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CD44 deficiency inhibits unloading-induced cortical bone loss through downregulation of osteoclast activity.

Li Y, Zhong G, Sun W, Zhao C, Zhang P, Song J, Zhao D, Jin X, Li Q, Ling S, Li Y - Sci Rep (2015)

Bottom Line: We found that CD44 expression was upregulated during osteoclastogenesis.CD44 deficiency can reduce osteoclast activity and counteract cortical bone loss in the hindlimb of unloaded mice.These results suggest that therapeutic inhibition of CD44 may protect from unloading induced bone loss by inhibiting osteoclast activity.

View Article: PubMed Central - PubMed

Affiliation: State Key Lab of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China.

ABSTRACT
The CD44 is cellular surface adhesion molecule that is involved in physiological processes such as hematopoiesis, lymphocyte homing and limb development. It plays an important role in a variety of cellular functions including adhesion, migration, invasion and survival. In bone tissue, CD44 is widely expressed in osteoblasts, osteoclasts and osteocytes. However, the mechanisms underlying its role in bone metabolism remain unclear. We found that CD44 expression was upregulated during osteoclastogenesis. CD44 deficiency in vitro significantly inhibited osteoclast activity and function by regulating the NF-κB/NFATc1-mediated pathway. In vivo, CD44 mRNA levels were significantly upregulated in osteoclasts isolated from the hindlimb of tail-suspended mice. CD44 deficiency can reduce osteoclast activity and counteract cortical bone loss in the hindlimb of unloaded mice. These results suggest that therapeutic inhibition of CD44 may protect from unloading induced bone loss by inhibiting osteoclast activity.

No MeSH data available.


Related in: MedlinePlus

CD44 deficiency inhibits the osteoclast differentiation of BMMs in vitro.(A) Schematic presentation of BMMs cultures, BMMs from two-month-old WT and CD44 KO mice were cultured in medium with M-CSF (30 ng/ml) and RANKL (50 ng/ml) for 5 days. (B) The CD44 mRNA level and (C) protein level was determined in the process of osteoclast differentiation of WT BMMs by qPCR. The expression level was normalized to Gapdh. Data are the mean ± SEM. n=3; **p < 0.01, compared to 0 day. (D) Immunofluorescence for CD44 (green) in the process of osteoclastogenesis on day 0, 3 and 5. (E-I) The mRNA levels of Clc7, Trap, CathepsinK, Mmp9 and NFATc1 in WT and CD44 KO BMMs were analyzed by qPCR. The transcripts levels were normalized to Gapdh. All data are the mean ± SEM. n=3, *p < 0.05, **p < 0.01, compared to WT.
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f1: CD44 deficiency inhibits the osteoclast differentiation of BMMs in vitro.(A) Schematic presentation of BMMs cultures, BMMs from two-month-old WT and CD44 KO mice were cultured in medium with M-CSF (30 ng/ml) and RANKL (50 ng/ml) for 5 days. (B) The CD44 mRNA level and (C) protein level was determined in the process of osteoclast differentiation of WT BMMs by qPCR. The expression level was normalized to Gapdh. Data are the mean ± SEM. n=3; **p < 0.01, compared to 0 day. (D) Immunofluorescence for CD44 (green) in the process of osteoclastogenesis on day 0, 3 and 5. (E-I) The mRNA levels of Clc7, Trap, CathepsinK, Mmp9 and NFATc1 in WT and CD44 KO BMMs were analyzed by qPCR. The transcripts levels were normalized to Gapdh. All data are the mean ± SEM. n=3, *p < 0.05, **p < 0.01, compared to WT.

Mentions: Bone marrow monocytes (BMMs) isolated from bone marrow cells were induced into osteoclasts in the presence of M-CSF (30 ng/mL) and RANKL (50 ng/mL) (Fig. 1A). To investigate the potential role of CD44 in this process, we examined the changes of its mRNA and protein levels during osteoclastogenesis, and found that they progressively increased during this process. Specifically, CD44 mRNA levels increased 6-fold on day 3 after induction, and reached 17-fold on day 5 compared to day 0 (Fig. 1B). CD44 protein levels were also significantly increased during osteoclastogenesis (Fig. 1C, see Supplementary Fig. S1A online). Immunofluorescence for CD44 showed the same results (Fig. 1D). When comparing the osteoclast differentiation potential of BMMs from wild-type (WT) and CD44-deficient (KO) mice, the expression levels of molecular marker genes for osteoclast function, including Clc7, Trap, CathepsinK, and Mmp9, were significantly reduced during osteoclast differentiation (Fig. 1E–H), and the transcription factor NFATc1, which plays a critical role in osteoclast differentiation, was also decreased (Fig. 1I). Western blotting results also revealed a much lower levels of NFATc1 and TRAP5 in osteoclasts from CD44 KO mice than that from WT mice (see Supplementary Fig. S1B online). These results indicate that CD44 plays an important role in the process of osteoclastogenesis.


CD44 deficiency inhibits unloading-induced cortical bone loss through downregulation of osteoclast activity.

Li Y, Zhong G, Sun W, Zhao C, Zhang P, Song J, Zhao D, Jin X, Li Q, Ling S, Li Y - Sci Rep (2015)

CD44 deficiency inhibits the osteoclast differentiation of BMMs in vitro.(A) Schematic presentation of BMMs cultures, BMMs from two-month-old WT and CD44 KO mice were cultured in medium with M-CSF (30 ng/ml) and RANKL (50 ng/ml) for 5 days. (B) The CD44 mRNA level and (C) protein level was determined in the process of osteoclast differentiation of WT BMMs by qPCR. The expression level was normalized to Gapdh. Data are the mean ± SEM. n=3; **p < 0.01, compared to 0 day. (D) Immunofluorescence for CD44 (green) in the process of osteoclastogenesis on day 0, 3 and 5. (E-I) The mRNA levels of Clc7, Trap, CathepsinK, Mmp9 and NFATc1 in WT and CD44 KO BMMs were analyzed by qPCR. The transcripts levels were normalized to Gapdh. All data are the mean ± SEM. n=3, *p < 0.05, **p < 0.01, compared to WT.
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f1: CD44 deficiency inhibits the osteoclast differentiation of BMMs in vitro.(A) Schematic presentation of BMMs cultures, BMMs from two-month-old WT and CD44 KO mice were cultured in medium with M-CSF (30 ng/ml) and RANKL (50 ng/ml) for 5 days. (B) The CD44 mRNA level and (C) protein level was determined in the process of osteoclast differentiation of WT BMMs by qPCR. The expression level was normalized to Gapdh. Data are the mean ± SEM. n=3; **p < 0.01, compared to 0 day. (D) Immunofluorescence for CD44 (green) in the process of osteoclastogenesis on day 0, 3 and 5. (E-I) The mRNA levels of Clc7, Trap, CathepsinK, Mmp9 and NFATc1 in WT and CD44 KO BMMs were analyzed by qPCR. The transcripts levels were normalized to Gapdh. All data are the mean ± SEM. n=3, *p < 0.05, **p < 0.01, compared to WT.
Mentions: Bone marrow monocytes (BMMs) isolated from bone marrow cells were induced into osteoclasts in the presence of M-CSF (30 ng/mL) and RANKL (50 ng/mL) (Fig. 1A). To investigate the potential role of CD44 in this process, we examined the changes of its mRNA and protein levels during osteoclastogenesis, and found that they progressively increased during this process. Specifically, CD44 mRNA levels increased 6-fold on day 3 after induction, and reached 17-fold on day 5 compared to day 0 (Fig. 1B). CD44 protein levels were also significantly increased during osteoclastogenesis (Fig. 1C, see Supplementary Fig. S1A online). Immunofluorescence for CD44 showed the same results (Fig. 1D). When comparing the osteoclast differentiation potential of BMMs from wild-type (WT) and CD44-deficient (KO) mice, the expression levels of molecular marker genes for osteoclast function, including Clc7, Trap, CathepsinK, and Mmp9, were significantly reduced during osteoclast differentiation (Fig. 1E–H), and the transcription factor NFATc1, which plays a critical role in osteoclast differentiation, was also decreased (Fig. 1I). Western blotting results also revealed a much lower levels of NFATc1 and TRAP5 in osteoclasts from CD44 KO mice than that from WT mice (see Supplementary Fig. S1B online). These results indicate that CD44 plays an important role in the process of osteoclastogenesis.

Bottom Line: We found that CD44 expression was upregulated during osteoclastogenesis.CD44 deficiency can reduce osteoclast activity and counteract cortical bone loss in the hindlimb of unloaded mice.These results suggest that therapeutic inhibition of CD44 may protect from unloading induced bone loss by inhibiting osteoclast activity.

View Article: PubMed Central - PubMed

Affiliation: State Key Lab of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China.

ABSTRACT
The CD44 is cellular surface adhesion molecule that is involved in physiological processes such as hematopoiesis, lymphocyte homing and limb development. It plays an important role in a variety of cellular functions including adhesion, migration, invasion and survival. In bone tissue, CD44 is widely expressed in osteoblasts, osteoclasts and osteocytes. However, the mechanisms underlying its role in bone metabolism remain unclear. We found that CD44 expression was upregulated during osteoclastogenesis. CD44 deficiency in vitro significantly inhibited osteoclast activity and function by regulating the NF-κB/NFATc1-mediated pathway. In vivo, CD44 mRNA levels were significantly upregulated in osteoclasts isolated from the hindlimb of tail-suspended mice. CD44 deficiency can reduce osteoclast activity and counteract cortical bone loss in the hindlimb of unloaded mice. These results suggest that therapeutic inhibition of CD44 may protect from unloading induced bone loss by inhibiting osteoclast activity.

No MeSH data available.


Related in: MedlinePlus