0 Harnessing the Osteogenic Capability of Neonatal Dura to Heal Critical Sized Defects Walter Sweeney B.S., Brendan Alleyne B.S., Adam Cash M.D., Christy Gliniak B.S., Gregory Cooper PhD., Arun Gosain M.D. Case Western Reserve University, Department of Plastic & Reconstructive Surgery, Cleveland, Ohio Presenter: Brendan Alleyne B.S.

1 Introduction Critical Sized Defects  Defects incapable of healing in the animals lifetime  Problematic for adults and children because vital structures are unprotected  Interestingly, children < 1 year of age can heal large cranial defects  Healing is due to osteogenic potency of dura but potency decreases with age  Can the dural osteogenic potency present in children be harnessed to heal critical sized defects?

2 Disclosure Nothing to disclose

3 Hypothesis  Rat neonatal dura transplanted into adult rat critical sized defects would retain the ability to induce osteogenesis and augment healing.

4 Materials and Methods  24 Adult Rats  24 Neonatal Rats Craniotomy with dural harvest from parietal aspect of animals 8, 17, and 45 days PN 8 days PN (n=6) 17 days PN (n=6) 45 days PN (n=6) 60 day old adult rats with 2.3mm defect 60 day old adult rats with 2.3mm defect 60 day old Adult rats with 2.3mm defect 60 day old Adult rats with 2.3mm defect Untreated

5 Materials and Methods 8,17,or 45 day old postnatal rat Craniotomy Dura Inlayed

6 Analysis Micro-CT images performed 5 weeks post-operatively  Image J was used to assess pixel density as a surrogate for bone formation  Pixel density was compared between the cranial defect and intact cranial bone  At 5 weeks only untreated defects and defects treated with 8 day old neonatal dura were evaluated Radiographic images performed 8 weeks post- operatively  Image J was used to measure the Bone Gap  Bone gap was defined as the distance between bone formation and edge of the defect  At 8 weeks the bone gap was measured for all animals

7 Results Untreated Treated w/ 8 day old dura  Micro-CT 5 weeks

8 Results Untreated Treated w/ 8 day old dura  Radiograph 8 wks

9 Results of Animals Evaluated with Micro-CT at 5 Weeks  Defects treated with 8 day old dura achieved pixel density equivalent to intact cranial bone  Pixel density of untreated defects was decreased 3 fold as compared to intact cranial bone Increased Pixel Density = Increased Bone Formation

10 Results of Animals Evaluated with Radiographs at 8 Weeks Decreased Bone Gap = Increased Bone Formation  Defects treated with 8 day old dura had the smallest bone gap and most bone formation  Bone gap was largest in untreated defects  Supporting evidence that dura becomes less osteogenic with age, the bone formation decreased as the age of the dura increased

11 Conclusion  First study to demonstrate the neonatal dura retains osteogenic potency following transplantation  This study supports that the osteogenic capability of dura decreases with age

12 Significance of the findings…  Dura can be harnessed to augment CSD healing  Future studies will focus on identifying growth factors responsible for cranial regeneration  Such findings will facilitate the engineering of biocompatible grafts capable of mimicking dural induced osteogenesis  Additionally, current studies aim to determine if fetal dura has an even greater degree of osteogenic potential than that of perinatal dura

13 Sincere thanks to…  Dr. Gosain  Walter Sweeney  Christy Gliniak  Davood Varghai

14 Harnessing the Osteogenic Capability of Neonatal Dura to Heal Critical Sized Defects Walter Sweeney B.S., Brendan Alleyne B.S., Davood Varghai M.D., Adam Cash M.D., Christy Gliniak B.S., Gregory Cooper PhD., Arun Gosain M.D. Case Western Reserve University, Department of Plastic & Reconstructive Surgery, Cleveland, Ohio Introduction ConclusionsResults MethodsFuture Investigation Moreira-Gonzalez, A., Jackson, I. T., Miyawaki, T., Barakat, K. & DiNick, V. Clinical outcome in cranioplasty: critical review in long-term follow-up. J. Craniofac. Surg. 14, (2003). Chim, H. & Gosain, A. K. Biomaterials in craniofacial surgery: experimental studies and clinical application. J. Craniofac. Surg. 20, (2009). Cho, Y. R. & Gosain, A. K. Biomaterials in craniofacial reconstruction. Clin. Plast. Surg. 31, , v (2004). David, L., Argenta, L. & Fisher, D. Hydroxyapatite cement in pediatric craniofacial reconstruction. J. Craniofac. Surg. 16, (2005). David, D. J. & Cooter, R. D. Craniofacial infection in 10 years of transcranial surgery. Plast. Reconstr. Surg. 80, (1987). Fearon, J. A. et al. Infections in craniofacial surgery: a combined report of 567 procedures from two centers. Plast. Reconstr. Surg. 100, (1997). Hobar, P. C., Masson, J. A., Wilson, R. & Zerwekh, J. The importance of the dura in craniofacial surgery. Plast. Reconstr. Surg. 98, (1996). Li, S., Quarto, N. & Longaker, M. T. Dura mater-derived FGF-2 mediates mitogenic signaling in calvarial osteoblasts. Am. J. Physiol. Cell. Physiol. 293, C (2007). Gosain, A. K. et al. Quantitative assessment of cranial defect healing and correlation with the expression of TGF-beta. J. Craniofac. Surg. 12, (2001). AnalysisReferences This study suggests that the in vivo osteogenic properties of dura are preserved with transplantation and can be harnessed to augment CSD healing. Future studies will focus on identifying factors responsible for cranial regeneration and engineering biocompatible grafts capable of mimicking dural induced osteogenesis. Additionally, future studies will aim at seeing if fetal dura has an even greater degree of osteogenic potential. Increased Pixel Density : Increased Bone Formation Defects treated with 8 day old dura achieved pixel density equivalent to intact cranial bone Pixel density of untreated defects was decreased 3 fold as compared to intact cranial bone Decreased Bone Gap : Increased Bone Formation Defects treated with 8 day old dura had the smallest bone gap and most bone formation Bone gap was largest in untreated defects Supporting evidence that dura becomes less osteogenic with age, the bone formation decreased as the age of the dura increased This is the first study to demonstrate that neonatal dura retains osteogenic potency following transplantation. This study supports that the osteogenic capability of dura decreases as the animal ages. Craniotomies were performed and 5x5 mm of parietal dura harvested from twenty- four Sprague Dawley rats at 8, 17, and 45 days postnatal. A 2.3 mm CSD was created in the parietal bone of twenty-four 60 day old Sprague Dawley rats. Animals were randomized into four experimental groups: A. 8-day old dura inlayed into CSD; B. 17-day old dura inlayed into CSD; C. 45 day old dura inlayed into CSD; or D. Untreated CSD. Four animals treated with 8-day old dura were evaluated five weeks post-operatively using micro-CT and the remaining animals were evaluated 8 weeks post-operatively with radiographs. Micro-CT images were analyzed for pixel density within the CSD. Radiographic images were evaluated by measuring the distance between new bone formation within the CSD and the edge of the cranial defect; we defined this as the bone gap. (1) 8,17,or 45 day old postnatal rat (3) Isolated dura mater(4) Inlayed dura mater (2) Isolated calvaria itical Sized Defects  Critical Sized Defects are defects incapable of healing in the animals lifetime  These are problematic for adults and children because vital structures are left unprotected  Interestingly, children < 1 year of age retain the ability to heal large cranial defects  Healing is due to the osteogenic potency of dura, however, potency decreases with age  Can the dural osteogenic potency present in children be harnessed to heal critical sized defects?  While the osteogenic properties of dura are thoroughly documented, the ability of dura to augment critical sized cranial defect (CSD) healing is less established  In the present study we evaluated whether transplanted dura retained sufficient osteogenic potential to aid in CSD repair Untreated Treated w/ 8 day old dura Untreated Treated w/ 8 day old dura