Schoonraad SA, Jaimes AA, Singh AJX, Croland KJ, Bryant SJ. Osteogenic effects of covalently tethered rhBMP-2 and rhBMP-9 in an MMP-sensitive PEG hydrogel nanocomposite.
Acta Biomater 2023;
170:53-67. [PMID:
37634836 PMCID:
PMC10831697 DOI:
10.1016/j.actbio.2023.08.045]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 08/21/2023] [Accepted: 08/22/2023] [Indexed: 08/29/2023]
Abstract
While bone morphogenic protein-2 (BMP-2) is one of the most widely studied BMPs in bone tissue engineering, BMP-9 has been purported to be a highly osteogenic BMP. This work investigates the individual osteogenic effects of recombinant human (rh) BMP-2 and rhBMP-9, when tethered into a hydrogel, on encapsulated human mesenchymal stem cells (MSCs). A matrix-metalloproteinase (MMP)-sensitive hydrogel nanocomposite, comprised of poly(ethylene glycol) crosslinked with MMP-sensitive peptides, tethered RGD, and entrapped hydroxyapatite nanoparticles was used. The rhBMPs were functionalized with free thiols and then covalently tethered into the hydrogel by a thiol-norbornene photoclick reaction. rhBMP-2 retained its full bioactivity post-thiolation, while the bioactivity of rhBMP-9 was partially reduced. Nonetheless, both rhBMPs were highly effective at enhancing osteogenesis over 12-weeks in a chemically-defined medium. Expression of ID1 and osterix, early markers of osteogenesis; collagen type I, a main component of the bone extracellular matrix (ECM); and osteopontin, bone sialoprotein II and dentin matrix protein I, mature osteoblast markers, increased with increasing concentrations of tethered rhBMP-2 or rhBMP-9. When comparing the two BMPs, rhBMP-9 led to more rapid collagen deposition and greater mineralization long-term. In summary, rhBMP-2 retained its bioactivity post-thiolation while rhBMP-9 is more susceptible to thiolation. Despite this shortcoming with rhBMP-9, both rhBMPs when tethered into this hydrogel, enhanced osteogenesis of MSCs, leading to a mature osteoblast phenotype surrounded by a mineralized ECM. STATEMENT OF SIGNIFICANCE: Osteoinductive hydrogels are a promising vehicle to deliver mesenchymal stem cells (MSCs) for bone regeneration. This study examines the in vitro osteoinductive capabilities when tethered bone morphogenic proteins (BMPs) are incorporated into a degradable biomimetic hydrogel with cell adhesive ligands, matrix metalloproteinase sensitive crosslinks for cell-mediated degradation, and hydroxyapatite nanoparticles. This study demonstrates that BMP-2 is readily thiolated and tethered without loss of bioactivity while bioactivity of BMP-9 is more susceptible to immobilization. Nonetheless, when either BMP2 or BMP9 are tethered into this hydrogel, osteogenesis of human MSCs is enhanced, bone extracellular matrix is deposited, and a mature osteoblast phenotype is achieved. This bone-biomimetic hydrogel is a promising design for stem cell-mediated bone regeneration.
Collapse