Background
The casein kinase 2-interacting protein-1 (
CKIP-1
) is important in the development of osteoblasts and cardiomyocytes. However, the effects of
CKIP-1
on osteoblast precursor mesenchymal stem cells (MSCs) remain unclear. This study aimed to determine whether
CKIP-1
affects osteogenic differentiation in MSCs and explore the relationship of
CKIP-1
and inflammation.
Methods
Bone marrow MSCs of
CKIP-1
wild type (WT) and knockout (KO) mice were cultivated
in vitro
. Cell phenotype was analyzed by flow cytometry, colony formation was detected to study the proliferative ability. Osteogenic and adipogenic induction were performed. The osteogenic ability was explored by alizarin red staining, alkaline phosphatase (ALP) staining and ALP activity detection. Quantitative real-time polymerase chain reaction (qRT-PCR) was carried out to determine the mRNA expression levels of osteoblast marker genes. The adipogenic ability was detected by oil red O staining. Content of the bone was analyzed to observe the differences of bone imaging parameters including trabecular bone volume/tissue volume (BV/TV), bone surface area fraction/trabecular BV, trabecular number (Tb.N), and trabecular spacing (Tb.sp). Interleukin (IL)-1β was injected on WT mice of 2 months old and 18 months old, respectively. Difference in
CKIP-1
expression was detected by RT-PCR and western blot. The relationship between
CKIP-1
and inflammation was explored by RT-PCR and western blot.
Results
ALP assays, alizarin red staining, and qRT-PCR showed that MSCs derived from
CKIP-1
KO mice exhibited a stronger capability for osteogenesis. Micro-computed tomography detection showed that among 18-month-old mice,
CKIP-1
KO mice presented significantly higher bone mass compared with WT mice (
P
= 0.02). No significant difference was observed in 2-month-old mice.
In vivo
data showed that expression of
CKIP-1
was higher in the bone marrow of aging mice than in young mice (4.3-fold increase at the mRNA level,
P
= 0.04). Finally, the expression levels of
CKIP-1
in bone marrow (3.2-fold increase at the mRNA level,
P
= 0.03) and cultured MSCs were up-regulated on chronic inflammatory stimulation by IL-1β.
Conclusions
CKIP-1
is responsible for negative regulation of MSC osteogenesis with age-dependent effects. Increasing levels of inflammation with aging may be the primary factor responsible for higher expression levels of
CKIP-1
but may not necessarily affect MSC aging.