Limits...
LRP6 in mesenchymal stem cells is required for bone formation during bone growth and bone remodeling.

Li C, Williams BO, Cao X, Wan M - Bone Res (2014)

Bottom Line: Lipoprotein receptor-related protein 6 (LRP6) plays a critical role in skeletal development and homeostasis in adults.However, the role of LRP6 in mesenchymal stem cells (MSCs), skeletal stem cells that give rise to osteoblastic lineage, is unknown.Osterix(+) osteoprogenitors and osteocalcin(+) osteoblasts significantly reduced at the secondary spongiosa area, but only moderately decreased at the primary spongiosa area in mutant mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine , Baltimore, MD 21205, USA.

ABSTRACT
Lipoprotein receptor-related protein 6 (LRP6) plays a critical role in skeletal development and homeostasis in adults. However, the role of LRP6 in mesenchymal stem cells (MSCs), skeletal stem cells that give rise to osteoblastic lineage, is unknown. In this study, we generated mice lacking LRP6 expression specifically in nestin(+) MSCs by crossing nestin-Cre mice with LRP6(flox) mice and investigated the functional changes of bone marrow MSCs and skeletal alterations. Mice with LRP6 deletion in nestin(+) cells demonstrated reductions in body weight and body length at 1 and 3 months of age. Bone architecture measured by microCT (µCT) showed a significant reduction in bone mass in both trabecular and cortical bone of homozygous and heterozygous LRP6 mutant mice. A dramatic reduction in the numbers of osteoblasts but much less significant reduction in the numbers of osteoclasts was observed in the mutant mice. Osterix(+) osteoprogenitors and osteocalcin(+) osteoblasts significantly reduced at the secondary spongiosa area, but only moderately decreased at the primary spongiosa area in mutant mice. Bone marrow MSCs from the mutant mice showed decreased colony forming, cell viability and cell proliferation. Thus, LRP6 in bone marrow MSCs is essential for their survival and proliferation, and therefore, is a key positive regulator for bone formation during skeletal growth and remodeling.

No MeSH data available.


Related in: MedlinePlus

Mice with LRP6 deletion in nestin+ MSCs have decreased osteoblastogenesis in bone. (a and b) Representative immunofluorescence staining and quantitative analysis of Osx in the primary spongiosa area (a and b) and secondary spongiosa area (c and d) of in femur sections of 3-month-old male Lrp6+/+, Lrp6+/− and Lrp6−/− mice. Positive cells are in red. Nuclei are in blue. Scale bars=100 µm. Number of Osx-positive cells per mm2 tissue area (N.Osx+ cells/T.Ar). (e–h) Representative immunohistochemical staining and quantitative analysis of Ocn in the primary spongiosa area (e and f) and secondary spongiosa area (g and h) of in femur sections of 3-month-old male Lrp6+/+, Lrp6+/− and Lrp6−/− mice. Scale bars=100 µm. Number of Ocn-positive cells per mm2 tissue area (N.Ocn+ cells/T.Ar). A total of three femur sections from each mouse, and five mice per treatment group were analyzed. *P<0.05, **P<0.001, vs. Lrp6+/+ group. Ocn, osteocalcin; Osx, osterix.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4472141&req=5

fig5: Mice with LRP6 deletion in nestin+ MSCs have decreased osteoblastogenesis in bone. (a and b) Representative immunofluorescence staining and quantitative analysis of Osx in the primary spongiosa area (a and b) and secondary spongiosa area (c and d) of in femur sections of 3-month-old male Lrp6+/+, Lrp6+/− and Lrp6−/− mice. Positive cells are in red. Nuclei are in blue. Scale bars=100 µm. Number of Osx-positive cells per mm2 tissue area (N.Osx+ cells/T.Ar). (e–h) Representative immunohistochemical staining and quantitative analysis of Ocn in the primary spongiosa area (e and f) and secondary spongiosa area (g and h) of in femur sections of 3-month-old male Lrp6+/+, Lrp6+/− and Lrp6−/− mice. Scale bars=100 µm. Number of Ocn-positive cells per mm2 tissue area (N.Ocn+ cells/T.Ar). A total of three femur sections from each mouse, and five mice per treatment group were analyzed. *P<0.05, **P<0.001, vs. Lrp6+/+ group. Ocn, osteocalcin; Osx, osterix.

Mentions: Bone marrow MSCs are skeletal stem cells that give rise to osteoblastic lineage of cells.23 We next examined whether LRP6 deletion in osteoblasts affects the number of osterix-positive (Osx+) cells, which are osteoblast-deriving osteoprogenitors, and osteocalcin-positive (Ocn+) mature osteoblasts, by immunohistochemical analysis. A dramatic reduction in the numbers of Osx+ cells in secondary spongiosa area of femora were detected in the mutant mice relative to WT littermates (>80% in Figure 5c and 5d). Similarly, Ocn+ mature osteoblasts on bone surface of the secondary spongiosa area of femora in mutant mice were also dramatically reduced. Ocn+ cell number in homozygous Lrp6−/− mice was only 18% of those in WT mice (Figure 5g and 5h). Interestingly, the numbers of both Osx+ cells and Ocn+ cells at the primary spongiosa were not changed significantly relative to those of WT littermates (Figure 5a, 5b, 5e and 5f), indicating a primary role of LRP6 in regulating the function of MSCs during bone remodeling. Taken together, these results, in combination of the fact of smaller bone observed in 1-month-old mice, suggest that LRP6 is required for the functional maintenance of bone marrow MSCs and consequent bone formation in both bone growth in young mice and bone remodeling in adults.


LRP6 in mesenchymal stem cells is required for bone formation during bone growth and bone remodeling.

Li C, Williams BO, Cao X, Wan M - Bone Res (2014)

Mice with LRP6 deletion in nestin+ MSCs have decreased osteoblastogenesis in bone. (a and b) Representative immunofluorescence staining and quantitative analysis of Osx in the primary spongiosa area (a and b) and secondary spongiosa area (c and d) of in femur sections of 3-month-old male Lrp6+/+, Lrp6+/− and Lrp6−/− mice. Positive cells are in red. Nuclei are in blue. Scale bars=100 µm. Number of Osx-positive cells per mm2 tissue area (N.Osx+ cells/T.Ar). (e–h) Representative immunohistochemical staining and quantitative analysis of Ocn in the primary spongiosa area (e and f) and secondary spongiosa area (g and h) of in femur sections of 3-month-old male Lrp6+/+, Lrp6+/− and Lrp6−/− mice. Scale bars=100 µm. Number of Ocn-positive cells per mm2 tissue area (N.Ocn+ cells/T.Ar). A total of three femur sections from each mouse, and five mice per treatment group were analyzed. *P<0.05, **P<0.001, vs. Lrp6+/+ group. Ocn, osteocalcin; Osx, osterix.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4472141&req=5

fig5: Mice with LRP6 deletion in nestin+ MSCs have decreased osteoblastogenesis in bone. (a and b) Representative immunofluorescence staining and quantitative analysis of Osx in the primary spongiosa area (a and b) and secondary spongiosa area (c and d) of in femur sections of 3-month-old male Lrp6+/+, Lrp6+/− and Lrp6−/− mice. Positive cells are in red. Nuclei are in blue. Scale bars=100 µm. Number of Osx-positive cells per mm2 tissue area (N.Osx+ cells/T.Ar). (e–h) Representative immunohistochemical staining and quantitative analysis of Ocn in the primary spongiosa area (e and f) and secondary spongiosa area (g and h) of in femur sections of 3-month-old male Lrp6+/+, Lrp6+/− and Lrp6−/− mice. Scale bars=100 µm. Number of Ocn-positive cells per mm2 tissue area (N.Ocn+ cells/T.Ar). A total of three femur sections from each mouse, and five mice per treatment group were analyzed. *P<0.05, **P<0.001, vs. Lrp6+/+ group. Ocn, osteocalcin; Osx, osterix.
Mentions: Bone marrow MSCs are skeletal stem cells that give rise to osteoblastic lineage of cells.23 We next examined whether LRP6 deletion in osteoblasts affects the number of osterix-positive (Osx+) cells, which are osteoblast-deriving osteoprogenitors, and osteocalcin-positive (Ocn+) mature osteoblasts, by immunohistochemical analysis. A dramatic reduction in the numbers of Osx+ cells in secondary spongiosa area of femora were detected in the mutant mice relative to WT littermates (>80% in Figure 5c and 5d). Similarly, Ocn+ mature osteoblasts on bone surface of the secondary spongiosa area of femora in mutant mice were also dramatically reduced. Ocn+ cell number in homozygous Lrp6−/− mice was only 18% of those in WT mice (Figure 5g and 5h). Interestingly, the numbers of both Osx+ cells and Ocn+ cells at the primary spongiosa were not changed significantly relative to those of WT littermates (Figure 5a, 5b, 5e and 5f), indicating a primary role of LRP6 in regulating the function of MSCs during bone remodeling. Taken together, these results, in combination of the fact of smaller bone observed in 1-month-old mice, suggest that LRP6 is required for the functional maintenance of bone marrow MSCs and consequent bone formation in both bone growth in young mice and bone remodeling in adults.

Bottom Line: Lipoprotein receptor-related protein 6 (LRP6) plays a critical role in skeletal development and homeostasis in adults.However, the role of LRP6 in mesenchymal stem cells (MSCs), skeletal stem cells that give rise to osteoblastic lineage, is unknown.Osterix(+) osteoprogenitors and osteocalcin(+) osteoblasts significantly reduced at the secondary spongiosa area, but only moderately decreased at the primary spongiosa area in mutant mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine , Baltimore, MD 21205, USA.

ABSTRACT
Lipoprotein receptor-related protein 6 (LRP6) plays a critical role in skeletal development and homeostasis in adults. However, the role of LRP6 in mesenchymal stem cells (MSCs), skeletal stem cells that give rise to osteoblastic lineage, is unknown. In this study, we generated mice lacking LRP6 expression specifically in nestin(+) MSCs by crossing nestin-Cre mice with LRP6(flox) mice and investigated the functional changes of bone marrow MSCs and skeletal alterations. Mice with LRP6 deletion in nestin(+) cells demonstrated reductions in body weight and body length at 1 and 3 months of age. Bone architecture measured by microCT (µCT) showed a significant reduction in bone mass in both trabecular and cortical bone of homozygous and heterozygous LRP6 mutant mice. A dramatic reduction in the numbers of osteoblasts but much less significant reduction in the numbers of osteoclasts was observed in the mutant mice. Osterix(+) osteoprogenitors and osteocalcin(+) osteoblasts significantly reduced at the secondary spongiosa area, but only moderately decreased at the primary spongiosa area in mutant mice. Bone marrow MSCs from the mutant mice showed decreased colony forming, cell viability and cell proliferation. Thus, LRP6 in bone marrow MSCs is essential for their survival and proliferation, and therefore, is a key positive regulator for bone formation during skeletal growth and remodeling.

No MeSH data available.


Related in: MedlinePlus