Performance of Repetitive Tasks Induces Decreased Grip Strength and Increased Fibrogenic Proteins in Skeletal Muscle: Role of Force and Inflammation

Authors

Samir M. Abdelmagid, Ann E. Barr, Mario Rico, Mamta Amin, Judith Litvin, Steven N. Popoff, Fayez F. Safadi, Mary F. Barbe

Abstract

This study elucidates exposure-response relationships between performance of repetitive tasks, grip strength declines, and fibrogenic-related protein changes in muscles, and their link to inflammation. Specifically, we examined forearm flexor digitorum muscles for changes in connective tissue growth factor (CTGF; a matrix protein associated with fibrosis), collagen type I (Col1; a matrix component), and transforming growth factor beta 1 (TGFB1; an upstream modulator of CTGF and collagen), in rats performing one of two repetitive tasks, with or without anti-inflammatory drugs. To examine the roles of force versus repetition, rats performed either a high repetition negligible force food retrieval task (HRNF), or a high repetition high force handle-pulling task (HRHF), for up to 9 weeks, with results compared to trained only (TR-NF or TR-HF) and normal control rats. Grip strength declined with both tasks, with the greatest declines in 9-week HRHF rats. Quantitative PCR (qPCR) analyses of HRNF muscles showed increased expression of Col1 in weeks 3–9, and CTGF in weeks 6 and 9. Immunohistochemistry confirmed PCR results, and also showed greater increases of CTGF and collagen matrix in 9-week HRHF rats than 9-week HRNF rats. ELISA, and immunohistochemistry revealed greater increases of TGFB1 in TR-HF and 6-week HRHF, compared to 6-week HRNF rats. To examine the role of inflammation, results from 6-week HRHF rats were compared to rats receiving ibuprofen or anti-TNF-α treatment in HRHF weeks 4–6. Both treatments attenuated HRHF-induced increases in CTGF and fibrosis by 6 weeks of task performance. Ibuprofen attenuated TGFB1 increases and grip strength declines, matching our prior results with anti-TNFα. Performance of highly repetitive tasks was associated with force-dependent declines in grip strength and increased fibrogenic-related proteins in flexor digitorum muscles. These changes were attenuated, at least short-term, by anti-inflammatory treatments.

Link to Article

http://dx.doi.org/10.1371/journal.pone.0038359

Early Response of Bone Marrow Osteoprogenitors to Skeletal Unloading and Sclerostin Antibody

Authors

Mohammad Shahnazari, Thomas Wronski, Vivian Chu, Alyssa Williams, Alicia Leeper, Marina Stolina, Hua Zhu Ke and Bernard Halloran

Abstract

Sclerostin functions as an antagonist to Wnt signaling and inhibits bone-forming activity. We studied the effects of skeletal unloading and treatment with sclerostin antibody (Scl-Ab) on mesenchymal stem cell, osteoprogenitor and osteoclast precursor pools, and their relationship to bone formation and resorption. Male C57BL/6 mice (5-months-old) were hind limb unloaded for 1 week or allowed normal ambulation and treated with Scl-Ab (25 mg/kg, s.c. injections on days 1 and 4) or placebo. Unloading decreased the serum concentration of bone formation marker P1NP (−35 %), number of colony-forming units (CFU) (−38 %), alkaline phosphatase–positive CFUs (CFU-AP+) (−51 %), and calcified nodules (−35 %); and resulted in a fourfold increase in the number of osteoclast precursors. The effects of Scl-Ab treatment on unloaded and normally loaded mice were nearly identical; Scl-Ab increased serum P1NP and the number of CFU, CFU-AP+, and calcified nodules in ex vivo cultures; and increased osteoblast and bone mineralizing surfaces in vivo. Although the marrow-derived osteoclast precursor population increased with Scl-Ab, the bone osteoclast surface did not change, and the serum concentration of osteoclast activity marker TRACP5b decreased. Our data suggest that short-term Scl-Ab treatment can prevent the decrease in osteoprogenitor population associated with skeletal unloading and increase osteoblast surface and bone mineralizing surface in unloaded animals. The anabolic effects of Scl-Ab treatment on bone are preserved during skeletal unloading. These findings suggest that Scl-Ab treatment can both increase bone formation and decrease bone resorption, and provide a new means for prevention and treatment of disuse osteoporosis.

Link to Article

http://dx.doi.org/10.1007/s00223-012-9610-9

The effects of PTH, loading and surgical insult on cancellous bone at the bone–implant interface in the rabbit

Authors

Anna Fahlgren, Xu Yang, Cesare Ciani, James A. Ryan, Natalie Kelly, Frank C. Ko, Marjolein C.H. van der Meulen, Mathias P.G. Bostrom

Abstract

Enhancing the quantity and quality of cancellous bone with anabolic pharmacologic agents may lead to more successful outcomes of non-cemented joint replacements. Using a novel rabbit model of cancellous bone loading, we examined two specific questions regarding bone formation at the bone–implant interface: (1) does the administration of intermittent PTH, a potent anabolic agent, and mechanical loading individually and combined enhance the peri-implant cancellous bone volume fraction; and, (2) does surgical trauma enhance the anabolic effect of PTH on peri-implant bone volume fraction. In this model, PTH enhanced peri-implant bone volume fraction by 30% in loaded bone, while mechanical loading alone increased bone volume fraction modestly (+ 10%). Combined mechanical loading and PTH treatment had no synergistic effect on any cancellous parameters. However, a strong combined effect was found in bone volume fraction with combined surgery and PTH treatment (+ 34%) compared to intact control limbs. Adaptive changes in the cancellous bone tissue included increased ultimate stress and enhanced remodeling activity. The number of proliferative osteoblasts increased as did their expression of pro-collagen 1 and PTH receptor 1, and the number of TRAP positive osteoclasts also increased. In summary, both loading and intermittent PTH treatment enhanced peri-implant bone volume, and surgery and PTH treatment had a strong combined effect. This finding is of clinical importance since enhancing early osseointegration in the post-surgical period has numerous potential benefits.

Link to Article

http://dx.doi.org/10.1016/j.bone.2012.05.005

Type 1 IFNs Suppress Accelerated Osteoclastogenesis and Prevent Loss of Bone Mass During Systemic Inflammatory Responses to Pneumocystis Lung Infection

Authors

Michelle Wilkison, Katherine Gauss, Yanchao Ran, Steve Searles, David Taylor, Nicole Meissner

Abstract

HIV infection causes loss of CD4+ T cells and type 1 interferon (IFN)–producing and IFN-responsive dendritic cells, resulting in immunodeficiencies and susceptibility to opportunistic infections, such as Pneumocystis. Osteoporosis and bone marrow failure are additional unexplained complications in HIV-positive patients and patients with AIDS, respectively. We recently demonstrated that mice that lack lymphocytes and type 1 IFN receptor (IFrag−/−) develop bone marrow failure after Pneumocystis lung infection, whereas lymphocyte-deficient, IFN α/β receptor–competent mice (RAG−/−) had normal hematopoiesis. Interestingly, infected IFrag−/− mice also exhibited bone fragility, suggesting loss of bone mass. We quantified bone changes and evaluated the potential connection between progressing bone fragility and bone marrow failure after Pneumocystis lung infection in IFrag−/− mice. We found that Pneumocystis infection accelerated osteoclastogenesis as bone marrow failure progressed. This finding was consistent with induction of osteoclastogenic factors, including receptor-activated nuclear factor-κB ligand and the proapoptotic factor tumor necrosis factor–related apoptosis-inducing ligand, in conjunction with their shared decoy receptor osteoprotegerin, in the bone marrow of infected IFrag−/− mice. Deregulation of this axis has also been observed in HIV-positive individuals. Biphosphonate treatment of IFrag−/− mice prevented bone loss and protected loss of hematopoietic precursor cells that maintained activity in vitro but did not prevent loss of mature neutrophils. Together, these data show that bone loss and bone marrow failure are partially linked, which suggests that the deregulation of the receptor-activated nuclear factor-κB ligand/osteoprotegerin/tumor necrosis factor–related apoptosis-inducing ligand axis may connect the two phenotypes in our model.

Link to Article

http://dx.doi.org/10.1016/j.ajpath.2012.03.023

Efficacy of zoledronic acid in treatment of osteoarthritis is dependent on the disease progression stage in rat medial meniscal tear model

Authors

De-gang Yu, Bo Yu, Yuan-qing Mao, Xin Zhao, Xiao-qing Wang, Hui-feng Ding, Lei Cao, Guang-wang Liu, Shao-bo Nie, Shen Liu and Zhen-an Zhu

Abstract

To investigate whether the stage of osteoarthritis (OA) progression influenced the efficacy of the third-generation bisphosphonate zoledronic acid in a rat medial meniscal tear model. Medial meniscal tear (MMT) was surgically induced in adult male Sprague Dawley rats. Zoledronic acid (ZOL, 100 μg/kg, sc, twice a week) was administered starting immediately, early (from 4 weeks) or late (from 8 weeks) after OA induction. The degeneration of articular cartilage was evaluated with toluidine blue O staining. Subchondral bone remodeling was evaluated with X-ray micro-CT scanning. Joint pain was measured with respect to weight-bearing asymmetry. Calcitonin gene-related peptide (CGRP) expression in dorsal root ganglia (DRGs) was examined using immunofluorescence analysis. The afferent neurons in DRGs innervating the joint were identified by retrograde labeling with fluorogold. Progressive cartilage loss was observed during 12 weeks after OA induction. Subchondral bone remodeling manifested as increased bone resorption at early stage (4 weeks), but as increased bone accretion at advanced stages (8 weeks). Immediately and early ZOL administration significantly improved subchondral microstructural parameters, attenuated cartilage degeneration, reduced weight-bearing asymmetry and CGRP expression, whereas the late ZOL administration had no significant effects. The stage of OA progression influences the efficacy of ZOL in treating joint degeneration and pain. To obtain the maximum efficacy, bisphosphonate treatment should be initiated in rat with early stages of OA pathogenesis.

Link to Article

http://dx.doi.org/10.1038/aps.2012.28

Intermittent PTH administration converts quiescent lining cells to active osteoblasts

Authors

Sang Wan Kim, Paola Divieti Pajevic, Martin Selig, Kevin J. Barry, Jae-Yeon Yang, Chan Soo Shin, Wook-Young Baek, Jung-Eun Kim, Henry M. Kronenberg

Abstract

Intermittent administration of parathyroid hormone (PTH) increases bone mass, at least in part, by increasing osteoblast number. One possible source of osteoblasts might be conversion of inactive lining cells to osteoblasts, and indirect evidence is consistent with this hypothesis. To better understand the possible effect of PTH on lining cell activation, a lineage tracing study was conducted using an inducible gene system. Dmp1-CreERt2 mice were crossed with ROSA26R reporter mice to render targeted mature osteoblasts and their descendents, lining cells and osteocytes, detectable by X-gal staining. Dmp1-CreERt2(+):ROSA26R mice were injected with 0.25 mg 4-OH-tamoxifen (4-OHTam) on postnatal day 3, 5, 7, 14, and 21. The animals were sacrificed on postnatal day 23, 33 or 43 (2, 12 or 22 days after the last 4-OHTam injection). On day 43, mice were challenged with a subcutaneous injection of human PTH (1–34, 80 µg/kg) or vehicle once daily for 3 days. By 22 days after the last 4-OHTam injection, most X-gal (+) cells on the periosteal surfaces of both the calvaria and tibia were flat. Moreover, bone formation rate and collagen I(α1) mRNA expression were decreased at day 43 compared to day 23. After 3 days of PTH injections, the thickness of X-gal (+) cells increased, as did their expression of osteocalcin and collagen I(α1) mRNA. Electron microscopy revealed X-gal-associated chromagen particles in both thin cells prior to PTH administration and cuboidal cells following PTH administration. These data support the hypothesis that intermittent PTH treatment can increase osteoblast number by converting lining cells to mature osteoblasts in vivo.

Link to Article

http://dx.doi.org/10.1002/jbmr.1665