An in vitro study to assess the effect of hyaluronan-based gels on muscle-derived cells: Highlighting a new perspective in regenerative medicine

Hyaluronan (HA) is a nonsulfated glycosaminoglycan that has been widely used for biomedical applications. Here, we have analyzed the effect of HA on the rescue of primary cells under stress as well as its potential to recover muscle atrophy and validated the developed model in vitro using primary muscle cells derived from rats. The potentials of different HAs were elucidated through comparative analyses using pharmaceutical grade a) high (HHA) and b) low molecular weight (LHA) hyaluronans, c) hybrid cooperative complexes (HCC) of HA in three experimental set-ups. The cells were characterized based on the expression of myogenin, a muscle-specific biomarker, and the proliferation was analyzed using Time-Lapse Video Microscopy (TLVM). Cell viability in response to H₂O₂ challenge was evaluated by 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay, and the expression of the superoxide dismutase enzyme (SOD-2) was assessed by western blotting. Additionally, in order to establish an in vitro model of atrophy, muscle cells were treated with tumor necrosis factor-alpha (TNF-α), along with hyaluronans. The expression of Atrogin, MuRF-1, nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-kB), and Forkhead-box-(Fox)-O-3 (FoxO3a) was evaluated by western blotting to elucidate the molecular mechanism of atrophy. The results showed that HCC and HHA increased cell proliferation by 1.15 and 2.3 folds in comparison to un-treated cells (control), respectively. Moreover, both pre- and post-treatments of HAs restored the cell viability, and the SOD-2 expression was found to be reduced by 1.5 fold in HA-treated cells as compared to the stressed condition. Specifically in atrophic stressed cells, HCC revealed a noteworthy beneficial effect on the myogenic biomarkers indicating that it could be used as a promising platform for tissue regeneration with specific attention to muscle cell protection against stressful agents.

Alveolar Rhabdomyosarcoma of the Paranasal Sinuses in a 57-Year-Old Woman With 1:16 Translocation

Alveolar rhabdomyosarcoma is an uncommon tumor. It is araremalignancy in adults and rarely occurs in paranasal sinuses in thoseaged older than 50 years. This report describes a locally invasi and destructive alveolar rhabdomyosarcoma arising in the ethmoidsinus of a 57-year-old woman. The small round blue cell tumors are positive for myogenin by immunohistochemistry and have a karyotype of 45, XX, -5, -13, der(16)t(1;1) (q21;q13) by cytogenetic analysis. Fluorescence in situ hybridization demonstrated a complex translocation with break apart of the FKHR region, which supports a diagnosis of alveolar rhabdomyosarcoma. This report characterizes this tumor through microscopic and cyto-genetic analysis and emphasizes the importance of considering rhabdomyosarcoma in the differential diagnosis of small round cell tumors of the head and neck region in the middle-aged adults.

[Childhood pleuropulmonary blastoma: a clinicopathologic study of 16 cases]

OBJECTIVE

To study the clinicopathological and immunohistochemical features, histogenesis and prognosis of pleuropulmonary blastoma (PPB) in children.

METHODS

PPB specimens from 16 pediatric cases with an age ranging from 1 year and 7 months to 5 years and 3 months (mean age of 3 years) were retrieved and analyzed by routine histological, immunohistochemical and electron methods.

RESULTS

Among 16 patients, there were 2 type I, 7 type II and 7 type III PPB cases. Type I PPB as multilocular cystic structure, consisted of thin fibrous wall lining the respiratory epithelium, subepithelial primitive blastema or immature mesenchymal cells, with or without rhabdomyoblastic differentiation or cartilage; Type II PPB as cystic-solid tumor, comparing with type I, consisted of intracystic components with appearance of anaplastic tumor cells. Type III PPB consisted of completely solid mass, the same as the solid region of type II, had mixed pattern including blastema, undifferentiated spindle-cell proliferations and sarcomas. In addition, anaplastic tumor cells and intra-and extra- cytoplasmic eosinophilic globules were also commonly present. Epithelial components in PPB were benign. Immunohistochemical study showed primitive mesenchymal differentiation of tumors. All cases were positive for vimentin, desmin, myogenin and SMA in tumors with skeletal muscle differentiation, S-100 was positive in tumors with cartilage differentiation. All tumors were negative for synaptophysin, CD99, and CD117. Benign epithelial components were positive for AE1/AE3 and EMA. In 12 cases, electron microscopy revealed few organelles in the primitive mesenchymal cells and rich heterochromatin in mesenchymal cells, the latter also demonstrating cytoplasmic myofilament dysplasia. Nine cases had clinical follow-up ranging from 5 to 48 months, of which 4 patients died.

CONCLUSIONS

PPB is a rare lung neoplasm of children under the age of 6 years, with distinct pathological morphology. PPB may arise from lung or pleura mesenchymal cells and has a poor clinical outcome.

[Extracardial rhabdomyoma: a clinicopathologic analysis of 9 cases]

OBJECTIVE

To investigate the clinicopathologic characteristics, differential diagnosis and biological behavior of extracardiac rhabdomyoma.

METHODS

Nine cases of extracardiac rhabdomyoma diagnosed between January of 1997 and July of 2014 were reviewed. The clinical, pathologic and immunohistochemical profiles were evaluated.

RESULTS

There were 5 males and 4 females at diagnosis with age ranging from 2 years and three months to 59 years (mean, 37.6 years). Sites included the head and neck region (7 cases), chest (1 case ) and vagina wall (1 case). Clinically, most cases manifested as a subcutaneous nodule or as a submucosal polypoid lesion with a mean diameter of 3.2 cm. Histologically, 4 were adult-type rhabdomyoma characterized by tightly packed large round or polygonal rhabdomyoblasts with abundant eosinophilic to clear cytoplasm; 3 were myxoid variant of fetal rhabdomyoma composed of immature myofibrils, spindled and primitive mesenchymal cells embedded in a myxoid background, 1 was an intermediate form of fetal rhabdomyoma consisting of densely arranged differentiated myoblasts with little myxoid stroma; 1 was a genital rhabdomyoma composed of elongated or strap-like myoblasts scattered in loose fibrous connective tissue. By immunohistochemistry, they showed diffuse and strong positivity for desmin, MSA and myoglobin with variable expression of myogenin. A case of intermediate type also stained for α-smooth muscle actin. Follow up data (2 months ~ 17 years) showed local recurrence in one patient 6 months after surgery.

CONCLUSIONS

Rhabdomyoma is a distinctively rare benign mesenchymal tumor showing skeletal muscle differentiation, which may occassionally recur if incompletely excised. Familiarity with its clinical and morphological variants is essential to avoid misdiagnosing this benign lesion as embryonal rhabdomyosarcoma.

In vitro characterization of proliferation and differentiation of trout satellite cells

Fish satellite cells have been extracted from various species, but the myogenic characteristics of these cells in culture remain largely unknown. We show here that 60%-70% of the adherent cells are myogenic based on their immunoreactivity for the myogenic regulatory factor MyoD. In DMEM containing 10% fetal calf serum (FCS), trout myoblasts display rapid expression of myogenin (18% of myogenin-positive cells at day 2) combined with rapid fusion into myotubes (50% of myogenin-positive nuclei and 30% nuclei in myosin heavy chain [MyHC]-positive cells at day 7). These kinetics of differentiation are reminiscent of the behavior of fetal myoblasts in mammals. However, not all the myogenic cells differentiate; this subpopulation of cells might correspond to the previously named "reserve" cells. More than 90% of the BrdU-positive cells are also positive for MyoD, indicating that myogenic cells proliferate in vitro. By contrast, less than 1% of myogenin-positive cells are positive for BrdU suggesting that myogenin expression occurs only in post-mitotic cells. In order to maximize either the proliferation or the differentiation of cells, we have defined new culture conditions based on the use of a proliferation medium (F10+10%FCS) and a differentiation medium (DMEM+2%FCS). Three days after switching the medium, the differentiation index (% MyHC-positive nuclei) is 40-fold higher than that in proliferation medium, whereas the proliferation index (% BrdU-positive nuclei) is three-fold lower. Stimulation of cell proliferation by insulin-like growth factor 1 (IGF1), IGF2, and FGF2 is greater in F10 medium. The characterization of these extracted muscle cells thus validates the use of this in vitro system of myogenesis in further studies of the myogenic activity of growth factors in trout.

[Medullomyoblastoma: a medulloblastoma with rhabdomyoblastic differentiation]

A 26 years old patient was operated for a tumor of cerebellar vermix, and then reoperated for a relapse at the age of 35 years, with a similar histological pattern in both cases. At pathologic examination, the tumor was composed of hypercellular sheets typical of medulloblastoma, containing also sparse large cells with eosinophilic cytoplasm and round nuclei containing voluminous nucleoli. Neuroblastic cells showed expression of neurofilament protein and synaptophysin. The large cells expressed desmin, myogenin, and neurofilament. These morphological and immunohistochemical features are characteristic of medullomyoblastoma. The patient deceased 11 years after the initial surgery. Medullomyoblastoma is a rare variant of medulloblastoma with a rhabdomyoblastic differentiation. The two tumoral populations share the same genetic alterations. The main differential diagnoses are atypical teratoid/rhabdoid tumor, immature teratoma, medulloepithelioma, primitive intracranial rhabdomyosarcoma and myoneurocytoma.

Primary osseous rhabdomyosarcoma with focal matrix formation mimicking osteosarcoma

We present an unusual case of primary osseous pleomorphic rhabdomyosarcoma with focal matrix formation mimicking osteosarcoma. The patient was a 21-year-old man who had suffered from pain and slight enlargement of his left calf for 2 months. A plain radiograph demonstrated a large, predominantly osteolytic mass in the region of the proximal fibula with features typical of malignant primary bone tumor. On open surgical biopsy, the tumor consisted of atypical cells, some of them presenting spindle morphology. Between them, there were bands of densely hyalinized matrix with osteoid appearance, but without definite lacunae or calcifications, and an osteosarcoma was diagnosed. Consequently, the tumor was removed. The postoperative tissue presented more pleomorphic cells with some definite rhabdomyoblasts. Desmin, actin, Myf4, and MyoD1 were positive in tumor cells, and a diagnosis of rhabdomyosarcoma was eventually made. Only few cases of primary pure bone rhabdomyosarcoma have been reported. Other bone tumors with rhabdomyosarcomatous differentiation have been described: dedifferentiated chondrosarcoma, fibrosarcoma, and osteosarcoma. Our case does not meet the criteria for sclerosing rhabdomyosarcoma, as matrix formation is focal and cells are spindle-shaped and pleomorphic. However, it is a further example of a diagnostic error in connection with primary osseous tumor.

A case of rhabdomyosarcoma masquerading as acute leukemia at presentation: a case report

Non-hematopoietic malignancies infiltrating bone marrow have always been a source of erroneous diagnosis. Among these, the small round cell tumors like neuroblastomas and rhabdomyosarcomas mimick the hematopoietic blasts. Several case reports of rhabdomyosarcoma mimicking acute leukemia, clinically and morphologically at presentation have been reported in the literature. To the best of our knowledge such an entity has not been reported in Indian literature. We report here one such case of alveolar rhabdomyosarcoma masquerading as acute leukemia. A thorough clinical examination with high degree of suspicion on bone marrow morphology and judicious use of appropriate immunohistochemistry markers will solve many of these cases.

Insulin-like growth factor-I has different effects on myogenin induction and cell cycle progression in human alveolar and embryonal rhabdomyosarcoma cells

Alveolar rhabdomyosarcoma (RMS) has a much poorer outcome than embryonal RMS. In this study, we found that IGF-I affected the induction of myogenin and cell cycle progression in alveolar RMS cells, but not in embryonal RMS cells. IGF-I enhanced the induction of myogenin protein in alveolar RMS SJ-Rh30 and KP-RMS-MS cells as it did in myoblast C2C12 cells, but not in embryonal RMS RD or KP-RMS-KH cells. IGF-I induction of myogenin protein was blocked by anti-IGF-IR monoclonal antibody alphaIR-3 and the mTOR-specific inhibitor rapamycin. In Rh30mTOR-rr cells, which stably express a rapamycin-resistant mutant mTOR, rapamycin did not inhibit IGF-I induction of myogenin protein. These data suggest that IGF-I induces myogenin in alveolar RMS cells through the IGF-IR/mTOR pathway. In C2C12 cells, IGF-I induces myogenin protein followed by cell cycle arrest leading to myogenic differentiation. IGF-I promoted G1-S cell cycle progression without any signs of terminal differentiation in alveolar RMS cells. On the other hand, IGF-I promoted neither cell cycle arrest nor G1-S cell cycle progression in embryonal RMS cells. In alveolar RMS SJ-Rh30 cells, 4E-BP1, one of two effectors downstream of mTOR, was continuously hyperphosphorylated by IGF-I, whereas in embryonal RMS RD cells, 4E-BP1 was only transiently hyperphosphorylated. These findings suggest that the different effects of IGF-I on myogenin induction and cell cycle progression in alveolar and embryonal RMS cells are due to a difference of phosphorylation status of 4E-BP1. These different responses to IGF-I help to explain immunohistochemical and clinical behavioral differences between alveolar and embryonal RMS.

Uterine leiomyomas with inclusion bodies: An immunohistochemical and ultrastructural analysis of 12 cases

We describe 12 cases of leiomyoma with intracytoplasmic inclusion bodies, which were detected in a group of 447 leiomyomas examined at our institution between December 2005 and March 2006. Ten of these tumors were typical leiomyomas, and two cases represented atypical (bizarre) leiomyoma. In some cases, the presence of intracytoplasmic inclusion bodies resulted in a rhabdoid or skeletal muscle-like appearance of the tumor cells. Ultrastructurally, there were two types of inclusions. One of them consisted of an abnormal aggregation of intermediate and actin filaments. Another type of inclusions was composed of dense granular material without an apparent fibrillar structure. The ultrastructure of the inclusions correlates with immunohistochemical and histochemical stainings. The inclusions with apparent fibrillar arrangements were PAS negative, stained red by trichrome, and were, at least at the periphery, actin-, desmin-, and h-caldesmon-positive. The dense granular inclusions were at least focally PAS-positive, stained red by trichrome, and were negative immunohistochemically. The intracytoplasmic inclusions were found in atypical (bizarre) leiomyomas of the uterus and occasionally in epithelioid leiomyomas and leiomyosarcomas. However, to the best of our knowledge, these inclusions have not been found in typical uterine leiomyomas to date.

Immunohistochemical detection of myogenin and p21 in methylcholanthrene-induced mouse rhabdomyosarcomas

3-Methylcholanthrene (MC)-induced 10 embryonal (ERSs) and 24 pleomorphic rhabdomyosarcomas (PRSs) of the dermis in mouse were examined immunohistochemically for myogenin, p21 and proliferating cell nuclear antigen (PCNA) nuclear reactivity and myosin reactivity. ERSs had higher expression of myogenin and p21 compared with that of myosin. PRSs were divided into two groups having high (moderate or marked reactivity; HLM) and low (mild reactivity; LLM) levels of myosin expression. Expression of p21 was higher in HLM-PRSs than in LLM-PRSs. Statistically significant association was observed between myosin and p21 expression in PRSs, but not between myosin and myogenin expression. Myogenin and p21 reactivity were observed in myoblast-like cells, but rarely in multinucleated cells. In ERSs, small undifferentiated myogenic precursor cells were also positive for p21. No difference of PCNA reactivity was observed between HLM-PRSs and LLM-PRSs, although its reactivity was higher in PRSs than in ERSs. The results suggest that myogenin is related to myoblast-like cell differentiation in PRSs and that p21 plays essential roles in myotube formation and myosin expression. In ERSs, p21 may be involved in inhibition of myogenic precursor cell proliferation and differentiation.

Myogenin and desmin immunohistochemistry in the assessment of post-chemotherapy genitourinary embryonal rhabdomyosarcoma: prognostic and management implications

PURPOSE

Posttreatment genitourinary embryonal rhabdomyosarcoma often shows well differentiated rhabdomyoblasts, which are detectable on routine histological staining. Definite areas of residual undifferentiated rhabdomyosarcoma indicate residual/recurrent disease. However, the recent use of immunohistochemical staining with desmin and myogenin in resected specimens and surveillance biopsies following adjuvant therapy may demonstrate scant positive staining cells that appear undifferentiated on light microscopy. To our knowledge the clinical significance of this finding is currently unknown. Therefore, we reviewed our retrospective experience with genitourinary embryonal rhabdomyosarcoma to examine the relationship between immunostain positive undifferentiated cells and subsequent clinical outcome.

MATERIALS AND METHODS

A total of 14 children with a median age of 2.75 years (range 8 months to 7 years) with genitourinary embryonal rhabdomyosarcoma were identified in the histopathology database. All had biopsy confirmation of the diagnosis, followed by multi-agent chemotherapy. Two children in whom there was obvious residual active tumor at the resection margins were excluded from further analysis. Histopathological findings in all patients on the resection/posttreatment biopsy were reviewed. All specimens were immunostained with desmin and myogenin to detect residual undifferentiated rhabdomyoblasts. The relation between histopathological findings and outcome was determined.

RESULTS

There were 14 cases of genitourinary embryonal rhabdomyosarcoma. In 2 cases (14%) residual embryonal tumor was pathologically confirmed following initial treatment. In 12 cases no obvious residual tumor was present following initial therapy. Rhabdomyosarcoma affected the bladder in 10 cases and the vagina in 2. There were no distant metastases in any child. Ten patients underwent local resection following chemotherapy and 2 underwent followup biopsies only without resection. A total of 11 cases showed well differentiated, posttreatment rhabdomyoblasts that was identifiable on routine hematoxylin and eosin staining with margins apparently free of tumor and 1 showed no morphological evidence of residual rhabdomyosarcoma. However, all cases demonstrated at least scant abnormal desmin and myogenin positive cells in the specimens. Four patients had no further treatment and none had clinical recurrence. All were well 10 years (range 8 to 13) after treatment. Eight patients received further treatment (chemotherapy and/or radiotherapy) based on clinical and pathological findings, followed by further resection in 3. One patient died of disease but 7 were well a median of 7.2 years (range 8 months to 13 years) after treatment.

CONCLUSIONS

The significance of undifferentiated myogenin/desmin positive cells in genitourinary embryonal rhabdomyosarcoma in the absence of morphological residual/recurrent embryonal rhabdomyosarcoma remains unclear since such cells can be detected in all cases of posttreatment embryonal rhabdomyosarcoma. In some cases findings are associated with clinical disease recurrence, while others with identical histopathological findings following initial treatment have no clinical sequelae even in the absence of further treatment. In genitourinary embryonal rhabdomyosarcoma close and regular clinical surveillance is essential. Desmin/myogenin immunohistochemistry to detect scattered undifferentiated cells does not appear to provide useful prognostic information.

Heart failure alters MyoD and MRF4 expressions in rat skeletal muscle

Heart failure (HF) is characterized by a skeletal muscle myopathy with increased expression of fast myosin heavy chains (MHCs). The skeletal muscle-specific molecular regulatory mechanisms controlling MHC expression during HF have not been described. Myogenic regulatory factors (MRFs), a family of transcriptional factors that control the expression of several skeletal muscle-specific genes, may be related to these alterations. This investigation was undertaken in order to examine potential relationships between MRF mRNA expression and MHC protein isoforms in Wistar rat skeletal muscle with monocrotaline-induced HF. We studied soleus (Sol) and extensor digitorum longus (EDL) muscles from both HF and control Wistar rats. MyoD, myogenin and MRF4 contents were determined using reverse transcription-polymerase chain reaction while MHC isoforms were separated using polyacrylamide gel electrophoresis. Despite no change in MHC composition of Wistar rat skeletal muscles with HF, the mRNA relative expression of MyoD in Sol and EDL muscles and that of MRF4 in Sol muscle were significantly reduced, whereas myogenin was not changed in both muscles. This down-regulation in the mRNA relative expression of MRF4 in Sol was associated with atrophy in response to HF while these alterations were not present in EDL muscle. Taken together, our results show a potential role for MRFs in skeletal muscle myopathy during HF.

Effects of testosterone supplementation on skeletal muscle fiber hypertrophy and satellite cells in community-dwelling older men

OBJECTIVE

In this study, we determined the effects of graded doses of testosterone on muscle fiber cross-sectional area (CSA) and satellite cell number and replication in older men.

PARTICIPANTS

Healthy men, 60-75 yr old, received a long-acting GnRH agonist to suppress endogenous testosterone production and 25, 50, 125, 300, or 600 mg testosterone enanthate im weekly for 20 wk.

METHODS

Immunohistochemistry, light and confocal microscopy, and electron microscopy were used to perform fiber typing and quantitate myonuclear and satellite cell number in vastus lateralis biopsies, obtained before and after 20 wk of treatment.

RESULTS

Testosterone administration in older men was associated with dose-dependent increases in CSA of both types I and II fibers. Satellite cell number increased dose dependently at the three highest doses (3% at baseline vs. 6.2, 9.2, and 13.0% at 125, 300, and 600 mg doses, P < 0.05). Testosterone administration was associated with an increase in the number of proliferating cell nuclear antigen+ satellite cells (1.8% at baseline vs. 3.9, 7.5, and 13% at 125, 300, and 600 mg doses, P < 0.005). The expression of activated Notch, examined only in the 300-mg group (baseline, 2.3 vs. 9.0% after treatment, P < 0.005), increased in satellite cells after testosterone treatment. The expression of myogenin (baseline, 6.2 vs. 20.7% after treatment, P < 0.005), examined only in the 300-mg group, increased significantly in muscle fiber nuclei after testosterone treatment, but Numb expression did not change.

CONCLUSIONS

Older men respond to graded doses of testosterone with a dose-dependent increase in muscle fiber CSA and satellite cell number. Testosterone-induced skeletal muscle hypertrophy in older men is associated with increased satellite cell replication and activation.

Results of a prospective minimal disseminated disease study in human rhabdomyosarcoma using three different molecular markers

BACKGROUND

Rhabdomyosarcoma (RMS) has 2 major histologic subtypes: alveolar (ARMS) and embryonal (ERMS). ARMS is more aggressive and prone to distant tumor dissemination, whereas ERMS tends to expand and recur locally. Little information is available on bone marrow involvement by RMS.

METHODS

We determined the sensitivity and specificity of MyoD1, myogenin, and PAX-FKHR transcripts as RMS markers and used them to study prospectively by reverse-transcriptase polymerase chain reaction (RT-PCR) a series of consecutive unselected RMS patients enrolled in the Italian Association of Pediatric Hematology and Oncology national trial. Prevalence of minimal disseminated disease (MDD) and its response kinetics to chemotherapy were assessed.

RESULTS

MyoD1 and myogenin were specifically associated with RMS, independently of histologic subtype, whereas PAX3/7-FKHR transcripts were expressed only in ARMS. Sensitivity was higher for MyoD1 compared with myogenin and PAX-FKHR. Out of a cohort of 40 patients, MDD positivity was limited to ARMS, with the sole exception of 1 ERMS. Prevalence of MDD positivity increased when a real-time polymerase chain reaction approach was used on a subgroup of patients. RT-PCR was more sensitive than microscopic examination of bone marrow biopsies. The study of the response kinetics of MDD showed that in approximately half of the cases, bone marrow was cleared of disease after 1 cycle of chemotherapy.

CONCLUSIONS

MyoD1 and myogenin transcripts can be used as tumor markers for MDD assessment in virtually all RMS cases, whereas PAX-FKHR is specific for ARMS. Sensitivity of RT-PCR methods was superior compared with standard morphologic assays. Our study suggests that bone marrow involvement is more common in ARMS compared with ERMS, and that MDD can be often cleared by the initial chemotherapy cycles.

Detection and clinical significance of disseminated tumour cells at diagnosis in bone marrow of children with localised rhabdomyosarcoma

Identification of patients with a poor prognosis for non-metastatic rhabdomyosarcoma (RMS) remains a clinical challenge. Prospective analysis for the presence of disseminated RMS cells in bone marrow at diagnosis, using immunocytochemistry, with MyoD1 and myogenin as markers, was carried out. Thirty-seven patients treated on RMS88 and RMS96 Italian protocols underwent staging investigations, and in addition marrow examination for occult tumour cells. All patients had negative marrow involvement using cytomorphology, but 10/37 were positive with immunostaining. With a median follow-up of 46 months (range, 12-115), 7 patients had died and 30 were disease-free. Overall survival probability was 92% in patients with no occult marrow infiltration, 47% with occult marrow infiltration (P=0.001); event-free survival probability was 89% in the former and 50% in the latter (P=0.01). Disseminated tumour cells are indicative of disease spread and are significantly linked to recurrence at distant sites and poorer outcome. Marrow examination at diagnosis using immunocytochemistry may be an additional tool to modulate treatment.

Caveolin-3 Is a Sensitive and Specific Marker for Rhabdomyosarcoma

Caveolin-3 (Cav-3) is a principal structural protein of caveolae membrane domains. Animal studies have revealed that Cav-3 is expressed in skeletal and cardiac myocytes but absent in other types of cells. Recent studies have shown that abnormalities in the Cav-3 gene are associated with some forms of muscular dystrophy, while skeletal muscle abnormalities have been observed in Cav-3 transgenic and knockout mice. In this study the authors evaluated the distribution of Cav-3 in normal human tissues and compared the expression of Cav-3 with that of myogenin and myoD1 in rhabdomyosarcoma (RMS), malignant mixed mullerian tumor (MMMT), and an array of neoplasms that mimic RMS to assess the utility of Cav-3 as a diagnostic marker for tumors with skeletal muscle differentiation. In nonneoplastic human tissues, crisp membrane staining for Cav-3 was present in cardiac and skeletal myocytes and occasionally in arterial smooth muscle cells and prostatic stromal cells, while other cell types were negative for Cav-3. Eighty-eight percent (21/24) of RMS studied were positive for Cav-3. Positive staining was generally observed in the more maturely differentiated tumor cells but not the primitive tumor cells. Eight of nine cases of MMMT stained strongly with Cav-3 in their rhabdomyosarcomatous component but not in other components. Fifty-four other neoplasms (13 leiomyosarcomas, 8 neuroblastomas, 5 lymphomas, 6 Wilms tumors without skeletal muscle differentiation, 5 Ewing sarcomas, 4 malignant fibrous histiocytomas, 4 angiosarcomas, 6 malignant melanomas, and 3 synovial sarcomas) were negative for Cav-3 expression. Nearly all (96% [23/24]) cases of RMS were positive for myogenin, while 88% (21/24) were positive for myoD1. Primitive tumor cells showed significantly increased expression of myoD1 and myogenin; conversely, more differentiated tumor cells were negative or weakly stained. The rhabdomyosarcomatous component of MMMT stained focally with myogenin and myoD1, in contrast to the strong Cav-3 labeling in these cells. These results demonstrate that Cav-3 is specifically expressed in human cardiac and skeletal myocytes. Furthermore, its high specificity and relatively high sensitivity (88%) for tumors with skeletal muscle differentiation suggest that Cav-3 is a valuable marker for these tumors and may be used to assess the degree of differentiation of RMS and to identify residual tumor cells in post-chemotherapy specimens.

Impaired expression of myogenic regulatory molecules in the pelvic floor muscles of murine embryos with anorectal malformations

BACKGROUND/PURPOSE

Recent biological studies have elucidated the molecular mechanism of muscle development, in which various regulatory factors (myogenic regulatory factors [MRFs]) play key roles during embryogenesis. To investigate the development of anorectal malformations (ARMs), we studied MRF expressions in myogenic cells in the pelvic floor using murine embryos affected with ARM.

METHODS

Anorectal malformation embryos were obtained from the 10.5th embryonal day (E10.5) to the 7.0th postnatal day (D7.0) in a natural mutant strain (Sd/+, RSV/Le). Serial frozen sections were prepared for immunohistochemistry using specific antibodies to M-cadherin, myoD, Myogenin, myosin heavy chain, and alfa-actin molecule.

RESULTS

In normal mice, embryonal caudal somites differentiated into myogenic stem cells and migrated to the pelvic floor between E11.0 and E14.0. In the ARM mice, however, caudal somites were irregularly arranged and MRF expressions in myogenic cells were markedly decreased in the dorsocaudal region at E11.5 to E13.0, leading to hypoplastic pelvic floor muscles.

CONCLUSIONS

The maldevelopment of pelvic floor muscles in ARM is derived from a deficient supply of myogenic stem cells, with impaired MRF expression. These results suggest that myogenic stem cells, available from bone marrow contents, may be used for postnatal muscle regeneration to reinforce the pelvic floor muscle function in children with ARM.

Skeletal myogenic differentiation of mesenchymal stem cells isolated from human umbilical cord blood

Human umbilical cord blood (UCB) has been regarded as an alternative source for cell transplantation and cell therapy because of its hematopoietic and nonhematopoietic (mesenchymal) potential. Although there has been debate about whether mesenchymal stem cells (MSCs) are invariably present in UCB, several reports showed that MSC-like cells could be consistently derived from human UCB and, moreover, could differentiate into various cells of a mesodermal origin. However, it remains unclear whether these UCB-derived MSCs are also capable of differentiating into skeletal muscle cells. In this study, we isolated MSCs from human UCB and induced them to differentiate into skeletal muscle cells. During cell culture expansion, UCB-derived mononuclear cells gave rise to adherent layers of fibroblast-like cells expressing MSC-related antigens such as SH2, SH3, alpha-smooth muscle actin, CD13, CD29, and CD49e. More important, when these UCB-derived MSCs were incubated in promyogenic conditions for up to 6 weeks, they expressed myogenic markers in accordance with myogenic differentiation pattern. Both flow cytometric and reverse transcriptase-polymerase reaction analyses showed that two early myogenic markers, MyoD and myogenin, were expressed after 3 days of incubation but not after 2 weeks. At week 6, more than half of UCB-derived MSCs expressed myosin heavy chain, a late myogenic marker. Our results demonstrate that UCB-derived MSCs possess a potential of skeletal myogenic differentiation and also imply that these cells could be a suitable source for skeletal muscle repair and a useful tool of muscle-related tissue engineering.

Spindle cell rhabdomyosarcoma of the tongue in an infant: a case report with emphasis on differential diagnosis of childhood spindle cell lesions

Malignant tumors are extremely uncommon in infants, specifically in the head and neck region. We present a three-day-old infant with a large, polypoid, soft tissue mass arising from the floor of the mouth. Histologically, this neoplasm consisted of hypercellular and myxoid areas. A mixture of poorly oriented, small, undifferentiated, hyperchromatic, and round to elongate spindle cells was seen. A high degree of striated muscle differentiation was present, along with areas marked by a herringbone pattern, as well as hemangiopericytic vessels and rare mitosis. Immunohistochemical examinations revealed strong nuclear staining for myogenin and diffuse cytoplasmic staining for desmin and muscle-specific actin (HHF-35). The tumor did not stain for S-100. Based on histologic results and immunostains, this lesion was diagnosed as spindle cell rhabdomyosarcoma. This type of lesion involving the tongue is rarely seen in females, neither in association with a herringbone pattern nor with hemangiopericytic vessels. Furthermore, rare benign and malignant spindle lesions, such as cellular fibromatosis, fetal rhabdomyoma, infantile hemangiopericytoma, infantile rhabdomyofibrosarcoma, and infantile fibrosarcoma, should be in the differential diagnosis and excluded.

Chemokine receptor CCR2 involvement in skeletal muscle regeneration

Chemokines, signaling through the CCR2 receptor, are highly expressed in injured skeletal muscle. Their target specificity depends on the cellular expression of the specific receptors. Here we demonstrate that, in freeze-injured muscle, CCR2 co-localized with Mac-3, a marker of activated macrophages as well as with myogenin, a marker of activated muscle precursor cells. The degeneration/regeneration process in skeletal muscle of CCR2-/- and wild-type mice was not significantly different at day 3. However in contrast to the regenerated muscle of the wild-type mice, the muscle from CCR2-/- mice was characterized by impaired regeneration, inflammation, and fibrotic response at day 14, increased fat infiltration, fibrosis, and calcification at day 21, and impaired strength recovery until at least 28 days post-injury. Consistently, the increased expression of Mac-1 and TNF-alpha was prolonged in the injured muscle of CCR2-/- mice. The expression pattern of the myogenic factors MyoD and myogenin was similar for both types of mice, while NCAM, which is associated with the initiation of fusion of muscle precursor cells, was more increased in the injured muscle of CCR2-/- mice. In conclusion, the study delineates that signaling through CCR2 is involved in muscle precursor cell activities necessary for complete and rapid regeneration of injured skeletal muscle.

[Dynamic changes in the expressions of myogenic regulatory factors MyoD and myogenin during repair of muscle injury]

OBJECTIVE

To observe the dynamic changes in the expressions of myogenic regulatory factors MyoD and myogenin during the repair of injured muscle.

METHODS

Muscular injury model was established by local injection of bupivacain, and at different time points following the injection, the gastrocnemius muscles were collected for preparation of cryosections. HE staining was performed for examination of the pathological changes in the injured muscles, and the expressions of MyoD and myogenin were detected by SABC.

RESULTS

MyoD-positive nuclei began to appear 18 h after muscle injury, reaching the peak till 48 h after the injury. Myogenin-positive nuclei appeared 24 h after muscle injury and peaked at 72 h.

CONCLUSIONS

MyoD and myogenin play a role in muscle regeneration after muscle injury, and they may serve as the indexes to identify muscle precursor cells and mark muscle regeneration process.

Localization of MyoD, myogenin and cell cycle regulatory factors in hypertrophying rat skeletal muscles

AIM

MyoD, myogenin, proliferating cell nuclear antigen (PCNA) and cyclin-dependent kinase inhibitor p21 (p21) proteins are key molecules in inducing the growth of myogenic cells in vitro. However, it has not been determined which cell types express these factors in hypertrophying skeletal muscles in vivo.

METHODS

Using immunohistochemical techniques, we examined the spatial and temporal expression patterns of MyoD, myogenin, PCNA and p21 proteins in functionally overloaded rat plantaris muscles induced by ablation of the soleus and gastrocnemius muscles.

RESULTS

MyoD and myogenin were detected in myonuclei located inside the dystrophin-positive plasma membrane of myofibres, m-cadherin-positive satellite cell nuclei and nuclei located in the interstitial spaces between myofibres on days 1, 3, 5 and 7 post-surgery. Entry of satellite cells into the cell cycle was indicated by the expression of PCNA on day 3 post-surgery, and withdrawal from the cell cycle was observed by the expression of p21 in satellite cell nuclei on day 5 post-surgery. However, the expression of both PCNA and p21 in satellite cell nuclei disappeared on day 7 post-surgery.

CONCLUSION

These results indicate that proliferated satellite cell-derived myoblasts and undefined myogenic cells located in the interstitial spaces may contribute to an increase in myonuclear number and/or hyperplasia. Furthermore, we provide evidence that all of myonuclei, satellite cells and undefined myogenic cells express both MyoD and myogenin proteins. These results suggest that continual expression of MyoD and myogenin proteins in these cells is an essential molecular event which induces the successful hypertrophy of skeletal muscles.

Early changes in rat diaphragm biology with mechanical ventilation

To better characterize the effects of 24-hour mechanical ventilation on diaphragm, the expression of myogenic transcription factors, myosin heavy chains, and sarcoplasmic/endoplasmic reticulum calcium-ATPase pumps was examined in rats. In the diaphragm of mechanically ventilated animals, the mRNA of MyoD, myosin heavy chain-2a and -2b, and sarcoplasmic/endoplasmic reticulum calcium-ATPase-1a decreased, whereas myogenin mRNA increased. In the diaphragm of anesthetized and spontaneously breathing rats, only the mRNA of MyoD and myosin heavy chain-2a decreased. MyoD and myogenin protein expression followed the changes at the mRNA, whereas the myosin heavy chain isoforms did not change. Parallel experiments involving the gastrocnemius were performed to assess the relative contribution of muscle shortening versus immobilization-induced deconditioning on muscle regulatory factor expression. Passive shortening produced no additional effects compared with immobilization-induced deconditioning. The overall changes followed a remarkably similar pattern except for MyoD protein expression, which increased in the gastrocnemius and decreased in the diaphragm while its mRNA diminished in both muscles. The early alterations in the expression of muscle protein and regulatory factors may serve as underlying molecular basis for the impaired diaphragm function seen after 24 hours of mechanical ventilation. Whether immobilization-induced deconditioning and/or passive shortening play a role in these alterations could not be fully unraveled.

Histological and histochemical analysis of embryoid bodies

We examined the histological structure of embryoid bodies arising from aggregation of mouse embryonic stem (ES D3) cells after 7, 12, 18 and 26 days of in vitro culture. Morphology of originally solid embryoid bodies was affected by the process of cavitation that resulted in formation of cystic embryoid bodies and by spontaneous differentiation of the ES D3 cells. We applied in situ immunophenotyping to characterise cell populations that spontaneously differentiated inside the embryoid bodies in the various stages. The most distinct cell populations that were found inside embryoid bodies were alpha-fetoprotein-positive endodermal cells and myogenic cells that expressed desmin, myogenin or smooth muscle actin. ES D3-derived endothelial cells generated during vasculogenesis inside the embryoid bodies differed from mature endothelial cells because they did not stain for von Willebrand factor. These cells also differed from endothelial cell that were generated during angiogenesis since they did not stain for the intermediate filament nestin. Our results demonstrate the usefulness of this in vitro model for studying early embryogenesis.

Myogenin and MyoD1 expression in paediatric rhabdomyosarcomas

The diagnosis of paediatric solid tumours is often based on small tissue needle biopsies in which many different entities demonstrate a "small round cell tumour" phenotype and in which there may be insufficient tissue to allow the interpretation of diagnostic architectural features, which may be present in larger specimens. Therefore, the extensive use of a panel of immunohistochemical markers is part of the routine handling and investigation of such biopsies to reach a definite diagnosis. However, in some cases the morphological and routine immunohistochemical findings may be insufficient for a precise diagnosis or they may be difficult to interpret in the given clinical context. Although many paediatric tumours exhibit characteristic chromosomal translocations with resultant specific fusion transcripts, these require molecular methods for their detection, usually on fresh tissue samples, which may not always be available. As more immunohistochemical markers become available, more precise diagnosis on such small biopsies may be possible. This review examines the use of the immunohistochemical markers, MyoD1 and myogenin, in the diagnosis of paediatric rhabdomyosarcoma, including its subtypes.

Lineage-specific identification of nonhematopoietic neoplasms by flow cytometry

To extend flow cytometry (FC) to the diagnosis of nonhematopoietic neoplasms, we have developed new flow cytometric assays to identify expression of cytokeratin, epithelial cell adhesion molecule (EpCAM)/epithelial glycoprotein-2, myogenin, and CD99. To validate these assays, we correlated the flow cytometric results with the histologic and immunohistochemical results on paraffin-embedded tissue in a series of 21 cases, including 17 carcinomas, 1 atypical carcinoid, 2 rhabdomyosarcomas, and 1 Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET). Six of 7 assayed carcinomas and the carcinoid were positive for cytoplasmic cytokeratin by the flow cytometric assay. EpCAM was expressed by 11 of 12 carcinomas that were assayed by FC. Both rhabdomyosarcomas expressed myogenin by FC, and the ES/PNET case expressed CD99. Interestingly, the blast-associated antigen CD90 was expressed uniformly on the ES/PNET case and on subsets of cells in the rhabdomyosarcoma and carcinoma cases. Potential applications of the flow cytometric assay to nonhematopoietic neoplasms will include evaluating samples with limited material, monitoring disease persistence and recurrence in patients with previous diagnoses, and making rapid diagnoses in urgent cases.

Gender differences in resistance-training-induced myofiber hypertrophy among older adults

We tested the hypothesis that older men (n = 9, 69 +/- 2 years) would experience greater resistance-training-induced myofiber hypertrophy than older women (n = 5, 66 +/- 1 years) following knee extensor training 3 days per week at 65-80% of one-repetition maximum for 26 weeks. Vastus lateralis biopsies were analyzed for myofiber areas, myosin heavy chain isoform distribution, and levels of mRNA for insulin-like growth factor 1 (IGF-1), IGFR1, and myogenin. Gender x Training interactions (p <.05) indicate greater myofiber hypertrophy for all three primary fiber types (I, IIa, IIx) and enhanced one-repetition maximum strength gain in men compared with women (p <.05). Covarying for serum IGF-1, dehydroepiandrosterone sulfate, or each muscle mRNA did not negate these interactions. In both genders, type IIx myofiber area distribution and myosin heavy chain type IIx distribution decreased with a concomitant increase in type IIa myofiber area distribution (p <.05). In summary, gender differences in load-induced myofiber hypertrophy among older adults cannot be explained by levels of circulating IGF-1 or dehydroepiandrosterone sulfate, or by expression of the myogenic transcripts examined.

Myogenin--a more specific target for RT-PCR detection of rhabdomyosarcoma than MyoD1

BACKGROUND

MyoD1 and myogenin are differentially expressed in early myogenesis and have been identified in rhabdomyosarcoma (RMS). This study evaluates reverse transcriptase-polymerase chain reaction (RT-PCR) for MyoD1 and myogenin mRNA as diagnostic markers of RMS, and the potential application of this method for the detection of small volume disease in bone marrow (BM) and peripheral blood (PB).

PROCEDURE

Expression of MyoD1 and myogenin mRNA was examined by RT-PCR in RMSs (9 alveolar RMS, 10 embryonal RMS, 1 pleomorphic RMS), and 21 other paediatric tumor samples (10 neuroblastoma, 10 Ewing sarcomas, and 1 Sarcoma (not otherwise specified) (S(NOS)). BM (n = 19) and PB (n = 22) samples from the same RMS study population were also examined for MyoD1 and myogenin mRNA expression.

RESULTS

Positive expression of both markers was demonstrated in adult muscle, but not in normal PB. Myogenin mRNA was expressed in 16/18 and MyoD1 mRNA in 12/12 RMSs studied. Myogenin was not expressed in 10/10 neuroblastomas, but was present in 2/10 Ewing sarcomas. However, MyoD1 mRNA was detected in 10/10 Ewing sarcomas and 7/10 neuroblastomas. Myogenin mRNA was detected in two BM samples from children with histologically negative BM and in 1/22 PB samples. Detection of MyoD1 mRNA in BM and PB was compromised by the amplification of a similar sized, non-specific product.

CONCLUSIONS

Myogenin mRNA is a more specific marker than MyoD1 for the diagnosis of RMS. Myogenin mRNA is potentially a useful target for the assessment of small volume disease in RMS.

Sclerosing rhabdomyosarcoma in adults: report of four cases of a hyalinizing, matrix-rich variant of rhabdomyosarcoma that may be confused with osteosarcoma, chondrosarcoma, or angiosarcoma

Rhabdomyosarcomas (RMSs) are classified into embryonal (ERMS), alveolar (ARMS), and pleomorphic (PRMS) subtypes. ERMS, including botryoid variants, typically occurs in young children, ARMS typically occurs in older children and young adults, and PRMS occurs in older adults. Although ARMSs show thin fibrous bands separating nests of cells, abundant extracellular matrix production is rare in RMS. In the course of reviewing hyalinizing sarcomas we discovered a distinctive RMS in adults that closely mimicked osteosarcoma or chondrosarcoma because of the extensive matrix production. Four RMSs with hyalinized matrix were retrieved from our files. These cases were evaluated with respect to patient age and sex, tumor site and size, growth pattern, nuclear grade, cellularity, mitotic figures/20 high power fields, vascular invasion, necrosis, the presence of rhabdomyoblasts, multinucleated cells, and alveolar growth pattern. Immunohistochemistry for desmin, myogenin, MyoD1, actin, cytokeratin, S-100 protein, collagen II, and CD99 was performed. Reverse transcriptase polymerase chain reaction for the ARMS-associated PAX3/FKHR and PAX7/PKHF was also performed on three cases. The cases involved the forearm, hand, orbit, and nasopharynx of a 40-year-old woman, a 50-year-old man, an 18-year-old man, and a 21-year-old man, respectively. The tumors ranged from 3.7 to 8 cm and consisted of lobules and infiltrating cords of small round malignant cells embedded in a densely hyalinized matrix having both a chondroid and osteoid-like appearance. No definite lacunae or matrix calcification was present. An alveolar pattern was only present focally, and tumor giant cells were not present. One case had a single focus of rhabdomyoblastic differentiation with strap cells. Mitotic activity was >20 mitotic figures/20 high power fields in three of four cases. Immunohistochemically, one case strongly expressed desmin, whereas three cases expressed it focally, with a dot-like pattern. Myogenin was only focally positive, but MyoD1 was present in nearly every cell of each case. Two cases expressed actin and one expressed CD99. No case expressed cytokeratin, S-100 protein, or collagen II. Only one case contained adequate RNA for reverse transcriptase polymerase chain reaction, and this case was negative for the ARMS-associated gene fusions. Follow-up showed one patient to be dead of metastatic disease at 60 months despite intensive therapy, another patient to be disease free at 26 months, and the third patient to be disease free at 5 months. The fourth case is recent. These cases are a distinctive-appearing rhabdomyosarcoma easily mistaken for variants of chondrosarcoma, osteosarcoma, or even sclerosing epithelioid fibrosarcoma because of their hyalinizing appearance compounded by their typically focal and dot-like desmin expression. These four cases are essentially identical to the three unusual RMSs recently reported by Mentzel and Katenkamp as "sclerosing, pseudovascular rhabdomyosarcoma in adults." Although the focal alveolar architecture and the primitive cytologic appearance of these hyalinizing RMS suggest a relationship with ARMS, the presence of abundant strap cells in one case, the predominant expression of MyoD1 rather than myogenin, and the absence of ARMS-associated fusions genes point more strongly toward a variant of ERMS. However, the late adult age in two cases is unusual for both EMRS and ARMS, suggesting that sclerosing RMS may prove to be a distinct subtype of RMS. Study of additional cases will be necessary to more fully elucidate its place among RMS and its prognostic significance.

Satellite cell proliferation and differentiation during postnatal growth of porcine skeletal muscle

Age-related changes in satellite cell proliferation and differentiation during rapid growth of porcine skeletal muscle were examined. Satellite cells were isolated from hindlimb muscles of pigs at 1, 7, 14, and 21 wk of age (4 animals/age group). Satellite cells were separated from cellular debris by using Percoll gradient centrifugation and were adsorbed to glass coverslips for fluorescent immunostaining. Positive staining for neural cell adhesion molecule (NCAM) distinguished satellite cells from nonmyogenic cells. The proportion of NCAM-positive cells (satellite cells) in isolates decreased from 1 to 7 wk of age. Greater than 77% of NCAM-positive cells were proliferating cell nuclear antigen positive at all ages studied. Myogenin-positive satellite cells decreased from 30% at 1 wk to 14% at 7 wk of age and remained at constant levels thereafter. These data indicate that a high percentage of satellite cells remain proliferative during rapid postnatal muscle growth. The reduced proportion of myogenin-positive cells during growth may reflect a decrease in the proportion of differentiating satellite cells or accelerated incorporation of myogenin-positive cells into myofibers.

Development of the pelvic floor muscles of murine embryos with anorectal malformations

BACKGROUND/PURPOSE

Recent biological studies have elucidated the molecular mechanism of muscle development, in which various regulatory molecules play key roles during embryogenesis. To determine possible myogenic abnormalities in anorectal malformations (ARM), the authors investigated the pelvic muscle development in murine embryos affected with ARM.

METHODS

ARM embryos were induced by all-trans retinoic acid (ATRA) on the ninth gestational day (E9.0). Embryonal specimens were obtained from the uteri between E10.5 and E16.0, and the frozen sections were prepared for immunohistochemistry using antibodies specific for MyoD, myogenin, and PGP9.5 molecules.

RESULTS

In ARM embryos, the neural tube was irregularly branched and formed an anomalous mass in the sacral region. Embryonal caudal somites differentiated into myogenic cells to form proper myotubes in the pelvis corresponding to the developmental stages between E12.5 and E15.0 both in affected embryos and the controls.

CONCLUSIONS

In ARM embryos, an impaired anatomic framework of the pelvis was caused by neural maldevelopment, whereas muscle development proceeded physiologically. These results support the hypothesis that pelvic floor muscles may function in ARM children, in whom neural abnormalities such as meningomyelocele or tethered spinal cord have been ruled out, if the surgical correction is appropriately completed.

The myotonic dystrophy expanded CUG repeat tract is necessary but not sufficient to disrupt C2C12 myoblast differentiation

Myotonic dystrophy type 1 (DM1) is a dominant neuromuscular disorder caused by a trinucleotide (CTG) repeat expansion. Mutant DMPK 3'-untranslated region (3'-UTR) transcripts aggregate in nuclear foci and are thought to impose dominant-negative effects by interacting with RNA binding proteins. We demonstrated previously that the mutant 3'-UTR RNA disrupted C2C12 myoblast differentiation, and that the CUG expansion was necessary for this effect. Several proteins are known to interact with the CUG tract or the region 3' (distal) to it. Here, using a library of transfected C2C12 clones, we show that although transcripts containing a CUG expansion alone or a CUG expansion plus the distal region of the DMPK 3'-UTR accumulate into RNA foci, neither of these RNAs affect C2C12 myogenesis. Thus, RNA foci formation, and perturbation of any RNA binding factors involved in this process, are not sufficient to block myoblast differentiation. Interestingly, we found that transcripts containing expanded CUG tracts can form both nuclear and cytoplasmic RNA foci, demonstrating that factors involved in foci formation are present in the nucleus and cytoplasm. RNA analysis of myogenic markers revealed that the mutant DMPK 3'-UTR mRNA does not affect myoblast determination factors MyoD or Myf5, but significantly impedes upregulation of the differentiation factors myogenin and p21. C2C12 provide a good model to study adult muscle regeneration. Our observations in this system may be relevant to the lack of a regenerative response to continued muscle wasting in DM, and point to defects in early events in the myogenic response to muscle damage.

Reparative myogenesis in long-term denervated skeletal muscles of adult rats results in a reduction of the satellite cell population

This study, conducted on 25-month denervated rat hindlimb muscles, was directed toward elucidating the basis for the poor regeneration that is observed in long-term denervated muscles. Despite a approximately 97.6% loss in mean cross-sectional area of muscle fibers, the muscles retained their fascicular arrangement, with the fascicles containing approximately 1.5 times more fibers than age-matched control muscles. At least three distinct types of muscle fibers were observed: degenerating, persisting (original), and newly formed (regenerated) fibers. A majority of newly formed fibers did not appear to undergo complete maturation, and morphologically they resembled myotubes. Sites of former motor end-plates remained identifiable in persisting muscle fibers. Nuclear death was seen in all types of muscle fibers, especially in degenerating fibers. Nevertheless, the severely atrophic skeletal muscles continued to express developmentally and functionally important proteins, such as MyoD, myogenin, adult and embryonic subunits of the nicotinic acetylcholine receptor, and neural-cell adhesion molecule. Despite the prolonged period of denervation, slow and fast types of myosin were found in surviving muscle fibers. The number of satellite cells was significantly reduced in long-term denervated muscles, as compared with age-matched control muscles. In 25-month denervated muscle, satellite cells were only attached to persisting muscle fibers, but were never seen on newly formed fibers. Our data suggest that the absence of satellite cells in a population of immature newly formed muscle fibers that has arisen as a result of continuous reparative myogenesis may be a crucial, although not necessarily the only, factor underlying the poor regenerative ability of long-term denervated muscle.

Pseudosarcomatous myofibroblastic tumor and myosarcoma of the urogenital tract

OBJECTIVE

Pseudosarcomatous myofibroblastic tumors (PMTs) of the urogenital tract are rare but distinctive lesions. Despite their benign behavior, they are frequently misinterpreted as leiomyosarcomas and rhabdomyosarcomas in preoperative biopsies and even in resected specimens because of their atypical spindle-cell features. Precise diagnosis of PMTs is important to avoid unnecessary radical therapy. We analyzed urogenital myoid tumors to clarify which of their characteristics are useful for the differential diagnosis.

METHODS

We evaluated 7 urogenital myoid tumors consisting of 3 PMTs, 2 leiomyosarcomas, and 2 rhabdomyosarcomas. We studied the expression of various immunohistochemical muscle-cell markers including desmin, muscle-specific actin, alpha-smooth muscle actin, high-molecular-weight caldesmon, and myogenin.

RESULTS

Desmin, muscle-specific actin, and alpha-smooth muscle actin were noted variably in all tumor types, whereas high-molecular-weight caldesmon was expressed only in leiomyosarcomas, and myogenin was expressed only in rhabdomyosarcomas.

CONCLUSION

High-molecular-weight caldesmon and myogenin are useful for differentiating urogenital PMTs from myosarcomas.

Different response of satellite cells in the kinetics of myogenic regulatory factors and ultrastructural pathology after Trichinella spiralis and T. pseudospiralis infection

Infection of an intracellular parasitic nematode, Trichinella spiralis, resulted in severe damage in muscle cells which was followed by activation and proliferation of satellite cells. The repairing process, shortly after the damage, histopathologically resembled those seen after mechanical injury. Resemblance was also true for kinetics of expression of myogenic regulatory factors (MyoD, myogenin and MRF4). The difference resided in the next step where the muscle cell infected with T. spiralis transformed to a unique cell which is parasitologically known as the nurse cell, and the proliferated satellite cells did not differentiate to the muscle cell but to the nurse cell (misdifferentiation). Thus the nurse cell was a fusion of the transformed infected muscle cell and misdifferentiated satellite cells. Infection with another species of Trichinella, T. pseudospiralis, also caused cell damage, but more extensively involving the entire length of the infected muscle cells because no septum was formed to minimize the affected area. Therefore, a large number of satellite cells were activated and proliferated. The myogenic regulatory factors such as MyoD and myogenin were activated for a longer period than in the case with T. spiralis infection. The infected muscle cell transformed to the nurse cell, whose cytoplasm was characterized by extensive smooth endoplasmic reticulum. Satellite cells misdifferentiated to the nurse cell, whose cytoplasm was amorphous, void of distinct cell organelles. The two kinds of cytoplasm did not fuse as examined thus far. Thus infection with T. spiralis and T. pseudospiralis caused misdifferentiation of satellite cells, but in a different way.

The effects of age and hindlimb supension on the levels of expression of the myogenic regulatory factors MyoD and myogenin in rat fast and slow skeletal muscles

In this study we tested the hypothesis that, compared to young adult rats, senescent rats have a reduced ability to respond to muscle unloading. Unloading of the muscles was induced by hindlimb suspension (HS) of young adult and senescent rats for 21 days. Plantaris muscles from young adult rats had significantly higher levels of myogenin mRNA and protein (890 % and 314 %, respectively, P < 0.05) than plantaris muscles from senescent rats and also a higher MyoD mRNA level (280 %, P < 0.05), but ageing did not increase MyoD protein levels. Although HS did not increase plantaris mRNA or protein levels of myogenin or MyoD in senescent rats (P = 0.22), myogenin mRNA and protein levels increased by 850 % and 580 % respectively, and MyoD mRNA and protein levels by 235 % and 1600 %, respectively in young adult rats (P < 0.05). Soleus muscles from senescent rats had 150 % and 85 % greater myogenin and MyoD mRNA levels, respectively (P < 0.05), than soleus muscles from young adult rats, whereas protein levels of myogenin were similar (P > 0.05) and MyoD protein levels were 60 % lower in the muscle of senescent rats (P < 0.05). In young rats, soleus muscle mRNA levels of myogenin and MyoD were not altered by HS but myogenin protein levels decreased by 57 % (P < 0.05) whereas MyoD protein levels increased by 187 % (P < 0.05). In senescent rats, HS decreased soleus muscle myogenin mRNA and protein levels by 42 % and 26 % respectively (P < 0.05), but MyoD protein and mRNA levels were not changed. MRF4 levels were not affected by ageing in either muscle. These data suggest that ageing reduces the ability of fast muscles to increase myogenin protein levels, and prevents both fast and slow muscles from increasing MyoD protein levels during muscle unloading. Experimental Physiology (2001) 86.4, 509-517.

Characterization of heterokaryons between skeletal myoblasts and somatic cells formed by fusion with HVJ (Sendai virus); effects on myogenic differentiation

In skeletal myogenic differentiation, myoblasts fuse with myogenic cells spontaneously, but do not fuse with non-myogenic cells either in vivo or in vitro, suggesting that the fusion of myoblasts with non-myogenic cells is unsuitable for differentiation. To understand the inevitability of the fusion among myoblasts, we prepared heterokaryons in crosses between quail myoblasts transformed with a temperature-sensitive mutant of Rous sarcoma virus (QM-RSV cells) and rodent non-myogenic cells, such as tumor cells, fibroblasts, or neurogenic cells by HVJ (Sendai virus) and examined how myogenic differentiation was influenced in the prepared heterokaryons, focusing on myogenin expression and myofibril formation as markers of differentiation. When presumptive QM-RSV cells were fused with non-myogenic cells by HVJ and induced to differentiate, both myogenin expression and myofibril formation were suppressed. When myotubes of QM-RSV cells that had already expressed myogenin and formed myofibrils were fused with non-myogenic cells, both myogenin and myofibrils disappeared. Especially, fibrous structures of myofibrils were significantly lost and dots or aggregations of F-actin were formed within 24 hr after formation of heterokaryons. However, the fusion of presumptive or differentiated QM-RSV cells with rodent myoblasts did not disturb myogenin expression or myofibril formation. These results suggest that mutual fusion of myoblasts is indispensable for normal myogenic differentiation irrespective of the species, and that some factors inhibiting myogenic differentiation exist in the cytoplasm of non-myogenic cells, but not in myoblasts.

Expression of basic helix-loop-helix proteins in the glomeruli

BACKGROUND

Basic helix loop helix (bHLH) proteins play a critical role in the differentiation of not only striated muscle cells but also adipocytes, neuron cells and smooth muscle cells. Previous studies have established in vitro mouse mesangial cells (MCs) to maintain the differentiated smooth muscle phenotype.

MATERIALS AND METHODS

The purpose of the present study was to clone bHLH proteins from these MCs using the primers designed from a homologous sequence specific to bHLH, and to analyze the presence of bHLH proteins in normal kidney in vivo. From the cloning of MCs in vitro, we identified myf5 and herculin mRNA but not myoD. The expression of bHLH proteins in vivo was examined by immunohistochemistry with each specific antibody.

RESULTS

The MCs in newborn mice possessed Id but did not express either protein herculin or myoD. On the other hand, mature MCs expressed both myf5 and herculin. The Id protein disappeared in mature glomeruli.

CONCLUSION

These results suggest that bHLH proteins are an important factor for mature MCs in vivo.

A new human pleomorphic rhabdomyosarcoma cell-line, HS-RMS-1, exhibiting MyoD1 and myogenin

A number of human cell lines derived from alveolar or embryonal rhabdomyosarcoma (RMS) have been described. To our knowledge, however, no cell line established from pleomorphic RMS has been reported. We describe here the establishment and characterization of a new human cell line, HS-RMS-1, which originated from a typical pleomorphic RMS arising in the gluteal muscle of a 26-year-old man. HS-RMS-1 cells had pseudotetraploid complex karyotypes with no specific abnormalities. Both in vitro and in vivo the cells on light microscopic examination exhibited pleomorphic features with immunopositive reaction for myogenic antigens including MyoD1 and myogenin, although no Z band-like structures were detected electron-microscopically. RT-PCR demonstrated the expression of MyoD1 and myogenin in HS-RMS-1 cells at the mRNA level, and direct sequencing analysis revealed cDNAs of MyoD1 and myogenin identical to those previously reported. This cell line, HS-RMS-1, established from pleomophic RMS will be useful for further studies including the molecular aspects of human RMS.

[Malignant glial tumor with skeletal muscle differentiation. Description of a case]

A case of CNS gliomyosarcoma, in a 71-year-old female with skeletal muscle differentiation is presented. The tumor was composed by two cell types: one showed features typical of glial cells, the other was constituted by elements having immunohistochemical positivity with desmin, sarcomeric actin, myoglobin and myogenin antisera. It is postulated an origin from a cell capable of dual differentiation.

Postnatal profiles of myogenic regulatory factors and the receptors of TGF-beta 2, LIF and IGF-I in the gastrocnemius and rectus femoris muscles of dy mouse

The dystrophin-deficient mdx mouse presents muscle fiber necrosis but active muscle regeneration, probably due to an extensive recruitment of myogenic regulatory factors (MRF), several growth factors and cytokines, and favorable interaction of satellite cells. In contrast, the laminin alpha 2 (merosin)-deficient dy mouse shows progressive muscle fiber necrosis and ineffective muscle regeneration. Using Western blot and immunohistochemical analyses, we investigated the adaptive changes in MRF, growth factors and cytokines and their receptors in the muscles of dy mice during postnatal growth. The relative volume of MyoD, myogenin and Myf-5 proteins was markedly lower in the gastrocnemius and rectus femoris muscles of dy mice. Transforming growth factor-beta 2, leukemia inhibitory factor (LIF) and basic fibroblast growth factor were not up-regulated in the muscles of dy mice. The levels of the LIF receptor and insulin-like growth factor-I receptor levels were markedly decreased in the muscles of dy mice during the entire postnatal period observed in this study. Therefore, unlike the situation in mdx mice, the milieu of regeneration following repetitive damage seems to be degraded in the muscles of dy mice.

Genetic variability of foetal bovine myoblasts in primary culture

Selected strains of adult bovines and those which either have high muscle growth capacity or are double-muscled present particular characteristics of muscle fibres and collagen at slaughter that favour meat tenderness. For double-muscled bovines, it has been shown that these characteristics originated during foetal life. However, no studies have been done to determine the origin of muscle growth superiority in bovine with high muscle growth capacity compared to those with a low muscle growth capacity. Therefore, the objective of this study was to examine the proliferation and differentiation phases of myoblasts in primary culture taken from high and low muscle growth capacity foetuses at 110 days post-conception. These cultures were analysed on 1, 2, 3, 4, 6, 8, 10 days of culture. The proliferation phase was monitored by appropriate marker antibodies. The differentiation was studied by immunocytochemistry with specific antibodies for foetal, I, II (IIa and IIb), I and IIb, I and IIa myosin heavy chains (MHCs) and connectin respectively, and by immunoblotting with desmin antibody. A higher proliferation, a lower fusion and a delayed differentiation of the 'late markers' namely MHCs fast (IIa and IIb) and connectin were shown in high muscle growth capacity foetuses compared to low capacity ones. The results indicate that the muscle growth superiority of high muscle growth capacity bovines seems, therefore, to have a similar foetal origin to that of double-muscled ones.