title: Amorphous polyphosphate/amorphous calcium carbonate implant material with enhanced bone healing efficacy in a critical-size defect in rats.
abstract: In this study the effect of amorphous calcium carbonate (ACC) microparticles and amorphous calcium polyphosphate (polyP) microparticles (termed aCa-polyP-MP) on bone mineral forming cells/tissue was investigated in vitro and in vivo. The ACC particles (termed ACC-P10-MP) were prepared in the presence of Na-polyP. Only the combinations of polyP and ACC microparticles enhanced the proliferation rate of human mesenchymal stem cells (MSCs). Gene expression studies revealed that ACC causes an upregulation of the expression of the cell membrane-associated carbonic anhydrase IX (CA IX; formation of ACC), while the transcript level of the alkaline phosphatase (ALP; liberation of orthophosphate from polyP) changes only relatively little. In contrast, aCa-polyP-MP primarily induces ALP expression. If both components are applied together a strong stimulation of expression of both marker genes is observed. In order to investigate whether ACC also enhances bone regeneration induced by polyP in vivo, the particles were encapsulated into PLGA (poly(d,l-lactide-co-glycolide)) microspheres (diameter ~800 μm) and implanted into rat critical-size calvarial defects. The studies revealed that animals that received aCa-polyP-MP microspheres showed an increased rate of regeneration compared to β-tri-calcium phosphate (β-TCP) controls. This effect is even accelerated if microspheres with both aCa-polyP-MP and ACC-P10-MP (1 : 1 weight ratio) are applied, resulting in an almost complete restoration of the defect area after 12 weeks. qRT-PCR analyses of tissue sections through the regeneration zone with microspheres containing both aCa-polyP-MP and ACC-P10-MP revealed a significantly higher upregulation of expression of the marker genes compared to each of the components alone. The Young's moduli for microspheres containing aCa-polyP-MP (1.74 MPa) and aCa-polyP-MP/ACC-P10-MP (2.38 MPa) were markedly higher compared to β-TCP-controls (0.63 mPa). Our results show that the combined application of ACC and Ca-polyP (both in the amorphous state) opens new strategies for the development of regenerative implants for the reconstruction of bone defects.
authors.affiliation: ERC Advanced Investigator Grant Research Group at the Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, D-55128 Mainz, Germany.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Wang
authors.forename: Maximilian
authors.initials: M
authors.lastname: Ackermann
authors.forename: Shunfeng
authors.initials: S
authors.lastname: Wang
authors.forename: Emad
authors.initials: E
authors.lastname: Tolba
authors.forename: Meik
authors.initials: M
authors.lastname: Neufurth
authors.forename: Qingling
authors.initials: Q
authors.lastname: Feng
authors.forename: Heinz C
authors.initials: HC
authors.lastname: Schröder
authors.forename: Werner E G
authors.initials: WE
authors.lastname: Müller
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001861:Bone Regeneration; D002130:Calcium Phosphates / Q000737:chemistry*; D055119:Elastic Modulus; D006801:Humans; D019344:Lactic Acid / Q000737:chemistry*; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D008863:Microspheres; D010006:Osteoblasts / Q000166:cytology; D010012:Osteogenesis / Q000187:drug effects; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011122:Polyphosphates / Q000737:chemistry; D011312:Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D054457:Tissue Scaffolds
chemical_list: D002130:Calcium Phosphates; D011122:Polyphosphates; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; C020243:calcium phosphate; D000469:Alkaline Phosphatase