Chondrocyte p21(WAF1/CIP1) expression is increased by dexamethasone but does not contribute to dexamethasone-induced growth retardation in vivo

Combined growth hormone and insulin-like growth factor-1 rescues growth retardation in glucocorticoid-treated mdxmice but does not prevent osteopenia

Short stature and osteoporosis are common in Duchenne muscular dystrophy (DMD) and its pathophysiology may include an abnormality of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis, which is further exacerbated by long-term glucocorticoid (GC) treatment. Hence, an agent that has anabolic properties and may improve linear growth would be beneficial in this setting and therefore requires further exploration. A 5-week-old x-linked muscular dystrophy (mdx) mice were used as a model of DMD. They were treated with prednisolone ± GH + IGF-1 for 4 weeks and then compared to control mdx mice to allow the study of both growth and skeletal structure. GC reduced cortical bone area, bone fraction, tissue area and volume and cortical bone volume, as assessed by micro computed tomography (CT) In addition, GC caused somatic and skeletal growth retardation but improved grip strength. The addition of GH + IGF-1 therapy rescued the somatic growth retardation and induced additional improvements in grip strength (16.9% increase, P < 0.05 compared to control). There was no improvement in bone microarchitecture (assessed by micro-CT and static histomorphometry) or biomechanical properties (assessed by three-point bending). Serum bone turnover markers (Serum procollagen 1 intact N-terminal propeptide (P1NP), alpha C-terminal telopeptide (αCTX)) also remained unaffected. Further work is needed to maximise these gains before proceeding to clinical trials in boys with DMD.

Bone health in glucocorticoid-treated childhood acute lymphoblastic leukemia

Glucocorticoids (GCs) are widely used in the treatment of childhood acute lymphoblastic leukemia (ALL), but their long-term use is also associated with bone-related morbidities. Among others, growth deficit, decreased bone mineral density (BMD) and increased fracture rate are well-documented and severely impact quality of life. Unfortunately, no efficient treatment for the management of bone health impairment in patients and survivors is currently available. The overall goal of this review is to discuss the existing data on how GCs impair bone health in pediatric ALL and attempts made to minimize these side effects.

A comparison of the bone and growth phenotype of mdx, mdx:Cmah-/- and mdx:Utrn +/- murine models with the C57BL/10 wild-type mouse

The muscular dystrophy X-linked (mdx) mouse is commonly used as a mouse model of Duchenne muscular dystrophy (DMD). Its phenotype is, however, mild, and other mouse models have been explored. The mdx:Cmah^−/− mouse carries a human-like mutation in the Cmah gene and has a severe muscle phenotype, but its growth and bone development are unknown. In this study, we compared male mdx, mdx:Utrn^+/−, mdx:Cmah^−/− and wild-type (WT) mice at 3, 5 and 7 weeks of age to determine the suitability of the mdx:Cmah^−/− mouse as a model for assessing growth and skeletal development in DMD. The mdx:Cmah^−/− mice were lighter than WT mice at 3 weeks, but heavier at 7 weeks, and showed an increased growth rate at 5 weeks. Cortical bone fraction as assessed by micro-computed tomography was greater in both mdx and mdx:Cmah^−/− mice versus WT mice at 7 weeks. Tissue mineral density was also higher in mdx:Cmah^−/− mice at 3 and 7 weeks. Gene profiling of mdx:Cmah^−/− bone identified increased expression of Igf1, Igf1r and Vegfa. Both the mdx and mdx:Cmah^−/− mice showed an increased proportion of regulated bone marrow adipose tissue (BMAT) but a reduction in constitutive BMAT. The mdx:Cmah^−/− mice show evidence of catch-up growth and more rapid bone development. This pattern does not mimic the typical DMD growth trajectory and therefore the utility of the mdx:Cmah^−/− mouse for studying growth and skeletal development in DMD is limited. Further studies of this model may, however, shed light on the phenomenon of catch-up growth.

This article has an associated First Person interview with the first author of the paper.

Summary: Unlike boys with DMD, the mdx:Cmah^−/− mouse shows increased weight gain and more rapid bone development; therefore, its utility for studying growth and skeletal development in DMD is limited.

Targeting Cell Senescence for the Treatment of Age-Related Bone Loss

PURPOSE OF REVIEW

We review cell senescence in the context of age-related bone loss by broadly discussing aging mechanisms in bone, currently known inducers and markers of senescence, the senescence-associated secretory phenotype (SASP), and the emerging roles of senescence in bone homeostasis and pathology.

RECENT FINDINGS

Cellular senescence is a state of irreversible cell cycle arrest induced by insults or stressors including telomere attrition, oxidative stress, DNA damage, oncogene activation, and other intrinsic or extrinsic triggers and there is mounting evidence for the role of senescence in aging bone. Cellular aging also instigates a SASP that exerts detrimental paracrine and likely systemic effects. With aging, multiple cell types in the bone microenvironment become senescent, with osteocytes and myeloid cells as primary contributors to the SASP. Targeting undesired senescent cells may be a favorable strategy to promote bone anabolic and anti-resorptive functions in aging bone, with the possibility of improving bone quality and function with normal aging and/or disease.

Tabernaemontana catharinensis leaves exhibit topical anti-inflammatory activity without causing toxicity

BACKGROUND

Tabernaemontana catharinensis, popularly known as snake skin, has been empirically used as an anti-inflammatory to treat cutaneous skin disorders. However, no study proves its effectiveness as a topical anti-inflammatory.

STUDY DESIGN

We investigated the topical anti-inflammatory effect of T.catharinensis leaves crude extract (TcE) in irritant contact dermatitis models in mice and its preliminary toxicity profile.

METHODS

The topical anti-inflammatory effect was evaluated by ear thickness measurement, inflammatory cell infiltration (MPO activity measurement and histological procedure) and cytokines levels. TcE qualitative phytochemical analysis was performed by UHPLC-ESI-HRMS and the TcE effect (therapeutic dose; 10 µg/ear) on preliminary toxicological parameters was also evaluated (on the 14° day of experiment).

RESULTS

TcE (10 μg/ear) prevented the development of ear edema induced by cinnamaldehyde, capsaicin, arachidonic acid, phenol, and croton oil with maximum inhibition of 100% to cinnamaldehyde, arachidonic acid, phenol, and croton oil and 75 ± 6% to capsaicin. Besides, the TcE (10 μg/ear) also prevented the increase of MPO activity by 96 ± 2%, 48 ± 7%, 100%, 87 ± 8%, and 93 ± 4%, respectively, to the same irritant agents. The positive controls also prevented both ear edema and the increased of MPO activity by 100% and 42 ± 8% (HC-030031), 54 ± 6% and 80 ± 4% (SB-366791), 100% and 54 ± 5% (indomethacin), 100% and 80 ± 4% (dexamethasone in skin inflammation model induced by phenol) and 100% and 97 ± 3% (dexamethasone in inflammation model induced by croton oil), respectively. TcE also prevented the inflammatory cells infiltration and the increase of MIP-2, IL-1β and TNF-α levels irritant agents-induced. TcE topical anti-inflammatory effect may be attributed to the combined effect of indole alkaloids, terpenes, and phenolic compounds found in the extract and identified by dereplication method. The TcE' therapeutic dose proved to be safe in preliminary toxicological tests.

CONCLUSION

Our results suggest that TcE could be an interesting strategy for the treatment of inflammatory diseases.

Nasturtium officinale R. Br. effectively reduces the skin inflammation induced by croton oil via glucocorticoid receptor-dependent and NF-κB pathways without causing toxicological effects in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Inflammatory skin diseases treatments currently used cause adverse effects. Nasturtium officinale (watercress) is used popularly as an anti-inflammatory. However, until now, no study proved its effectiveness as a topical treatment to inflammatory skin diseases. The topical anti-inflammatory activity of N. officinale crude extract leaves (NoE) on an irritant contact dermatitis (ICD) model croton oil-induced in mice was investigated.

MATERIALS AND METHODS

ICD models were induced by a single (1 mg/ear; acute) or repeated (0.4 mg/ear; chronic; 9 days total) croton oil application. NoE and dexamethasone solutions' (diluted in acetone; 20 μL/ear) or NoE gel, dexamethasone gel and base gel (15 mg/ear) were topically applied immediately after croton oil application. The NoE topical anti-inflammatory effect was evaluated for inflammatory parameters (ear edema, inflammatory cells infiltration, and inflammatory cytokines levels). NoE topical anti-inflammatory mechanism (NF-κB pathway and effect glucocorticoid-like) were assessed by western blot and ear edema analyses, respectively. UHPLC-MS/MS chromatography, gels accelerated stability and preliminary study of adverse effects was also performed.

RESULTS

UHPLC-MS/MS of the NoE revealed the presence of coumaric acid, rutin, and ferulic acid. NoE gels stability study showed no relevant changes at low temperature. NoE, dexamethasone, NoE gel and dexamethasone gel inhibited the ear edema croton oil-induced by 82 ± 6% (1 mg/ear), 99 ± 1% (0.1 mg/ear), 81 ± 8% (3%) and 70 ± 6% (0.5%) for the acute model, and 49 ± 7% (1 mg/ear), 80 ± 4% (0.1 mg/ear), 41 ± 8% (3%) and 46 ± 14% (0.5%) for the chronic model, respectively. The same treatments also reduced the inflammatory cells infiltration by 62 ± 3% (1 mg/ear), 97 ± 2% (0.1 mg/ear), 60 ± 3% (3%) and 66 ± 6% (0.5%) for the acute model, respectively, and 25 ± 8% (1 mg/ear) to NoE and 83 ± 13% to dexamethasone to the chronic model. NoE and NoE gel reduced the pro-inflammatory cytokines levels (acute ICD model) by 62 ± 5% and 71 ± 3% (MIP-2) and 32 ± 3% and 44 ± 4% (IL-1β), while dexamethasone solution's and gel reduced by 79 ± 7% and 44 ± 4% to MIP-2 and 98 ± 2% and 83 ± 9% to IL-1β, respectively. NoE' and dexamethasone' solutions inhibited the reduction of IkB-α protein expression induced by croton oil by 100% and 80 ± 14%, respectively. Besides, the mifepristone (glucocorticoid receptor antagonist) pre-treatment prevented the topical anti-edematogenic effect of NoE' and dexamethasone' solutions by 61 ± 5% to NoE and 78 ± 16% to dexamethasone. The repeated topical application of NoE did not cause adverse effects.

CONCLUSION

Our results suggest the N. officinale use in the cutaneous inflammatory process treatment and demonstrate the NoE potential to develop a promising topical anti-inflammatory agent to treat inflammatory disorders.

Animal models to explore the effects of glucocorticoids on skeletal growth and structure

Glucocorticoids (GCs) are effective for the treatment of many chronic conditions, but their use is associated with frequent and wide-ranging adverse effects including osteoporosis and growth retardation. The mechanisms that underlie the undesirable effects of GCs on skeletal development are unclear, and there is no proven effective treatment to combat them. An in vivo model that investigates the development and progression of GC-induced changes in bone is, therefore, important and a well-characterized pre-clinical model is vital for the evaluation of new interventions. Currently, there is no established animal model to investigate GC effects on skeletal development and there are pros and cons to consider with the different protocols used to induce osteoporosis and growth retardation. This review will summarize the literature and highlight the models and techniques employed in experimental studies to date.

Growth and the Growth Hormone-Insulin Like Growth Factor 1 Axis in Children With Chronic Inflammation: Current Evidence, Gaps in Knowledge, and Future Directions

Growth failure is frequently encountered in children with chronic inflammatory conditions like juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis. Delayed puberty and attenuated pubertal growth spurt are often seen during adolescence. The underlying inflammatory state mediated by proinflammatory cytokines, prolonged use of glucocorticoid, and suboptimal nutrition contribute to growth failure and pubertal abnormalities. These factors can impair growth by their effects on the GH-IGF axis and also directly at the level of the growth plate via alterations in chondrogenesis and local growth factor signaling. Recent studies on the impact of cytokines and glucocorticoid on the growth plate further advanced our understanding of growth failure in chronic disease and provided a biological rationale of growth promotion. Targeting cytokines using biological therapy may lead to improvement of growth in some of these children, but approximately one-third continue to grow slowly. There is increasing evidence that the use of relatively high-dose recombinant human GH may lead to partial catch-up growth in chronic inflammatory conditions, although long-term follow-up data are currently limited. In this review, we comprehensively review the growth abnormalities in children with juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis, systemic abnormalities of the GH-IGF axis, and growth plate perturbations. We also systematically reviewed all the current published studies of recombinant human GH in these conditions and discussed the role of recombinant human IGF-1.

Promyelocytic leukemia zinc finger mediates glucocorticoid-induced cell cycle arrest in the chondroprogenitor cell line ATDC5

Glucocorticoids (GCs) affect the proliferation of growth plate chondrocytes. In this study, we investigated the role of the GC-inducible promyelocytic leukemia zinc finger (PLZF) gene in chondrocyte differentiation by using the chondrogenic cell line ATDC5. PLZF overexpression suppressed cell cycle progression (p < 0.01) and promoted differentiation into hypertrophic chondrocytes by inducing mRNA expression of alkaline phosphatase (p < 0.01), and the cyclin-dependent kinase (CDK) inhibitor p21 (p < 0.01). In contrast, PLZF knockdown impaired differentiation into hypertrophic chondrocytes and promoted cell cycle progression (p < 0.01). Treatment with the GC analogue dexamethasone (10(-6) M) suppressed cell cycle progression in ATDC5 cells. PLZF shRNA attenuated dexamethasone-induced cell cycle arrest (p < 0.01) by downregulating the mRNA expression of the CDK inhibitors p21 and p57 (p < 0.01). These results clearly indicated that PLZF promoted differentiation into hypertrophic chondrocytes and mediated dexamethasone-induced cell cycle arrest by regulating CDK inhibitors.

Increased linear bone growth by GH in the absence of SOCS2 is independent of IGF-1

Growth hormone (GH) signaling is essential for postnatal linear bone growth, but the relative importance of GHs actions on the liver and/or growth plate cartilage remains unclear. The importance of liver derived insulin like‐growth factor‐1 (IGF‐1) for endochondral growth has recently been challenged. Here, we investigate linear growth in Suppressor of Cytokine Signaling‐2 (SOCS2) knockout mice, which have enhanced growth despite normal systemic GH/IGF‐1 levels. Wild‐type embryonic ex vivo metatarsals failed to exhibit increased linear growth in response to GH, but displayed increased Socs2 transcript levels (P < 0.01). In the absence of SOCS2, GH treatment enhanced metatarsal linear growth over a 12 day period. Despite this increase, IGF‐1 transcript and protein levels were not increased in response to GH. In accordance with these data, IGF‐1 levels were unchanged in GH‐challenged postnatal Socs2^‐/‐ conditioned medium despite metatarsals showing enhanced linear growth. Growth‐plate Igf1 mRNA levels were not elevated in juvenile Socs2^‐/‐ mice. GH did however elevate IGF‐binding protein 3 levels in conditioned medium from GH challenged metatarsals and this was more apparent in Socs2^‐/‐ metatarsals. GH did not enhance the growth of Socs2^‐/‐ metatarsals when the IGF receptor was inhibited, suggesting that IGF receptor mediated mechanisms are required. IGF‐2 may be responsible as IGF‐2 promoted metatarsal growth and Igf2 expression was elevated in Socs2^‐/‐ (but not WT) metatarsals in response to GH. These studies emphasise the critical importance of SOCS2 in regulating GHs ability to promote bone growth. Also, GH appears to act directly on the metatarsals of Socs2^‐/‐ mice, promoting growth via a mechanism that is independent of IGF‐1. J. Cell. Physiol. 9999: 2796–2806, 2015. © 2015 Wiley Periodicals, Inc.

Knockdown of the cell cycle inhibitor p21 enhances cartilage formation by induced pluripotent stem cells

The limited regenerative capacity of articular cartilage contributes to progressive joint dysfunction associated with cartilage injury or osteoarthritis. Cartilage tissue engineering seeks to provide a biological substitute for repairing damaged or diseased cartilage, but requires a cell source with the capacity for extensive expansion without loss of chondrogenic potential. In this study, we hypothesized that decreased expression of the cell cycle inhibitor p21 would enhance the proliferative and chondrogenic potential of differentiated induced pluripotent stem cells (iPSCs). Murine iPSCs were directed to differentiate toward the chondrogenic lineage with an established protocol and then engineered to express a short hairpin RNA (shRNA) to reduce the expression of p21. Cells expressing the p21 shRNA demonstrated higher proliferative potential during monolayer expansion and increased synthesis of glycosaminoglycans (GAGs) in pellet cultures. Furthermore, these cells could be expanded ∼150-fold over three additional passages without a reduction in the subsequent production of GAGs, while control cells showed reduced potential for GAG synthesis with three additional passages. In pellets from extensively passaged cells, knockdown of p21 attenuated the sharp decrease in cell number that occurred in control cells, and immunohistochemical analysis showed that p21 knockdown limited the production of type I and type X collagen while maintaining synthesis of cartilage-specific type II collagen. These findings suggest that manipulating the cell cycle can augment the monolayer expansion and preserve the chondrogenic capacity of differentiated iPSCs, providing a strategy for enhancing iPSC-based cartilage tissue engineering.

Interleukin-1β promotes proliferation and inhibits differentiation of chondrocytes through a mechanism involving down-regulation of FGFR-3 and p21

The proinflammatory cytokine IL-1β is elevated in many childhood chronic inflammatory diseases as well as obesity and can be associated with growth retardation. Here we show that IL-1β affects bone growth by directly disturbing the normal sequence of events in the growth plate, resulting in increased proliferation and widening of the proliferative zone, whereas the hypertrophic zone becomes disorganized, with impaired matrix structure and increased apoptosis and osteoclast activity. This was also evident in vitro: IL-1β increased proliferation and caused a G1-to-S phase shift in the cell cycle in ATDC5 chondrocytes, accompanied by a reduction in fibroblast growth factor receptor-3 (FGFR-3) and its downstream gene, the cell-cycle inhibitor p21 and its family member p57, whereas the cell-cycle promoter E2F-2 was increased. The reduction in FGFR-3, p21, and p57 was followed by delayed cell differentiation, manifested by decreases in proteoglycan synthesis, mineralization, alkaline phosphatase activity, and the expression of Sox9, RunX2, collagen type II, collagen type X, and other matrix proteins. Taken together, we suggest that IL-1β alters normal chondrogenesis and bone growth through a mechanism involving down-regulation of FGFR-3 and p21.

SOCS2 is the critical regulator of GH action in murine growth plate chondrogenesis

Suppressor of Cytokine Signaling-2 (SOCS2) is a negative regulator of growth hormone (GH) signaling and bone growth via inhibition of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway. This has been classically demonstrated by the overgrowth phenotype of SOCS2(-/-) mice, which has normal systemic insulin-like growth factor 1 (IGF-1) levels. The local effects of GH on bone growth are equivocal, and therefore this study aimed to understand better the SOCS2 signaling mechanisms mediating the local actions of GH on epiphyseal chondrocytes and bone growth. SOCS2, in contrast to SOCS1 and SOCS3 expression, was increased in cultured chondrocytes after GH challenge. Gain- and loss-of-function studies indicated that GH-stimulated chondrocyte STATs-1, -3, and -5 phosphorylation was increased in SOCS2(-/-) chondrocytes but not in cells overexpressing SOCS2. This increased chondrocyte STAT signaling in the absence of SOCS2 is likely to explain the observed GH stimulation of longitudinal growth of cultured SOCS2(-/-) embryonic metatarsals and the proliferation of chondrocytes within. Consistent with this metatarsal data, bone growth rates, growth plate widths, and chondrocyte proliferation were all increased in SOCS2(-/-) 6-week-old mice as was the number of phosphorylated STAT-5-positive hypertrophic chondrocytes. The SOCS2(-/-) mouse represents a valid model for studying the local effects of GH on bone growth.

A semi-autonomous model of endochondral ossification for developmental tissue engineering

Bone tissue engineering is currently undergoing a paradigm shift regarding the concepts used to develop cell-based therapies for skeletal repair. In place of the "trial and error" approach, researchers aim at developing cellular concepts that mirror developmental and postnatal processes. Herein, we describe a model for in vivo endochondral remodeling of an in vitro derived cartilaginous intermediate and its applicability to bone engineering. In vitro differentiation of the continuous cell line, ATDC5, in pellet culture was enhanced in a medium containing ascorbic acid, insulin-transferrin-selenium, dexamethasone, and transforming growth factor β1, when compared with other tested preparations. This differentiation was characterized by the elevated expression of Collagen type II and X along with glycosaminoglycan (GAG) accumulation and the onset of hypertrophy. On combination with NuOss™, a clinically used bone void filler, and implantation in nude mice, the differentiated pellets further matured into GAG rich cartilaginous intermediates after 4 weeks. This was subsequently partially remodeled into osteocalcin-positive bone tissue after 8 weeks without further external manipulation, indicating the semi-autonomous nature of this implant. Mineralized tissue along with active osteoclast resorption and neo-angiogenesis was apparent throughout the implant. The bone volume was approximately eightfold higher (10.70%±0.99%) when using a cartilaginous intermediate (based on differentiated cell pellets) than when observed with cell-seeded scaffolds (1.19%±0.24% and 1.48%±0.35%), in both a differentiated and an undifferentiated state. This study highlights the potential of endochondral strategies for bone tissue engineering and allows the identification of the key cellular parameters for this process.

Altered bone development and an increase in FGF-23 expression in Enpp1(-/-) mice

Nucleotide pyrophosphatase phosphodiesterase 1 (NPP1) is required for the conversion of extracellular ATP into inorganic pyrophosphate (PP(i)), a recognised inhibitor of hydroxyapatite (HA) crystal formation. A detailed phenotypic assessment of a mouse model lacking NPP1 (Enpp1(-/-)) was completed to determine the role of NPP1 in skeletal and soft tissue mineralization in juvenile and adult mice. Histopathological assessment of Enpp1(-/-) mice at 22 weeks of age revealed calcification in the aorta and kidney and ectopic cartilage formation in the joints and spine. Radiographic assessment of the hind-limb showed hyper-mineralization in the talocrural joint and hypo-mineralization in the femur and tibia. MicroCT analysis of the tibia and femur disclosed altered trabecular architecture and bone geometry at 6 and 22 weeks of age in Enpp1(-/-) mice. Trabecular number, trabecular bone volume, structure model index, trabecular and cortical thickness were all significantly reduced in tibiae and femurs from Enpp1(-/-) mice (P<0.05). Bone stiffness as determined by 3-point bending was significantly reduced in Enpp1(-/-) tibiae and femurs from 22-week-old mice (P<0.05). Circulating phosphate and calcium levels were reduced (P<0.05) in the Enpp1(-/-) null mice. Plasma levels of osteocalcin were significantly decreased at 6 weeks of age (P<0.05) in Enpp1(-/-) mice, with no differences noted at 22 weeks of age. Plasma levels of CTx (Ratlaps™) and the phosphaturic hormone FGF-23 were significantly increased in the Enpp1(-/-) mice at 22 weeks of age (P<0.05). Fgf-23 messenger RNA expression in cavarial osteoblasts was increased 12-fold in Enpp1(-/-) mice compared to controls. These results indicate that Enpp1(-/-) mice are characterized by severe disruption to the architecture and mineralization of long-bones, dysregulation of calcium/phosphate homeostasis and changes in Fgf-23 expression. We conclude that NPP1 is essential for normal bone development and control of physiological bone mineralization.