title: Development and regeneration of the neonatal digit tip in mice.
abstract: The digit tips of children and rodents are known to regenerate following amputation. The skeletal structure that regenerates is the distal region of the terminal phalangeal bone that is associated with the nail organ. The terminal phalanx forms late in gestation by endochondral ossification and continues to elongate until sexual maturity (8 weeks of age). Postnatal elongation at its distal end occurs by appositional ossification, i.e. direct ossification on the surface of the terminal phalanx, whereas proximal elongation results from an endochondral growth plate. Amputation through the middle of the terminal phalanx regenerates whereas regenerative failure is observed following amputation to remove the distal 2/3 of the bone. Regeneration is characterized by the formation of a blastema of proliferating cells that appear undifferentiated and express Bmp4. Using chondrogenic and osteogenic markers we show that redifferentiation does not occur by endochondral ossification but by the direct ossification of blastema cells that form the rudiment of the digit tip. Once formed the rudiment elongates by appositional ossification in parallel with unamputated control digits. Regenerated digits are consistently shorter than unamputated control digits. Finally, we present a case study of a child who suffered an amputation injury at a proximal level of the terminal phalanx, but failed to regenerate despite conservative treatment and the presence of the nail organ. These clinical and experimental findings expand on previously published observations and initiate a molecular assessment of a mammalian regeneration model.
authors.affiliation: Division of Developmental Biology, Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA.
authors.forename: Manjong
authors.initials: M
authors.lastname: Han
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Yang
authors.forename: Jangwoo
authors.initials: J
authors.lastname: Lee
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Allan
authors.forename: Ken
authors.initials: K
authors.lastname: Muneoka
mesh_terms: D000671:Amputation, Surgical; D000818:Animals; D000831:Animals, Newborn; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism; D001861:Bone Regeneration / Q000502:physiology*; D001842:Bone and Bones / Q000166:cytology / Q000502:physiology*; D002454:Cell Differentiation; D049109:Cell Proliferation; D002675:Child, Preschool; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005385:Fingers / Q000000981:diagnostic imaging / Q000601:surgery; D005452:Fluoresceins / Q000378:metabolism; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051957:MSX1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D051379:Mice; D015675:Osteocalcin / Q000378:metabolism; D011859:Radiography; D013997:Time Factors; D014034:Toes / Q000502:physiology* / Q000601:surgery; D016896:Treatment Outcome; D014945:Wound Healing
chemical_list: C525809:BMP4 protein, human; C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D005452:Fluoresceins; D018398:Homeodomain Proteins; D051957:MSX1 Transcription Factor; C084119:MSX2 protein; D015675:Osteocalcin; C007740:fluorexon