Changes in Biomechanical Strain and Morphology of Rat Calvarial Sutures and Bone After Tgf‐β3 Inhibition of Posterior Interfrontal Suture Fusion

Abstract

Craniofacial sutures are bone growth fronts that respond and adapt to biomechanical environments. Little is known of the role sutures play in regulating the skull biomechanical environment during patency and fusion conditions, especially how delayed or premature suture fusion will impact skull biomechanics. Tgf-β3 has been shown to prevent or delay suture fusion over the short term in rat skulls, yet the long-term patency or its consequences in treated sutures is not known. It was therefore hypothesized that Tgf-β3 had a long-term impact to prevent suture fusion and thus alter the skull biomechanics. In this study, collagen gels containing 3 ng Tgf-β3 were surgically placed superficial to the posterior interfrontal suture and deep to the periosteum in postnatal day 9 (P9) rats. At P9, P24, and P70, biting forces and strains over left parietal bone, posterior interfrontal suture, and sagittal suture were measured with masticatory muscles bilaterally stimulated, after which the rats were sacrificed and suture patency analyzed histologically. Results demonstrated that Tgf-β3 treated sutures showed less fusion over time than control groups, and strain patterns in the skulls of the Tgf-β3 treated group were different from that of the control group. While bite force increased with age, no alterations in bite force were attributable to Tgf-β3 treatment. These findings suggest that the continued presence of patent sutures can affect strain patterns, perhaps when higher bite forces are present as in adult animals.

Enzyme replacement for craniofacial skeletal defects and craniosynostosis in murine hypophosphatasia

“…Localized hypermineralization of long bone metaphyses has been reported in children with HPP, and theorized to occur as a compensatory response to otherwise mechanically incompetent bone structure [49,50]. Cranial bones are not weight bearing but do experience forces from mastication [51]. Pediatric cranial bones also deform to a significantly greater extent than adult cranial bones in response to mechanical force [52].…”

Assessment of the mechanical role of cranial sutures in the mammalian skull: Computational biomechanical modelling of the rat skull

“…In adult skulls, sutures are often described as fibrous and relatively immobile joints, yet sutures can be sites of skull mobility, especially in more patent (unfused) contacts like those in reptiles (Smith & Hylander, 1985 ). Multiple in vitro and in vivo studies have attempted to characterise the mechanical environment of sutures (tensile or compressive) across various species (Behrents et al, 1978 ; Byron, 2009 ; Herring & Mucci, 1991 ; Jaslow & Biewener, 1995 ; Rafferty & Herring, 1999 ; Shibazaki et al, 2007 ; Shibazaki‐Yorozuya et al, 2012 ). However, although in vitro and in vivo studies are of value in determining local strain environments, it is important to exercise caution when inferring whole‐skull responses to loading (Curtis et al, 2013 ).…”

“…Considering this complexity, our aim was to build an anatomically detailed biomechanical model of the rat skull to evaluate the mechanical role of the sutures on cranial strain during biting. The albino rat ( Rattus norvegicus ) was chosen because it is common throughout laboratories around the world and is an important model species for research in biomechanics, biomedical and behavioural sciences (Meakin et al, 2014 ; Shibazaki et al, 2007 ; Shibazaki‐Yorozuya et al, 2012 ). Rats have also been an important species in understanding the relationships between diet, ecology, and evolution within rodents (Cox et al, 2011 , 2012 ; Ginot et al, 2018 ).…”

Signaling mechanisms implicated in cranial sutures pathophysiology: Craniosynostosis

“…Thus, sutures are bone growth sites which respond to biomechanical signals which are induced by the underlying brain. These signals are translated into cell signaling at sutures, resulting in the transcription of osteoblast differentiation, thus bone ossification [11].…”