Bone growth mechanisms and the effects of cytotoxic drugs

Cisplatin triggers oxidative stress, apoptosis and pro-inflammatory responses by inhibiting the SIRT1-mediated Nrf2 pathway in chondrocytes

Although the height of the proliferating layer that was suppressed in the growth plate has been recognized as an adverse effect of cisplatin in pediatric cancer survivors, the detailed pathological mechanism has not been elucidated. Sirtuin-1 (SIRT1) has been reported as an essential modulator of cartilage homeostasis, but its role in cisplatin-induced damage of chondrocytes remains unclear. In this study, we examined how cisplatin affected the expression of SIRT1 and cell viability. Next, we showed downregulation of SIRT1 after cisplatin treatment resulted in suppression of Peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α), leading to inhibition of Nrf2 nuclear translocation and subsequently decreased Heme oxygenase-1(HO-1) and NAD(P)H Quinone Dehydrogenase 1(NQO-1) expression. Blockage of the SIRT1/ PGC-1α axis not only increased oxidative stress with lower antioxidant SOD and GSH, but also contributed to mitochondrial dysfunction evidenced by the collapse of membrane potential and repression of mitochondrial DNA copy number and ATP. We also found that Cisplatin up-regulated the p38 phosphorylation, pro-inflammatory events and matrix metalloproteinases (MMPs) in chondrocytes through the SIRT1-modulated antioxidant manner. Collectively, our findings suggest that preservation of SIRT1 in chondrocytes may be a potential target to ameliorate growth plate dysfunction for cisplatin-receiving pediatric cancer survivors.

Differences in skeletal growth pattern of yoga practising adolescent girls: A cross-sectional study

Background

Yogasana improves both mental and physical health. There is sparse systematic research on the growth of yogasana practising adolescents.

Objectives

This study aims to assess the differential skeletal growth pattern among pre-adolescent and adolescent girls as a result of yoga practice.

Methods

A cross-sectional anthropometric study was conducted on stature (height), sitting height and leg length of 757 school-going girls (4-15 years old), divided in two groups, Yoga Group (YG) (n=380) and age matched Control Group (CG) (n=377) participants participating in recreational games other than yoga. Descriptive and inferential statistical analyses were applied. Unpaired t-test was performed for assessment of level of significance and Pearson's correlation (r) test was performed to to identify the association between growth pattern of stature and leg length at specific ages.

Results

The physical growth showed an ascending trend in both Yoga group (YG)2 participants and control group (CG)3 . At the onset of adolescence (10–12 years) the mean stature and leg length of YG participants were retarded (p < 0.05). Sitting height in YG was significantly (p < 0.05) low only in 10-year-olds. The similar trends were observed in stature and leg length in YG participants at 10 years (5th and 10th percentile) and 12 years (90th and 95th percentile). There was strong positive relationship between stature and leg length of YG participants (10 years, r = 0.86, p < 0.01; 11 years, r = 0.86, p < 0.01; 12 years, r = 0.72, p < 0.01). The stunted growth in YG participants during adolescence may be related to retarded growth of leg length.

Conclusions

Intense yogasana practice with greater skeletal stress possibly hinders stature in adolescent girls from 10 to 12 years. This may compromise with the natural growth pattern, necessitating special care during yoga training among adolescents while selecting the type, intensity and duration of yogasanas practice.

Longitudinal Bone Growth Stimulating Effect of Allium macrostemon in Adolescent Female Rats

Allium macrostemon (AM) may affect bone growth by regulating bone formation and resorption. To examine the effect of AM on bone growth, 48 rats were divided into four administration groups in which either distilled water, AM (100 and 300 mg/kg), or recombinant human growth hormone (rhGH; 20 μg/kg) was administered for 10 days. On day 9, all animals were intraperitoneally injected with tetracycline hydrochloride (20 mg/kg), and 48 h after the injection, the rats were sacrificed. Their tibial sections were photographed to measure bone growth. Antigen-specific immunohistochemistry was performed to detect insulin-like growth factor-1 (IGF-1) and bone morphogenetic protein-2 (BMP-2). The food intake of the AM 100 mg/kg group was higher; however, the food intake of the AM 300 mg/kg group was less than that of the control group. The rhGH and AM 100 mg/kg groups showed greater rates of bone growth (359.0 ± 23.7 and 373.1 ± 28.0 μm/day, respectively) compared with the control group. IGF-1 and BMP-2 in the AM and rhGH groups were highly expressed. Indigestion at higher doses of AM led to nonsignificant bone growth in spite of increased IGF-1 and BMP-2 expression. Therefore, a suitable amount of AM could increase bone growth.

Paley's multiplier method does not accurately predict adult height in children with bone sarcoma

BACKGROUND

The majority of patients with osteosarcoma and Ewing's sarcoma are diagnosed before skeletal maturity. Paley's multiplier is used for height prediction in healthy children, and has been suggested as a method to make growth predictions for children with osteosarcoma and Ewing's sarcoma when considering limb salvage options. To our knowledge, no evaluation of this method in this particular patient group has been performed, but a temporary growth deficit has been observed in children undergoing chemotherapy.

QUESTIONS/PURPOSES

We asked whether (1) Paley's formula reliably predicts growth in children who received polychemotherapy; (2) chemotherapy impairs growth velocity; and (3) final adult height is impaired in these patients.

METHODS

Retrospectively, data for 94 patients with osteosarcoma and Ewing's sarcoma were retrieved from databases of two sarcoma centers. Onset before 14 years of age in girls and 16 years in boys and a minimum followup until 18 years were required (mean, 67 months; range, 31-124 months) criteria. Exclusion criteria were the intake of growth hormones or no chemotherapy. Thirty-three patients (35%) fulfilled all inclusion criteria. Predicted adult heights were compared with actual adult height. The development of a growth deficit was evaluated for 23 children (without chemotherapy for recurrence) using age- and gender-specific standard deviation scores for height (WHO Z-scores).

RESULTS

Height prediction using Paley's method showed a high percentage of false predictions (outside ± 1 SD, 70%; outside ± 2 SD, 61%). On average, the mean total height of the patients was overestimated (2.3 cm). The median absolute error of prediction was 5.0 cm (range, -17 to 8). Patients with osteosarcoma and Ewing's sarcoma showed a significant growth impairment during polychemotherapy. A catchup phase in growth before skeletal maturity was observed in patients with osteosarcoma but not with Ewing's sarcoma.

CONCLUSIONS

Owing to its lack of reliability in this patient group, methods other than Paley's should be evaluated to predict adult height. Although limited by a small number of patients, our study results indicate a decreased adult height in patients with bone sarcoma after chemotherapy.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Instructions for Authors for complete description of levels of evidence.

Twenty two cases of canine neural angiostrongylosis in eastern Australia (2002-2005) and a review of the literature

Cases of canine neural angiostrongylosis (NA) with cerebrospinal fluid (CSF) evaluations in the peer-reviewed literature were tabulated. All cases were from Australia. A retrospective cohort of 59 dogs was contrasted with a series of 22 new cases where NA was diagnosed by the presence of both eosinophilic pleocytosis and anti-Angiostrongylus cantonensis immunloglobulins (IgG) in CSF, determined by ELISA or Western blot. Both cohorts were drawn from south east Queensland and Sydney. The retrospective cohort comprised mostly pups presented for hind limb weakness with hyperaesthesia, a mixture of upper motor neurone (UMN) and lower motor neurone (LMN) signs in the hind limbs and urinary incontinence. Signs were attributed to larval migration through peripheral nerves, nerve roots, spinal cord and brain associated with an ascending eosinophilic meningo-encephomyelitis. The contemporary cohort consisted of a mixture of pups, young adult and mature dogs, with a wider range of signs including (i) paraparesis/proprioceptive ataxia (ii) lumbar and tail base hyperaesthesia, (iii) multi-focal central nervous system dysfunction, or (iv) focal disease with neck pain, cranial neuropathy and altered mentation. Cases were seen throughout the year, most between April and July (inclusive). There was a preponderance of large breeds. Often littermates, or multiple animals from the same kennel, were affected simultaneously or sequentially. A presumptive diagnosis was based on consistent signs, proximity to rats, ingestion/chewing of slugs or snails and eosinophilic pleocytosis. NA was diagnosed by demonstrating anti-A. cantonensis IgG in CSF. Detecting anti-A. cantonensis IgG in serum was unhelpful because many normal dogs (20/21 pound dogs; 8/22 of a hospital population) had such antibodies, often at substantial titres. Most NA cases in the contemporary series (19/22) and many pups (16/38) in the retrospective cohort were managed successfully using high doses of prednisolone and opioids. Treatment often included antibiotics administered in case protozoan encephalomyelitis or translocated bacterial meningitis was present. Supportive measures included bladder care and physiotherapy. Several dogs were left with permanent neural deficits. Dogs are an important sentinel species for NA. Human cases and numerous cases in tawny frogmouths were reported from the same regions as affected dogs over the study period.

The herbal formula HT042 induces longitudinal bone growth in adolescent female rats

The effect of HT042, a blend of three herbal extracts, on longitudinal bone growth was investigated in short- and long-term rat models. In the short-term model, we divided female Sprague-Dawley rats (3 weeks old) into six groups, according to treatment: vehicle, HT042 (100 mg/kg), Phlomis umbrosa (100 mg/kg), Astragalus membranaceus (100 mg/kg), and Eleutherococcus senticosus (100 mg/kg) were administered twice daily, and recombinant human growth hormone (rhGH) (1 IU) was subcutaneously injected once daily. Treatments were maintained for 4 days in each case. On day 3, tetracycline (20 mg/kg) was injected intraperitoneally (20 mg/kg) to form the fluorescent band on the growth plates. On days 2-4, 5-bromo-2'-deoxyuridine (BrdU) (50 mg/kg) was injected intraperitoneally to label proliferating cells. On day 5, the tibias were dissected and fixed in 30% sucrose. Dehydrated bone was sectioned at a thickness of 40 μm and observed. The bone growth in groups administered HT042 and rhGH was significantly increased to 433.50 ± 21.61 and 434.49 ± 15.21 μm/day, respectively, from 410.03 ± 17.4 μm/day (control). The height of the growth plates in the HT042 and rhGH groups was also significantly increased to 556.5 ± 21.1 and 544.2 ± 21.1 μm (P < .05), respectively, from 518.1 ± 4.1 μm (normal). The number of BrdU-positive cells in chondrocytes of the HT042 and rhGH groups was increased to 389 ± 36 and 627 ± 39 cells/mm² (P < .001), respectively, from 264 ± 17 cells/mm² (control). Insulin-like growth factor-1 and bone morphogenetic protein-2 in the HT042 group were highly expressed in the growth plate. In the long-term rat model, the body weight, nose-tail length, and nose-anus length were measured by microknemometry for 4 weeks. The body weight of the rhGH group was significantly increased. The nose-anus length of the HT042 and rhGH groups was significantly greater at 18.5 ± 0.3 and 18.7 ± 0.3 cm compared to 18.2 ± 0.2 cm (control).

Methotrexate toxicity in growing long bones of young rats: a model for studying cancer chemotherapy-induced bone growth defects in children

The advancement and intensive use of chemotherapy in treating childhood cancers has led to a growing population of young cancer survivors who face increased bone health risks. However, the underlying mechanisms for chemotherapy-induced skeletal defects remain largely unclear. Methotrexate (MTX), the most commonly used antimetabolite in paediatric cancer treatment, is known to cause bone growth defects in children undergoing chemotherapy. Animal studies not only have confirmed the clinical observations but also have increased our understanding of the mechanisms underlying chemotherapy-induced skeletal damage. These models revealed that high-dose MTX can cause growth plate dysfunction, damage osteoprogenitor cells, suppress bone formation, and increase bone resorption and marrow adipogenesis, resulting in overall bone loss. While recent rat studies have shown that antidote folinic acid can reduce MTX damage in the growth plate and bone, future studies should investigate potential adjuvant treatments to reduce chemotherapy-induced skeletal toxicities.

Histopathologic changes in metabolic bone disease

Metabolic bone disease encompasses a heterogeneous group of disorders that influence skeletal metabolism and structure. They are generally diagnosed at an advanced stage and manifest clinically with stunted skeletal growth in children and pathologic fractures in adults. Biochemical markers for bone metabolism are equivocal and microscopic examination of labeled bone remains the gold standard for the diagnosis and accurate monitoring of the response to therapy. This article reviews the role of microscopic bone changes in the diagnosis and management of metabolic bone disease.

Effect of short-term fasting on bone elongation rates: an analysis of catch-up growth in young male rats

Bone elongation in the postnatal animal is a result of cellular activity during endochondral ossification. Growth plate chondrocytes undergo a differentiation cascade involving stem cell clonal expansion and cellular enlargement during hypertrophy. Nutritional status has a significant effect on rates of bone growth, and a period of accelerated growth will occur if nutritional stunting of growth in early childhood can be corrected. This study focuses on changes in rates of increase in bone length in a model of catch-up growth in 4-wk-old male rats. Animals fasted for 3 d reached a weight approximately 60% of the control littermates. By 28 d postfasting, fasted animals had regained weight to 95% of control levels. A 3-d fast caused an immediate and profound decrease in rate of growth in the proximal tibial growth plate to only 30% of that of control animals, while stopping growth in the distal tibial growth plate. During the rapid initial rate acceleration of bone elongation, growth rate in both growth plates reached that of the control littermates by 7 d postfasting. The proximal tibial growth plate then maintained rates that were 10-15% higher than control over the rest of the experimental period. By 10 d postfasting, the previously fasted animals were on the same weight/rate trajectory as the control littermates. Changes in elongation rates were reflected by dramatic changes in growth plate morphology in all cellular zones. This is the first study to directly correlate weight recovery during catch-up with growth rate responses at the level of the growth plate.

Short-term effects on linear growth and bone turnover in children randomized to receive prednisolone or dexamethasone

AIM

To compare the relative potency of prednisolone (Pred) and dexamethasone (Dex) on short-term growth and bone turnover.

METHOD

Prospective study over 16 weeks of children randomized to receive Pred (40 mg/m2) or Dex (6.5 mg/m2) for the first 5 weeks as part of the MRC-ALL97/99 induction chemotherapy for acute lymphoblastic leukaemia (ALL).

MEASUREMENTS

Lower leg length velocity (LLLV) and weight, serum IGF-I, serum bone alkaline phosphatase (bALP) levels and creatinine-adjusted, urinary excretion of deoxypyridinoline cross-links (DPD).

SUBJECTS

Nineteen children (eight boys, 11 girls) with a median age of 5.9 years (range 2.6-13) and with a diagnosis of ALL.

RESULTS

At week 2 of therapy, median LLLV in the Dex group was -1.5 mm/week (range 0.7 to -2.1) and significantly lower than the LLLV in the Pred group which was -0.1 mm/week (range 0.20 to -0.28; P < 0.05). In the Dex group, LLLV remained lower at week 8 (med LLLV, -0.3 mm/week, range 0 to -1.3) compared to LLLV in the Pred group at 0.3 mm/week (range 0.2-1.0; P < 0.05). Body weight showed an increase after week 2 and reached a peak in both groups of children at week 6. The change in weight from baseline was greater in the Dex group than the Pred group reaching a maximum change by week 5 of 17.5% (range 5-25) and 8.7% (range -3 to 18), respectively (P < 0.05). At presentation, median IGF-I level for the whole group was 83.5 micro g/l (range 31.8-293). IGF-I levels fell markedly during Dex therapy and continued to remain lower than baseline. At weeks 4, 6 and 8, median change in IGF-I from baseline was lower in the Dex group than the Pred group. From week 1 to week 3, median change in bALP was 72% (range -8 to 304) in the Pred group, whereas in the Dex group change in bALP was -1% (range 23 to -28; P < 0.005). By week 3, median bALP was higher in the Pred group at 65 U/l (range 36-187) than in the Dex group at 39 U/l (range 26-60; P < 0.05) but by week 6 median bALP in the Pred group had fallen to a similar level to the Dex group. At presentation, median DPD was 22 nmol/l (range 17-38) and 20 nmol/l (range 12-26) in the Pred and Dex groups, respectively (ns), reaching a nadir between weeks 3 and 6. The median percentage change in DPD in the Pred and Dex group from week 1 to week 3 was -34% (range -7 to 14) and -53% (range -6 to -69), respectively (ns). By week 8, DPD excretion had started to rise more dramatically in the Pred group such that the median DPD was 35 nmol/l (range 10-53) in the Pred group and 22 (range 9-30) in the Dex group (P < 0.05). On average, between weeks 2 and 8, LLLV was three times lower, percentage gain in weight was three times higher, bALP was 1.3 times lower and DPD was 1.5 times lower in the Dex group than the Pred group.

CONCLUSION

Pred and Dex both affect short-term growth and bone turnover. The mechanism of the effect on bone formation may be different between the two drugs. Dex may be about 18 times more potent than Pred at suppressing short-term linear growth and stimulating weight gain, and about nine times more potent at suppressing bone turnover. Glucocorticoids have a variable effect on different parameters of growth and bone turnover and the intensity may depend on the steroid used.