Everyyear,>1millionpatientsundergobonerepairproceduresintheUnitedStates.Autologousbonegrafting remainsthepreferredtreatmentforbonedefects,butthispracticeislimitedbyboneavailabilityanddonorsite morbidity from harvesting the bone. Alternatively, the development of therapies that exploit the osteogenic potential of bone marrow-derived mesenchymal stem cells (bmMSCs) continues to be a priority in osteoregenerative medicine. However, efforts remain largely empirical due to poor understanding of the mechanismsregulatingbmMSCengraftmentandosteogenicactivityinvivo.Ourlong-termgoalistodevelopa regenerative therapy that is based on bioengineering an osteoinductive niche for human bmMSCs. We have foundthattheinvivopreservationofhumanbmMSCosteogenicpotentialdependsonsustainingproximityto endothelialcells(ECs)andonthetimelyengraftmentofbmMSCsasperivascularcells(Linetal.,PNAS2014). WehavealsofoundthatvascularnetworksbioengineeredusinghumaniliaccresttrabecularboneECs(bECs) couldspontaneouslyinduceosteogenicdifferentiationofbmMSCsatectopicsites.Incontrast,ECsfromother human tissues could not. In addition, we have identified five candidate genes (BMP2, BMP7, NOG, KITLG, MSX1)differentiallyupregulatedinbECs.Ouroverarchinghypothesisisthatbioengineeredmicrovesselslined withbECsserveasstablenichesforbmMSCsandautonomouslydriveosteogenesisviaregulationofspecific osteoinductivegenes.Moreover,wepostulatethatinducedpluripotentstemcells(iPSCs)couldofferaplentiful source of surrogate bECs, eliminating the need for harvesting autologous trabecular bone. To test these hypotheses and to elucidate the precise osteoinductive factors whereby human trabecular bECs uniquely regulateosteogenesis,weproposethreeSpecificAims.
In Aim -1,wewillbioengineervascularnetworkswith humanbECsandbmMSCsanddeterminethecapacitytoregeneratecritical-sizedorthotopicbonedefects.
In Aim -2, we will determine the factors responsible for the unique in vivo osteoinductive potential of human trabecular bECs. We will knockout each candidate bEC gene and will determine the effect on in vivo osteogenesis.Tothisend,wewillusealuciferase-reporterdrivenbythehumanosterixpromotertomeasure bmMSCosteogenicactivityviabioluminescence.
In Aim -3,wewilldetermineconditionstogeneratesurrogate bECsfromiPSCs.WewillexaminewhetheriPSC-derivedECs(iECs)acquireosteoinductivepropertiesupon transplantationintobonesitesandareinturnabletoautonomouslyregulatetheosteogenicactivityofbmMSCs in vivo. We will use our murine calvarial bone defect model to determine the extent of in vivo osteogenic education of iECs by measuring (i) transcriptional profile modifications (RNAseq) and (ii) osteoinductive propertiesinengraftediECs.Wewillalsodeterminethelong-term(16weeks)bonerepaircapabilityofconstructs containingiECsandwhetherimplantingpre-educatediECsimprovestheextentofbonerepair.Collectively,we envisionthisresearchcouldbecomethebasisforanewstrategyintherepairofbonedefects.

Public Health Relevance

Bone grafting remains as the preferred treatment for bone defects, but this practice is limited by donor site morbidity.Alternatively,weseektodeveloptherapiesthatexploitthebone-regeneratingpotentialofaspecific type of bone marrow-derived stem cells. Here, we propose studies to better understand the mechanisms by whichbloodvesselsregulatetheactivityofthesehumanstemcells.Weenvisionthisresearchwillpavetheway toamorerationaluseofstemcellsintheregenerationofbonedefects.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR069038-05
Application #
9898291
Study Section
Musculoskeletal Tissue Engineering Study Section (MTE)
Program Officer
Wang, Fei
Project Start
2016-05-16
Project End
2021-04-30
Budget Start
2020-05-01
Budget End
2021-04-30
Support Year
5
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Boston Children's Hospital
Department
Type
DUNS #
076593722
City
Boston
State
MA
Country
United States
Zip Code
02115
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