Increased excretion of collagen crosslinks in irradiated patients indicates destruction of collagen

Relations Between Bone Quantity, Microarchitecture, and Collagen Cross-links on Mechanics Following In Vivo Irradiation in Mice

Humans are exposed to ionizing radiation via spaceflight or cancer radiotherapy, and exposure from radiotherapy is known to increase risk of skeletal fractures. Although irradiation can reduce trabecular bone mass, alter trabecular microarchitecture, and increase collagen cross‐linking, the relative contributions of these effects to any loss of mechanical integrity remain unclear. To provide insight, while addressing both the monotonic strength and cyclic‐loading fatigue life, we conducted total‐body, acute, gamma‐irradiation experiments on skeletally mature (17‐week‐old) C57BL/6J male mice (n = 84). Mice were administered doses of either 0 Gy (sham), 1 Gy (motivated by cumulative exposures from a Mars mission), or 5 Gy (motivated by clinical therapy regimens) with retrieval of the lumbar vertebrae at either a short‐term (11‐day) or long‐term (12‐week) time point after exposure. Micro‐computed tomography was used to assess trabecular and cortical quantity and architecture, biochemical composition assays were used to assess collagen quality, and mechanical testing was performed to evaluate vertebral compressive strength and fatigue life. At 11 days post‐exposure, 5 Gy irradiation significantly reduced trabecular mass (p < 0.001), altered microarchitecture (eg, connectivity density p < 0.001), and increased collagen cross‐links (p < 0.001). Despite these changes, vertebral strength (p = 0.745) and fatigue life (p = 0.332) remained unaltered. At 12 weeks after 5 Gy exposure, the trends in trabecular bone persisted; in addition, regardless of irradiation, cortical thickness (p < 0.01) and fatigue life (p < 0.01) decreased. These results demonstrate that the highly significant effects of 5 Gy total‐body irradiation on the trabecular bone morphology and collagen cross‐links did not translate into detectable effects on vertebral mechanics. The only mechanical deficits observed were associated with aging. Together, these vertebral results suggest that for spaceflight, irradiation alone will likely not alter failure properties, and for radiotherapy, more investigations that include post‐exposure time as a positive control and testing of both failure modalities are needed to determine the cause of increased fracture risk. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Effects of zoledronate on the radiation-induced collagen breakdown: a prospective randomized clinical trial

BACKGROUND

A negative side effect of therapeutic irradiation is the radiation-induced bone loss which can lead, in long term, to pathological fractures. Until today, the detailed mechanism is unknown. If osteoclasts would mainly contribute to the pathological bone loss, bisphosphonates could potentially counteract the osteolytic process and possibly help to prevent long-term complications. The aim of this study was to evaluate the effect of zoledronic acid on the early radiation-induced degradation of bone collagen fibrils by monitoring the urinary excretion of hydroxylysylpyridinoline and lysylpyridinoline under radiotherapy.

PATIENTS AND METHODS

A total of 40 patients with skeletal metastases were assigned for a local radiotherapy and bisphosphonate treatment. The patients were prospectively randomized into two treatment groups: group A (n = 20) received the first zoledronate administration after and group B (n = 20) prior to the radiotherapy. Urine samples were collected from each patient on the first day, in the middle, and on the last day of the radiation therapy. Measurement of the bone metabolites hydroxylysylpyridinoline and lysylpyridinoline was performed by high-performance liquid chromatography. Statistical analysis was performed using the Mann-Whitney U test.

RESULTS

The hydroxylysylpyridinoline and lysylpyridinoline excretion decreased significantly in the combined bisphosphonate and radiotherapy group (p = 0.02, p = 0.08). No significant change of the hydroxylysylpyridinoline and lysylpyridinoline excretion was determined in the patients that received solely irradiation.

CONCLUSION

The results indicate the ability of zoledronate to prevent the early radiation-induced bone collagen degradation suggesting that the radiation-induced bone loss is mainly caused by osteoclastic bone resorption rather than by a direct radiation-induced damage.

Effects of zoledronate on irradiated bone in vivo: analysis of the collagen types I, V and their cross-links lysylpyridinoline, hydroxylysylpyridinoline and hydroxyproline

Radiotherapy can lead to a reduction of bone density with an increased risk of pathological fractures. Bisphosphonates may represent a preventive treatment option by increasing the density of anorganic bone mineral. Yet it is unknown how bisphosphonates act on irradiated collagen cross-links, which play an essential role for the mechanical stability of bone. The aim of this study was to evaluate the effects of zoledronate on bone collagens and their cross-links after irradiation. The right femur of 37 rats was irradiated with a single dose of 9.5 Gy at a high dose rate using an afterloading machine. Half of the rats (n=18) received additionally a single dose zoledronate (0.1 mg/kg body weight). Fourteen and 100 days after irradiation the femora were collected for histologic evaluation and determination of the collagen cross-links lysylpyridinoline, hydroxylysylpyridinoline, and hydroxyproline. The collagen types were characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Fourteen days after treatment the lysylpyridinoline levels of all treatment groups were significantly lower compared to the untreated control. After 100 days, in the combined radiotherapy+zoledronate group significantly lower lysylpyridinoline values were determined (p=0.009). Radiotherapy and/or zoledronate did not change significantly the level of hydroxylysylpyridinoline. The concentration of hydroxyproline was 14 days after irradiation significantly higher in the combined treatment group compared to the control. No significant differences were observed 100 days after treatment. Zoledronate does not have the ability to restore the physiological bone collagen cross-link levels after radiotherapy. However, this would be necessary for regaining the physiological mechanical stability of bone after irradiation and therefore to prevent effectively radiation-induced fractures.

Local radiotherapy increases the level of autoantibodies to ribosomal P0 protein but not to heat shock proteins, extracellular matrix molecules and EGFR/ErbB2 receptors in prostate cancer patients

Prostate cancer is a common cancer among men in developed countries. Although hormonotherapy and radiotherapy (RT) represent valid therapies for prostate cancer treatment, novel immunological approaches have been explored. The development of clinical trials employing cancer vaccines has indicated that immune response to tumor antigens can be boosted and that vaccine administration can improve patient survival. Immune response to tumor antigens could also be enhanced after standard therapies. In the present study, we determined the occurrence of antibodies to extracellular matrix (ECM) molecules, heat shock protein (HSP), ribosomal P0 protein, EGFR, ErbB2 and prostate-specific antigen (PSA) in 35 prostate cancer patients prior to and following local RT and hormonotherapy. We demonstrated that immunity to P0, ECM molecules [collagens (C) CI, CIII, CV, fibronectin (FN) and laminin (LM)] and to HSP90 was associated with malignancy in untreated patients. None of the patient sera showed antibodies to EGFR, while 2 and 1 patients showed reactivity to ErbB2 and PSA, respectively. We also demonstrated that 8 months after therapy the IgG serum levels to CI, CIII, FN and HSP90 significantly decreased. Conversely, the level of P0 autoantibodies increased after therapy in 10 patients. Five of the 10 patients with increased levels of P0 autoantibodies were treated with RT plus hormonotherapy. Treatment of patients did not change the levels of antibodies against EGFR, ErbB2 and PSA. Our results indicated that the modification of antibody level to self molecules after standard treatment of prostate cancer patients is influenced by the type of antigen. Ribosomal P0 protein appears to be a high immunogenic antigen and its immunogenicity increases following RT. In addition, 10 patients with increased levels of autoantibodies to P0 showed PSA mean levels lower than the remaining 25 patients at 18 months. This study may contribute to a better understanding of the immunobiological behavior of prostate cancer patients following standard treatment.

Stem cell therapy: a novel & futuristic treatment modality for disaster injuries

Stem cell therapy hold the potential to meet the demand for transplant cells/tissues needed for treating damages resulting from both natural and man-made disasters. Pluripotency makes embryonic stem cells and induced pluripotent stem cells ideal for use, but their teratogenic character is a major hindrance. Therapeutic benefits of bone marrow transplantation are well known but characterizing the potentialities of haematopoietic and mesenchymal cells is essential. Haematopoietic stem cells (HSCs) have been used for treating both haematopoietic and non-haematopoietic disorders. Ease of isolation, in vitro expansion, and hypoimmunogenecity have brought mesenchymal stem cells (MSCs) into limelight. Though differentiation of MSCs into tissue-specific cells has been reported, differentiation-independent mechanisms seem to play a more significant role in tissue repair which need to be addressed further. The safety and feasibility of MSCs have been demonstrated in clinical trials, and their use in combination with HSC for radiation injury treatment seems to have extended benefit. Therefore, using stem cells for treatment of disaster injuries along with the conventional medical practice would likely accelerate the repair process and improve the quality of life of the victim.

The cytotoxic effects of three different bisphosphonates in-vitro on human gingival fibroblasts, osteoblasts and osteogenic sarcoma cells

INTRODUCTION

Osteonecrosis of the jaw (ONJ) is an emerging condition in patients undergoing long-term administration of bisphosphonates (BP) for the treatment of osteoporosis and hypercalcaemia associated with malignancy, multiple myeloma, and metastatic breast and prostate cancers. This is a follow-up study, its purpose was to examine the effects in-vitro of intravenous zoledronic acid (ZOL) and pamidronate (PAM) and oral alendronate (FOS) on the human oral cavity using gingival fibroblasts and osteoblasts cells and, in addition, osteogenic sarcoma cells (SaOS-2-cells).

MATERIALS AND METHODS

Human gingival fibroblasts, osteoblasts and SaOS-2-cells were seeded on multiple 6-well plates at a density of 5 × 10(5)cells in a 4-week cell culture. Four different concentrations (1, 5, 10, 20 μM) of each BP (ZOL, PAM, FOS) and pyrophosphate were used in this study.

RESULTS

All BP decreased collagen production and lowered cell proliferation in-vitro. ZOL was the component with most inhibitory effect.

CONCLUSION

The findings in this study suggest that ZOL, PAM and FOS generally diminish cell proliferation and collagen production of human gingival fibroblasts, osteoblasts and SaOS-2-cells. The present follow-up study shows that not only ZOL and PAM but also FOS have a strong inhibitory effect on collagen production and cell survival in-vitro.

Local irradiation alters bone morphology and increases bone fragility in a mouse model

Insufficiency fracture following radiation therapy (RTx) is a challenging clinical problem and typical bone mass measures fail to predict these fractures. The goals of this research were to develop a mouse model that results in reduced bone strength following focal irradiation, quantify morphological and strength changes occurring over time, and determine if a positive correlation between bone morphology and strength is retained after irradiation. Right hind limbs of 13 week-old female Balb/c mice were irradiated (5 or 20 Gy) using a therapeutic X-ray unit. Left limbs served as control. Animals were euthanized at 2, 6, 12, or 26 weeks. Axial compression tests of the distal femur were used to quantify whole bone strength. Specimen-specific, non-linear finite element (FE) analyses of the mechanical tests were performed using voxel-based meshes with two different material failure models: a linear bone density-strength relationship and a non-linear 'embrittled' relationship. Radiation resulted in a dose dependent increase in cortical bone density and marked loss of trabecular bone, measured using micro-CT. An early (2 week) increase in bone volume was associated with an increase in bone strength following irradiation; at 12 weeks there was a loss of bone strength despite higher bone volume for irradiated limbs. There was a positive correlation between bone volume bone and strength in control (r²=0.63) but not irradiated femora (r²=0.08). FE analysis with a constant strain failure model resulted in improved prediction of bone strength for irradiated limbs (r²=0.34) and this was improved further with the embrittled material model (r²=0.46). In summary, focal irradiation leads to substantial changes in bone morphology and strength with time, where there is a decreased bone strength following irradiation in the face of increasing bone mass; FE models with a non-linear embrittled material model were most successful in simulating these experimental findings.