103in Cba1/Runx2 (osteoblast marker) but no signifi cant relationship between age and
SOX9 (adipocyte marker). Similarly with osteogenic differentiation, Roura et al.
( 2006 ) also found a strong negative correlation with donor age when comparing two
groups with mean ages of 24 and 77. However, no signifi cant differences with age
were found when analysing adipogenic differentiation on CD105+ bone marrow
MSCs.
On the other hand, investigating osteogenic differentiation of infrapatellar fat
pad-derived MSCs found no differences with age of donor (Khan et al. 2009 ).
Alizarin red staining and AlkP enzyme activity assays also showed no difference
between the two age groups (mean ages 57 and 86 years old). Similarly, Evans et al.
( 1990 ) also noticed no change in osteogenic differentiation of MSCs obtained from
trabecular bone as osteocalcin levels, and AlkP synthesis did not show any change
with increasing donor age. When investigating chondrogenic d ifferentiation,
Scharstuhl et al. ( 2007 ) reported no age-dependant changes in differentiation after
investigating with 98 MSC samples from the femur.
5.5 Ageing and Cell Surface Characterisation
Cell surface character isation ha s been achieved by looking at cluster of differentia-
tion (CD) markers and cell surface proteins via fl ow cytometry and cell surface stain-
ing. The origin of the cell and its differentiation potential can be shown by
characterisation (Khan et al. 2009 ). The International Society for Cytotherapy has
suggested that for a population of cells to qualify as MSCs, they should have positive
expression for CD73, CD90 and CD105 and be negative for CD14, CD34, CD45 or
CD11b, CD79a or CD19 and HLA-DR surface molecules (Dominici et al. 2006 ).
There is little literature on the effect of age on cell surface characterisation. Khan
et al. ( 2009 ) found no differences of cell surface marker expression between two
groups with mean ages of 57 and 86 when investigating the effect of age on cell
surface characterisation using human fat pad-derived MSCs. Similar trends have
also been noted by Mareschi and colleagues in a study using BMSCs. They reported
that there was no signifi cant difference in the expression of cell surface markers
with age after analysing them throughout ten passages (77 days) (Mareschi et al.
2006 ). In comparison, Stolzing et al. ( 2008 ) reported that BMSCs were positive for
CD13, CD44, CD90, CD105, STRO-1 and D7-Fib, and of those markers the major-
ity (CD44, CD90, CD105 and STRO-1) were found to have signifi cant age-related
changes in expression when looking at three age groups (7–18 years old, 19–40
years old and >40 years old). It is important to determine how age affects cell sur-
face characterisation, as consistently expressed markers can then be used to isolate
MSC populations regardless of age of donor.
Although cell surface characterisation is important to identify cells, results between
studies are not always reliable as the expression of markers can differ depending on
the amount of time cells spent in culture, levels of foetal calf serum (FCS) in culture
medium which inhibits expression of some surface markers (Garcia-Pacheco et al.
2001 ), antib ody source and variability and donor variations (Fossett et al. 2012 ).
5 The Effects of Ageing on Proliferation Potential, Differentiation Potential...