Yoko Kawase-Koga

Timing Specific Requirement of microRNA Function is Essential for Embryonic and Postnatal Hippocampal Development

The adult hippocampus consists of the dentate gyrus (DG) and the CA1, CA2 and CA3 regions and is essential for learning and memory functions. During embryonic development, hippocampal neurons are derived from hippocampal neuroepithelial cells and dentate granular progenitors. The molecular mechanisms that control hippocampal progenitor proliferation and differentiation are not well understood. Here we show that noncoding microRNAs (miRNAs) are essential for early hippocampal development in mice. Conditionally ablating the RNAase III enzyme Dicer at different embryonic time points utilizing three Cre mouse lines causes abnormal hippocampal morphology and affects the number of hippocampal progenitors due to altered proliferation and increased apoptosis. Lack of miRNAs at earlier stages causes early differentiation of hippocampal neurons, in particular in the CA1 and DG regions. Lack of miRNAs at a later stage specifically affects neuronal production in the CA3 region. Our results reveal a timing requirement of miRNAs for the formation of specific hippocampal regions, with the CA1 and DG developmentally hindered by an early loss of miRNAs and the CA3 region to a late loss of miRNAs. Collectively, our studies indicate the importance of the Dicer-mediated miRNA pathway in hippocampal development and functions.

Short Lingual Osteotomy Using a Piezosurgery Ultrasonic Bone-Cutting Device During Sagittal Split Ramus Osteotomy.

Short lingual osteotomy is a useful method for the performance of sagittal split ramus osteotomy involving interference between the proximal and distal bone fragments when lateral differences exist in the setback distance. However, this procedure occasionally results in abnormal fracture and nerve injury; expert surgical skill is thus required. We herein describe a novel technique involving the use of an ultrasonic bone-cutting device (Piezosurgery; Mectron Medical Technology, Carasco, Italy) for vertical osteotomy posterior to the mandibular foramen. Successful short lingual osteotomy was performed using this technique with avoidance of abnormal fracture and neurovascular bundle damage.

Reconstruction of a complex midface defect from excision of a squamous cell carcinoma, according to regional aesthetic units

Extensive squamous cell carcinoma involving the skin of the upper lip, nasal ala, and cheek is relatively rare. Although numerous reconstruction techniques for the midface including lip, nose, and cheek have been described in the literature, reconstruction of large defects in this area continues to be challenging, as it is difficult to obtain satisfactory results with single-stage surgery. This case report concerns a 53-year-old woman with squamous cell carcinoma extending from the upper lip to the alar base and the cheek. It describes a step-by-step surgery undertaken according to defined regional aesthetic units of the face using several reconstruction methods, including a microvascular free flap, forehead flap, and conchal cartilage graft, rather than multistage reconstruction surgeries after first immediate reconstruction. Satisfactory functional and aesthetic results were achieved despite the extensive facial defects.

Human immunodeficiency virus-associated Burkitt lymphoma in a Japanese patient with early submandibular swelling: a case report

BackgroundPatients infected with the human immunodeficiency virus (HIV) are at risk of developing malignancies and have an increased susceptibility to infection. HIV-associated Burkitt lymphoma (BL) is relatively rare in developed countries, but remains prevalent in developing counties and is sometimes compounded by the fact that patients may be unaware that they are HIV-positive.Case presentationA 37-year-old Japanese man was referred to our department for diagnosis and management of submandibular swelling. He was unaware that he was HIV-positive at the initial visit. Here, we describe our diagnostic approach, in which we used hematological and immunological investigations, biopsy, fluorescence-activated cell sorting and fluorescence in situ hybridization to confirm the diagnosis of HIV-associated BL. The patient has no risk factors for HIV infection, and the source of infection remains unclear.ConclusionsIn this case, submandibular swelling was the first clinical sign of pathology and the patient’s HIV-positive status only became evident later. It is highly likely that BL was triggered by HIV infection.

Complications after intraoral vertical ramus osteotomy: relationship to the shape of the osteotomy line

Intraoral vertical ramus osteotomy (IVRO) is used widely to correct mandibular prognathism. However, several disadvantages of this procedure have been reported, such as condylar luxation and bony interference at the osteotomy site. The aim of this study was to survey the incidence of complications (condylar luxation and bony interference) based on the shape of the osteotomy line. One hundred and eighty-five rami in 118 patients with jaw deformities, which were treated with IVRO, were examined retrospectively. The shape of the osteotomy line and the postoperative complications were examined on panoramic radiographs. Osteotomy lines were classified into three types: vertical, C-shaped, and oblique. Of the 185 osteotomy sites, 98 were vertical, 37 C-shaped, and 50 oblique. Condylar luxation was found in six rami (3.2%); four had undergone vertical osteotomy and two had undergone C-shaped osteotomy. Bony interference occurred in seven rami (3.8%), all with vertical type osteotomy lines. Most complications occurred in the vertical type cases and no complications were found in oblique type cases. Condylar luxation was found mainly in unilateral IVRO cases and bony interference was found in bilateral IVRO cases. These results suggest that the oblique type of osteotomy line has the advantage of avoiding complications.

Role of cyclin-dependent kinase (Cdk)6 in osteoblast, osteoclast, and chondrocyte differentiation and its potential as a target of bone regenerative medicine

Abstract In the oral and maxillofacial region, conditions such as bone fracture, trauma-induced bone or cartilage defects, and tumor or birth defects are common, and it is necessary to elucidate the molecular mechanisms that control the differentiation of cells to establish new treatment strategies for these conditions. Therefore, numerous studies have investigated the role or involvement of factors that are thought to be crucial for differentiation of cells, including cell cycle factors, transcription factors, and growth factors. One of these types of factors, the cell cycle factors, critically influence the differentiation of cells, since a temporal arrest in the G 1 phase of the cell cycle or withdrawal from the cell cycle is thought to be a prerequisite for cell differentiation. In a previous attempt to identify cell cycle factor(s) controlling the commitment for differentiation of cells, we discovered that cyclin-dependent kinase (Cdk)6, one of the G 1 cell cycle factors, is a critical regulator of the differentiation efficiency of osteoblasts, osteoclasts, and chondrocytes. In addition, individual groups have also reported the importance of Cdk6 in differentiation in other cell types. Herein, we review the role of Cdk6 in differentiation of cells with a particular focus on osteoblast, osteoclast, and chondrocyte differentiation and discuss the potential of Cdk6 as a target of bone regenerative medicine.

A novel technique for preventing skin pressure sores using a rubber tube during surgical treatment of mandibular condyle fractures.

Craniofacial surgery occasionally results in sores and necrosis of the facial skin because of pressure from surgical instruments. During surgical treatment of mandibular condylar process fractures, the main mandibular fragment is routinely retracted downward using a wire to achieve a satisfactory anatomic reduction. This procedure may injure the facial skin. This potential complication is easily overlooked by medical staff, but it is easily preventable. We herein describe a method of using a rubber tube to avoid causing pressure sores of the facial skin during surgical treatment of mandibular condylar process fractures.