Growth Factors FGF8 and FGF2 and Their Receptor FGFR1, Transcriptional Factors Msx-1 and MSX-2, and Apoptotic Factors p19 and RIP5 Participate in the Early Human Limb Development

Acta Histochem. 2018 Apr;120(3):205-214. doi: 10.1016/j.acthis.2018.01.008. Epub 2018 Feb 4.

Abstract

The expression pattern of fibroblast growth factors FGF8 and FGF2 and their receptor FGFR1, transcription factors MSX-1 and MSX-2, as well as cell proliferation (Ki-67) and cell death associated caspase-3, p19 and RIP5 factors were analyzed in histological sections of eight 4th-9th-weeks developing human limbs by immunohistochemistry and semi-thin sectioning. Increasing expression of all analyzed factors (except FGF8) characterized both the multilayered human apical ectodermal ridge (AER), sub-ridge mesenchyme (progress zone) and chondrocytes in developing human limbs. While cytoplasmic co-expression of MSX-1 and MSX-2 was observed in both limb epithelium and mesenchyme, p19 displayed strong cytoplasmic expression in non-proliferating cells. Nuclear expression of Ki-67 proliferating cells, and partly of MSX-1 and MSX-2 was detected in the whole limb primordium. Strong expression of factors p19 and RIP5, both in the AER and mesenchyme of human developing limbs indicates their possible involvement in control of cell senescence and cell death. In contrast to animal studies, expression of FGFR1 in the surface ectoderm and p19 in the whole limb primordium might reflect interspecies differences in limb morphology. Expression of FGF2 and downstream RIP5 gene, and transcription factors Msx-1 and MSX-2 did not show human-specific changes in expression pattern. Based on their spatio-temporal expression during human limb development, our study indicates role of FGFs and Msx genes in stimulation of cell proliferation, limb outgrowth, digit elongation and separation, and additionally MSX-2 in control of vasculogenesis. The cascade of orchestrated gene expressions, including the analyzed developmental factors, jointly contribute to the complex human limb development.

Keywords: Growth factors; Human limb development; MSX-1; MSX-2; p19.

MeSH terms

  • Apoptosis
  • Cell Proliferation
  • Chondrocytes / cytology
  • Fibroblast Growth Factor 2 / genetics
  • Fibroblast Growth Factor 2 / metabolism*
  • Fibroblast Growth Factor 8 / metabolism*
  • Fluorescent Antibody Technique
  • Gene Expression
  • Homeodomain Proteins / metabolism*
  • Humans
  • Immunohistochemistry
  • Limb Buds / growth & development
  • Limb Buds / metabolism*
  • MSX1 Transcription Factor / metabolism*
  • Receptor-Interacting Protein Serine-Threonine Kinases / genetics
  • Receptor-Interacting Protein Serine-Threonine Kinases / metabolism*
  • Receptors, Growth Factor / metabolism*
  • Stathmin / metabolism*

Substances

  • FGF8 protein, human
  • Homeodomain Proteins
  • MSX1 Transcription Factor
  • MSX2 protein
  • Msx1 protein, rat
  • Receptors, Growth Factor
  • Stathmin
  • Fibroblast Growth Factor 2
  • Stmn1 protein, rat
  • Fibroblast Growth Factor 8
  • Receptor-Interacting Protein Serine-Threonine Kinases
  • DSTYK protein, human