Enzyme replacement for craniofacial skeletal defects and craniosynostosis in murine hypophosphatasia.

Abstract

Hypophosphatasia (HPP) is an inborn-error-of-metabolism disorder characterized by deficient bone and tooth mineralization due to loss-of function mutations in the gene (Alpl) encoding tissue-nonspecific alkaline phosphatase (TNAP). Alpl(-/-) mice exhibit many characteristics seen in infantile HPP including long bone and tooth defects, vitamin B6 responsive seizures and craniosynostosis. Previous reports demonstrated that a mineral-targeted form of TNAP rescues long bone, vertebral and tooth mineralization defects in Alpl(-/-) mice. Here we report that enzyme replacement with mineral-targeted TNAP (asfotase-alfa) also prevents craniosynostosis (the premature fusion of cranial bones) and additional craniofacial skeletal abnormalities in Alpl(-/-) mice. Craniosynostosis, cranial bone volume and density, and craniofacial shape abnormalities were assessed by microscopy, histology, digital caliper measurements and micro CT. We found that craniofacial shape defects, cranial bone mineralization and craniosynostosis were corrected in Alpl(-/-) mice injected daily subcutaneously starting at birth with recombinant enzyme. Analysis of Alpl(-/-) calvarial cells indicates that TNAP deficiency leads to aberrant osteoblastic gene expression and diminished proliferation. Some but not all of these cellular abnormalities were rescued by treatment with inorganic phosphate. These results confirm an essential role for TNAP in craniofacial skeletal development and demonstrate the efficacy of early postnatal mineral-targeted enzyme replacement for preventing craniofacial abnormalities including craniosynostosis in murine infantile HPP.

• Authors: Jin Liu, Cassie Campbell, Hwa Kyung Nam, Alexandre Caron, Manisha C Yadav, José Luis Millán, Nan E Hatch
• Journal: Bone (Bone) Vol. 78 Pg. 203-11 (Sep 2015) ISSN: 1873-2763 [Electronic] United States
• PMID: 25959417 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 Elsevier Inc. All rights reserved.

Chemical References

• Immunoglobulin G
• Phosphates
• Recombinant Fusion Proteins
• ALPL protein, mouse
• Alkaline Phosphatase
• asfotase alfa

Topics

• 3T3 Cells
• Alkaline Phosphatase (genetics, therapeutic use)
• Animals
• Bone and Bones (pathology)
• Calcification, Physiologic
• Cell Proliferation
• Craniofacial Abnormalities (genetics)
• Craniosynostoses (drug therapy, physiopathology)
• Crosses, Genetic
• Disease Models, Animal
• Enzyme Replacement Therapy
• Enzyme Therapy
• Hypophosphatasia (drug therapy, genetics, physiopathology)
• Immunoglobulin G (therapeutic use)
• Mice
• Mice, Inbred C57BL
• Mice, Transgenic
• Phosphates (chemistry)
• Recombinant Fusion Proteins (therapeutic use)
• X-Ray Microtomography