The Interaction of Androgenic Hormone and Craniofacial Variation: Relationship Between Epigenetics and the Environment on the Genome with an Eye Toward Non-Syndromic Craniosynostosis

James John Cray, Jr.

PhD Thesis 2009

Recent research suggests that diversity in craniofacial morphology is produced by a complex interaction of environmental variables including 1) muscle function, 2) genetic factors related to skull growth, 3) timing and heritability of suture fusion (cessation of growth of the joints connecting the bones of the skull), 4) growth and morphology of the brain, and 5) other non-genetic factors including hormones of the endocrine system. How these factors interact in cranial growth and development is not well understood. This dissertation investigated the influence of androgenic hormone on suture bone biology. Methodology used including in vitro cellular challenges, protein analyses, and in vivo therapies. The work described here utilized a large sample size to establish the role of testosterone as a modulator of bone morphogenetic protein and subsequent effects on osteoblast differentiation. Testosterone increased the effect of BMP on osteoblasts, increasing differentiation. The increased differentiation effect was successfully blocked using flutamide, an androgen receptor blocker. Bone cells harvested from non suture calvaria in craniosynostotic rabbits were most susceptible to flutamide administration. The presence of androgen receptors in cells harvested from the suture and non suture bone of craniosynostotic or wild type rabbits could not be confirmed due to a lack of an effective antibody. In vivo administration of flutamide to the coronal suture of craniosynostotic rabbits resulted in greater growth across the coronal suture. However, no correction of craniofacial growth was observed. These results suggest 1) an alternative pathway for dihydrotestosterone’s and testosterone’s effect on the suture, similar to the adrenal androgens, via the MAP kinase pathway, 2) lack of an effective delivery system of the flutamide treatment, or 3) that an androgen receptor blocker-based therapy is not effective for delaying the eventual fusion of the coronal suture in this model.