Involvement of integrins in the adhesion of osteoblastic cells to a type-I collagen matrix

Abstract

Several biomaterials
have been developed with applications
in bone tissue engineering. In this context,
there is a growing interest in developing
bone implant materials with
improved biocompatibility and cell adhesion
properties. The aim of this
study was to research which integrin
receptors participate in the attachment
of osteoblastic-like cells to a type-
I collagen matrix. Two osteoblast-like
cells, the UMR106 rat osteosarcoma
cell line and the MC3T3E1 mouse calvaria-
derived cells, were analyzed.
Cells were plated for one hour either
on plastic or a type-I collagen film,
alone or co-incubated with different
peptides: (a) b-Peptide, a 13-aminoacid
oligopeptide corresponding to preserved
sequence 113-125 of the b-subunit
of integrin receptors; (b) RGD
(Arg-Gly-Asp), which corresponds to
the a-subunit recognition sequence of
a1,5b1 integrins; or (c) DGEA (Asp-Gly-
Glu-Ala), the a-subunit recognition
sequence of a2b1 integrins. Cell adhesion
and spreading were evaluated
microscopically after fixing and staining
the cells with Giemsa. The results
showed that osteoblast-like cells adhere
more easily to a type-I collagen
substratum than to plastic (86 ± 5 cells/
field vs. 69 ± 4 cells/field for type-I collagen
vs. plastic, respectively, p < 0.02).
The b-peptide inhibited the adhesion
of both cell lines to the collagen matrix
in dose-dependent way. Additionally, this peptide induced an increase
in UMR106 cells clumping and a decrease
in cells spreading. These morphological
features would suggest an
increase in cell-cell interactions and a
decrease in cell-matrix interactions,
possibly mediated by b-peptide. The
RGD and DGEA peptides significantly
decreased UMR106 and MC3T3E1 adhesion
to the collagen matrix (ranging
from 20 to 30 % inhibition). On the
other hand, UMR106 cells grown on
collagen in the presence of DGEA exhibited
greater spreading with cellular
extensions in multiple directions.
Altogether, the obtained results suggest
that both a and b subunits of several
integrin receptors are involved in
the attachment of osteoblast-like cells
to a type-I collagen matrix. The coating
of different biomaterials with specific
recognition peptides as well as
with whole collagen molecules, could
improve the boneintegration of implants
to be used in bone tissue repairing.