The effect of sputtered calcium phosphate coatings of different crystallinity on osteoblast differentiation.
BACKGROUND
Coating titanium implants with hydroxyapatite (HA) has been suggested to increase osseointegration by stimulating early osteoblast function. The goal of this study was to determine the extent to which the crystalline content of the HA surface affected osteoblast function in vitro.


METHODS
Osteoblasts were isolated from fetal rat calvaria. Titanium coupons were sputter coated and analyzed. Mineralized nodule formation on plastic using von Kossa staining was compared to tetracycline and procion dye labeling. Cell proliferation, adhesion, alkaline phosphatase activity, morphology and spreading, and cytoskeletal arrangement were analyzed. Reverse transcription-polymerase chain reaction (RT-PCR) was used to determine the expression of mRNA for specific proteins.


RESULTS
The percent crystallinity of coatings was 0% (HA1), 1.9% +/- 0.4% (HA2), and 66.4% +/- 2.8% (HA3). The nodule formation and cell number were greatest on titanium and HA3 compared to HA1 and HA2 (P < 0.01). At weeks 2 to 4, all samples showed strong alkaline phosphatase, osteocalcin, monocyte-colony stimulating factor (M-CSF), and receptor activator of nuclear factor kappa B ligand (RANKL) expression, but the specific activity of alkaline phosphatase decreased. Cell adherence was greater than 60% of applied cells for all surfaces except HA3. The cells were significantly more elongated on titanium, with no difference on the HA-coated surfaces. Actin filaments were arranged peripherally at 5 hours but arranged parallel to the long axis of the cell at 20 hours.


CONCLUSIONS
Procion labeling is a valid method for evaluating mineralized nodule formation on opaque surfaces. There were no major differences in osteoblast function using titanium or high-crystalline coatings, and most functions were decreased on amorphous or low-crystalline coatings.
Berube
Patricia
P
Department of Periodontics, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
Yang
Yunzhi
Y
Carnes
David L
DL
Stover
Robert E
RE
Boland
Edward J
EJ
Ong
Joo L
JL
D000818:Animals; D002130:Calcium Phosphates / Q000737:chemistry / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D020099:Coated Materials, Biocompatible; D004396:Coloring Agents; D018360:Crystallography, X-Ray; D017886:Durapatite / Q000737:chemistry* / Q000494:pharmacology*; D005333:Fetus; D050866:Liquid Crystals; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects*; D051381:Rats; D012886:Skull / Q000166:cytology; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014025:Titanium; D014227:Triazines
D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; D004396:Coloring Agents; D014227:Triazines; C011535:procion brilliant red H 3B; D017886:Durapatite; C020243:calcium phosphate; D014025:Titanium