Toshiaki Hitora

Mechanical stretching force promotes collagen synthesis by cultured cells from human ligamentum flavum via transforming growth factor-β1

Although mechanical stress as a result of spinal instability is known to cause hypertrophy of the ligamentum flavum resulting in degenerative spinal canal stenosis, the mechanism of the ligament hypertrophy is not well understood. In the present study, we investigated the effect of mechanical stretching force on collagen synthesis and transforming growth factor‐β1 (TGF‐β1) production using ligament cells isolated from human ligamentum flavum in vitro. Ligamentum flavum cells (LFCs) were isolated from human ligamentum flavum obtained from patients who underwent lumbar spine surgery. The LFCs were subjected to a mechanical stretching force using a commercially available stretching device that physically deformed the cells. Collagen synthesis and TGF‐β1 production levels in the LFCs were then examined. Notable increases were observed in the gene expressions of collagen types I, III, and V in LFCs subjected to mechanical stretching force. The increase in collagen gene expression of LFCs was inhibited in the presence of anti‐TGF‐β1 antibodies. Production of TGF‐β1 by the LFCs also increased significantly by the mechanical stretching force. Exogenous application of TGF‐β1 was confirmed to increase collagen synthesis of the LFCs. This data indicated that mechanical stretching force can promote TGF‐β1 production by LFCs, resulting in hypertrophy of the ligament.

Fibroma of tendon sheath originating from the knee joint capsule

We present a rare case of fibroma of the tendon sheath originating from the posterior joint capsule of the knee in a 50-year-old man. Magnetic resonance (MR) imaging revealed a lesion posterior to the medial femoral condyle. The lesion showed hypointensity on all T1-weighted, T2-weighted, short tau inversion recovery (STIR), and contrast-enhanced T1-weighted images. Plain computed tomographic (CT) scans showed a lesion with isodensity to muscle. The lesion showed no enhancement on postcontrast CT scans.

Hsp90 inhibitor induces autophagy and apoptosis in osteosarcoma cells

Heat shock protein 90 (Hsp90) is constitutively expressed at 2-10-fold higher levels in tumor cells compared to normal cells, suggesting that it may be critically important for tumor cell growth and survival. These features make Hsp90 a potential target for anticancer drug development. Inhibition of Hsp90 activity not only results in rapid degradation of Hsp90 client proteins but also induces apoptosis of various tumor cells. Hsp90 also plays an important role in autophagy. An Hsp90 inhibitor induces autophagy through inhibition of mTOR. It is still under debate whether chemotherapy-induced autophagy in tumor cells is a protective response or is invoked to promote cell death. The aim of this study was to examine the effects of the Hsp90 inhibitor, geldanamycin (GA), on KTHOS osteosarcoma cells. We further examined whether a combination of GA and the autophagy inhibitor 3-methyl-adenine (3-MA) enhanced GA-induced apoptosis in KTHOS cells. GA had an inhibitory effect on cell proliferation and inhibited the Akt/mTOR signaling pathway in KTHOS cells. GA alone induced autophagy and apoptosis in KTHOS cells, but treatment with a combination of GA and 3-MA suppressed autophagy and induced apoptosis to a much greater extent than GA alone in these cells. It was considered that the autophagy inhibitor 3-MA suppressed a protective mechanism induced by Hsp90 inhibitor in tumor cells and induced apoptosis. Therefore, the combination of an Hsp90 inhibitor and an autophagy inhibitor may be an effective treatment for osteosarcoma because this combination effectively induces apoptotic pathways.

A large amount of microdamages in the cortical bone around fracture site in a patient of atypical femoral fracture after long-term bisphosphonate therapy

A breast cancer patient developed an atypical femoral fracture after 9 years of bisphosphonate therapy for the treatment of multiple bone metastases. We histopathologically analyzed the femoral cortical bone at the fracture site and the iliac cancellous bone. Four months prior to the fracture, the patient had experienced pain in the right femur and underwent plain radiography and bone scintigraphy which revealed cortical thickening and radioisotope accumulation at each site, respectively. The patient had also experienced a non-traumatic fracture at the same site on the contralateral side 2 years earlier. Based on these findings, atypical femoral fracture was diagnosed and intramedullary nailing performed. A cortical bone specimen taken from near the fracture site during surgery showed marked microdamages, and analysis of the iliac cancellous bone specimen revealed severely suppressed bone turnover. These findings suggest that microdamage and severely suppressed bone turnover are associated with atypical femoral fracture reported in this patient with long-term bisphosphonate therapy.

Neurilemmoma in the Foot as a Cause of Heel Pain: A Report of Two Cases

Two cases of deep-seated neurilemmoma that arose from plantar branches of the posterior tibial nerve and caused chronic heel pain are described. At the initial examination, one case was misdiagnosed as tarsal tunnel syndrome and the other was overlooked as plantar fasciitis; both cases were treated for long periods prior to operation. Deep-seated neurilemmomas in the foot can easily be overlooked and misdiagnosed as tarsal tunnel syndrome or plantar fasciitis because of the rarity, absence of palpable mass, and similarity of symptoms to those of other frequently encountered foot disorders. Magnetic resonance imaging provides the best modality for differential diagnosis. In the present cases, surgical excision of the tumors resulted in immediate and complete relief of chronic heel pain. Surgeons should consider neurilemmoma as a cause of persistent chronic heel pain despite the rarity of the disease.

Apophysitis of the ischial tuberosity mimicking a neoplasm on magnetic resonance imaging

We present multimodality imaging features of an ischial tuberosity apophysitis in a 13-year-old boy who was an active baseball pitcher. Roentgenography of the pelvis and computed tomography showed mild irregularity in the inferior margin of the left ischial tuberosity. T1-weighted MRI showed a wide area with low signal intensity in the left ischial body; T2-weighted fat-suppression images showed areas with markedly high signal intensity in the ischial apophysis and body and the surrounding periosteum; contrast-enhanced T1-weighted fat-suppression MRI showed that the ischial body, surrounding periosteum, and origin of the hamstring muscles strongly enhanced; technetium-99m scintigraphic scans showed increased isotope uptake in the entire ischial body. Histological specimens obtained from the bone showed increased osteoblastic activity, edema, and proliferation of benign spindle cells and small vessels in the bone marrow spaces. In the present case, because MR imaging demonstrated extensive signal abnormalities involving the apophysis, periosteum, and intramedullary portion of bone, a neoplasm could not be excluded, and a biopsy was undertaken.

Periosteal osteoblastoma of the distal femur.

Osteoblastomas located on the surface of the cortical bone, so-called periosteal osteoblastomas, are extremely rare. We report on a case of periosteal osteoblastoma arising from the posterior surface of the right distal femur in a 17-year-old man. Roentgenographic, computed tomographic, magnetic resonance imaging, and histologic features of the case are presented. Periosteal osteoblastoma should be radiologically and histologically differentiated from myositis ossificans, avulsive cortical irregularity syndrome, osteoid osteoma, parosteal osteosarcoma, periosteal osteosarcoma, and high-grade surface osteosarcoma. Although periosteal osteoblastoma is rare, this tumor should be included in the differential diagnosis of surface-type bone tumors.

Expression of Transforming Growth Factor β Isoforms and Their Receptors in Malignant Fibrous Histiocytoma of Soft Tissues

Purpose: Transforming growth factor β (TGF-β) is a multifunctional growth factor that variably affects proliferation, differentiation, and extracellular matrix formation. Little information is currently available on the TGF-β expression in malignant fibrous histiocytoma (MFH). The aims of the present study were to investigate the expression of TGF-β isoforms and their receptors in human MFH specimens. Experimental Design: The expression of TGF isoforms, and TGF-β receptors (TGF-βR1 and -βR2) were immunohistochemically evaluated in 43 paraffin-embedded MFH specimens. Furthermore, the correlation of the TGF-β and receptor expression with tumor proliferative activity assessed by MIB-1 indices was analyzed. Results: Positive immunoreactivity for TGF-β1, -β2, and -β3 was identified in tumor cells of 42, 40, and 38 of the 43 MFHs, respectively. In each TGF-β isoform immunostaining, the specimens were divided into two groups based on the number of positive tumor cells: those with low (<25%) and those with high (≧25%) immunoreactivity. There were no statistically significant differences in the MIB-1 indices between the two groups. Positive immunoreactivity for TGF-βR1 and -βR2 was identified in tumor cells of 36 and 24 of the MFHs, respectively. The specimens were divided into two groups based on their receptor expression patterns: those with both TGF-βR1- and -βR2-positive immunoreactivity (n = 23), and those with both or either TGF-βR1- and -βR2-negative immunoreactivity (n = 20). The MIB-1 indices in the both-TGF-βR1- and -βR2-positive group were significantly higher than those in the other group (P = 0.0102). There was no significant difference in pulmonary metastasis ratios between the two groups. Conclusions: These findings strongly suggest an association of the TGF-β ligand/receptor system with a significantly higher MIB-1 index in human MFHs. Investigation of the TGF-βR1 and -βR2 coexpression might be useful in predicting tumor behavior of MFHs.

Multimodality imaging features of primary xanthoma of the calcaneus

Secondary xanthomatous features are histologically observed in various bone lesions, but primary xanthoma of bone is rare. We present a primary xanthoma of the right calcaneus in a 51-year-old woman who had no aberrant lipid metabolism. Roentgenograms showed a small osteolytic lesion in the calcaneal triangle, partially surrounded by bone sclerosis. Computed tomographic scans of the calcaneus showed multiple osteolytic areas, with an irregular trabecular pattern in the surrounding sclerotic bone. T1-weighted magnetic resonance images showed a lesion with central low signal intensity, surrounded by a peripheral ring with high signal intensity. The entire lesion showed high signal intensity on T2-weighted images, partially surrounded by areas with low signal intensity, concordant with reactive bone sclerosis. Histologically, the lesion consisted of numerous lipid-laden histiocytes arranged in sheets, scattered multinucleated giant cells and lymphocytes, and granulation tissues. There was no evidence of pre-existing lesions. Total excision of the tumor was curative.

Subacute osteomyelitis of long bones:Diagnostic usefulness of the “penumbra sign” on MRI

Although subacute osteomyelitis of long bones is not uncommon, it is usually confined to metaphysis. Two unusual cases of subacute osteomyelitis that traversed a growth plate are described. There may be some radiological difficulties in distinguishing it from other malignant or benign lesions. On magnetic resonance (MR) imaging, both of the present cases showed characteristic four-layered appearance and the penumbra sign. These characteristic findings on MR imaging are considered to facilitate establishing the radiologic diagnosis.