title: Dense distribution of macrophages in flexor aspects of the hand and foot of mid-term human fetuses.
abstract: In the developing human musculoskeletal system, cell death with macrophage accumulation occurs in the thigh muscle and interdigital area. To comprehensively clarify the distribution of macrophages, we immunohistochemically examined 16 pairs of upper and lower extremities without the hip joint (left and right sides) obtained from 8 human fetuses at approximately 10-15 weeks of gestation. Rather than in muscles, CD68-positive macrophages were densely distributed in loose connective tissues of the flexor aspects of the extremities, especially in the wrist, hand and foot. In contrast, no or fewer macrophages were evident in the shoulder and the extensor aspects of the extremities. The macrophages were not concentrated at the enthesis of the tendon and ligament, but tended to be arranged along other connective tissue fibers. Deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling revealed apoptosis in the hand lumbricalis muscles, but not in the area of macrophage accumulation. Likewise, podoplanin-positive lymphatic vessels were not localized to areas of macrophage accumulation. Re-organization of the connective tissue along and around the flexor tendons of the hand and foot, such as development of the bursa or tendon sheath at 10-15 weeks, might require the phagocytotic function of macrophages, although details of the mechanism remain unknown.
authors.affiliation: Department of Anatomy, Chonbuk National University Medical School, Jeonju, Korea.
authors.forename: Ji Hyun
authors.initials: JH
authors.lastname: Kim
authors.forename: Shinichi
authors.initials: S
authors.lastname: Abe
authors.forename: Shunichi
authors.initials: S
authors.lastname: Shibata
authors.forename: Sachiko
authors.initials: S
authors.lastname: Asakawa
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Maki
authors.forename: Gen
authors.initials: G
authors.lastname: Murakami
authors.forename: Baik Hwan
authors.initials: BH
authors.lastname: Cho
keywords: CD68-positive macrophages; Enthesis; Hand and foot; Human fetus; Lymphatic vessels