Site-specific characteristics of bone marrow mesenchymal stromal cells modify the effect of aging on the skeleton

Authors

Dr. Xing Wang, Xuan Zou, Dr. Jing Zhao, Dr. Xia Wu, Dr. Lin Feng, Dr. Lingling E, Dongsheng Wang, Guilan Zhang, Dr. Helin Xing, and Dr. Hongchen Liu

Abstract

Bone is a self-renewing tissue. Bone marrow mesenchymal stromal cells (BMSCs) are located in the adult skeleton and are believed to be involved in the maintenance of skeletal homeostasis throughout life. With increasing age, the ability of the skeleton to repair itself decreases, possibly due to the reduced functional capacity of BMSCs. Recent evidence has suggested the existence of at least two populations of BMSCs with different embryonic origins that cannot be interchanged during stem cell recruitment: craniofacial BMSCs (neural crest origin) and appendicular BMSCs (mesoderm origin). Questions arise as to whether the site-specific characteristics alter the effect of aging on the skeleton. In this study, the effects of biological aging on human BMSCs were compared with BMSCs derived from craniofacial bone vs. BMSCs derived from the appendicular skeleton. The phenotype, proliferation and functional characteristics (osteogenic differentiation, cytokine secretion and bone formation in vivo) of the BMSCs were investigated. The results demonstrated that the proliferative capacity and osteogenic differentiation of the BMSCs decrease significantly with age both in vitro and in vivo. For age-matched groups, the osteogenic differentiation capacity of alveolar BMSCs was higher than that of femoral BMSCs in the middle-aged and old groups while there was no significant difference for the young groups. Compared with old alveolar BMSCs, old femoral BMSCs had a significantly longer population doubling time, a smaller colony-forming population and less bone formation in vivo while there was no significant difference for the young and middle-aged groups. Distinct differences in the expression of cytokine factors were also found. In conclusion, human BMSCs display an age-related decrease in functional capacity, and embryonic origins may play a critical role in mediating the aging rate of BMSCs. These data provide novel insights into the skeletal site-specific characteristics of aged BMSCs.

Link to Article

http://dx.doi.org/10.1089/rej.2015.1766

Hydrogen Sulfide Is a Novel Regulator of Bone Formation Implicated in the Bone Loss Induced by Estrogen Deficiency

Authors

Francesco Grassi, Abdul Malik Tyagi, John W. Calvert, Laura Gambari, Lindsey D. Walker, Mingcan Yu, Jerid Robinson, Jau-Yi Li, Gina Lisignoli, Chiara Vaccaro, Jonathan Adams, and Roberto Pacifici

Abstract

Hydrogen sulfide (H2S) is a gasotransmitter known to regulate bone formation and bone mass in unperturbed mice. However, it is presently unknown whether H2S plays a role in pathologic bone loss. Here we show that ovariectomy (ovx), a model of postmenopausal bone loss, decreases serum H2S levels and the bone marrow (BM) levels of two key H2S-generating enzymes, cystathione β-synthase (CBS) and cystathione γ-lyase (CSE). Treatment with the H2S-donor GYY4137 (GYY) normalizes serum H2S in ovx mice, increases bone formation and completely prevents the loss of trabecular bone induced by ovx. Mechanistic studies revealed that GYY increases murine osteoblastogenesis by activating Wnt signaling through increased production of the Wnt ligands Wnt16, Wnt2b, Wnt6 and Wnt10b in the BM. Moreover, in vitro treatment with 17β-estradiol upregulates the expression of CBS and CSE in human BM stromal cells (hSCs), while a H2S-releasing drug induces osteogenic differentiation of hSCs. In summary, regulation of H2S levels is a novel mechanism by which estrogen stimulates osteoblastogenesis and bone formation in mice and human cells. Blunted production of H2S contributes to ovx induced bone loss in mice by limiting the compensatory increase in bone formation elicited by ovx. Restoration of H2S levels is a potential novel therapeutic approach for postmenopausal osteoporosis.

Link to Article

http://dx.doi.org/10.1002/jbmr.2757

Gut-derived serotonin induced by depression promotes breast cancer bone metastasis through the RUNX2/PTHrP/RANKL pathway in mice

Authors

Jian‑Chun Zong, Xing Wang, Xiang Zhou, Chen Wang, Liang Chen, Liang‑Jun Yin, Bai‑Cheng He, Zhong‑Liang Deng

Abstract

Breast cancer metastasizes to the bone in a majority of patients with advanced disease resulting in bone destruction. The underlying mechanisms are complex, and both processes are controlled by an interaction between locally and systemically derived signals. Clinically, breast cancer patients with depression have a higher risk of bone metastasis, yet the etiology and mechanisms are yet to be elucidated. MDA‑MB‑231 breast cancer cells were used to establish a bone metastasis model by using intracardiac injection in nude mice. Chronic mild stress (CMS) was chosen as a model of depression in mice before and after inoculation of the cells. Knockdown of the RUNX‑2 gene was performed by transfection of the cells with shRNA silencing vectors against human RUNX‑2. A co‑culture system was used to test the effect of the MDA‑MB‑231 cells on osteoclasts and osteoblasts. RT‑PCR and western blotting were used to test gene and protein expression, respectively. We confirmed that depression induced bone metastasis by promoting osteoclast activity while inhibiting osteoblast differentiation. Free serotonin led to an increase in the expression of RUNX2 in breast cancer cells (MDA‑MB‑231), which directly inhibited osteoblast differentiation and stimulated osteoclast differentiation by the PTHrP/RANKL pathway, which caused bone destruction and formed osteolytic bone lesions. Additionally, the interaction between depression and breast cancer cells was interrupted by LP533401 or RUNX2 knockdown. In conclusion, depression promotes breast cancer bone metastasis partly through increasing levels of gut‑derived serotonin. Activation of RUNX2 in breast cancer cells by circulating serotonin appears to dissociate coupling between osteoblasts and osteoclasts, suggesting that the suppression of gut‑derived serotonin decreases the rate of breast cancer bone metastasis induced by depression.

Link to Article

http://www.spandidos-publications.com/10.3892/or.2015.4430

In vivo evaluation of biofunctionalized implant surfaces with a synthetic peptide (P-15) and its impact on osseointegration. A preclinical animal study

Authors

Christian M. Schmitt, Markus Koepple, Tobias Moest, Konrad Neumann, Tamara Weisel, Karl Andreas Schlegel

Abstract

The overall aim of the study was to investigate a biofunctionalized implant surface with electrochemically deposition of hydroxyapatite and the synthetic peptide (P-15) and its effect on osseointegration.

Three modified implant types of ANKYLOS® C/X implants were used; (1) machined implants used as negative control (M, n = 20), (2) implants with the FRIADENT® plus surface (grit blasted and acid-etched) used as positive control (P, n = 20), and (3) implants with a biomimetic surface consisting of hydroxyapatite and the synthetic 15 aminoacids containing peptide P-15 (BP, n = 40). The implants were randomly inserted in the mandibles of 10 beagle dogs following 4 months after tooth extraction (P1-P4). Three animals were sacrificed 2 and 7 days after implant insertion, respectively, and four animals were sacrificed 6 months post implant insertion. Bone-to-implant contacts (BICs) were analyzed via histomorphometrical analyses at five different region of interests (ROIs); two at the middle part on either side of the implant (ROI 1/4), two at the apical part of the implant at each side (ROI 2/3), and one at the tip of the implant (ROI 5).

All implant surfaces showed a high level of osseointegration and osteoconductivity. The cumulative implant survival rate (CSR) was 93.8%, 100% in the M, 85% in the P, and 95% in the BP group. No statistical difference in BICs at ROI 1/4, 2/3, and 5 could be shown between implant types following 2 and 7 days of healing. BIC values increased in all groups over time. After 6 months of healing the BP group showed superiority in BIC in ROI 2/3 (73.2 ± 15.6%) compared to the P (48.3 ± 10.6%) and M group (66.3 ± 30.2%) with a significant difference between BP and P (P = 0.002).

It is hypothesized, that the surface biofunctionalization improves peri-implant bone formation and remodeling, leading to an increased bone-to implant contact. However, within the limitations of the study set-up no benefit in the early phase of osseointegration could be established for dental implants with P-15 containing surface in this study.

Link to Article

http://dx.doi.org/10.1111/clr.12723

A comprehensive study of long-term skeletal changes after spinal cord injury in adult rats

Authors

Tiao Lin, Wei Tong, Abhishek Chandra, Shao-Yun Hsu, Haoruo Jia, Ji Zhu, Wei-Ju Tseng, Michael A Levine, Yejia Zhang, Shi-Gui Yan, X Sherry Liu, Dongming Sun, Wise Young & Ling Qin

Abstract

Spinal cord injury (SCI)-induced bone loss represents the most severe osteoporosis with no effective treatment. Past animal studies have focused primarily on long bones at the acute stage using adolescent rodents. To mimic chronic SCI in human patients, we performed a comprehensive analysis of long-term structural and mechanical changes in axial and appendicular bones in adult rats after SCI. In this experiment, 4-month-old Fischer 344 male rats received a clinically relevant T13 contusion injury. Sixteen weeks later, sublesional femurs, tibiae, and L4 vertebrae, supralesional humeri, and blood were collected from these rats and additional non-surgery rats for micro-computed tomography (µCT), micro-finite element, histology, and serum biochemical analyses. At trabecular sites, extreme losses of bone structure and mechanical competence were detected in the metaphysis of sublesional long bones after SCI, while the subchondral part of the same bones showed much milder damage. Marked reductions in bone mass and strength were also observed in sublesional L4 vertebrae but not in supralesional humeri. At cortical sites, SCI induced structural and strength damage in both sub- and supralesional long bones. These changes were accompanied by diminished osteoblast number and activity and increased osteoclast number and activity. Taken together, our study revealed site-specific effects of SCI on bone and demonstrated sustained inhibition of bone formation and elevation of bone resorption at the chronic stage of SCI.

Link to Article

http://dx.doi.org/10.1038%2Fboneres.2015.28

Prolonged performance of a high repetition low force task induces bone adaptation in young adult rats, but loss in mature rats

Authors

Vicky S. Massicotte, Nagat Frara, Michele Y. Harris, Mamta Amin, Christine K. Wade, Steven N. Popoff, Mary F. Barbe

Abstract

We have shown that prolonged repetitive reaching and grasping tasks lead to exposure-dependent changes in bone microarchitecture and inflammatory cytokines in young adult rats. Since aging mammals show increased tissue inflammatory cytokines, we sought here to determine if aging, combined with prolonged performance of a repetitive upper extremity task, enhances bone loss. We examined the radius, forearm flexor muscles, and serum from 16 mature (14–18 months of age) and 14 young adult (2.5–6.5 months of age) female rats after performance of a high repetition low force (HRLF) reaching and grasping task for 12 weeks. Young adult HRLF rats showed enhanced radial bone growth (e.g., increased trabecular bone volume, osteoblast numbers, bone formation rate, and mid-diaphyseal periosteal perimeter), compared to age-matched controls. Mature HRLF rats showed several indices of radial bone loss (e.g., decreased trabecular bone volume, and increased cortical bone thinning, porosity, resorptive spaces and woven bone formation), increased osteoclast numbers and inflammatory cytokines, compared to age-matched controls and young adult HRLF rats. Mature rats weighed more yet had lower maximum reflexive grip strength, than young adult rats, although each age group was able to pull at the required reach rate (4 reaches/min) and required submaximal pulling force (30 force-grams) for a food reward. Serum estrogen levels and flexor digitorum muscle size were similar in each age group. Thus, mature rats had increased bone degradative changes than in young adult rats performing the same repetitive task for 12 weeks, with increased inflammatory cytokine responses and osteoclast activity as possible causes.

Link to Article

http://dx.doi.org/10.1016/j.exger.2015.10.014