102
higher for MSCs from older patients throughout passages 1–4. This is also supported
by Zhou et al. ( 2008 ) and Mareschi et al. ( 2006 ) who both reported a doubling time
for BMSCs of older donors that was almost double that of younger donor MSCs.
In comparison, many studies have reported no effect of age on proliferation of
MSCs. Acquiring 98 samples of MSCs from the femoral shaft, Scharstuhl and col-
leagues found no correlation of age with proliferation, as well as MSC yield and cell
size (Scharstuhl et al. 2007 ). A study extracting MSCs from the neck of femur
showed the same results as from the femoral neck: that proliferation has no correla-
tion with age of donor (Suva et al. 2004 ). No statistical relationship was found by
Phinney and colleagues when growth rates of 22 samples of MSCs from the iliac
crest were correlated against age (Phinney et al. 1999 ). One study using infrapatel-
lar fat pad-derived MSCs measured cell numbers on fi ve occasions (day 2, 4, 6, 8
and 10) using a haemocytometer for two age groups. The re were no signifi cant dif-
ferences between cell numbers from each group at each time point or any difference
between proliferation rates up to day 10 (Khan et al. 2009 ).
5.4 Ageing and Differentiation Potential
The ability o f MSCs to dif ferentiate in vitro makes them useful in cell-based thera-
pies; however, there is no conclusive answer as to whether MSC differentiation
potential is affected by age of donor. Most studies looking at the effect of age on
differentiation have explored osteogenic differentiation potential of MSCs. Some
work has suggested that osteogenic differentiation potential is the fi rst to be lost by
MSCs during ageing and that MSCs increase their adipogenic potential (Meunier
et al. 1971 ). However, other work states that adipogenic differentiation is lost fi rst
(Muraglia et al. 2000 ).
In 2008, Zhou and colleagues investigated the effect of age on osteoblastogenesis
of human BMSCs of 17–90-year-olds. When measuring alkaline phosphatase (AlkP)
enzyme activity, they reported that there was a signifi cant decrease of AlkP activity in
older donors compared to younger. Similar trends inferring that osteogenic differen-
tiation decreases with increasing age were confi rmed when semi- quantitative RT-PCR
analysis was carried out showing a signifi cantly greater expression of osteoblast
marker genes (Cbfa1/Runx2, osterix, AlkP, bone sialoprotein (BSP) and osteocalcin
(OC)) from BMSCs of younger donors (Zhou et al. 2008 ). A study by Stolzing et al.
( 2008 ) investigated osteogenic, chondrogenic and adipogenic differentiation potential
also using BMSCs, in three age groups: 7–18, 19–40 and >40 years old. Results
showed that the “Aged” group (>40 years old) had the lowest AlkP activity, lowest
amou nt of Oil Red O positive cells and lowest amount of GAG concentration com-
pared to the “Young” (7–18 years old) and “Adult” (19–40 years old) groups, imply-
ing that BMSCs from older donors had a decreased differentiation potential down all
three lineages. Interestingly, one study that also looked at mRNA expression by exe-
cuting quantitative RT-PCR found a positive correlation of RANKL (osteoclast
marker) and PPAR-gamma (adipocyte marker) with increasing age in BMSCs from
females but not males (Jiang et al. 2008 ). They also reported an age- related decrease
E. Fossett et al.