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M. Pilmane et al.
Investigation of Cow Bone Tissue Structure
Table 2
Distribution of relative number of the osteocytes and chondrocytes containing bone
morphogenetic protein, growth factor, and matrix metalloproteinases and
the occurrence of apoptosis in the visual field of cow’s humerus
No.
BMP2/4
FGFR1
Apoptosis
(TUNEL)
MMP2
MMP9
C
B
C
B
C
B
C
B
C
B
1.
+
–
+++
+
+++
+
++++
–
++++
++
2.
+
+
++++
+
++++
++
–
+
+++
+++
3.
+
+
++++
+
++++
++
+++
+++
++++
++
4.
+
+
+++
+
+++
++
+++
–
++
+
5.
+
–
+++
+
+++
++
++
+
++
+
Notations: C – cartilage; B – bone; MMP – matrix metalloproteinasis; BMP – bone morphogenetic protein;
FGFR – fibroblast growth factor receptor;
– – lack of cells containing BMP2/4, FGFR1, MMP2, MMP9, and absence of apoptosis;
+ – small number of cells containing BMP2/4, FGFR1, MMP2, and MMP9;
++ – moderate number of cells containing BMP2/4, FGFR1, MMP2, and MMP9;
+++ – numerous cells containing BMP2/4, FGFR1, MMP2, and MMP9;
++++ – significant number of cells containing BMP2/4, FGFR1, MMP2, and MMP9.
during lactation (Benzie et al., 1955). Bone provides
Ca for milk synthesis in lactating dairy cows (Horst
et al., 1997). Normally calcium found in cow’s milk
is supplied from both feeding and bone-resorption
sources in approximately equal proportions (Maylin
and Krook, 1982). However, the negative calcium
balance has been particularly noticed in lactating
cattle after calving (Beighle, 1999).
The other important changes in bone were
variations of osteocytes per mm2 and also
thinned trabecules in spongy bone. This might be
connected to the bone disease like osteoporosis,
because during this disorder morphofunctional
activity of osteoblasts is usually changed, which
is followed by decreased bone formation and
changes in osteocyte number. So, normally in
healthy humans, number of osteocytes decreases
for one third part from about 30 years of age until
90 years. Aging changes in bone cell number in
cows are not known, however, we suggest about
persistence of the same morphopathogenetical
principle in these animals. It means that number of
osteocytes increases while their lacunae decrease,
because osteoblasts produce lesser amount of
bone substance in comparison with intact bone,
which explains the thinned trabeculae (Mullender
et al., 1996). Additionally, osteoporosis is the most
common type of bone disease in humans and also
a problem in high productive cows. Osteopenia in
this disease means also decrease in the amount of
calcium and phosphorus in the bone, bones can
become weak and brittle, thus increasing the risk
for fractures (Dou, 2006). Disturbances in cows’
LLU Raksti 18 (313), 2007; 51-57
organism metabolism (milk fever) and skeletal
fluorosis are diseases bounded with osteoporosis.
These bone diseases have been described in some
regions of Canada (Obel, 1971; Shupe, 1972).
Interesting data have been found about presence of
growth factor BMP in bone and cartilage of seemingly
healthy cows, where it is known to stimulate growth.
Osteoinduction is the process of building, healing and
remodeling of bone stimulated by bone morphogenetic
proteins (Pecina et al., 2002). The investigations of
BMP have discovered a family of these substances in
human blood and bones able to promote the formation
of bone and skeleton and to help mend broken bones
(Reddi, 1994; Sakou, 1998).
The role of BMP in the cows investigated in the
present research seems more compensatory giving
evidence about stimulating of growth also in adult
animals with some problems in bones. FGFR was
detected mainly in cartilage in our animals and in lesser
amount it was expressed by bone cells. The research
suggests correlations and interactions between FGFR
and apoptosis, and both matrix metalloproteinases in
which distribution the same relation was observed. The
most important interaction between all these indices
indicates the growth and proliferation stimulating role
of FGF in the background of degradation in matrix,
mainly observed in cartilage (despite its almost
unchanged structure in routine slides) and apoptosis,
also mainly affecting the cartilage. The relations of
these factors also discover the real damage of the same
hyaline cartilage. Our data respond to the data about
fibroblast growth factors as family of growth factors
are involved not only in embryonic development,
55