Radiation-induced changes to bone composition extend beyond periosteal bone

Collagen molecular organization preservation in human fascia lata and periosteum after tissue engineering

Large bone defect regeneration remains a major challenge for orthopedic surgeons. Tissue engineering approaches are therefore emerging in order to overcome this limitation. However, these processes can alter some of essential native tissue properties such as intermolecular crosslinks of collagen triple helices, which are known for their essential role in tissue structure and function. We assessed the persistence of extracellular matrix (ECM) properties in human fascia lata (HFL) and periosteum (HP) after tissue engineering processes such as decellularization and sterilization. Harvested from cadaveric donors (N = 3), samples from each HFL and HP were decellularized following five different chemical protocols with and without detergents (D1-D4 and D5, respectively). D1 to D4 consisted of different combinations of Triton, Sodium dodecyl sulfate and Deoxyribonuclease, while D5 is routinely used in the institutional tissue bank. Decellularized HFL tissues were further gamma-irradiated (minimum 25 kGy) in order to study the impact of sterilization on the ECM. Polarized light microscopy (PLM) was used to estimate the thickness and density of collagen fibers. Tissue hydration and content of hydroxyproline, enzymatic crosslinks, and non-enzymatic crosslinks (pentosidine) were semi-quantified with Raman spectroscopy. ELISA was also used to analyze the maintenance of the decorin (DCN), an important small leucine rich proteoglycan for fibrillogenesis. Among the decellularization protocols, detergent-free treatments tended to further disorganize HFL samples, as more thin fibers (+53.7%) and less thick ones (-32.6%) were recorded, as well as less collagen enzymatic crosslinks (-25.2%, p = 0.19) and a significant decrease of DCN (p = 0.036). GAG content was significantly reduced in both tissue types after all decellularization protocols. On the other hand, HP samples were more sensitive to the D1 detergent-based treatments, with more disrupted collagen organization and greater, though not significant loss of enzymatic crosslinks (-37.4%, p = 0.137). Irradiation of D5 HFL samples, led to a further and significant loss in the content of enzymatic crosslinks (-29.4%, p = 0.037) than what was observed with the decellularization process. Overall, the results suggest that the decellularization processes did not significantly alter the matrix. However, the addition of a gamma-irradiation is deleterious to the collagen structural integrity of the tissue.

Aromatase deficiency in transplanted bone marrow cells improves vertebral trabecular bone quantity, connectivity, and mineralization and decreases cortical porosity in murine bone marrow transplant recipients

Estradiol is an important regulator of bone accumulation and maintenance. Circulating estrogens are primarily produced by the gonads. Aromatase, the enzyme responsible for the conversion of androgens to estrogen, is expressed by bone marrow cells (BMCs) of both hematopoietic and nonhematopoietic origin. While the significance of gonad-derived estradiol to bone health has been investigated, there is limited understanding regarding the relative contribution of BMC derived estrogens to bone metabolism. To elucidate the role of BMC derived estrogens in male bone, irradiated wild-type C57BL/6J mice received bone marrow cells transplanted from either WT (WT(WT)) or aromatase-deficient (WT(ArKO)) mice. MicroCT was acquired on lumbar vertebra to assess bone quantity and quality. WT(ArKO) animals had greater trabecular bone volume (BV/TV p = 0.002), with a higher trabecular number (p = 0.008), connectivity density (p = 0.017), and bone mineral content (p = 0.004). In cortical bone, WT(ArKO) animals exhibited smaller cortical pores and lower cortical porosity (p = 0.02). Static histomorphometry revealed fewer osteoclasts per bone surface (Oc.S/BS%), osteoclasts on the erosion surface (ES(Oc+)/BS, p = 0.04) and low number of osteoclasts per bone perimeter (N.Oc/B.Pm, p = 0.01) in WT(ArKO). Osteoblast-associated parameters in WT(ArKO) were lower but not statistically different from WT(WT). Dynamic histomorphometry suggested similar bone formation indices' patterns with lower mean values in mineral apposition rate, label separation, and BFR/BS in WT(ArKO) animals. Ex vivo bone cell differentiation assays demonstrated relative decreased osteoblast differentiation and ability to form mineralized nodules. This study demonstrates a role of local 17β-estradiol production by BMCs for regulating the quantity and quality of bone in male mice. Underlying in vivo cellular and molecular mechanisms require further study.

The Contribution of Perilacunar Composition and Mechanical Properties to Whole-Bone Mechanical Outcomes in Streptozotocin-Induced Diabetes

Osteocytes are the most abundant cell type in bone and remodel their local perilacunar matrix in response to a variety of stimuli and diseases. How the perilacunar composition and mechanical properties are affected by type 1 diabetes (T1D), and the contribution of these local changes to the decline in whole-bone functional properties that occurs with diabetes remains unclear. 12-14 week old C57/BL6 male mice were administered a series of low-dose streptozotocin injections and sacrificed at baseline (BL), 3 (D3) and 7 weeks (D7) following confirmation of diabetes, along with age-matched controls (C3, C7). Femora were then subjected to a thorough morphological (μCT), mechanical (four-point bending, nanoindentation), and compositional (HPLC for collagen cross-links, Raman spectroscopy) analysis at the whole-bone and local (perilacunar and intracortical) levels. At the whole-bone level, D7 mice exhibited 10.7% lower ultimate load and 26.4% lower post-yield work relative to C7. These mechanical changes coincided with 52.2% higher levels of pentosidine at D7 compared to C7. At the local level, the creep distance increased, while modulus and hardness decreased in the perilacunar region relative to the intracortical for D7 mice, suggesting a spatial uncoupling in skeletal adaptation. D7 mice also exhibited increased matrix maturity in the 1660/1690 cm-1 ratio at both regions relative to C7. The perilacunar matrix maturity was predictive of post-yield work (46%), but perilacunar measures were not predictive of ultimate load, which was better explained by cortical area (26%). These results show that diabetes causes local perilacunar composition perturbations that affect whole-bone level mechanical properties, implicating osteocyte maintenance of its local matrix in the progression of diabetic skeletal fragility.

Relative Effects of Radiation-Induced Changes in Bone Mass, Structure, and Tissue Material on Vertebral Strength in a Rat Model

The observed increased risk of fracture after cancer radiation therapy is presumably due to a radiation-induced reduction in whole-bone strength. However, the mechanisms for impaired strength remain unclear, as the increased fracture risk is not fully explained by changes in bone mass. To provide insight, a small animal model was used to determine how much of this whole-bone weakening effect for the spine is attributable to changes in bone mass, structure, and material properties of the bone tissue and their relative effects. Further, because women have a greater risk of fracture after radiation therapy than men, we investigated if sex had a significant influence on bone's response to irradiation. Fractionated in vivo irradiation (10 × 3 Gy) or sham irradiation (0 Gy) was administered daily to the lumbar spine in twenty-seven 17-week-old Sprague-Dawley rats (n = 6-7/sex/group). Twelve weeks after final treatment, animals were euthanized, and lumbar vertebrae (L4 and L5 ) were isolated. Using a combination of biomechanical testing, micro-CT-based finite element analysis, and statistical regression analysis, we separated out the effect of mass, structural, and tissue material changes on vertebral strength. Compared with the sham group (mean ± SD strength = 420 ± 88 N), the mean strength of the irradiated group was lower by 28% (117 N/420 N, p < 0.0001). Overall, the response of treatment did not differ with sex. By combining results from both general linear regression and finite element analyses, we calculated that mean changes in bone mass, structure, and material properties of the bone tissue accounted for 56% (66 N/117 N), 20% (23 N/117 N), and 24% (28 N/117 N), respectively, of the overall change in strength. As such, these results provide insight into why an elevated clinical fracture risk for patients undergoing radiation therapy is not well explained by changes in bone mass alone. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Collagen cross-link profiles and mineral are different between the mandible and femur with site specific response to perturbed collagen

Compromises to collagen and mineral lead to a decrease in whole bone quantity and quality in a variety of systemic diseases, yet, clinically, disease manifestations differ between craniofacial and long bones. Collagen alterations can occur through post-translational modification via lysyl oxidase (LOX), which catalyzes enzymatic collagen cross-link formation, as well as through non-enzymatic advanced glycation end products (AGEs) such as pentosidine and carboxymethyl-lysine (CML). Characterization of the cross-links and AGEs, and comparison of the mineral and collagen modifications in craniofacial and long bones represent a critical gap in knowledge. However, alterations to either the mineral or collagen in bone may contribute to disease progression and, subsequently, the anatomical site dependence of a variety of diseases. Therefore, we hypothesized that collagen cross-links and AGEs differ between craniofacial and long bones and that altered collagen cross-linking reduces mineral quality in an anatomic location dependent. To study the effects of cross-link inhibition on mineralization between anatomical sites, beta-aminoproprionitrile (BAPN) was administered to rapidly growing, 5-8 week-old male mice. BAPN is a dose-dependent inhibitor of LOX that pharmacologically alters enzymatic cross-link formation. Long bones (femora) and craniofacial bones (mandibles) were compared for mineral quantity and quality, collagen cross-link and AGE profiles, and tissue level mechanics, as well as the response to altered cross-links via BAPN. A highly sensitive liquid chromatography/mass spectrometry (LC-MS) method was developed which allowed for quantification of site-dependent accumulation of the advanced glycation end-product, carboxymethyl-lysine (CML). CML was ∼8.3× higher in the mandible than the femur. The mandible had significantly higher collagen maturation, mineral crystallinity, and Young's modulus, but lower carbonation, than the femur. BAPN also had anatomic specific effects, leading to significant decreases in mature cross-links in the mandible, and an increase in mineral carbonation in the femur. This differential response of both the mineral and collagen composition to BAPN between the mandible and femur highlights the need to further understand how inherent compositional differences in collagen and mineral contribute to anatomic-site specific manifestations of disease in both craniofacial and long bones.

Orchestrated delivery of PTH [1-34] followed by zoledronic acid prevents radiotherapy-induced bone loss but does not abrogate marrow damage

Postradiotherapy bone fragility fractures are a frequent late-onset complication in cancer survivors. There is a critical need to develop preventative interventions, and the use of Food and Drug Administration-approved drugs remains an attractive option. Prior data from our lab and others have shown that parathyroid hormone [1-34] mitigates radiotherapy-induced bone loss, but only for the duration of drug delivery. Utilizing a murine hindlimb radiotherapy model, we investigated whether orchestrated delivery of single-dose zoledronic acid could extend these anabolic benefits after cessation of parathyroid hormone delivery. We then explored the potential use of parathyroid hormone as a bone marrow radioprotectant. While the addition of zoledronic acid to parathyroid hormone increased irradiated bone mass, there was no increase in femur bending strength. In this model, the parathyroid hormone was not effective as a marrow radioprotectant, although this could be due to the short course of parathyroid hormone treatment. Marrow repopulation kinetics differed from those in total body irradiation, with hematopoietic stem cell repopulation occurring relatively early at four weeks postirradiation. Furthermore, we found radiation induced a loss of marrow stromal cells and an increase in inflammatory monocytes. Statement of Clinical Significance: Staged delivery of parathyroid hormone and zoledronic acid shows promise as an off-the-shelf intervention to mitigate post-radiotherapy bone damage in cancer patients, but parathyroid hormone is unlikely to function as a broad-spectrum marrow radioprotectant.

Constitutive bone marrow adipocytes suppress local bone formation

BM adipocytes (BMAd) are a unique cell population derived from BM mesenchymal progenitors and marrow adipogenic lineage precursors. Although they have long been considered to be a space filler within bone cavities, recent studies have revealed important physiological roles in hematopoiesis and bone metabolism. To date, the approaches used to study BMAd function have been confounded by contributions by nonmarrow adipocytes or by BM stromal cells. To address this gap in the field, we have developed a BMAd-specific Cre mouse model to deplete BMAds by expression of diphtheria toxin A (DTA) or by deletion of peroxisome proliferator-activated receptor gamma (Pparg). We found that DTA-induced loss of BMAds results in decreased hematopoietic stem and progenitor cell numbers and increased bone mass in BMAd-enriched locations, including the distal tibiae and caudal vertebrae. Elevated bone mass appears to be secondary to enhanced endosteal bone formation, suggesting a local effect caused by depletion of BMAd. Augmented bone formation with BMAd depletion protects mice from bone loss induced by caloric restriction or ovariectomy, and it facilitates the bone-healing process after fracture. Finally, ablation of Pparg also reduces BMAd numbers and largely recapitulates high-bone mass phenotypes observed with DTA-induced BMAd depletion.

Irradiation Induced Biochemical Changes in Human Mandibular Bone: A Raman Spectroscopic Study

Understanding the biochemical changes in irradiated human mandible after radiotherapy of cancer patients is critical for oral rehabilitation. The underlying mechanism for radiation-associated changes in the bone at the molecular level could lead to implant failure and osteoradionecrosis. The study aimed to assess the chemical composition and bone quality in irradiated human mandibular bone using Raman spectroscopy. A total of 33 bone biopsies from 16 control and 17 irradiated patients were included to quantify different biochemical parameters from the Raman spectra. The differences in bone mineral and matrix band intensities between control and irradiated groups were analyzed using unpaired Student's t-test with statistical significance at p < 0.05. Findings suggest that the intensity of the phosphate band is significantly decreased and the carbonate band is significantly increased in the irradiated group. Further, the mineral crystallinity and carbonate to phosphate ratio are increased. The mineral to matrix ratio is decreased in the irradiated group. Principal component analysis (PCA) based on the local radiation dose and biopsy time interval of irradiated samples did not show any specific classification between irradiation sub-groups. Irradiation disrupted the interaction and bonding between the organic matrix and hydroxyapatite minerals affecting the bone biochemical properties. However, the normal clinical appearance of irradiated bone would have been accompanied by underlying biochemical and microscopical changes which might result in radiation-induced delayed complications.

Influence of Radiotherapy on Ossification of Vascularized Osseous Reconstruction of the Jaw: A Radiological Retrospective Cohort Study Based on Panoramic Radiographs

Background: The aim of this study was to evaluate the impact of irradiation and time of irradiation on the ossification of jaws reconstructed with free bone grafts. Methods: In total, 100 reconstructions of the jaw were retrospectively evaluated for ossification between bone segments by two raters based on postoperative panoramic radiographs (immediate postOP, approximately 6, 12 and 24 months follow-up). Three subgroups were divided according to the time of irradiation: preoperative radiation therapy (n = 41), postoperative radiation therapy (n = 26) and patients without any radiation therapy (n = 33) as the control group. Ossification time and influencing factors were documented. Results: The fastest ossification with a median of 304 ± 37 days was observed (p < 0.001) in the nonirradiated control group. No significant difference (p = 0.087) in ossification was found between the pre- (447 ± 136 days) and postoperative (510 ± 112 days) radiation groups. Ossification between two graft segments (336 ± 38 days) showed significantly (p < 0.001) faster ossification than between the original and grafted bone (448 ± 85 days). Moreover, closer initial contact between the segments resulted in faster ossification (p < 0.001). When analyzing cofactors, tobacco consumption was the only negative factor aggravating ossification (p = 0.006). Conclusion: Head and neck radiation corresponded with the impaired and prolonged ossification of jaw reconstructions with free bone grafts. There was no difference in ossification if radiotherapy was performed before or after reconstructive surgery. A close bony contact was particularly important for ossification between the original and grafted bone.

Assessment of bone dose response using ATR-FTIR spectroscopy: A potential method for biodosimetry

The health care application of ionizing radiation has expanded worldwide during the last several decades. While the health impacts of ionizing radiation improved patient care, inaccurate handling of radiation technology is more prone to potential health risks. Therefore, the present study characterizes the bone dose response using bovine femurs from a slaughterhouse. The gamma irradiation was designed into low-doses (0.002, 0.004 and 0.007 kGy) and high-doses (1, 10, 15, 25, 35, 50 and 60 kGy), all samples received independent doses. The combination of FTIR spectroscopy and PLS-DA allows the detection of differences in the control group and the ionizing dose, as well as distinguishing between high and low radiation doses. In this way, our findings contribute to future studies of the dose response to track ionizing radiation effects on biological systems.

Influence of Metastatic Bone Lesion Type and Tumor Origin on Human Vertebral Bone Architecture, Matrix Quality, and Mechanical Properties

Metastatic spine disease is incurable, causing increased vertebral fracture risk and severe patient morbidity. Here, we demonstrate that osteolytic, osteosclerotic, and mixed bone metastasis uniquely modify human vertebral bone architecture and quality, affecting vertebral strength and stiffness. Multivariable analysis showed bone metastasis type dominates vertebral strength and stiffness changes, with neither age nor gender having an independent effect. In osteolytic vertebrae, bone architecture rarefaction, lower tissue mineral content and connectivity, and accumulation of advanced glycation end-products (AGEs) affected low vertebral strength and stiffness. In osteosclerotic vertebrae, high trabecular number and thickness but low AGEs, suggesting a high degree of bone remodeling, yielded high vertebral strength. Our study found that bone metastasis from prostate and breast primary cancers differentially impacted the osteosclerotic bone microenvironment, yielding altered bone architecture and accumulation of AGEs. These findings indicate that therapeutic approaches should target the restoration of bone structural integrity. © 2022 American Society for Bone and Mineral Research (ASBMR).

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.

[Oncologic aspects in treatment of pathologic fractures]

BACKGROUND

Pathological fractures are not only incisive events for tumor patients often with the need of surgical treatment but also often represent a relevant challenge in the overall concept of oncological treatment.

OBJECTIVE

The aim of this article is to illustrate the necessity of a pre-interventional interdisciplinary consideration of disease-specific and patient-specific characteristics.

MATERIAL AND METHODS

A literature search and evaluation of existing guidelines were carried out including the keywords "bone metastases" and "pathological fractures" with respect to the oncological and radiotherapeutic treatment.

RESULTS

An essential classification of the surgical and other needs for treatment is carried out by the identification of the underlying disease and dissemination situation. For tumor-related pathological fractures a palliative treatment situation is present in most cases. Nevertheless, a possible oligometastasis and an increasing number of effective systemic treatment methods must be taken into consideration when planning the surgical treatment. In addition to the therapeutic emergency indications in spinal compression or symptomatic hypercalcemia, both additive radiotherapy and supplementary pharmaceutical osteoprotection have to be addressed in this context. Radiotherapy in particular represents an effective alternative option for symptom and tumor control.

CONCLUSION

The work-up of the multifaceted oncological treatment concept represents an interdisciplinary challenge, which ideally defines the further treatment procedure, including fracture treatment, in an interdisciplinary tumor board within an overall oncological concept.

The Side Effects of Therapeutic Radioiodine-131 on the Structure of Enamel and Dentin in Permanent Human Teeth

Simple Summary

Our research suggest radioiodine-131 used for differentiated thyroid carcinomas has an impact on the oral health of patients. We found that alteration of dental hard tissues starts after 6 h post-radioiodine administration. These findings highlight the importance of the multidisciplinary team management in the quality of life of the oncological patient.

Abstract

Radioiodine-131 (I-131) is an essential therapy for patients with differentiated thyroid carcinomas (DTC). Generally, I-131 is safe and well tolerated, but patients may present early or late complications in the oral and maxillofacial areas. Thus, the aim of this study was to evaluate in-vitro, the alteration of enamel and dentin after I-131 exposure using histopathological assessment, scanning electron microscopy (SEM) and atomic force microscopy (AFM). For I-131 irradiation, an in-vitro protocol was used that simulates the procedure for irradiation therapy performed for patients with DTCs. A total of 42 teeth were divided into seven groups (n = 6) and irradiated as follows: control, irradiation groups (3, 6, 12, 36, 48 h, 8 days). Histological changes were observed at 48 h (enamel surface with multifocal and irregular areas) and at 8 days (enamel surface with multiple, very deep, delimited cavities). SEM imaging revealed the enamel destruction progresses along with the treatment time increasing. The alterations are extended into the enamel depth and the dislocated hydroxyapatite debris is overwhelming. The enamel-dentine interface shows small gaps after 6 h and a very well developed valley after 12 h; the interface microstructure resulted after 8 days is deeply altered. The AFM imaging shows that I-131 affects the protein bond between hydroxyapatite nano-crystals causing loss of cohesion, which leads to significant increasing of nano-particles diameter after 6 h. In conclusion, both enamel and dentin appear to be altered between 12 and 48 h and after 8 days of treatment are extended in depth.

Outcome and prognosis for canine appendicular osteosarcoma treated with stereotactic body radiation therapy in 123 dogs

Canine appendicular osteosarcoma is commonly treated with limb amputation; however, limb-sparing options are frequently desired or necessary for a subset of patients. We evaluated 123 patients and 130 sites treated with stereotactic body radiation therapy (SBRT). Eighty-two out of 98 dogs (84%) had maximum lameness improvement at a median of 3 weeks for a median of 6 months duration. Histopathologic evaluation of available samples from amputation or necropsy revealed >80% tumor necrosis in 50% of limbs consistent with local disease control. Of evaluable patients, 41% fractured and 21% pursued an amputation after treatment. Fine needle aspirate (n = 52) and needle core biopsy (n = 28) did not result in increased fracture risk compared to those without tumor sampling (n = 50). Median survival time (MST) was 233 days and time to first event was 143 days. Gross tumor volume and planned target volume were significantly inversely associated with survival and tumor location was significantly associated with survival. Dogs with salvage amputation had a significantly longer MST compared to those without (346 vs 202 days; P = .04). The presence of metastatic disease at the time of treatment in 15 dogs did not significantly impact survival time (200 vs 237 days without metastasis; P = .58). Skin side effects correlated significantly with dose with 33% of patients with acute grade 3 effects developing consequential late grade 3 effects. While SBRT improves lameness in most patients, further investigation is needed to identify candidates with minimal early fracture risk prior to initiating therapy.