title: Nanofibrous spongy microspheres for the delivery of hypoxia-primed human dental pulp stem cells to regenerate vascularized dental pulp.
abstract: Dental pulp infection and necrosis are widespread diseases. Conventional endodontic treatments result in a devitalized and weakened tooth. In this work, we synthesized novel star-shaped polymer to self-assemble into unique nanofibrous spongy microspheres (NF-SMS), which were used to carry human dental pulp stem cells (hDPSCs) into the pulp cavity to regenerate living dental pulp tissues. It was found that NF-SMS significantly enhanced hDPSCs attachment, proliferation, odontogenic differentiation and angiogenesis, as compared to control cell carriers. Additionally, NF-SMS promoted vascular endothelial growth factor (VEGF) expression of hDPSCs in a 3D hypoxic culture. Hypoxia-primed hDPSCs/NF-SMS complexes were injected into the cleaned pulp cavities of rabbit molars for subcutaneous implantation in mice. After 4 weeks, the hypoxia group significantly enhanced angiogenesis inside the pulp chamber and promoted the formation of ondontoblast-like cells lining along the dentin-pulp interface, as compared to the control groups (hDPSCs alone group, NF-SMS alone group, and hDPSCs/NF-SMS group pre-cultured under normoxic conditions). Furthermore, in an in situ dental pulp repair model in rats, hypoxia-primed hDPSCs/NF-SMS were injected to fully fill the pulp cavity and regenerate pulp-like tissues with a rich vasculature and a histological structure similar to the native pulp.
  
  
  CONCLUSIONS
  Vascularization is key to the regeneration of many vital tissues. However, it is challenging to create a suitable microenvironment for stem cells to regenerate vascularized tissue structure. This manuscript reports a novel star-shaped block copolymer that self-assembles into unique nanofibrous spongy microspheres, which as an injectable scaffold recapitulate the cell-cell and cell-matrix interactions in development. Using a clinically-relevant surgical procedure and a hypoxic treatment, the nanofibrous spongy microspheres were used to deliver stem cells and successfully regenerate dental pulp with a rich vasculature and a complex histologic structure similar to that of the native dental pulp. The novel microspheres can likely be used to regenerate many other vascularized tissues.
authors.affiliation: Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48109, USA; State Key Laboratory of Military Stomatology, Department of Operative Dentistry and Endodontics, School of Stomatology, Fourth Military Medical University, Xi'an 710032, People's Republic of China.
authors.forename: Rong
authors.initials: R
authors.lastname: Kuang
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Zhanpeng
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Jin
authors.affiliation: Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Jiang
authors.initials: J
authors.lastname: Hu
authors.affiliation: Department of Anatomy and Cell Biology, School of Dental Medicine, University of Pennsylvania, 240 S. 40th Street, Philadelphia, PA 19104, USA.
authors.forename: Songtao
authors.initials: S
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Operative Dentistry and Endodontics, School of Stomatology, Fourth Military Medical University, Xi'an 710032, People's Republic of China. Electronic address: nilx2007@gmail.com.
authors.forename: Longxing
authors.initials: L
authors.lastname: Ni
authors.affiliation: Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48109, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Macromolecular Science and Engineering Center, University of Michigan, Ann Arbor, MI 48109, USA; Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA. Electronic address: mapx@umich.edu.
authors.forename: Peter X
authors.initials: PX
authors.lastname: Ma
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D015687:Cell Hypoxia; D049109:Cell Proliferation; D060833:Cellular Microenvironment; D003757:Dental Implantation; D003782:Dental Pulp / Q000098:blood supply* / Q000166:cytology*; D006801:Humans; D008819:Mice, Nude; D008863:Microspheres; D057139:Nanofibers / Q000737:chemistry* / Q000648:ultrastructure; D018919:Neovascularization, Physiologic; D011817:Rabbits; D011923:Rats, Nude; D012038:Regeneration; D033581:Stem Cell Transplantation; D013234:Stem Cells / Q000166:cytology*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D042461:Vascular Endothelial Growth Factor A
keywords: Biomaterial; Dental pulp; Hypoxic; Microcarrier; Regeneration; Stem cell
references.citation: Acta Biomater. 2010 Oct;6(10 ):3856-63
references.pmid: 20406702
references.citation: J Dent Res. 2002 Oct;81(10 ):695-700
references.pmid: 12351668
references.citation: Nat Biotechnol. 2003 Sep;21(9):1025-32
references.pmid: 12949568
references.citation: J Endod. 2009 May;35(5):673-81
references.pmid: 19410081
references.citation: Front Biosci (Elite Ed). 2011 Jan 01;3:788-800
references.pmid: 21196351
references.citation: Curr Med Chem. 2012;19(1):90-7
references.pmid: 22300081
references.citation: Tissue Eng Part C Methods. 2008 Jun;14(2):149-56
references.pmid: 18489245
references.citation: J Cell Sci. 2012 Jul 15;125(Pt 14):3343-56
references.pmid: 22467856
references.citation: Science. 1993 May 14;260(5110):920-6
references.pmid: 8493529
references.citation: Cytokine Growth Factor Rev. 2009 Oct-Dec;20(5-6):435-40
references.pmid: 19896887
references.citation: Acta Biomater. 2005 Nov;1(6):643-52
references.pmid: 16701845
references.citation: Proc Natl Acad Sci U S A. 2000 Dec 5;97(25):13625-30
references.pmid: 11087820
references.citation: Circ Res. 2003 Oct 3;93(7):664-73
references.pmid: 12958144
references.citation: Blood. 2005 Jan 15;105(2):659-69
references.pmid: 15374877
references.citation: Nat Rev Neurosci. 2004 Jun;5(6):437-48
references.pmid: 15152194
references.citation: Aust Endod J. 2008 Aug;34(2):52-67
references.pmid: 18666990
references.citation: Proc Natl Acad Sci U S A. 2010 Aug 24;107(34):15211-6
references.pmid: 20696917
references.citation: Endocr Rev. 1997 Feb;18(1):4-25
references.pmid: 9034784
references.citation: Science. 2002 Feb 8;295(5557):1014-7
references.pmid: 11834817
references.citation: Nat Rev Mol Cell Biol. 2006 Mar;7(3):211-24
references.pmid: 16496023
references.citation: Biomaterials. 2011 Nov;32(31):7822-30
references.pmid: 21663962
references.citation: Acta Biomater. 2010 Aug;6(8):3199-207
references.pmid: 20197122
references.citation: Mol Cell Biol. 1996 Sep;16(9):4604-13
references.pmid: 8756616
references.citation: Proc Natl Acad Sci U S A. 2003 May 13;100(10):5807-12
references.pmid: 12716973
references.citation: Nat Nanotechnol. 2011 Jan;6(1):13-22
references.pmid: 21151110
references.citation: Adv Healthc Mater. 2015 Sep 16;4(13):1993-2000
references.pmid: 26138254
references.citation: Oncogene. 2001 Nov 15;20(52):7624-34
references.pmid: 11753640
references.citation: Nature. 1992 Oct 29;359(6398):843-5
references.pmid: 1279431
references.citation: Science. 2003 Feb 7;299(5608):890-3
references.pmid: 12574630
references.citation: J Endod. 2003 Oct;29(10):638-43
references.pmid: 14606785
references.citation: Endod Dent Traumatol. 1992 Apr;8(2):45-55
references.pmid: 1521505
references.citation: Nat Med. 2003 Jun;9(6):685-93
references.pmid: 12778167
references.citation: J Endod. 2010 Oct;36(10):1633-7
references.pmid: 20850667
references.citation: Nat Med. 2003 Jun;9(6):677-84
references.pmid: 12778166
references.citation: J Endod. 2012 Jun;38(6):796-802
references.pmid: 22595115
references.citation: Nat Mater. 2011 May;10(5):398-406
references.pmid: 21499313
references.citation: Arch Oral Biol. 2002 Jul;47(7):529-36
references.pmid: 12208077
references.citation: Curr Opin Genet Dev. 1998 Oct;8(5):588-94
references.pmid: 9794818
references.citation: Biomaterials. 1999 Jun;20(12):1133-42
references.pmid: 10382829
references.citation: Science. 2001 Oct 19;294(5542):559-63
references.pmid: 11577199