerative diseases, cancer and repair of damaged tissues for which there are currently no or limited therapeutic options. The potential of stem cell therapies has long been recognised and the creation of induced pluripotent stem cells (iPSC) has boosted the stem cell field leading to increasing development and scientific knowledge. Despite the clinical potential of stem cell based medicinal products there are also potential and unanticipated risks. These risks deserve a thorough discussion within the perspective of current scientific knowledge and experience. Evaluation of potential risks should be a prerequisite step before clinical use of stem cell based medicinal products.

The risk profile of stem cell based medicinal products depends on many risk factors, which include the type of stem cells, their differentiation status and proliferation capacity, the route of administration, the intended location, in vitro culture and/or other manipulation steps, irreversibility of treatment, need/possibility for concurrent tissue regeneration in case of irreversible tissue loss, and long-term survival of engrafted cells. Together these factors determine the risk profile associated with a stem cell based medicinal product. The identified risks (i.e. risks identified in clinical experience) or potential/theoretical risks (i.e. risks observed in animal studies) include tumour formation, unwanted immune responses and the transmission of adventitious agents.

Currently, there is no clinical experience with pluripotent stem cells (i.e. embryonal stem cells and iPSC). Based on their characteristics of unlimited self-renewal and high proliferation rate the risks associated with a product containing these cells (e.g. risk on tumour formation) are considered high, if not perceived to be unacceptable. In contrast, the vast majority of small-sized clinical trials conducted with mesenchymal stem/stromal cells (MSC) in regenerative medicine applications has not reported major health concerns, suggesting that MSC therapies could be relatively safe. However, in some clinical trials serious adverse events have been reported, which emphasizes the need for additional knowledge, particularly with regard to biological mechanisms and long term safety.

Ultrastructure of Low-grade Intraosseous Osteosarcoma of Bone: A Comparative Study with Fibrous Dysplasia and Parosteal Osteosarcoma

The ultrastructure of low-grade intraosseous osteosarcoma (LGOS) is not well documented in the literature. Four cases of LGOS are described with an emphasis on its distinguishing characteristics as well those it shares with other lesions. The predominant cells of LGOS are fibroblasts with well-developed rough endoplasmic reticulum and mild focal immunoreactivity to SMA and MSA. Few osteoblasts and myofibroblasts are present. Transition cells between fibroblasts and osteoblasts are also noted. The fibroblasts are closely related to osteoblasts from a histological and functional point of view, and phenotypically are probably modified osteoblasts. Comparative ultrastructural studies between LGOS and fibrous dysplasia (FD) reveal basic similarities, although the cells in LGOS are larger with more of an abundance of organelles. Therefore, accurate differentiation between these two lesions rests at the histological and radiological levels. LGOS and parosteal osteosarcomas (PO) also share similar ultrastructural features. In the case samples in this study, an unusual type of multilayered amorphous material was found in the osteoid matrix of a case of LGOS and one of PO. This probably emphasizes the morphologic similarities between these 2 tumors.

Sarcoma derived from cultured mesenchymal stem cells

To study the biodistribution of MSCs, we labeled adult murine C57BL/6 MSCs with firefly luciferase and DsRed2 fluorescent protein using nonviral Sleeping Beauty transposons and coinfused labeled MSCs with bone marrow into irradiated allogeneic recipients. Using in vivo whole-body imaging, luciferase signals were shown to be increased between weeks 3 and 12. Unexpectedly, some mice with the highest luciferase signals died and all surviving mice developed foci of sarcoma in their lungs. Two mice also developed sarcomas in their extremities. Common cytogenetic abnormalities were identified in tumor cells isolated from different animals. Original MSC cultures not labeled with transposons, as well as independently isolated cultured MSCs, were found to be cytogenetically abnormal. Moreover, primary MSCs derived from the bone marrow of both BALB/c and C57BL/6 mice showed cytogenetic aberrations after several passages in vitro, showing that transformation was not a strain-specific nor rare event. Clonal evolution was observed in vivo, suggesting that the critical transformation event(s) occurred before infusion. Mapping of the transposition insertion sites did not identify an obvious transposon-related genetic abnormality, and p53 was not overexpressed. Infusion of MSC-derived sarcoma cells resulted in malignant lesions in secondary recipients. This new sarcoma cell line, S1, is unique in having a cytogenetic profile similar to human sarcoma and contains bioluminescent and fluorescent genes, making it useful for investigations of cellular biodistribution and tumor response to therapy in vivo. More importantly, our study indicates that sarcoma can evolve from MSC cultures.

Osteosarcoma. Ultrastructural and immunohistochemical studies on alkaline phosphatase-positive tumor cells constituting a variety of histologic types

The osteosarcomas were subclassified into osteoblastic, fibroblastic, chondroblastic and telangiectatic types and examined by electron microscopy. Their immunohistochemical reactions were also studied. In an overall survey of the above types, fibroblast-like cells revealed poorly developed cytoplasmic organelles with rather short, branching rough endoplasmic reticulum, mixed with osteoblast-like cells that were hardly distinguishable from the former. They appeared to be an early stage of an osteoblastic cell lineage from the distribution and development of their cell organelles and highly positive vimentin activity. The tumor cells in malignant cartilage varied in appearance from chondroblast-like to osteoblast-like cells. All types of tumor cells expressed alkaline phosphatase activity to a significant degree. Immunohistochemical staining showed a mixture of procollagen type I-positive cells among the cells positive for both procollagen type II and S-100 protein in the malignant cartilage. Irrespective of any ultrastructural differences between these various tumor cell types, they all revealed a significant degree of ALPase activity unlike other types of bone tumors, suggesting that the tumor cells which constitute the various types of osteosarcoma are derived from a common precursor cell.

Human osteogenic sarcoma: fine structural localization of adenosine triphosphatase

The localization of ATPases in 7 osteogenic sarcomas of osteoblastic, chondroblastic and fibroblastic type was investigated at the fine structural level using two types of substrates: one with lead as capturing ion and one with strontium (the latter presumed to reveal sites of Na+-K+-dependent transport ATPase). Reaction product with the lead-ATP medium was located on the plasma membrane and the membranes bordering subjacent vesicles and vacuoles in all the various types of osteoblastlike and fibroblastlike cells and also in types 1 and 3 chondroblastlike cells, and multinucleated giant cells believed to be neoplastic. Furthermore, deposits of reaction product were demonstrated in lysosomelike organelles in all the aforementioned cells. Except in the case of chondroblastlike cells, precipitates marking the localization of enzyme were confined to areas of the plasma membrane where adjacent cells were closely applied (the free surface lacked precipitates). In chondroblastlike cells the reaction product was usually deposited along the whole plasma membrane. Presence of L-Homoarginine or L-Tetramisole in the incubation medium in concentrations that have been shown to completely abolish alkaline phosphatase activity did not affect the occurrence of the reaction product with ATP as substrate indicating that the enzyme hydrolysing ATP was substrate-specific. Reaction product marking sites of Na+-K+-dependent ATPase was confined to plasma membranes and lysosomes of cells in vessel walls. The observations strengthen the notion obtained in studies on the localization of alkaline phosphatase, namely that osteoblastlike, chondroblastlike, and fibroblastlike cells in osteogenic sarcomas are histogenetically related to one another and to those multinucleated giant cells that presumably are of a neoplastic nature.

Quantitation of the nuclear DNA content in tissue prepared for electron microscopy

The possibility of determining the cellular DNA content in tissue prepared for electron microscopy (EM) was investigated. Comparative cell population DNA analyses of deparaffinized and Epon-embedded sections of equal thickness (2 micron) from the same tumor (osteosarcoma) showed almost identical DNA distribution curves. The methodologic prerequisites for both EM and DNA analyses of identical cells was then investigated. Using a special technique involving consecutive sections of 500-600 A and 2-micron thickness for EM morphology and Feulgen staining, respectively, nuclear parts of identical cells could be identified in both types of sections. Thus, cells selected in ultrathin sections could be identified in corresponding Feulgen-stained Epon-embedded sections for cytophotometric DNA analysis. All normal cells (lymphocytes, fibroblasts, macrophages), as defined and selected at the ultrastructural level, proved to be diploid (with normal DNA content) as determined in the corresponding Feulgen-stained Epon-embedded sections, whereas all analyzed osteosarcoma cells, except one, were aneuploid. The results indicate that 2-micron thick Feulgen-stained, Epon-embedded specimens from osteosarcoma, previously fixed in glutaraldehyde and OsO4, may be used for cytophotometric DNA measurements. Since aneuploidy is almost exclusively found in malignant cells, this criterion may serve as a marker for such cells. Consequently, whenever it is questionable whether in a mixed population a given cell selected for ultrastructural study is malignant or not, DNA cytophotometry may give decisive information, provided aneuploidy can be demonstrated.

Human osteogenic sarcoma: fine structure of hard tissue areas

The structure of hard tissue areas (with osteoid and calcified matrix) in 10 osteoblastic, chondroblastic, and fibroblastic osteogenic sarcomas was studied in the electron microscope. Neoplastic cells commonly associated with these areas and presumably actively involved in the production of hard tissue were osteoblast-like cells types 1 and 3, chondroblast-like cells type 1, and fibroblast-like cells, as defined and characterized in previous studies. The cells differed from those in soft tissue areas of osteogenic sarcomas in but one respect: they usually showed presence of irregular extrusions at their surfaces. Other types of osteoblast-like and chondroblast-like cells occurred rarely or not at all. Two types of multinucleated giant cells were recognized in these areas, one showing a fine structure reminiscent of that in osteoclasts, the other probably being of a neoplastic nature and engaged in the production of the calcifying matrix. The evidence suggested that neoplastic osteoblast-like, chondroblast-like, and fibroblast-like cells as well as certain multinucleated giant cells might all be involved in the mineralization process and/or the formation of osteoid in osteogenic sarcomas. Although phenotypically of highly variable appearance, all these different cells may thus functionally (and probably histogenetically) be closed related. The mineralization process in the tumor tissue appeared to be a modification of what occurs in normal ossification, possibly with an alternative or complementary pathway involving the production of spherical bodies with layered contents.

Human osteogenic sarcoma: fine structural localization of alkaline phosphatase

The localization of alkaline phosphatase in eight osteogenic sarcomas of osteoblastic. chondroblastic, and fibroblastic type was investigated at the fine structural level using beta-glycerophosphate as substrate and lead as capturing ion. Final product marking localization of alkaline phosphatase was deposited over plasma membranes and associated subplasmalemmal vesicles and vacuoles in various types of osteoblastlike, chondroblastlike, and fibroblastlike cells as well as certain multinucleated giant cells. Presence of L-homoarginine or L-tetramisole in the incubation medium, and incubation at 65 degrees C, prevented the deposition of final product, suggesting that the enzyme studied was "bone specific." The evidence obtained was compatible with the notion that the different cells showing presence of reaction product were functionally and histogenetically closely related and all were likely to be capable of bone production.

Human osteogenic sarcoma: fine structure of the fibroblastic type

The fine structure of representative regions of nine fibroblastic osteogenic sarcomas was studied. As judged by light microscopic criteria, the tumors represented both highly malignant (grades 3-4) and less malignant (grade 2) varieties. By electron microscopy, six basic cell types were found in the selected regions (fibroblastlike, histiocytelike, and myofibroblastlike cells, along with xanthoma cells, multinucleated giant cells, and undifferentiated cells). In addition, occasional osteoblastlike cells were encountered. Fibroblastlike cells in general, and especially in grade 2 tumors, showed a fine structure, enabling differentiation from osteoblastlike cells. Multinucleated giant cells were of two morphologic types, and the fine structure appeared to be related to the malignancy potential and differentiation of the tumors. Many multinucleated giant cells in grade 2 tumors had a ruffled border and appeared to be highly active in digestive events (especially phagocytosis of whole cells and portions of cells). Accumulation of variable amounts of lipid in droplet form was common in the various types of cells present in the tissues. The observations were discussed with particular emphasis on the interrelationships and functional roles of the cells.

Human osteogenic sarcoma: fine structure of the chondroblastic type

The fine structure of representative regions of four chondroblastic osteogenic sarcomas was studied. These regions contained four morphologically distinguishable subtypes of chondroblastlike cells. In addition, multinucleated giant cells, fibroblastlike cells, and macrophagelike cells were present, along with small populations of unclassifiable cells forming at least two subgroups of cells likely to be of a neoplastic nature. With only one exception, all types of chondroblastlike cells were separated by wide zones of extracellular matrix. The large multinucleated cells showed a fine structure that differed from that seen in multinucleated giant cells of other tissues. The evidence suggested that the multinucleated cells in the chondroblastic osteogenic sarcomas were active in phagocytic functions. It is not clear whether or not they are neoplastic in nature. Osteoblastlike cells were not encountered in the chondroid areas of the osteogenic sarcomas studied. On the basis of the findings it is concluded that the observed fine structural polymorphism of the chondroblastlike cells may reflect differences in maturation and differentiation among these cells. The most well-differentiated cells (type 1) appear to be able to exert secretory functions.