Effects of acute 5-fluorouracil chemotherapy and insulin-like growth factor-I pretreatment on growth plate cartilage and metaphyseal bone in rats

Skeletal effects following developmental flame-retardant exposure are specific to sex and chemical class in the adult Wistar rat

Introduction: Accumulating evidence reveals that endocrine disrupting chemicals (EDCs) can disrupt aspects of metabolic programming, suggesting that skeletal development may be at risk, a possibility that is rarely examined. The commercial flame retardant (FR) mixture, Firemaster 550 (FM 550), has repeatedly been shown to negatively influence metabolic programming, raising concerns that skeletal integrity may consequently be impaired. We have previously shown that gestational and lactational exposure to 1,000 µg FM 550 negatively affected sex-specific skeletal traits in male, but not female, rats assessed at 6 months of age. Whether this outcome is primarily driven by the brominated (BFR) or organophosphate ester (OPFR) portions of the mixture or the effects persist to older ages is unknown. Materials and methods: To address this, in the present study, dams were orally exposed throughout gestation and lactation to either 1,000 μg BFR, 1,000 µg OPFR, or 2,000 µg FM 550. Offspring (n = 8/sex/exposure) were weaned at PND 21 and assessed for femoral cortical and trabecular bone parameters at 8 months of age by high-resolution X-ray micro-computed tomography (micro-CT). Serum levels of serotonin, osteocalcin, alkaline phosphatase, and calcium were quantified. Results: FM 550 affected both sexes, but the females were more appreciably impacted by the OPFRs, while the males were more vulnerable to the BFRs. Conclusion: Although sex specificity was expected due to the sexual dimorphic nature of skeletal physiology, the mechanisms accounting for the male- and female-specific phenotypes remain to be determined. Future work aims to clarify these unresolved issues.

The influence of antineoplastic agents on the peri-implant bone around osseointegrated titanium implants: an in vivo histomorphometric and immunohistochemical study

BACKGROUND AND OBJECTIVE

The interaction between antineoplastic drugs used for treating cancer and non-affected tissues remains poorly assessed and may be critical for maintaining the quality of life for patients during and after treatment. This pre-clinical study evaluated the effects of cisplatin (CIS) and 5-fluorouracil (5-FU) on the peri-implant repair process around osseointegrated titanium implants installed in the tibiae of rats.

MATERIAL AND METHODS

Were used 90 male rats, randomly divided into three groups (n = 30): physiological saline solution (PSS), CIS, and 5-FU. Titanium implants (4.0 × 2.2 mm) were inserted in both tibiae of all animals at day 0. The animals received either PSS, CIS, or 5-FU at 35 and 37 days. Euthanasia was performed at 50, 65, and 95 days after surgery. Histometric (bone/implant contact [BIC]) and bone area fraction occupancy (% BAFO), histological, and immunohistochemical (for bone morphogenetic protein 2/4 [BMP2/4], Runt-related transcription factor 2 [RUNX2], osteocalcin [OCN], and tartrate-resistant acid phosphatase [TRAP]) analyses were performed. Data were statistically analyzed.

RESULTS

Groups CIS and 5-FU presented lower BIC and lower BAFO as compared with PSS in all time points. The imbalance in bone turnover was observed by the lower number of BMP2/4-, RUNX2-, and OCN-positive cells/mm2 and the higher number of TRAP-positive cells/mm in groups CIS and 5-FU as compared with PSS in all time points. Persistent and exacerbated inflammation was observed in groups CIS and 5-FU.

CONCLUSIONS

Both antineoplastic agents interfered negatively in the bone turnover around osseointegrated titanium implants.

CLINICAL RELEVANCE

Closer and more careful follow-up of patients with osseointegrated implants that will undergo chemotherapy with either CIS or 5-FU shall be performed.

Antineoplastic agents aggravate the damages caused by nicotine on the peri-implant bone: an in vivo histomorphometric and immunohistochemical study in rats

OBJECTIVE

To assess the interaction between chemotherapy and normal tissues is critical to assure quality of life during and after the treatment of cancer. This study evaluated the influence of cisplatin (CIS) and 5-fluorouracil (5-FU) over the peri-implant tissues around osseointegrated titanium implants in animals previously exposed to nicotine. Materials and methods One hundred twenty male rats were divided into two groups, receiving via subcutaneous injection, either physiological saline solution (PSS) (n = 30) or nicotine hemissulfate (NIC) (n = 90) for 30 days prior to implants' placement. One titanium implant (4.0 × 2.2 mm) was installed in each tibia of all animals. PSS and NIC were continued for 30 days after surgery. Five days after cessation, rats were subdivided into three subgroups in accordance with systemic treatments with either PSS, CIS, or 5-FU. Euthanasia was performed at 50, 65, and 95 days post-surgery. Histometric, histopathological, and immunohistochemical analyses were performed.

RESULTS

NIC-CIS and NIC-5FU presented lower BIC (50, 65, and 95 days) and bone area fraction occupancy (BAFO) (65 and 95 days) than group NIC. Intense inflammatory infiltration, severe tissue breakdown, reduced expression of bone formation biomarkers, and upregulation of TRAP were observed in NIC-CIS and NIC-5FU when compared with group NIC. TRAP expression was significantly higher in NIC-5FU as compared with NIC-CIS at 50 and 95 days. Groups NIC, NIC-CIS, and NIC-5FU presented statistically significant negative impact in all outcome parameters than group PSS.

CONCLUSION

CIS and 5-FU severely disrupted the peri-implant tissues around osseointegrated implants in animals previously exposed to nicotine.

CLINICAL RELEVANCE

Assessing the interaction between chemotherapy and normal tissues is critical to assure quality of life during and after the cancer treatment.

IGF-1 TMJ injections enhance mandibular growth and bone quality in juvenile rats

OBJECTIVES

Dentofacial orthopaedic treatment of mandibular hypoplasia has unpredictable skeletal outcomes. Although several biomodulators including insulin-like growth factor 1 (IGF-1) are known to contribute to chondrocyte proliferation, their efficacy in modulating mandibular growth has not been validated. The aim of this study was to determine the effect of locally delivered IGF-1 on mandibular growth and condylar bone quality/quantity in juvenile rats.

SETTING AND SAMPLE POPULATION

Institutional vivarium using twenty-four 35-day-old male Sprague-Dawley rats.

METHODS

PBS or 40 µg/kg (low-dose) IGF-1 or 80 µg/kg (high-dose) IGF-1 was injected bilaterally into the temporomandibular joints of the rats at weekly intervals for four weeks. Cephalometric and micro-computed tomography measurements were used to determine mandibular dimensions. Bone and tissue mineral density, volume fraction and mineral content were determined, and serum IGF-1 concentrations assayed.

RESULTS

Intra-articular administration of high-dose IGF-1 contributed to a significant 6%-12% increase in mandibular body and condylar length compared to control and low-dose IGF-1-treated animals. Additionally, IGF-1 treatment resulted in a significant decrease in the angulation of the lower incisors to mandibular plane. Condylar bone volume, bone volume fraction, mineral content and mineral density were significantly increased with high-dose IGF-1 relative to control and low-dose IGF-1 groups. Serum IGF-1 levels were similar between all groups confirming limited systemic exposure to the locally administered IGF-1.

CONCLUSION

Local administration of high-dose 80 µg/kg IGF-1 enhances mandibular growth and condylar bone quality and quantity in growing rats. The findings have implications for modulating mandibular growth and potentially enhancing condylar bone health and integrity.

Synergistic effects of Ficus Carica extract and extra virgin olive oil against oxidative injury, cytokine liberation, and inflammation mediated by 5-Fluorouracil in cardiac and renal tissues of male albino rats

5-Fluorouracil (5-FU), a chemotherapeutic drug, has adverse effects on heart and kidney functions. Ficus Carica (fig) and extra virgin olive oil (EVOO) are natural sources which have antioxidant effects. This study investigated the synergistic effects of fig extract and EVOO against cardiac and renal damage induced by 5-FU. Forty rats were equally divided into five groups and treated with physiological saline (control), five intravenous injections of 5-FU (40 mg/kg b.w) (5-FU), fig (1 g/kg b.w/day, orally) with 5-FU (Fig/5-FU), EVOO (7 g/kg b.w/day, orally) with 5-FU (EVOO/5-FU), combined treatment of fig and EVOO with five 5-FU injections (Fig/EVOO/5-FU). After 30 days, blood and tissue samples (Heart and kidney) were collected to be used in the examinations. 5-FU significantly increased serum creatine kinase activity, renal biomarkers, cholesterol, triglycerides, C-reactive protein, tumor necrosis factor-α, and interleukin-1β as well as cardiac and renal lipid peroxides (malondialdehyde). Meanwhile, serum levels of immunoglobulins, interleukins (IL-10, IL-12), and antioxidants of heart and kidney tissues were significantly decreased in 5-FU group. It also downregulated cardiac and renal Bcl2, and upregulated cardiac troponin and renin gene expressions. As well, histological alterations clarified that 5-FU induced cardiac cell damage, distorted renal corpuscles and tubules, inflammatory cell infiltrations, and severe congestion and hemorrhage in the blood vessels. The treatment with fig and olive oil, especially the combined treatment, modulated the toxic effect of 5-FU on the heart and kidney. Our results revealed that fig extract and EVOO have a powerful antioxidant and many protective effects against cardiac and renal toxicity induced by 5-FU, especially when using fig and EVOO together as a combined treatment.

Release of CXCL12 From Apoptotic Skeletal Cells Contributes to Bone Growth Defects Following Dexamethasone Therapy in Rats

Dexamethasone (Dex) is known to cause significant bone growth impairment in childhood. Although previous studies have suggested roles of osteocyte apoptosis in the enhanced osteoclastic recruitment and local bone loss, whether it is so in the growing bone following Dex treatment requires to be established. The current study addressed the potential roles of chemokine CXCL12 in chondroclast/osteoclast recruitment and bone defects following Dex treatment. Significant apoptosis was observed in cultured mature ATDC5 chondrocytes and IDG-SW3 osteocytes after 48 hours of 10^-6  M Dex treatment, and CXCL12 was identified to exhibit the most prominent induction in Dex-treated cells. Conditioned medium from the treated chondrocytes/osteocytes enhanced migration of RAW264.7 osteoclast precursor cells, which was significantly inhibited by the presence of the anti-CXCL12 neutralizing antibody. To investigate the roles of the induced CXCL12 in bone defects caused by Dex treatment, young rats were orally gavaged daily with saline or Dex at 1 mg/kg/day for 2 weeks, and received an intraperitoneal injection of anti-CXCL12 antibody or control IgG (1 mg/kg, three times per week). Aside from oxidative stress induction systemically, Dex treatment caused reductions in growth plate thickness, primary spongiosa height, and metaphysis trabecular bone volume, which are associated with induced chondrocyte/osteocyte apoptosis and enhanced chondroclast/osteoclast recruitment and osteoclastogenic differentiation potential. CXCL12 was induced in apoptotic growth plate chondrocytes and metaphyseal bone osteocytes. Anti-CXCL12 antibody supplementation considerably attenuated Dex-induced chondroclast/osteoclast recruitment and loss of growth plate cartilage and trabecular bone. CXCL12 neutralization did not affect bone marrow osteogenic potential, adiposity, and microvasculature. Thus, CXCL12 was identified as a potential molecular linker between Dex-induced skeletal cell apoptosis and chondroclastic/osteoclastic recruitment, as well as growth plate cartilage/bone loss, revealing a therapeutic potential of CXCL12 functional blockade in preventing bone growth defects during/after Dex treatment. © 2018 American Society for Bone and Mineral Research.

Characterization of 5-Fluorouracil Daily Oral Dosing versus Dietary Restriction on Femoral Growth Plates in Rats

We evaluated the growth plates (GPs) of rats after a 14-day reduction in food consumption caused by either daily oral dosing with 5-fluorouracil (5-FU: a positive control reducing food consumption and affecting the GPs) or a direct reduction in food consumption to determine whether the observed changes were attributable to a direct effect of drug toxicity. Histomorphometric analyses of the femoral GP were performed for a nontreated (NT) control group, three groups treated with 5-FU (12, 15, and 18 mg/kg/day) and three groups with food intake restricted to levels corresponding to those consumed by the rats in the three 5-FU-treated groups. Compared with the NT group, the GP widths and the number of chondrocytes in the proliferative zone decreased significantly in all the 5-FU-treated groups and the dietary restriction groups. Importantly, no significant differences between the 5-FU-treated groups and the groups with matched dietary restrictions were seen for most parameters. Thus, the 14-day dietary restriction caused significant changes in the proliferative zone of the GP, and similar changes observed in the 5-FU-treated groups were presumed to result from the comparable reduction in food intake rather than being a direct toxic effect of the drug.

Bone Marrow Adipose Tissue and Skeletal Health

PURPOSE OF REVIEW

To summarize and discuss recent progress and novel signaling mechanisms relevant to bone marrow adipocyte formation and its physiological/pathophysiological implications for bone remodeling.

RECENT FINDINGS

Skeletal remodeling is a coordinated process entailing removal of old bone and formation of new bone. Several bone loss disorders such as osteoporosis are commonly associated with increased bone marrow adipose tissue. Experimental and clinical evidence supports that a reduction in osteoblastogenesis from mesenchymal stem cells at the expense of adipogenesis, as well as the deleterious effects of adipocyte-derived signaling, contributes to the etiology of osteoporosis as well as bone loss associated with aging, diabetes mellitus, post-menopause, and chronic drug therapy. However, this view is challenged by findings indicating that, in some contexts, bone marrow adipose tissue may have a beneficial impact on skeletal health. Further research is needed to better define the role of marrow adipocytes in bone physiology/pathophysiology and to determine the therapeutic potential of manipulating mesenchymal stem cell differentiation.

Astragalus Extract Mixture HT042 Increases Longitudinal Bone Growth Rate by Upregulating Circulatory IGF-1 in Rats

Astragalus extract mixture HT042 is a standardized ingredient of health functional food approved by Korean FDA with a claim of “height growth of children.” HT042 stimulates bone growth rate and increases local IGF-1 expression in growth plate of rats which can be considered as direct stimulation of GH and its paracrine/autocrine actions. However, it remains unclear whether HT042 stimulates circulatory IGF-1 which also plays a major role to stimulate bone growth. To determine the effects on circulatory IGF-1, IGF-1 and IGFBP-3 expressions and phosphorylation of JAK2/STAT5 were evaluated in the liver after 10 days of HT042 administration. HT042 upregulated liver IGF-1 and IGFBP-3 mRNA expression, IGF-1 protein expression, and phosphorylation of JAK2/STAT5. HT042 also increased bone growth rate and proliferative zonal height in growth plate. In conclusion, HT042 stimulates bone growth rate via increment of proliferative rate by upregulation of liver IGF-1 and IGFBP-3 mRNA followed by IGF-1 protein expression through phosphorylation of JAK2/STAT5, which can be regarded as normal functioning of GH-dependent endocrine pathway.

The potential protective role of taurine against 5-fluorouracil-induced nephrotoxicity in adult male rats

Nephrotoxicity is common with the use of the chemotherapeutic agent 5-Fluorouracil (5-FU). The current study aimed to investigate the probable protective effect of taurine (TAU) against 5-FU-induced nephrotoxicity in rats using biochemical, histological and ultrastructural approaches. Twenty-four rats were equally divided into control, TAU, 5-FU and 5-FU+TAU groups. 5-FU significantly elevated levels of blood urea nitrogen (BUN), creatinine, and uric acid; while it reduced activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). Also, 5-FU induced significant elevation in malondialdehyde (MDA) levels accompanied with marked decline in γ-glutamyltranspeptidase (GGT) and alkaline phosphatase (AP) levels in kidney tissues. These biochemical alterations were accompanied by histopathological changes marked by destruction of the normal renal structure, in addition to ultrastructural alterations represented by thickened and irregular glomerular basement membranes, congested glomerular capillaries, damaged lining fenestrated endothelium, mesangial cells hyperplasia with expanded mesangial matrix, and distorted podocyte's processes. Also, the proximal (PCT) and distal (DCT) convoluted tubules showed thickened basement membranes, destructed apical microvilli and loss of basal infoldings of their epithelial cells. Administration of TAU to 5-FU-treated rats reversed most of the biochemical, histological, and ultrastructural alterations. These results indicate that TAU has a protective effect against 5-FU-induced nephrotoxicity.

Combination chemotherapy with cyclophosphamide, epirubicin and 5-fluorouracil causes trabecular bone loss, bone marrow cell depletion and marrow adiposity in female rats

The introduction of anthracyclines to adjuvant chemotherapy has increased survival rates among breast cancer patients. Cyclophosphamide, epirubicin and 5-fluorouracil (CEF) combination therapy is now one of the preferred regimens for treating node-positive breast cancer due to better survival with less toxicity involved. Despite the increasing use of CEF, its potential in causing adverse skeletal effects remains unclear. Using a mature female rat model mimicking the clinical setting, this study examined the effects of CEF treatment on bone and bone marrow in long bones. Following six cycles of CEF treatment (weekly intravenous injections of cyclophosphamide at 10 mg/kg, epirubicin at 2.5 mg/kg and 5-flurouracil at 10 mg/kg), a significant reduction in trabecular bone volume was observed at the metaphysis, which was associated with a reduced serum level of bone formation marker alkaline phosphatase (ALP), increased trends of osteoclast density and osteoclast area at the metaphysis, as well as an increased size of osteoclasts being formed from the bone marrow cells ex vivo. Moreover, a severe reduction of bone marrow cellularity was observed following CEF treatment, which was accompanied by an increase in marrow adipose tissue volume. This increase in marrow adiposity was associated with an expansion in adipocyte size but not in marrow adipocyte density. Overall, this study indicates that six cycles of CEF chemotherapy may induce some bone loss and severe bone marrow damage. Mechanisms for CEF-induced bone/bone marrow pathologies and potential preventive strategies warrant further investigation.

Genetically engineered flavonol enriched tomato fruit modulates chondrogenesis to increase bone length in growing animals

Externally visible body and longitudinal bone growth is a result of proliferation of chondrocytes. In growth disorder, there is delay in the age associated increase in height. The present study evaluates the effect of extract from transgenic tomato fruit expressing AtMYB12 transcription factor on bone health including longitudinal growth. Constitutive expression of AtMYB12 in tomato led to a significantly enhanced biosynthesis of flavonoids in general and the flavonol biosynthesis in particular. Pre-pubertal ovary intact BALB/c mice received daily oral administration of vehicle and ethanolic extract of wild type (WT-TOM) and transgenic AtMYB12-tomato (MYB12-TOM) fruits for six weeks. Animal fed with MYB12-TOM showed no inflammation in hepatic tissues and normal sinusoidal Kupffer cell morphology. MYB12-TOM extract significantly increased tibial and femoral growth and subsequently improved the bone length as compared to vehicle and WT-TOM. Histomorphometry exhibited significantly wider distal femoral and proximal tibial growth plate, increased number and size of hypertrophic chondrocytes in MYB12-TOM which corroborated with micro-CT and expression of BMP-2 and COL-10, marker genes for hypertrophic cells. We conclude that metabolic reprogramming of tomato by AtMYB12 has the potential to improve longitudinal bone growth thus helping in achievement of greater peak bone mass during adolescence.

The Protective Effects of Exclusive Enteral Nutrition Formulas on Growth Factor Expression and the Proximal Tibial Epiphyseal Growth Plate in a TNBS-Induced IBD Rat Model

OBJECTIVE

This study aimed to evaluate the effectiveness of different types of nutritional formulas in a rat model of TNBS-induced IBD.

METHODS

IBD was induced with TNBS in 4-week-old rats that were then fed different exclusive enteral nutrition diets for 7 days. The length of the tibia and the number of chondrocytes in the proximal tibias were analyzed at 7 days after supplementation. Immunohistochemical analysis, ELISA and real-time PCR were performed to evaluate the levels of growth hormone receptor (GHR) and insulin-like growth factor-I receptor (IGF-IR), the growth factors IGF-I and insulin-like growth factor-binding protein-3 (IGFBP3) , bone morphogenetic protein (BMP)-2 and BMP-6 respectively.

RESULTS

The results demonstrated that the tibia length of the peptide formula group was longer than that of the IBD-Modulen(®) formula and normal diet groups (P < 0.05). Furthermore, the number of chondrocytes of the proximal tibial was more pronounced in the peptide formula group compared to the other groups (P < 0.05). The peptide formula was also more effective in increasing the expression of GHR compared to the other groups (P < 0.05), while the expression of IGF-IR was not significantly different (P > 0.05). In addition, the IGF-I and IGFBP3 levels were more pronounced in the peptide formula supplement group (P < 0.05), and the expression of BMP-2 and BMP-6 mRNA in the proximal tibia growth plate from the peptide formula group was higher than that in the ordinary formula and normal diet groups (P < 0.05).

CONCLUSIONS

EEN, and particularly a peptide formula, exerted protective effects on the proximal tibial epiphyseal growth plate in a TNBS-induced IBD model.

Dietary emu oil supplementation suppresses 5-fluorouracil chemotherapy-induced inflammation, osteoclast formation, and bone loss

Cancer chemotherapy can cause osteopenia or osteoporosis, and yet the underlying mechanisms remain unclear, and currently, no preventative treatments are available. This study investigated damaging effects of 5-fluorouracil (5-FU) on histological, cellular, and molecular changes in the tibial metaphysis and potential protective benefits of emu oil (EO), which is known to possess a potent anti-inflammatory property. Female dark agouti rats were gavaged orally with EO or water (1 ml·day(-1)·rat(-1)) for 1 wk before a single ip injection of 5-FU (150 mg/kg) or saline (Sal) was given. The treatment groups were H(2)O + Sal, H(2)O + 5-FU, EO + 5-FU, and EO + Sal. Oral gavage was given throughout the whole period up to 1 day before euthanasia (days 3, 4, and 5 post-5-FU). Histological analysis showed that H(2)O + 5-FU significantly reduced heights of primary spongiosa on days 3 and 5 and trabecular bone volume of secondary spongiosa on days 3 and 4. It reduced density of osteoblasts slightly and caused an increase in the density of osteoclasts on trabecular bone surface on day 4. EO supplementation prevented reduction of osteoblasts and induction of osteoclasts and bone loss caused by 5-FU. Gene expression studies confirmed an inhibitory effect of EO on osteoclasts since it suppressed 5-FU-induced expression of proinflammatory and osteoclastogenic cytokine TNFα, osteoclast marker receptor activator of nuclear factor-κB, and osteoclast-associated receptor. Therefore, this study demonstrated that EO can counter 5-FU chemotherapy-induced inflammation in bone, preserve osteoblasts, suppress osteoclast formation, and potentially be useful in preventing 5-FU chemotherapy-induced bone loss.

Methotrexate chemotherapy reduces osteogenesis but increases adipogenic potential in the bone marrow

Intensive use of cancer chemotherapy is increasingly linked with long-term skeletal side effects such as osteopenia, osteoporosis and fractures. However, cellular mechanisms by which chemotherapy affects bone integrity remain unclear. Methotrexate (MTX), used commonly as an anti-metabolite, is known to cause bone defects. To study the pathophysiology of MTX-induced bone loss, we examined effects on bone and marrow fat volume, population size and differentiation potential of bone marrow stromal cells (BMSC) in adult rats following chemotherapy for a short-term (five once-daily doses at 0.75 mg/kg) or a 6-week term (5 doses at 0.65 mg/kg + 9 days rest + 1.3 mg/kg twice weekly for 4 weeks). Histological analyses revealed that both acute and chronic MTX treatments caused a significant decrease in metaphyseal trabecular bone volume and an increase in marrow adipose mass. In the acute model, proliferation of BMSCs significantly decreased on days 3-9, and consistently the stromal progenitor cell population as assessed by CFU-F formation was significantly reduced on day 9. Ex vivo differentiation assays showed that while the osteogenic potential of isolated BMSCs was significantly reduced, their adipogenic capacity was markedly increased on day 9. Consistently, RT-PCR gene expression analyses showed osteogenic transcription factors Runx2 and Osterix (Osx) to be decreased but adipogenic genes PPARγ and FABP4 up-regulated on days 6 and 9 in the stromal population. These findings indicate that MTX chemotherapy reduces the bone marrow stromal progenitor cell population and induces a switch in differentiation potential towards adipogenesis at the expense of osteogenesis, resulting in osteopenia and marrow adiposity.

Characterization of a small animal growth plate injury model using microcomputed tomography

Injuries to the growth plate remain a significant clinical challenge. The need to better understand mechanisms of growth disruption following transphyseal injuries and evaluate new therapeutic approaches to growth restoration motivates development of a well characterized model of growth plate injury. The goals of this study were to develop a growth plate defect model in the rat and to use microcomputed tomography (micro-CT) imaging to detect and quantify associated changes in growth plate morphology and mineralization over time following injury and in response to treatment. Three-dimensional images of the growth plate were created from micro-CT scans and used to quantify the volume of mineralized tissue within the defect site. Growth plate thickness and volume as well as the degree of growth plate fusion were also measured from the reconstructed 3D images. Growth deficiency was then quantified as a function of time post-injury from whole limb micro-CT scans. Finally, this model was used to determine the ability of an injectable in situ gelling hydrogel to prevent formation of a bony bridge within the defect and the subsequent effect on limb length deficiency and changes to growth plate morphology. Growth plate injury resulted in significant shortening of the defect limb by day 28 and significant thinning and fusion of the surrounding growth plate up to day 112. Limb length reduction was correlated with changes in the growth plate volume and average thickness at day 56. Injection of an in situ gelling agarose into the defect resulted in a reduction of limb length discrepancy as well as a thicker growth plate on average compared to empty defect controls. These results establish a novel method of characterizing changes in whole bone and growth plate morphology due to a growth plate injury and indicate that treatment with agarose hydrogel reduces limb length discrepancy but is not sufficient to regenerate growth plate tissue or fully restore growth function.

Chemotherapy-associated osteonecrosis in cancer patients with solid tumours: a systematic review

Non-traumatic osteonecrosis of bone is recognized as a potential complication in solid-tumour cancer patients receiving treatment with cytotoxic chemotherapy. This review summarizes recent reports of osteonecrosis associated with chemotherapy in cancer patients, and describes the possible underlying pathophysiology and options available for its diagnosis, prevention and treatment. Fifty-four reported cases of non-traumatic osteonecrosis in adult patients with solid tumours receiving chemotherapy were identified by searching for reports in the medical literature. Osteonecrosis was observed most commonly in men receiving chemotherapy for testicular cancer. Osteonecrosis was also seen in patients receiving chemotherapy for breast, ovarian, small-cell lung cancer and osteosarcoma. Most patients had received corticosteroids, had femoral head involvement and had delayed onset of osteonecrosis. It appears that patients at higher risk for osteonecrosis with chemotherapy are identifiable. As the long-term survival of patients with solid tumours receiving chemotherapy increases, the prevalence of treatment-related osteonecrosis may also increase. Patients should be informed that osteonecrosis is a potential complication of cancer treatment. Measures to reduce risk should be taken, and patients should be monitored for early symptoms. Routine screening for chemotherapy-associated osteonecrosis is not recommended; however, a high index of clinical suspicion in patients at risk may allow for early intervention and preservation of the joints.

Cellular mechanisms for methotrexate chemotherapy-induced bone growth defects

Methotrexate (MTX) is a commonly used anti-metabolite in childhood oncology and is known to cause bone growth arrest and osteoporosis; yet the underlying mechanisms for MTX-induced bone growth defects remain largely unclear. This study characterized damaging effects in young rats of acute chemotherapy with 5 once-daily doses of MTX (0.75 mg/kg) on the cellular activities in the growth plate in producing calcified cartilage and trabecular bone and on activities of osteoblastic cells in the metaphysis. MTX treatment significantly induced chondrocyte apoptosis. MTX also suppressed chondrocyte proliferation and reduced collagen-II mRNA expression and total thickness of the growth plate, with the damage being most obvious on day 9 after the first injection, and with the growth plate histological structure returning normal on day 14. In the adjacent metaphyseal bone, mirroring the decrease in the width of the growth plate, production of primary spongiosa bone was markedly reduced and bone volume of the secondary spongiosa was decreased. Furthermore, MTX treatment significantly induced osteocyte apoptosis in the primary spongiosa and reduced proliferation of osteoblasts and preosteoblasts particularly in the secondary spongiosa. These observations suggest that methotrexate chemotherapy may cause bone growth defects by arresting cellular activities in the growth plate in producing calcified cartilage and primary trabecular bone and by decreasing pools of metaphyseal osteoblastic cells. However, this short-term MTX treatment only caused transit suppressions on growth plate cartilage and trabecular bone, as most cellular and histological parameters had recovered by day 14 or 21.

Continuous infusion of insulin-like growth factor-I into the epiphysis of the tibia

We have developed a method to promote longitudinal bone growth at the level of a specific growth-plate (GP) in young rabbits. Insulin-like growth factor-I (IGF-I) was continuously infused by means of an osmotic pump into the bone marrow cavity of the proximal epiphysis of the tibia. Radiological measurement showed a 2-mm overgrowth of the tibia after 4 weeks of treatment, while histological analysis demonstrated a 15% increase in the thickness of the selected GP. The local infusion of IGF-I increased the numbers of both proliferative and hypertrophic chondrocytes and promoted hyperplasia of bony trabeculae within the epiphysis. The distribution of material infused locally into the epiphysis was simulated by the infusion of Indian ink using the same methodology (osmotic pump) as that for IGF-I. Most of the dye remained within the bone marrow cavity of the epiphysis, but a portion infiltrated into the GP, reaching the deep layer of the physeal chondrocytes and primary spongiosa of the metaphysis. These results suggest that the method reported here is a valid one for delivering cytokines or growth factors to the selected GP and for controlling the growth and differentiation of physeal chondrocytes.

Probiotic effects on 5-fluorouracil-induced mucositis assessed by the sucrose breath test in rats

The sucrose breath test (SBT) was employed to noninvasively assess the efficacy of probiotics in 5-fluorouracil (5-FU)-induced intestinal mucositis. Dark Agouti rats were allocated to 5 groups (n = 10): 5-FU + L. fermentum BR 11, 5-FU + L. rhamnosus GG, 5-FU + B. lactis BB 12, 5-FU + skim milk (SM), and saline + SM. Probiotics were administered by oral gavage for 10 days. Mucositis was induced on day 7 by intraperitoneal injection of 5-FU (150 mg/kg) or vehicle (saline). Rats were sacrificed 72 h after 5-FU injection. The SBT measured breath 13CO2 (expressed as percentage cumulative dose at 90 min; %CD90) on days 0, 7, and 10. %CD90 was significantly lower in 5-FU-treated controls compared with that in saline-treated controls on day 10. 5-FU caused an 83% reduction in sucrase and a 510% increase in MPO activity. The SBT detected damage induced by 5-FU and is a simple, noninvasive indicator of small bowel injury. The probiotics assessed offered no protection from mucositis at the dose tested.

Damage and recovery of the bone growth mechanism in young rats following 5-fluorouracil acute chemotherapy

Chemotherapy-induced bone growth arrest and osteoporosis are significant problems in paediatric cancer patients, and yet how chemotherapy affects bone growth remains unclear. This study characterised development and resolution of damage caused by acute chemotherapy with antimetabolite 5-fluorouracil (5-FU) in young rats in the growth plate cartilage and metaphyseal bone, two important tissues responsible for bone lengthening. In metaphysis, 5-FU induced apoptosis among osteoblasts and preosteoblasts on days 1-2. In growth plate, chondrocyte apoptosis appeared on days 5-10. Interestingly, Bax was induced prior to apoptosis and Bcl-2 was upregulated during recovery. 5-FU also suppressed cell proliferation on days 1-2. While proliferation returned to normal by day 3 in metaphysis, it recovered partially on day 3, overshot on days 5-7 and normalised by day 10 in growth plate. Histologically, growth plate heights decreased by days 4-5 and returned normal by day 10. In metaphysis, primary spongiosa height was also reduced, mirroring changes in growth plate thickness. In metaphyseal secondary spongiosa, a reduced bone volume was observed on days 7-10 as there were fewer but more separated trabeculae. Starting from day 4, expression of some cartilage/bone matrix proteins and growth factors (TGF-beta1 and IGF-I) was increased. By day 14, cellular activity, histological structure and gene expression had returned normal in both tissues. Therefore, 5-FU chemotherapy affects bone growth directly by inducing apoptosis and inhibiting proliferation at growth plate cartilage and metaphyseal bone; after the acute damage, bone growth mechanism can recover, which is associated with upregulated expression of matrix proteins and growth factors.

Folinic acid attenuates methotrexate chemotherapy-induced damages on bone growth mechanisms and pools of bone marrow stromal cells

Chemotherapy often induces bone growth defects in pediatric cancer patients; yet the underlying cellular mechanisms remain unclear and currently no preventative treatments are available. Using an acute chemotherapy model in young rats with the commonly used antimetabolite methotrexate (MTX), this study investigated damaging effects of five once-daily MTX injections and potential protective effects of supplementary treatment with antidote folinic acid (FA) on cellular activities in the tibial growth plate, metaphysis, and bone marrow. MTX suppressed proliferation and induced apoptosis of chondrocytes, and reduced collagen-II expression and growth plate thickness. It reduced production of primary spongiosa bone, volume of secondary spongiosa bone, and proliferation of metaphyseal osteoblasts, preosteoblasts and bone marrow stromal cells, with the cellular activities being most severely damaged on day 9 and returning to or towards near normal levels by day 14. On the other hand, proliferation of marrow pericytes was increased early after MTX treatment and during repair. FA supplementation significantly suppressed chondrocyte apoptosis, preserved chondrocyte proliferation and expression of collagen-II, and attenuated damaging effects on production of calcified cartilage and primary bone. The supplementation also significantly reduced MTX effects on proliferation of metaphyseal osteoblastic cells and of bone marrow stromal cells, and enhanced pericyte proliferation. These observations suggest that FA supplementation effectively attenuates MTX damage on cellular activities in producing calcified cartilage and primary trabecular bone and on pools of osteoblastic cells and marrow stromal cells, and that it enhances proliferation of mesenchymal progenitor cells during bone/bone marrow recovery.

Osteoprotegerin and bone mass in squamous cell head and neck cancer patients

Osteoprotegerin (OPG) is considered one of the main regulators of bone remodeling. Various patterns of serum OPG levels have been described in different types of tumors. We undertook this study to determine serum OPG levels in patients with squamous cell head and neck cancer (SCHNC), analyzing their relationship with other metabolic bone parameters and bone mineral density (BMD), as well as the possible influence of chemotherapy. Forty male patients with localized SCHNC were studied, and their results were compared with those of 40 healthy male controls. The type of treatment followed by each patient was noted. Age, weight, height, and lifestyle habits were recorded; and OPG, Ca(2+), intact parathyroid hormone (iPTH), 25-Hydroxyvitamin D (25OHD) and 1,25-Dihydroxyvitamin D (1,25(OH)(2)D), bone alkaline phosphatase, osteocalcin, and serum C-terminal cross-links telopeptide of type I collagen (ICTP) were determined. Dual-energy X-ray absorptiometry BMD at the lumbar spine, femoral neck, and hip was also measured. Serum OPG was higher in patients than in controls (91.7 +/- 25.8 vs. 77.2 +/- 26.3, P = 0.02). ICTP (a bone resorption marker) was 37% higher in patients (P = 0.007). Bone mass was lower in patients at the lumbar spine, femoral neck, and total hip. Lumbar spine Z-score showed a significant progressive decrease in controls, stage I-III patients, and stage IV patients. Logistic regression analysis showed a significant association between the disease and serum OPG levels, the odds ratio per standard deviation increase of this being 1.9 (95% confidence interval 1.1-3.8, P = 0.04) after adjusting for bone mass and ICTP serum levels, as well as for alcohol and smoking history. Adjustment for alcohol intake and tobacco use did not cancel out BMD differences between patients and controls. Patients with SCHNC show increased OPG serum levels, increased bone resorption, and decreased bone mass. The OPG rise appears to be unrelated to the BMD decrease, and the BMD decrease seems to be, at least in part, independent of smoking and drinking habits. No differences in either OPG or BMD were seen between patients with and without chemotherapy. Further studies are needed to clarify the mechanisms responsible for OPG and BMD changes in SCHNC.

The insulin-like growth factor-I gene and osteoporosis: a critical appraisal

Osteoporosis, a disorder of skeletal fragility, is common in the elderly, and its prevalence is increasing as more individuals with low bone mineral density (BMD), the strongest predictor of fracture risk, are detected. Previous basic and clinical studies imply there is a significant role for insulin-like growth factor-I (IGF-I) in determining BMD. Recently, polymorphisms upstream of the P1 promoter region of the human IGF-I gene have been found to be associated with serum levels of IGF-I, BMD and fracture risk in various ethnic groups. Multiple quantitative trait loci (QTLs) have been identified that underlie serum IGF-I in a mouse intercross between two inbred strains. The most promising QTL on mouse chromosome 6 has provided clues for unraveling the molecular mechanisms that regulate osteoblast differentiation. Genomic engineering resulting in IGF-I deficient mice, and mice with targeted over-expression of IGF-I reinforce the essential role of IGF-I in bone development at both the embryonic and postnatal stages. Thus, it is apparent that significant new insights into the role of the IGF-I gene in bone remodeling occur through several distinct mechanisms: (1) the skeletal IGF regulatory system; (2) the systemic growth hormone/IGF-I axis; (3) parathyroid hormone signaling; (4) sex steroids; and (5) the OPG/RANKL/RANK cytokine system. Molecular dissection of the IGF regulatory system and its signaling pathway in bone may reveal novel therapeutic targets for the treatment of osteoporosis.