Analysis of Bone-Cartilage-Stromal Progenitor Populations in Trauma Induced and Genetic Models of Heterotopic Ossification.

Heterotopic ossification (HO), the formation of extra-skeletal bone in soft tissues, is a pathologic process occurring after substantial burns or trauma, or in patients with type I bone morphogenetic protein (BMP) receptor hyperactivating mutations. Identifying the cells responsible for de novo bone formation during adulthood is of critical importance for therapeutic and regenerative purposes. Using a model of trauma-induced HO with hind limb Achilles' tenotomy and dorsal burn injury and a genetic nontrauma HO model (Nfatc1-Cre/caAcvr1(fl/wt) ), we demonstrate enrichment of previously defined bone-cartilage-stromal progenitor cells (BCSP: AlphaV+/CD105+/Tie2-/CD45-/Thy1-/6C3-) at the site of HO formation when compared with marrow isolated from the ipsilateral hind limb, or from tissue of the contralateral, uninjured hind limb. Upon transplantation into tenotomy sites soon after injury, BCSPs isolated from neonatal mice or developing HO incorporate into the developing lesion in cartilage and bone and express chondrogenic and osteogenic transcription factors. Additionally, BCSPs isolated from developing HO similarly incorporate into new HO lesions upon transplantation. Finally, adventitial cells, but not pericytes, appear to play a supportive role in HO formation. Our findings indicate that BCSPs contribute to de novo bone formation during adulthood and may hold substantial regenerative potential. Stem Cells 2016;34:1692-1701.

NELL-1 expression in benign and malignant bone tumors.

NELL-1 (NEL-like Protein 1) is an osteoinductive protein with increasing usage as a bone graft substitute in preclinical animal models. NELL-1 was first identified to have bone-forming properties by its overexpression in fusing cranial sutures. Since this time, addition of recombinant NELL-1 has been used to successfully induce bone formation in the calvarial, axial and appendicular skeleton. With increasing interest in the use of NELL-1 as a bone-graft substitute, we sought to examine the expression of NELL-1 in a wide spectrum of benign and malignant bone-forming skeletal tumors. Immunohistochemical expression was examined in human pathologic specimens. Quantitative RT-PCR evaluated NELL-1 expression among OS cell lines in vitro. Results showed NELL-1 expression in all bone tumors. Likewise, all OS cell lines demonstrated increased NELL-1 expression in comparison to non-lesional human bone marrow stromal cells. Among, benign bone tumors (osteoid osteoma and osteoblastoma), strong and diffuse staining was observed, which spatially correlated with markers of osteogenic differentiation. In contrast, a relative reduction in NELL-1 staining was observed in osteosarcoma, accompanied by increased variation between tumors. Among osteosarcoma specimens, NELL-1 expression did not correlate well with markers of osteogenic differentiation. Surprisingly, among osteosarcoma subtypes, fibroblastic osteosarcoma demonstrated the highest expression of NELL-1. In summary, NELL-1 demonstrates diffuse and reliable expression in benign but not malignant bone-forming skeletal tumors. Future studies will further define the basic biologic, diagnostic and prognostic importance of NELL-1 in bone neoplasms.

Embryo Rescue Protocol for Interspecific Hybridization in Squash.

Interspecific hybridization in Cucurbita crops (squash) is desirable for widening genetic variation and for the introgression of useful alleles. Immature embryos generated from these wide crosses must be regenerated using appropriate embryo rescue techniques. Although this technique is well established for many crops, a detailed description of the appropriate methodology for squash that would allow its routine application is lacking. Here, we describe an embryo rescue protocol useful for interspecific hybridization of C. pepo and C. moschata. To identify viable combinations for embryo rescue, 24 interspecific crosses were performed. Fruit set was obtained from twenty-two crosses, indicating a 92% success rate. However, most of the fruits obtained were parthenocarpic, with seeds devoid of embryos (empty seeds). Only one cross combination contained immature embryos that could be regenerated using basal plant growth media. A total of 10 embryos were rescued from the interspecific F1 fruit, and the success rate of embryo rescue was 80%. The embryo rescue protocol developed here will be useful for interspecific hybridization in squash breeding programs.

Whole Genome Re-sequencing and Bulk Segregant Analysis Reveals Chromosomal Location for Papaya Ringspot Virus W Resistance in Squash.

Squash (Cucurbita moschata) is among the most important cucurbit crops grown worldwide. Plant pathogen, Papaya ringspot virus W (PRSV-W) causes significant yield loss in commercial squash production globally. The development of virus-resistant cultivars can complement integrated disease management and mitigate losses due to viral infections. However, the genetic loci and molecular markers linked to PRSV-W resistance that could facilitate marker-assisted selection (MAS) for accelerated cultivar development are unknown. In this study, quantitative trait loci (QTL), molecular markers, and candidate genes associated with PRSV-W resistance in squash were identified in an F2 population (n = 118) derived from a cross between Nigerian Local accession (resistant) and Butterbush cultivar (susceptible). Whole genome re-sequencing-based bulked segregant analysis (QTLseq method; n = 10 for each bulk) and non-parametric interval mapping were used to identify a major QTL associated with PRSV-W resistance on chromosome 9 (QtlPRSV-C09) (p < 0.05) of C. moschata. QtlPRSV-C09 extended from 785,532 to 5,093,314 bp and harbored 12,245 SNPs among which 94 were high-effect variants. To validate QtlPRSV-C09, 13 SNP markers were assayed as Kompetitive allele-specific PCR (KASP) markers in the F2 population and tested for the association with PRSV-W resistance. Among these, two KASP markers (Ch09_2080834 and Ch09_5023865-1) showed significant association with PRSV-W resistance (p < 0.05). The two SNPs were located within exons of putative disease-resistant genes encoding the clathrin assembly family and actin cytoskeleton-regulatory complex proteins, which are implicated in disease resistance across plant species. The findings of this study will facilitate MAS for PRSV-W resistance in squash and allow further understanding of the functional mechanisms underlying potyvirus resistance in Cucurbita species.

Genomic Position and Markers Associated with the Hull-Less Seed Trait in Pumpkin.

Pumpkin (Cucurbita pepo) seeds are nutritious and valued as a source of vegetable oil, protein, healthy fatty acids, and minerals. Pumpkin seeds that are naturally devoid of the seedcoat (hull-less) are preferred by the industry as they eliminate the need for de-hulling prior to use. A single recessive gene, designated as n or h, controls the hull-less seed trait in pumpkin. Visual selection for the trait is easy, however, it is resource intensive when applied to large breeding populations. High throughput genotyping assays can aid in the identification of suitable individuals in segregating populations through marker-assisted selection. In the current study, the QTL-seq approach was used to identify genetic loci, SNP markers and candidate genes associated with the hull-less trait in a segregating F2 population (n = 143) derived from a cross between Kakai (hull-less) × Table Gold Acorn (hulled). The segregation of the hull-less trait in the F2 population fit a 3:1 ratio (p < 0.05). QTL-seq analysis detected a single QTL on chromosome 12 (Qtlhull-less-C12) which was significantly associated with the hull-less trait in C. pepo. Twenty-eight SNPs were genotyped in the population, two among which (Ch12_3412046 and Ch12_3417142) were significantly associated (p < 0.05) with the hull-less trait in cultivars and accessions of diverse genetic background. Several candidate genes fall within the Qtlhull-less-C12 interval, among them is the No Apical meristem (NAC) domain-containing protein and a Fiber Protein fb11 gene involved in lignin accumulation and cell wall deposition across plant species, respectively. The findings of this study will facilitate the marker-assisted selection for the hull-less seed trait in pumpkin and further our understanding of the functional mechanisms underlying the trait across cucurbit crops.

A Novel QTL for Resistance to Phytophthora Crown Rot in Squash.

Phytophthora capsici Leonian causes significant yield losses in commercial squash (Cucurbita pepo) production worldwide. The deployment of resistant cultivars can complement integrated management practices for P. capsici, but resistant cultivars are currently unavailable for growers. Moderate resistance to Phytophthora crown rot in a selection of accession PI 181761 (C. pepo) (designated line #181761-36P) is controlled by three dominant genes (R4, R5 and R6). Introgression of these loci into elite germplasm through marker-assisted selection (MAS) can accelerate the release of new C. pepo cultivars resistant to crown rot, but these tools are currently unavailable. Here we describe the identification of a quantitative trait locus (QTL), molecular markers and candidate genes associated with crown rot resistance in #181761-36P. Five hundred and twenty-three SNP markers were genotyped in an F2 (n = 83) population derived from a cross between #181761-36P (R) and Table Queen (S) using targeted genotyping by sequencing. A linkage map (2068.96 cM) consisting of twenty-one linkage groups and an average density of 8.1 markers/cM was developed for the F2 population. The F2:3 families were phenotyped in the greenhouse with a virulent strain of P. capsica, using the spore-spray method. A single QTL (QtlPC-C13) was consistently detected on LG 13 (chromosome 13) across three experiments and explained 17.92-21.47% of phenotypic variation observed in the population. Nine candidate disease resistance gene homologs were found within the confidence interval of QtlPC-C13. Single nucleotide polymorphism (SNP) markers within these genes were converted into Kompetitive Allele Specific PCR (KASP) assays and tested for association with resistance in the F2 population. One SNP marker (C002686) was significantly associated with resistance to crown rot in the F2 population (p < 0.05). This marker is a potential target for MAS for crown rot resistance in C. pepo.

Genetic Loci Associated with Resistance to Zucchini Yellow Mosaic Virus in Squash.

Zucchini Yellow Mosaic Virus (ZYMV) is an aphid-transmitted potyvirus that causes severe yield losses in squash (Cucurbita moschata) production worldwide. Development of resistant cultivars using traditional breeding approaches relies on rigorous and resource-intensive phenotypic assays. QTL-seq, a whole genome re-sequencing based bulked segregant analysis, is a powerful tool for mapping quantitative trait loci (QTL) in crop plants. In the current study, the QTL-seq approach was used to identify genetic loci associated with ZYMV resistance in an F2 population (n = 174) derived from a cross between Nigerian Local (resistant) and Butterbush (susceptible). Whole genome re-sequencing of the parents and bulks of resistant and susceptible F2 progeny revealed a mapping rate between 94.04% and 98.76%, and a final effective mapping depth ranging from 81.77 to 101.73 across samples. QTL-seq analysis identified four QTLs significantly (p < 0.05) associated with ZYMV resistance on chromosome 2 (QtlZYMV-C02), 4 (QtlZYMV-C04), 8 (QtlZYMV-C08) and 20 (QtlZYMV-C20). Seven markers within the QTL intervals were tested for association with ZYMV resistance in the entire F2 population. For QtlZYMV-C08, one single nucleotide polymorphism (SNP) marker (KASP-6) was found to be significantly (p < 0.05) associated with ZYMV resistance, while two SNPs (KASP-1 and KASP-3) and an indel (Indel-2) marker were linked to resistance within QtlZYMV-C20. KASP-3 and KASP-6 are non-synonymous SNPs leading to amino acid substitutions in candidate disease resistant gene homologs on chromosomes 20 (CmoCh20G003040.1) and 8 (CmoCh08G007140.1), respectively. Identification of QTL and SNP markers associated with ZYMV resistance will facilitate marker-assisted selection for ZYMV resistance in squash.

Repeatable Stair-step Assay to Access the Allelopathic Potential of Weedy Rice (Oryza sativa ssp.).

Weed competition contributes significantly to yield losses in cropping systems worldwide. The evolution of resistance in many weed species to continuously applied herbicides has presented the need for additional management methods. Allelopathy is a physiological process that some plant species possess that provide the plant with an advantage over its neighbors. Allelopathic crop varieties would be equipped with the ability to suppress the growth of surrounding competitors, thus reducing potential yield loss due to weed interference. This paper focuses on the construction and operation of a stair-step assay used for the screening of the allelopathic potential of a donor species (Oryza sativa) against a receiver weed species (Echinochloa crus-galli) in a greenhouse setting. The structure described in this paper serves as a stand for the plant samples and incorporates a timed watering system for the accumulation and distribution of allelochemicals. Allelochemicals produced by the plant roots are allowed to flow downward through a series of four pots separately into a collection tank and recycled back to the top plant through electric pumps. This method of screening provides an avenue for the allelochemicals from the donor plant to reach receiver plants without any resource competition, thus allowing quantitative measurement of the allelopathic potential of the selected donor plant. The allelopathic potential is measurable through the height reduction of the receiver plants. Preliminary screening data for the effectiveness of this method demonstrated height reduction in the receiver species, barnyardgrass (E. crus-galli), and thus the presence of allelopathic residues from the donor plant, weedy rice (Oryza sativa).

Effects of WNT3A and WNT16 on the Osteogenic and Adipogenic Differentiation of Perivascular Stem/Stromal Cells.

Human perivascular stem/stromal cells (hPSC) are a multipotent mesenchymogenic stromal cell population defined by their perivascular locale. Recent studies have demonstrated the high potential for clinical translation of this fluorescence-activated cell sorting (FACS)-derived cell population for autologous bone tissue engineering. However, the mechanisms underlying the osteogenic differentiation of PSC are incompletely understood. The current study investigates the roles of canonical and noncanonical Wnt signaling in the osteogenic and adipogenic differentiation of PSC. Results showed that both canonical and noncanonical Wnt signaling activity transiently increased during PSC osteogenic differentiation in vitro. Sustained WNT3A treatment significantly decreased PSC osteogenic differentiation. Conversely, sustained treatment with Wnt family member 16 (WNT16), a mixed canonical and noncanonical ligand, increased osteogenic differentiation in a c-Jun N-terminal kinase (JNK) pathway-dependent manner. Conversely, WNT16 knockdown significantly diminished PSC osteogenic differentiation. Finally, WNT16 but not WNT3A increased the adipogenic differentiation of PSC. These results indicate the importance of regulation of canonical and noncanonical Wnt signaling for PSC fate and differentiation. Moreover, these data suggest that WNT16 plays a functional and necessary role in PSC osteogenesis.

Combining Smoothened Agonist and NEL-Like Protein-1 Enhances Bone Healing.

BACKGROUND: Nonhealing bone defects represent an immense biomedical burden. Despite recent advances in protein-based bone regeneration, safety concerns over bone morphogenetic protein-2 have prompted the search for alternative factors. Previously, the authors examined the additive/synergistic effects of hedgehog and Nel-like protein-1 (NELL-1) on the osteogenic differentiation of mesenchymal stem cells in vitro. In this study, the authors sought to leverage their previous findings by applying the combination of Smoothened agonist (SAG), hedgehog signal activator, and NELL-1 to an in vivo critical-size bone defect model. METHODS: A 4-mm parietal bone defect was created in mixed-gender CD-1 mice. Treatment groups included control (n = 6), SAG (n = 7), NELL-1 (n = 7), and SAG plus NELL-1 (n = 7). A custom fabricated poly(lactic-co-glycolic acid) disk with hydroxyapatite coating was used as an osteoinductive scaffold. RESULTS: Results at 4 and 8 weeks showed increased bone formation by micro-computed tomographic analyses with either stimulus alone (SAG or NELL-1), but significantly greater bone formation with both components combined (SAG plus NELL-1). This included greater bone healing scores and increased bone volume and bone thickness. Histologic analyses confirmed a significant increase in new bone formation with the combination therapy SAG plus NELL-1, accompanied by increased defect vascularization. CONCLUSIONS: In summary, the authors' results suggest that combining the hedgehog signaling agonist SAG and NELL-1 has potential as a novel therapeutic strategy for the healing of critical-size bone defects. Future directions will include optimization of dosage and delivery strategy for an SAG and NELL-1 combination product.

Ang-2 but not Ang-1 expression in perivascular soft tissue tumors.

Perivascular soft tissue tumors are relatively uncommon neoplasms of unclear line of differentiation, although most are presumed to originate from pericytes. Previously, we reported a shared immunophenotype across these related tumor types. Here, we extend these findings to examine the expression of the pericyte markers angiopoietin-1 and -2 (Ang-1 and -2) among perivascular soft tissue tumors. Results showed consistent Ang-2 but not Ang-1 expression across tumor types. In summary, the absence of Ang-1 expression distinguishes perivascular from vascular soft tissue tumors. Ang-2 expression is present across perivascular soft tissue tumors, with some variation between histologic subtypes.

Ang-1 and Ang-2 expression in angiomyolipoma and PEComa family tumors.

OBJECTIVE: Perivascular epithelioid cell tumors (PEComa) are an uncommon family of soft tissue tumors. Previously, we described that the presence of pericyte antigens among PEComa family tumors differs extensively by histologic appearance. METHODS: Here, we extend our findings using the pericyte antigens Angiopoietin-1 (Ang-1) and Angiopoietin-2 (Ang-2), using immunohistochemical detection in human tumor samples. RESULTS: While Ang-1 showed no expression across any PEComa family tumor, Ang-2 showed expression that like other pericyte markers was largely determined by cytologic appearance. CONCLUSION/IMPLICATIONS: Pericytic marker expression in PEComa may represent a true pericytic cell of origin, or alternatively aberrant pericyte marker adoption.

The pericyte antigen RGS5 in perivascular soft tissue tumors.

Perivascular soft tissue tumors are relatively uncommon neoplasms of unclear lineage of differentiation, although most are presumed to originate from or differentiate to pericytes or a modified perivascular cell. Among these, glomus tumor, myopericytoma, and angioleiomyoma share a spectrum of histologic findings and a perivascular growth pattern. In contrast, solitary fibrous tumor was once hypothesized to have pericytic differentiation--although little bona fide evidence of pericytic differentiation exists. Likewise the perivascular epithelioid cell tumor (PEComa) family shares a perivascular growth pattern, but with distinctive dual myoid-melanocytic differentiation. RGS5, regulator of G-protein signaling 5, is a novel pericyte antigen with increasing use in animal models. Here, we describe the immunohistochemical expression patterns of RGS5 across perivascular soft tissue tumors, including glomus tumor (n = 6), malignant glomus tumor (n = 4), myopericytoma (n = 3), angioleiomyoma (n = 9), myofibroma (n = 4), solitary fibrous tumor (n = 10), and PEComa (n = 19). Immunohistochemical staining and semi-quantification was performed, and compared to αSMA (smooth muscle actin) expression. Results showed that glomus tumor (including malignant glomus tumor), myopericytoma, and angioleiomyoma shared a similar diffuse immunoreactivity for RGS5 and αSMA across all tumors examined. In contrast, myofibroma, solitary fibrous tumor and PEComa showed predominantly focal to absent RGS5 immunoreactivity. These findings further support a common pericytic lineage of differentiation in glomus tumors, myopericytoma and angioleiomyoma. The pericyte marker RGS5 may be of future clinical utility for the evaluation of pericytic differentiation in soft tissue tumors.

Calvarial Defect Healing Induced by Small Molecule Smoothened Agonist.

Hedgehog (Hh) signaling positively regulates both endochondral and intramembranous ossification. Use of small molecules for tissue engineering applications poses several advantages. In this study, we examined whether use of an acellular scaffold treated with the small molecule Smoothened agonist (SAG) could aid in critical-size mouse calvarial defect repair. First, we verified the pro-osteogenic effect of SAG in vitro, using primary neonatal mouse calvarial cells (NMCCs). Next, a 4 mm nonhealing defect was created in the mid-parietal bone of 10-week-old CD-1 mice. The scaffold consisted of a custom-fabricated poly(lactic-co-glycolic acid) disc with hydroxyapatite coating (measuring 4 mm diameter × 0.5 mm thickness). Treatment groups included dimethylsulfoxide control (n = 6), 0.5 mM SAG (n = 7) or 1.0 mM SAG (n = 7). Evaluation was performed at 4 and 8 weeks postoperative, by a combination of high-resolution microcomputed tomography, histology (H & E, Masson's Trichrome), histomorphometry, and immunohistochemistry (BSP, OCN, VEGF). In vivo results showed that SAG treatment induced a significant and dose-dependent increase in calvarial bone healing by all radiographic parameters. Histomorphometric analysis showed an increase in all parameters of bone formation with SAG treatment, but also an increase in blood vessel number and density. In summary, SAG is a pro-osteogenic, provasculogenic stimulus when applied locally in a bone defect environment.

Pericytic mimicry in well-differentiated liposarcoma/atypical lipomatous tumor.

Pericytes are modified smooth muscle cells that closely enwrap small blood vessels, regulating and supporting the microvasculature through direct endothelial contact. Pericytes demonstrate a distinct immunohistochemical profile, including expression of smooth muscle actin, CD146, platelet-derived growth factor receptor ß, and regulator of G-protein signaling 5. Previously, pericyte-related antigens have been observed to be present among a group of soft tissue tumors with a perivascular growth pattern, including glomus tumor, myopericytoma, and angioleiomyoma. Similarly, malignant tumor cells have been shown to have a pericyte-like immunoprofile when present in a perivascular location, seen in malignant melanoma, glioblastoma, and adenocarcinoma. Here, we examine well-differentiated liposarcoma specimens, which showed some element of perivascular areas with the appearance of smooth muscle (n = 7 tumors). Immunohistochemical staining was performed for pericyte antigens, including smooth muscle actin, CD146, platelet-derived growth factor receptor ß, and regulator of G-protein signaling 5. Results showed consistent pericytic marker expression among liposarcoma tumor cells within a perivascular distribution. MDM2 immunohistochemistry and fluorescence in situ hybridization for MDM2 revealed that these perivascular cells were of tumor origin (7/7 tumors), whereas double immunohistochemical detection for CD31/CD146 ruled out an endothelial cell contribution. These findings further support the concept of pericytic mimicry, already established in diverse malignancies, and its presence in well-differentiated liposarcoma. The extent to which pericytic mimicry has prognostic significance in liposarcoma is as yet unknown.

Vertebral Implantation of NELL-1 Enhances Bone Formation in an Osteoporotic Sheep Model.

BACKGROUND: Vertebral compression fractures related to osteoporosis greatly afflict the aging population. One of the most commonly used therapy today is balloon kyphoplasty. However, this treatment is far from ideal and is associated with significant side effects. NELL-1, an osteoinductive factor that possesses both pro-osteogenic and anti-osteoclastic properties, is a promising candidate for an alternative to current treatment modalities. This study utilizes the pro-osteogenic properties of recombinant human NELL-1 (rhNELL-1) in lumbar spine vertebral defect model in osteoporotic sheep. METHODS: Osteoporosis was induced through ovariectomy, dietary depletion of calcium and vitamin D, and steroid administration. After osteoporotic induction, lumbar vertebral body defect creation was performed. Sheep were randomly implanted with the control vehicle, comprised of hyaluronic acid (HA) with hydroxyapatite-coated ß-tricalcium phosphate (ß-TCP), or the treatment material of rhNELL-1 protein lyophilized onto ß-TCP mixed with HA. Analysis of lumbar spine defect healing was performed by radiographic, histologic, and computer-simulated biomechanical testing. RESULTS: rhNELL-1 treatment significantly increased lumbar spine bone formation, as determined by bone mineral density, % bone volume, and mean cortical width as assessed by micro-computed tomography. Histological analysis revealed a significant increase in bone area and osteoblast number and decrease in osteoclast number around the implant site. Computer-simulated biomechanical analysis of trabecular bone demonstrated that rhNELL-1-treatment resulted in a significantly more stress-resistant composition. CONCLUSION: Our findings suggest rhNELL-1-based vertebral implantation successfully improved cortical and cancellous bone regeneration in the lumbar spine of osteoporotic sheep. rhNELL-1-based bone graft substitutes represent a potential new local therapy.

Sclerostin expression in skeletal sarcomas.

Sclerostin (SOST) is an extracellular Wnt signaling antagonist which negatively regulates bone mass. Despite this, the expression and function of SOST in skeletal tumors remain poorly described. Here, we first describe the immunohistochemical staining pattern of SOST across benign and malignant skeletal tumors with bone or cartilage matrix (n=68 primary tumors). Next, relative SOST expression was compared to markers of Wnt signaling activity and osteogenic differentiation across human osteosarcoma (OS) cell lines (n=7 cell lines examined). Results showed immunohistochemical detection of SOST in most bone-forming tumors (90.2%; 46/51) and all cartilage-forming tumors (100%; 17/17). Among OSs, variable intensity and distribution of SOST expression were observed, which highly correlated with the presence and degree of neoplastic bone. Patchy SOST expression was observed in cartilage-forming tumors, which did not distinguish between benign and malignant tumors or correlate with regional morphologic characteristics. Finally, SOST expression varied widely between OS cell lines, with more than 97-fold variation. Among OS cell lines, SOST expression positively correlated with the marker of osteogenic differentiation alkaline phosphatase and did not correlate well with markers of Wnt/ß-catenin signaling activity. In summary, SOST is frequently expressed in skeletal bone- and cartilage-forming tumors. The strong spatial correlation with bone formation and the in vitro expression patterns are in line with the known functions of SOST in nonneoplastic bone, as a feedback inhibitor on osteogenic differentiation. With anti-SOST as a potential therapy for osteoporosis in the near future, its basic biologic and phenotypic consequences in skeletal tumors should not be overlooked.

Review of microRNA in osteosarcoma and chondrosarcoma.

MicroRNAs (miRNAs) are small noncoding RNAs, which play a complex role in posttranscriptional gene expression and can theoretically be used as a diagnostic or prognostic tool, or therapeutic target for neoplasia. Despite advances in the diagnosis and treatment of skeletal sarcomas, including osteosarcoma and chondrosarcoma, much remains unknown regarding their underpinning molecular mechanisms. Given the recent increasing knowledge base of miRNA roles in neoplasia, both as oncogenes and tumor suppressor genes, this review will focus on the available literature regarding the expression profiles and potential roles of miRNA in skeletal sarcomas. Although this is an emerging field, miRNA profiling may be of use in clarifying competing diagnoses of skeletal sarcomas and possibly indicate patient risk of resistance to traditional chemotherapeutic agents. While detecting and targeting miRNAs is currently limited to experimental investigations, miRNA may be utilized for future clinical management of skeletal sarcomas.

An unusual complex karyotype in myopericytoma.

INTRODUCTION: Myopericytoma is a perivascular neoplasm commonly found in the skin and soft tissue of extremities. These lesions often exhibit concentric vascular proliferation of spindle shaped myoid cells. METHODS/RESULTS: We present a case of a 76-year old male who was diagnosed with myopericytoma and subsequent cytogenetic analysis found a highly abnormal karyotype. This karyotype includes cytogenetic mutations that have not been described in previous case studies of myopericytoma. CONCLUSIONS: Some of these aberrations occur on genes that are involved in hedgehog signaling as well as pericyte proliferation, indicating a potential pericyte origin for myopericytoma tumors.

NELL-1 expression in tumors of cartilage.

BACKGROUND/AIMS: NELL-1 is a novel osteochondral differentiation factor protein with increasing usage in tissue engineering. Previously, we reported the expression patterns of NELL-1 in bone-forming skeletal tumors. With increasing interest in the use of NELL-1 protein, we sought to examine the expression of NELL-1 in cartilage-forming tumors. METHODS: Immunohistochemical expression was examined in human pathologic specimens. RESULTS: Consistent NELL-1 overexpression across all cartilage-forming tumors was observed. Similar degrees of expression were observed in enchondroma, chondrosarcoma, and chondroblastic osteosarcoma. NELL-1 expression did not significantly vary by tumor grade. CONCLUSION: In summary, NELL-1 demonstrates reliable and consistent expression across cartilage-forming skeletal tumors.