Keiichi Akita

Interactions between FGF and Wnt signals and Tbx3 gene expression in mammary gland initiation in mouse embryos

Interactions between Wnts, Fgfs and Tbx genes are involved in limb initiation and the same gene families have been implicated in mammary gland development. Here we explore how these genes act together in mammary gland initiation. We compared expression of Tbx3, the gene associated with the human condition ulnar–mammary syndrome, expression of the gene encoding the dual‐specificity MAPK phosphatase Pyst1/MKP3, which is an early response to FGFR1 signalling (as judged by sensitivity to the SU5402 inhibitor), and expression of Lef1, encoding a transcription factor mediating Wnt signalling and the earliest gene so far known to be expressed in mammary gland development. We found that Tbx3 is expressed earlier than Lef1 and that Pyst1 is also expressed early but only transiently. Patterns of expression of Tbx3, Pyst1 and Lef1 in different glands suggest that the order of mammary gland initiation is 3, 4, 1, 2 and 5. Consistent with expression of Pyst1 in the mammary gland, we detected expression of Fgfr1b, Fgf8 and Fgf9 in both surface ectoderm and mammary bud epithelium, and Fgf4 and Fgf17 in mammary bud epithelium. Beads soaked in FGF‐8 applied to the flank of mouse embryos, at a stage just prior to mammary bud initiation, induce expression of Pyst1 and Lef1 and maintain Tbx3 expression in flank tissue surrounding the bead. Grafting beads soaked in the FGFR1 inhibitor, SU5402, abolishes Tbx3, Pyst1 and Lef1 expression, supporting the idea that FGFR1 signalling is required for early mammary gland initiation. We also showed that blocking Wnt signalling abolishes Tbx3 expression but not Pyst1 expression. These data, taken together with previous findings, suggest a model in which Tbx3 expression is induced and maintained in early gland initiation by both Wnt and Fgf signalling through FGFR1.

Anatomic basis of chronic groin pain with special reference to sports hernia.

Chronic pain on the ventral surface of the scrotum and the proximal ventro-medial surface of the thigh especially in athletes has been diagnosed in various ways; recently, in Europe the concept of “sports hernia” has been advocated. However, since few reports discuss the detailed course of the nerves in association with the pain, we examined the cutaneous branches in the inguinal region in 54 halves of 27 adult male cadavers. From our results, in addition to the cutaneous branches from the ilioinguinal n. (in 49 of 54: 90.7%), cutaneous branches originating from the genital branches of the genitofemoral nerve were found in the inguinal region in 19 of 54 halves (35.2%). In 7 cases (in 7 of 54: 13.0%) the genital branch and the ilioinguinal nerve united in the inguinal canal. In 6 cases the genital branch pierced the inguinal lig. to enter the inguinal canal, and in three cases the genital branch pierced the border between the ligament and the aponeurosis of the obliquus externus m. to be distributed to the inguinal region. Therefore, the courses of the genital branches vary considerably, and may have a very important role in chronic groin pain produced by groin hernia. In addition, entrapment by the ligament may be a reasonable candidate for the cause of chronic groin pain.

The superior capsule of the shoulder joint complements the insertion of the rotator cuff

BACKGROUND To date, there are no studies about the attachment of the articular capsule of the superior shoulder joint. The aim of this study was to measure the width of the attachment of the articular capsule on the humerus, and to clarify the anatomy and the relationship to the footprint of the rotator cuff. METHODS The attachment of the articular capsule on the greater tuberosity was exposed. The width of the attachment of the capsule and the footprint of the rotator cuff were measured. RESULTS The maximum capsular width was located at the border between the infraspinatus and the teres minor, and measured 9.1 mm. The minimum capsular width was 3.5 mm, and it was located at 10.9 mm posterior to the anterior margin of the greater tuberosity and 1.5 mm anterior to the posterior margin of the supraspinatus. CONCLUSION Prior studies have overestimated the rotator cuff footprint width due to the lack of discrimination between the actual cuff insertion and capsule. The attachment of the articular capsule of the shoulder joint occupied a substantial area of the greater tuberosity. In particular, at the border between the infraspinatus and the teres minor, the very thick attachment of the articular capsule compensated for the lack of attachment of muscular components. The thinnest point of the articular capsule was 11 mm posterior to the anterior margin of the greater tuberosity and very close to the posterior edge of the tapered insertion of the supraspinatus, which could contribute to the etiology of degenerative rotator cuff tears.

Positional relationships between the masticatory muscles and their innervating nerves with special reference to the lateral pterygoid and the midmedial and discotemporal muscle bundles of temporalis.

For an accurate assessment of jaw movement, it is crucial to understand the comprehensive formation of the masticatory muscles with special reference to the relationship to the disc of the temporomandibular joint. Detailed dissection was performed on 26 head halves of 14 Japanese cadavers in order to obtain precise anatomical information of the positional relationships between the masticatory muscles and the branches of the mandibular nerve. After complete removal of the bony elements, the midmedial muscle bundle in all specimens and the discotemporal muscle bundle in 6 specimens, derivatives of the temporalis, which insert into the disc were observed. On the anterior area of the articular capsule and the disc of the temporomandibular joint, the upper head of the lateral pterygoid, the midmedial muscle bundle of temporalis and the discotemporal bundle of temporalis were attached mediolaterally, and in 3 specimens the posterosuperior margin of the zygomaticomandibularis was attached to the anterolateral area of the disc. It is suggested that these muscles and muscle bundles contribute to various mandibular movements. Although various patterns of the positional relationships between the muscles and muscle bundles and the their innervating nerves are observed in the present study, relative positional relationships of the muscles and muscle bundles and of nerves of the mandibular nerve are consistent. A possible scheme of the developmental formation of the masticatory muscles based on the findings of the positional relationships between the muscles and the nerves is presented.

Anatomic study of the attachment of the medial patellofemoral ligament and its characteristic relationships to the vastus intermedius

PurposeThe aim of this study was to investigate the attachment of the medial patellofemoral ligament (MPFL) using cadaver specimens and establish an anatomic basis for optimal MPFL reconstruction to achieve better patella stability.MethodsSixteen knees of eight cadavers were used in this study. The relationship of the MPFL with quadriceps muscles was investigated from outside after removal of the distal part of the vastus medialis and the rectus femoris and then evaluated from intra-articular side after release of lateral margin of the vastus lateralis muscle, patella and patella tendon.ResultsThe proximal fibres of MPFL were mainly attached to the vastus intermedius tendon, without tight adhesion to the vastus medialis. The distal fibres of MPFL were interdigitated with the deep layer of the medial retinaculum that was attached to the medial margin of the patella tendon.ConclusionThese findings imply that MPFL, which was directly attached to the vastus intermedius and patella and indirectly continued to the patella tendon, could keep pulling them medially as one unit and consequently make the patella move smoothly on the trochlea during whole movement of the knee. Clinically, dysfunction of both proximal and distal MPFL fibres should be considered in the diagnosis and treatment of patella instability after traumatic patella dislocation. MPFL reconstruction with both fibres has a possibility to lead ideal function of MPFL and better instability of the patella.

Morphological evidence of the importance of epithelial tissue during mouse tongue development.

The morphogenesis of fungiform papillae occurs in a stereotyped pattern on the dorsal surface of the tongue in mice from embryonic day 12 (E12) to E17. The histological results and ultrastructural observations showed the development of specific structures in the epithelium into fungiform papillae. Prior to the morphological changes, the Bmp-4 and Shh transcripts are expressed in a restricted area on the dorsal surface. These results suggest that the development of fungiform papillae requires an epithelium and mesenchyme interaction during morphogenesis. In order to obtain direct evidence of the epithelium and mesenchyme interaction during tongue papillae morphogenesis, the formation of fungiform papillae was examined after a recombination assay. In order to confirm the epithelium and mesenchyme interactions during the early development of the mouse tongue, a recombination assay was conducted after the recombination assay at E12.5 and E13.5 for 2 days using an in vitro organ culture. From the recombination assay results, the E13.5 epithelial portion of the fungiform papillae could determine the position of the newly formed fungiform papillae with the epithelial signaling molecules. E13.5 was a critical stage for fungiform papillae morphogenesis. Fungiform papillae can be considered to be small epithelial appendages, which are formed via the epithelium and mesenchyme interactions.

Anatomical study of the obturator internus, gemelli and quadratus femoris muscles with special reference to their innervation

The manner of innervation of the obturator internus, superior and inferior gemelli, and the quadratus femoris in humans (101 pelvic halves) and in rhesus monkeys (Macaca mulatta: 8 pelvic halves) were investigated. In most specimens, the inferior gemellus originated from the lateral surface of the ischial tuberosity and also from the medial surface (intrapelvic origin) just beneath the obturator internus and was covered by the falciform process of the sacrotuberous ligament. The superior gemellus was frequently innervated by the nerve to the obturator internus and the nerve to the quadratus femoris (60.4%), and the inferior gemellus was innervated by the obturator internus nerve in two specimens. The quadratus femoris nerve originated from more cranial segments than the obturator internus nerve, however these nerves had various communication patterns inside and outside the muscles. According to the intramuscular nerve distribution, in some specimens the branches to the superior gemellus from the quadratus femoris nerve extended to the inferior gemellus, and the branches to the inferior gemellus were distributed to the obturator internus. The present findings revealed that the positional relationships among the branches to the obturator internus and gemelli muscles are relatively constant, although the branching patterns and innervation patterns were varied. The various patterns and routes are considered to reflect the variability of the differentiation patterns of the anlage of the muscles. A possible schematic model of the positional relationships between the muscles and the nerves is proposed. Anat Rec 263:41–52, 2001.

The subclavius posticus muscle: a factor in arterial, venous or brachial plexus compression ?

During dissection practice in 1993 and 1995 to 1999, we found an aberrant muscle which connected the first costal cartilage and the superior margin of the scapula in 12 sides (4.8%) of 11 cadavers (8.9%) among 248 sides of 124 cadavers. The muscle originated from the cranial surface of the sternal end of the first rib, ran laterodorsally, and inserted into the superior margin of the scapula. According to the origin and insertion, the aberrant muscle was considered to be the subclavius posticus (Rosenmüller, 1800). We also examined the supraclavicular region of a living subject by MR imaging to estimate the course of such an aberrant muscle. It is thought that the aberrant muscle runs on the anterior surface of the subclavian vein and crosses over the brachial plexus. Such a muscle could be considered as a possible factor causing the Paget-von Schrötter syndrome which is recognized as spontaneous or effort-related thrombosis of the axillo-subclavian vein. It is recommended to take into account the possible existence of such an aberrant muscle during the examination of patients with thoracic outlet syndrome, especially in those with symptoms of venous compression.

The Role of Fibers in the Femoral Attachment of the Anterior Cruciate Ligament in Resisting Tibial Displacement

Purpose The purpose was to clarify the load-bearing functions of the fibers of the femoral anterior cruciate ligament (ACL) attachment in resisting tibial anterior drawer and rotation. Methods A sequential cutting study was performed on 8 fresh-frozen human knees. The femoral attachment of the ACL was divided into a central area that had dense fibers inserting directly into the femur and anterior and posterior fan-like extension areas. The ACL fibers were cut sequentially from the bone: the posterior fan-like area in 2 stages, the central dense area in 4 stages, and then the anterior fan-like area in 2 stages. Each knee was mounted in a robotic joint testing system that applied tibial anteroposterior 6-mm translations and 10° or 15° of internal rotation at 0° to 90° of flexion. The reduction of restraining force or moment was measured after each cut. Results The central area resisted 82% to 90% of the anterior drawer force; the anterior fan-like area, 2% to 3%; and the posterior fan-like area, 11% to 15%. Among the 4 central areas, most load was carried close to the roof of the intercondylar notch: the anteromedial bundle resisted 66% to 84% of the force and the posterolateral bundle resisted 16% to 9% from 0° to 90° of flexion. There was no clear pattern for tibial internal rotation, with the load shared among the posterodistal and central areas near extension and mostly the central areas in flexion. Conclusions Under the experimental conditions described, 66% to 84% of the resistance to tibial anterior drawer arose from the ACL fibers at the central-proximal area of the femoral attachment, corresponding to the anteromedial bundle; the fan-like extension fibers contributed very little. This work did not support moving a single-bundle ACL graft to the side wall of the notch or attempting to cover the whole attachment area if the intention was to mimic how the natural ACL resists tibial displacements. Clinical Relevance There is ongoing debate about how best to reconstruct the ACL to restore normal knee function, including where is the best place for ACL graft tunnels. This study found that the most important area on the femur, in terms of resisting displacement of the tibia, was in the central-anterior part of the femoral ACL attachment, near the roof of the intercondylar notch. The testing protocol did not lead to data that would support using a large ACL graft tunnel that attempts to cover the whole natural femoral attachment area.

Innervation analysis of the small muscle bundles attached to the temporalis: truly new muscles or merely derivatives of the temporalis?

Detailed examinations were performed in ten temporal muscles from five cadavers to identify the muscle bundle arrangements of the temporalis and their innervation. Three additional muscle bundles were clearly observed in the main part of the fan-shaped temporalis: the anteromedial, anterolateral, and mid-lateral muscle bundles. Based on the origins, insertions and detailed innervation patterns, these bundles were considered as parts of the temporalis rather than independent muscles, although the anteromedial and anterolateral bundles had been recently reported as newly described muscles. A possible schematic model of the origins of these muscle bundles is proposed. We also report a branch from the posterior deep temporal nerve which was distributed to the temporal fascia and to the skin of the temporal region.