BMP-2 and OP-1 exert direct and opposite effects on renal branching morphogenesis

Am J Physiol. 1997 Dec;273(6):F961-75. doi: 10.1152/ajprenal.1997.273.6.F961.

Abstract

The bone morphogenetic proteins, BMP-2 and OP-1, are candidates for growth factors that control renal branching morphogenesis. We examined their effects in embryonic kidney explants and in the mIMCD-3 cell model of collecting duct morphogenesis (mIMCD-3 cells are derived from the terminal inner medullary collecting duct of the SV40 mouse). Osteogenic protein-1 (OP-1), at a dose of 0.25 nM, increased explant growth by 30% (P = 0.001). In contrast, 100-fold greater concentrations of OP-1 (28 nM) decreased explant growth by 10% (P < 0.001). BMP-2 was entirely inhibitory (maximum inhibition of 7% at 5 nM, P < 0.0004). In an in vitro model for branching morphogenesis utilizing the kidney epithelial cell line, mIMCD-3, low doses of OP-1 (< 0.5 nM) increased the number of tubular structures formed by 28 +/- 5% (P = 0.01), whereas concentrations > 0.5 nM decreased that number by 22 +/- 8% (P = 0.02). All concentrations of BMP-2 (0.05-10 nM) were inhibitory (maximum inhibition at 10 nM of 88 +/- 3%, P < 0.0001). Stimulatory doses of OP-1 increased tubular length (P = 0.003) and the number of branch points/structure (3.2-fold increase, P = 0.0005) compared with BMP-2. To determine the molecular basis for these effects, we demonstrated that BMP-2 is bound to mIMCD-3 cells by the type I serine/threonine kinase receptor, ALK-3, and that OP-1 bound to an approximately 80-kDa protein using ligand-receptor affinity assays. To demonstrate that OP-1 can exert both stimulatory and inhibitory effects within a developing kidney, embryonic explants were treated with agarose beads saturated with 2 microM OP-1. OP-1 decreased the number of ureteric bud/collecting duct branches adjacent to the beads by 58 +/- 1% (P < 0.0001). In contrast, the number of branches in tissue distal to the OP-1 beads was enhanced, suggesting a stimulatory effect at lower doses of OP-1. We conclude that OP-1 and BMP-2 directly control branching morphogenesis and that the effects of OP-1 are dependent on its local concentration within developing kidney tissue.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activin Receptors
  • Activin Receptors, Type I
  • Animals
  • Bone Morphogenetic Protein 2
  • Bone Morphogenetic Protein 7
  • Bone Morphogenetic Protein Receptors, Type II
  • Bone Morphogenetic Proteins / pharmacology*
  • Cell Division / drug effects
  • Cell Line
  • Embryo, Mammalian
  • Gestational Age
  • Kidney / cytology
  • Kidney / drug effects
  • Kidney / embryology*
  • Kidney Medulla / cytology
  • Kidney Medulla / drug effects
  • Kidney Tubules, Collecting / cytology
  • Kidney Tubules, Collecting / drug effects
  • Mice
  • Mice, Transgenic
  • Morphogenesis / drug effects
  • Organ Culture Techniques
  • Polymerase Chain Reaction
  • Protein-Serine-Threonine Kinases / biosynthesis
  • RNA, Messenger / biosynthesis
  • Receptors, Growth Factor / biosynthesis
  • Receptors, Transforming Growth Factor beta / biosynthesis
  • Simian virus 40 / genetics
  • Transcription, Genetic
  • Transforming Growth Factor beta / pharmacology

Substances

  • Bmp2 protein, mouse
  • Bone Morphogenetic Protein 2
  • Bone Morphogenetic Protein 7
  • Bone Morphogenetic Proteins
  • RNA, Messenger
  • Receptors, Growth Factor
  • Receptors, Transforming Growth Factor beta
  • Transforming Growth Factor beta
  • Protein-Serine-Threonine Kinases
  • Activin Receptors
  • Activin Receptors, Type I
  • Bmpr2 protein, mouse
  • Bone Morphogenetic Protein Receptors, Type II