One-step Repair Of Large Area Skull Defects With Elastic Bone Patch

BackgroundSkull defect is a particularly common disease in clinical practice,which is mainly caused by traffic accidents,violent trauma,open intracranial tumor surgery and falls.Although the skull bone tissue has the ability to repair itself,it is difficult to fully repair the large area skull defect,the diameter of defect site is longer than critical defect size,only by self-healing capability.The human intervention is necessary for healing of lager area skull defect.Large area skull defects are often accompanied by craniocerebral injury,which still have high mortality although great progresses have been made in current treatments.And large area skull defect with craniocerebral injury often causes intracranial hypertension because of secondary cerebral hemorrhage and cerebral edema,which poses a huge threat to the patient’s life.Currently,the two-step therapy,craniotomy and cranioplasty,is the most commonly used treatment for large skull defects with craniocerebral injury.Craniectomy performed in early stage can reduce intracranial pressure and prevent intracranial hypertension from damaging brain tissue.Cranioplasty performed in later stage can restore beautiful appearance and protect intracranial tissue.In the two-step therapy process,not only does the patient need to undergo the pain of two surgeries,but also the brain tissue that lacks the protection of the skull is likely to cause secondary damage after the skull resected.Therefore,the current clinical challenge of large area skull defect is repairing the defect site with one-step.The materials currently used for the repair of large area skull defects mainly include autogenous bone,allogeneic bone and artificial bone substitute materials.Autogenous bone is recognized as the most ideal material for repairing large area skull defects,however,it is still very difficult to preserve the bone tissue with activity for a long time.On the other hand,hydrogels possess elastic and can be used to cover skull defect sites with intracranial hypertension after injury.Therefore,we hypothesized that the combination of auto-active bone fragments and hydrogel could repair the skull defect with intracranial injury in one-step,which provided a new strategy for the repair of large area skull defects accompanied by intracranial injury.ObjectiveResearch and development of a hydrogel with excellent biocompatibility and mechanical properties.And this hydrogel could combine with autologous bone fragments to form elastic bone patches,which could achieve one-step repair of large area skull defects accompanied by craniocerebral injury.This study provides a feasible experimental basis for clinical application of one-step therapy to quickly repair large area skull defects with craniocerebral injury.Method(1)Material preparation: In the dark condition,the GelMA/HA-NB/LAP hydrogel was prepared at a ratio of 20:20:1 with 10%(w/v)GelMA,5%(w/v)HA-NB,4%(w/v)LAP solution,respectively.In a sterile environment,the skull of Sprague Dawley(SD)rats was washed with normal saline,and then the skull was cut into bone fragments with tissue scissors.(2)In vitro cell experiments:The ADSCs of SD rats were cultured and passaged until the third generation in vitro,and then dead/live staining was used to evaluate the viability of ADSCs encapsulated in GelMA/HA-NB/LAP hydrogel,and the CCK-8 test was used to evaluate the cytotoxicity of this hydrogel.(3)Mechanical test of elastic bone patch: The elastic bone patch was prepared by embedding skull bone fragments into GelMA/HA-NB/LAP hydrogel,and then irradiating with ultraviolet(UV)light to crosslink.Then,using an electronic universal testing machine to assess the tensile properties of the elastic bone patch,and using the burst pressure test to evaluate the maximum pressure that the elastic bone patch can withstand.(4)In vivo animal experiments: GelMA/HA-NB/LAP hydrogels were implanted into the dorsal subcutaneous of SD rats,and evaluate the biodegradability of this hydrogel after 1,2,4,and 8 weeks.Large area skull defect models were constructed with SD rats,12 rats were randomly divided into three groups:control group,hydrogel group,and elastic autologous bone patch group.And micro-CT scanning,H&E staining,and immunohistochemical staining were used to evaluate the effect of bone regeneration of large area skull defect sites at8 weeks post-implantation.Result(1)Cell experiments indicated that rat ADSCs maintained high cell viability when encapsulated and co-cultured in GelMA/HA-NB/LAP hydrogel,and this hydrogel possessed low cytotoxicity.(2)The mechanical test of the elastic bone patch shows that the maximum pressure that the elastic bone patch can withstand is far greater than the intracranial pressure,and can continuously stretch with the tensile stress increases.(3)The biodegradation experiments of GelMA/HA-NB/LAP hydrogel in vivo showed that this hydrogel can gradually degrade in SD rats.Large area skull defects repair in SD rats showed that both elastic autologous bone patch and hydrogel could promote bone regeneration,and the repair effect of elastic autologous bone patch is the best.ConclusionThe GelMA/HA-NB/LAP hydrogel possesses good biocompatibility,and the elastic bone patch has suitable stretchability which make the elastic bone patch stretched with intracranial pressure increasing.The elastic bone patch is able to promote bone regeneration in rats,and can repair large area skull defects faster and better.It provides an experimental theoretical basis for applying the elastic autologous bone patch to clinical treatment of large skull bone defect accompanied by craniocerebral injury.