Suppression of proteolipid protein rescues Pelizaeus-Merzbacher disease.

Mutations in PLP1, the gene that encodes proteolipid protein (PLP), result in failure of myelination and neurological dysfunction in the X-chromosome-linked leukodystrophy Pelizaeus-Merzbacher disease (PMD)1,2. Most PLP1 mutations, including point mutations and supernumerary copy variants, lead to severe and fatal disease. Patients who lack PLP1 expression, and Plp1-null mice, can display comparatively mild phenotypes, suggesting that PLP1 suppression might provide a general therapeutic strategy for PMD1,3-5. Here we show, using CRISPR-Cas9 to suppress Plp1 expression in the jimpy (Plp1jp) point-mutation mouse model of severe PMD, increased myelination and restored nerve conduction velocity, motor function and lifespan of the mice to wild-type levels. To evaluate the translational potential of this strategy, we identified antisense oligonucleotides that stably decrease the levels of Plp1 mRNA and PLP protein throughout the neuraxis in vivo. Administration of a single dose of Plp1-targeting antisense oligonucleotides in postnatal jimpy mice fully restored oligodendrocyte numbers, increased myelination, improved motor performance, normalized respiratory function and extended lifespan up to an eight-month end point. These results suggest that PLP1 suppression could be developed as a treatment for PMD in humans. More broadly, we demonstrate that oligonucleotide-based therapeutic agents can be delivered to oligodendrocytes in vivo to modulate neurological function and lifespan, establishing a new pharmaceutical modality for myelin disorders.

Intranasal corticosteroids for non-allergic rhinitis.

BACKGROUND: Non-allergic rhinitis is defined as dysfunction and non-infectious inflammation of the nasal mucosa that is caused by provoking agents other than allergens or microbes. It is common, with an estimated prevalence of around 10% to 20%. Patients experience symptoms of nasal obstruction, anterior rhinorrhoea/post-nasal drip and sneezing. Several subgroups of non-allergic rhinitis can be distinguished, depending on the trigger responsible for symptoms; these include occupation, cigarette smoke, hormones, medication, food and age. On a cellular molecular level different disease mechanisms can also be identified. People with non-allergic rhinitis often lack an effective treatment as a result of poor understanding and lack of recognition of the underlying disease mechanism. Intranasal corticosteroids are one of the most common types of medication prescribed in patients with rhinitis or rhinosinusitis symptoms, including those with non-allergic rhinitis. However, it is unclear whether intranasal corticosteroids are truly effective in these patients. OBJECTIVES: To assess the effects of intranasal corticosteroids in the management of non-allergic rhinitis. SEARCH METHODS: The Cochrane ENT Information Specialist searched the Cochrane ENT Register; Cochrane Central Register of Controlled Trials (CENTRAL 2019, Issue 7); PubMed; Ovid Embase; CINAHL; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the search was 1 July 2019. SELECTION CRITERIA: Randomised controlled trials (RCTs) comparing intranasal corticosteroids, delivered by any means and in any volume, with (a) placebo/no intervention or (b) other active treatments in adults and children (aged ≥ 12 years). DATA COLLECTION AND ANALYSIS: We used the standard methodological procedures expected by Cochrane. The primary outcomes were patient-reported disease severity and a significant adverse effect - epistaxis. Secondary outcomes were (disease-specific) health-related quality of life, objective measurements of airflow and other adverse events. We used GRADE to assess the certainty of the evidence for each outcome. MAIN RESULTS: We included 34 studies (4452 participants); however, only 13 studies provided data for our main comparison, intranasal corticosteroids versus placebo. The participants were mainly defined as patients with perennial rhinitis symptoms and negative allergy tests. No distinction between different pheno- and endotypes could be made, although a few studies only included a specific phenotype such as pregnancy rhinitis, vasomotor rhinitis, rhinitis medicamentosa or senile rhinitis. Most studies were conducted in a secondary or tertiary healthcare setting. No studies reported outcomes beyond three months follow-up. Intranasal corticosteroid dosage in the review ranged from 50 µg to 2000 µg daily. Intranasal corticosteroids versus placebo Thirteen studies (2045 participants) provided data for this comparison. These studies used different scoring systems for patient-reported disease severity, so we pooled the data in each analysis using the standardised mean difference (SMD). Intranasal corticosteroid treatment may improve patient-reported disease severity as measured by total nasal symptom score compared with placebo at up to four weeks (SMD -0.74, 95% confidence interval (CI) -1.15 to -0.33; 4 studies; 131 participants; I2 = 22%) (low-certainty evidence). However, between four weeks and three months the evidence is very uncertain (SMD -0.24, 95% CI -0.67 to 0.20; 3 studies; 85 participants; I2 = 0%) (very low-certainty evidence). Intranasal corticosteroid treatment may slightly improve patient-reported disease severity as measured by total nasal symptom score change from baseline when compared with placebo at up to four weeks (SMD -0.15, 95% CI -0.25 to -0.05; 4 studies; 1465 participants; I2 = 35%) (low-certainty evidence). All four studies evaluating the risk of epistaxis showed that there is probably a higher risk in the intranasal corticosteroids group (65 per 1000) compared to placebo (31 per 1000) (risk ratio (RR) 2.10, 95% CI 1.24 to 3.57; 4 studies; 1174 participants; I2 = 0%) (moderate-certainty evidence). The absolute risk difference (RD) was 0.04 with a number needed to treat for an additional harmful outcome (NNTH) of 25 (95% CI 16.7 to 100). Only one study reported numerical data for quality of life. It did report a higher quality of life score in the intranasal corticosteroids group (152.3 versus 145.6; SF-12v2 range 0 to 800); however, this disappeared at longer-term follow-up (148.4 versus 145.6) (low-certainty evidence). Only two studies provided data for the outcome objective measurements of airflow. These data could not be pooled because they used different methods of outcome measurement. Neither found a significant difference between the intranasal corticosteroids and placebo group (rhinomanometry SMD -0.46, 95% CI -1.06 to 0.14; 44 participants; peak expiratory flow rate SMD 0.78, 95% CI -0.47 to 2.03; 11 participants) (very low-certainty evidence). Intranasal corticosteroids probably resulted in little or no difference in the risk of other adverse events compared to placebo (RR 0.99, 95% CI 0.87 to 1.12; 3 studies; 1130 participants; I2 = 0%) (moderate-certainty evidence). Intranasal corticosteroids versus other treatments Only one or a few studies assessed each of the other comparisons (intranasal corticosteroids versus saline irrigation, intranasal antihistamine, capsaicin, cromoglycate sodium, ipratropium bromide, intranasal corticosteroids combined with intranasal antihistamine, intranasal corticosteroids combined with intranasal antihistamine and intranasal corticosteroids with saline compared to saline alone). It is therefore uncertain whether there are differences between intranasal corticosteroids and other active treatments for any of the outcomes reported. AUTHORS' CONCLUSIONS: Overall, the certainty of the evidence for most outcomes in this review was low or very low. It is unclear whether intranasal corticosteroids reduce patient-reported disease severity in non-allergic rhinitis patients compared with placebo when measured at up to three months. However, intranasal corticosteroids probably have a higher risk of the adverse effect epistaxis. There are very few studies comparing intranasal corticosteroids to other treatment modalities making it difficult to draw conclusions.

Capsaicin for non-allergic rhinitis.

BACKGROUND: There are many forms of rhinitis. Patients are diagnosed with non-allergic rhinitis when anatomic, infectious and allergic aetiologies have been excluded. The symptoms, including nasal congestion, blockage or obstruction, clear rhinorrhoea, sneezing and, less frequently, nasal itching, can range from mild to debilitating. It affects between 25% and 50% of patients with rhinitis. Several medications are widely used in the treatment of non-allergic rhinitis, including oral and topical nasal antihistamines, intranasal and (rarely) systemic corticosteroids, and anticholinergics. Capsaicin, the active component of chili peppers, delivered intranasally, is considered a treatment option for non-allergic rhinitis. OBJECTIVES: To assess the effectiveness of capsaicin in the management of non-allergic rhinitis compared with no therapy, placebo or other topical or systemic medications, or two or more of the above therapies in combination, or different capsaicin regimens. SEARCH METHODS: We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL 2015, Issue 5); PubMed; EMBASE; CINAHL; Web of Science; Cambridge Scientific Abstracts; ICTRP and additional sources for published and unpublished trials. The date of the search was 24 June 2015. SELECTION CRITERIA: Randomised controlled trials in adult patients with non-allergic rhinitis comparing intranasal capsaicin with no therapy, placebo or other topical or systemic medications, or their combinations. DATA COLLECTION AND ANALYSIS: We used the standard methodological procedures expected by The Cochrane Collaboration. MAIN RESULTS: We included four studies (five publications) involving 302 participants with idiopathic non-allergic rhinitis. All the included studies described patients with moderately severe, idiopathic non-allergic rhinitis who were between the ages of 16 and 65. Studies had follow-up periods ranging from four to 38 weeks. The overall risk of bias in the studies was either high or unclear (two studies had overall high risk of bias, while two others had low to unclear risk of bias). Using the GRADE system we assessed the evidence as being of low to moderate quality. A meta-analysis was not possible, given lack of similarity of the reported outcomes.Two studies compared capsaicin with placebo. One study reported that capsaicin resulted in an improvement of overall nasal symptoms (a primary outcome) measured on a visual analogue scale (VAS) of 0 to 10. There was a mean difference (MD) of -3.34 (95% confidence interval (CI) -5.24 to -1.44), MD -3.73 (95% CI -5.45 to -2.01) and MD -3.52 (95% CI -5.55 to -1.48) at two, 12 and 36 weeks post-treatment, respectively. Another study reported that, compared to placebo, capsaicin (at 4 µg/puff) was more likely to produce overall symptom resolution (reduction in nasal blockage, sneezing/itching/coughing and nasal secretion measured with a daily record chart) at four weeks post-treatment (a primary outcome). The risk ratio (RR) was 3.17 (95% CI 1.38 to 7.29).One study compared capsaicin to budesonide (an intranasal corticosteroid). This study found that patients treated with capsaicin had a better overall symptom score compared to those treated with budesonide (MD 2.50, 95% CI 1.06 to 3.94, VAS of 0 to 10). However, there were no differences in the individual symptom scores for headache, postnasal drip, rhinorrhoea, nasal blockage, sneezing and sore throat assessed during the last three days of a four-week treatment.One study compared two different regimens of capsaicin administration: five treatments in one day versus five treatments given every two to three days during two weeks. Using daily record charts, the study reported significant improvement of individual symptom scores for rhinorrhoea in patients treated five times per day, however numerical data were not presented. There were no improvements in the other outcomes: rhinorrhoea, nasal obstruction, sneezing and overall nasal symptoms, measured on a VAS.Finally, one of these studies also compared three doses of capsaicin (to placebo). Patients treated with a 1 µg versus 4 µg per puff dose of capsaicin had a worse daily record chart overall symptom score resolution (RR 0.63, 95% CI 0.34 to 1.16).Only one study attempted to measure adverse effects (a primary outcome), however due to methodological issues with the assessment we are unable to draw any conclusions.We sought to include other secondary outcomes (e.g. quality of life measures, treatment dropouts, endoscopic scores, turbinate or mucosal size, cost of therapy), but none of these were measured or reported in the included studies. AUTHORS' CONCLUSIONS: Capsaicin may be an option in the treatment of idiopathic non-allergic rhinitis. It is given in the form of brief treatments, usually during the same day. It appears to have beneficial effects on overall nasal symptoms up to 36 weeks after treatment, based on a few, small studies (low-quality evidence). Well-conducted randomised controlled trials are required to further advance our understanding of the effectiveness of capsaicin in non-allergic rhinitis, especially in patients with non-allergic rhinitis of different types and severity, and using different methods of capsaicin application.

Disease-specific quality-of-life questionnaires in rhinitis and rhinosinusitis: review and evaluation.

Quality of life (QoL) measurements are the best approximation of the burden of disease for the patient. Patient-reported outcome measurements (PROMs) estimate health-related quality of life (HRQoL). PROMs can be generic or disease-specific. Generic PROMs allow comparisons between different diseases but can be relatively insensitive for measuring changes within a disease. Recommended QoL questionnaires in allergic rhinitis and rhinoconjunctivitis are the RQLQ (or adapted versions), in chronic rhinosinusitis, the SNOT-22 or RSOM-31, and in acute rhinosinusitis, the modified SNOT-16. PROMs can be used both for daily clinical work and for research. In daily practice, a quick evaluation of the questionnaire directly indicates how the patient is doing. It makes sure that symptoms important for the patient are not overlooked and, during the consultation, the physician can elaborate on specific aspects of the symptomatology. It is important, especially in research, to realize that disease-specific questionnaires are only validated for specific diseases and are not automatically valid for other diseases.

Correcting a bent septum by a k-wire stabilization during an extracorporeal septal reconstruction.

BACKGROUND: Extracorporeal septoplasty has been successfully employed in difficult cases of septal deviation. A novel technique of wire fixation during extracorporeal septoplasty is presented. METHODS: All patients had complete or near complete nasal airway blockage. The quadrangular cartilage was entirely removed through an open approach. The bent areas were scored, and K-wires were placed to fix the cartilage in the straightened position. The cartilage was replaced and fixated to the bony septum, upper lateral cartilages, and anterior maxillary crest. The K-wire was removed after 6 weeks. RESULTS: Fifteen of 17 patients retained straightness of the septum, and 13 of 17 achieved subjective improvement in nasal breathing. There was one skin infection which was treated with oral antibiotics with complete resolution. Two wires required a percutaneous incision to remove. CONCLUSIONS: The presented technique of extracorporeal septoplasty with wire fixation can be successfully employed for extreme septal deviations. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Non-canonical Targets of HIF1a Impair Oligodendrocyte Progenitor Cell Function.

Mammalian cells respond to insufficient oxygen through transcriptional regulators called hypoxia-inducible factors (HIFs). Although transiently protective, prolonged HIF activity drives distinct pathological responses in different tissues. Using a model of chronic HIF1a accumulation in pluripotent-stem-cell-derived oligodendrocyte progenitors (OPCs), we demonstrate that HIF1a activates non-canonical targets to impair generation of oligodendrocytes from OPCs. HIF1a activated a unique set of genes in OPCs through interaction with the OPC-specific transcription factor OLIG2. Non-canonical targets, including Ascl2 and Dlx3, were sufficient to block differentiation through suppression of the oligodendrocyte regulator Sox10. Chemical screening revealed that inhibition of MEK/ERK signaling overcame the HIF1a-mediated block in oligodendrocyte generation by restoring Sox10 expression without affecting canonical HIF1a activity. MEK/ERK inhibition also drove oligodendrocyte formation in hypoxic regions of human oligocortical spheroids. This work defines mechanisms by which HIF1a impairs oligodendrocyte formation and establishes that cell-type-specific HIF1a targets perturb cell function in response to low oxygen.

CSO (Canadian Society of Otolaryngology - Head & Neck Surgery) position paper on rhinologic and skull base surgery during the COVID-19 pandemic.

Healthcare services in many countries have been partially or completely disrupted by the Coronavirus (COVID-19) pandemic since its onset in the end of 2019. Amongst the most impacted are the elective medical and surgical services in order to conserve resources to care for COVID-19 patients. As the number of infected patients decrease across Canada, elective surgeries are being restarted in a staged manner. Since Otolaryngologists - Head & Neck Surgeons manage surgical diseases of the upper aerodigestive tract where the highest viral load reside, it is imperative that these surgeries resume in a safe manner. The aim of this document is to compile the current best evidence available and provide expert consensus on the safe restart of rhinologic and skull base surgeries while discussing the pre-operative, intra-operative, and post-operative care and tips. Risk assessment, patient selection, case triage, and pre-operative COVID-19 testing will be analyzed and discussed. These guidelines will also consider the optimal use of personal protective equipment for specific cases, general and specific operative room precautions, and practical tips of intra-operative maneuvers to optimize patient and provider safety. Given that the literature surrounding COVID-19 is rapidly evolving, these recommendations will serve to start our specialty back into elective rhinologic surgeries over the next months and they may change as we learn more about this disease.

A late recognition of tapia syndrome: a case report and literature review.

Tapia syndrome is characterized by concurrent paralysis of the recurrent laryngeal and hypoglossal nerves. The mechanism is associated with airway manipulation in 70% of patients and is attributed to compression or stretching of these nerves. Diagnosis is based on recognition of the concurrent paralyses and investigations to exclude central or vascular causes. Treatment is supportive, with emphasis on empiric corticosteroids and dysphagia therapy. Recovery is excellent in 30% of patients, incomplete in 39% of patients, and none in over 26% of patients. A case of a 48-year-old woman is described, who was diagnosed with Tapia syndrome 3 years after the suspected injury.

Osteoradionecrosis of the mandible: a case series at a single institution.

BACKGROUND: Osteoradionecrosis (ORN) defines exposed irradiated bone, which fails to heal over a period of 3-6 months without evidence of residual or recurrent tumor. In the previous decades, a staging and treatment protocol suggested by Marx, has dominated the approach to ORN. However, recently this paradigm is shifting. The purpose of this study was to evaluate our institutional experience in managing ORN through a retrospective review of case series from a large urban academic cancer centre. METHODS: A retrospective chart review was conducted to include all ORN cases from 2003 to 2009 diagnosed at the Department of Otolaryngology - Head and Neck Surgery and the Department of Dentistry. The staging of ORN was assessed as affected by tumor site, tumor stage, radiotherapy modality and dose, chemotherapy, dental work, and time to diagnosis. The effectiveness of hyperbaric oxygen therapy (HBO) and surgery in the management of ORN was evaluated. RESULTS: Fourteen cases of ORN were documented (incidence 0.84%). Primary subsites included tonsils, tongue, retromolar trigone, parotid gland, soft palate and buccal mucosa. There were 5 (35.7%) stage 1, 3 (21.4%) stage 2, and 6 (42.9%) stage 3 cases. ORN severity was not significantly associated with gender, smoking, alcohol use, tumor site, T stage, N stage, AJCC stage, or treatment modality (radiation alone, surgery with adjuvant radiation or adjuvant chemoradiation). Patients treated with intensity-modulated radiotherapy developed less severe ORN compared to those treated with conventional radiotherapy (p < 0.015). ORN stage did not correlate with radiation dose. In one patient only dental procedures were performed following radiation and could be implicated as the cause of ORN. HBO therapy failed to prevent ORN progression. Surgical treatment was required for most stage 2 (partial resections and free tissue transfers) and stage 3 patients (mandibulectomies and free tissue transfers, including two flaps in one patient). At an average follow up of 26 months, all patients were cancer-free, and there was no evidence of ORN in 84% of patients. CONCLUSIONS: In early ORN, we advocate a conservative approach with local care, while reserving radical resections with robust reconstruction with vascularized free tissue for advanced stages.

Bisphosphonate-induced necrosis of the jaws: a reconstructive nightmare.

PURPOSE OF REVIEW: Bisphosphonates are used for the management of metastatic bone disease, prevention and treatment of osteoporosis and Paget's disease of bone. An increasing number of reports have associated the use of bisphosphonates with the occurrence of osteoradionecrosis of the jaw. The purpose of this review is to summarize the recent literature in this area, specifically focusing on its management. RECENT FINDINGS: Osteoradionecrosis of the jaw mostly results from the use of intravenous bisphosphonates for metastatic bone disease and multiple myeloma; cases from oral treatment for osteoporosis and Paget's disease have also been reported. It mostly affects the posterior maxilla, followed by the posterior mandible. In more than half of the affected patients, there has been preceding dental trauma or procedure. Many treatment modalities have been attempted in order to limit disease progression. Conservative management with antibiotic therapy and mouthwashes seems to be most beneficial. Surgery should be reserved for refractory and symptomatic cases. SUMMARY: It is important for the reconstructive head and neck surgeon to recognize the clinical presentation of bisphosphonate-induced osteoradionecrosis of the jaw and the role of conservative management in consistently achieving good results.

Supraorbital artery myocutaneous island flap for forehead defect reconstruction.

The frontalis musculocutaneous island flap offers advantages of immediate repair for small to medium-sized forehead defects (0.5-5 x 0.5-5 cm). Based on the supraorbital artery, the flap is both adaptable and dependable. Advantages of this flap include the ability to perform the procedure immediately and in one stage, rapid aesthetic restoration, minor donor-site morbidity, and technical ease. A clinical report demonstrating the use of this flap for repair of an electrothermal injury to the glabella is presented.

Radiation effects and radioprotection in MC3T3-E1 mouse calvarial osteoblastic cells.

BACKGROUND: Little is known about the mechanisms and treatment of radiation-induced inhibition of craniofacial bone growth. In an earlier study, the radioprotector amifostine (WR-2721) administered to rabbits before irradiation radioprotected cultured orbitozygomatic complex periosteal osteoblast-like cells. This study assessed the effects of amifostine and its active metabolite on the radiation survival, function, and phenotype of mouse calvarial osteoblast-like cells in a cell culture model. METHODS: MC3T3-E1 newborn mouse calvarial osteoblast-like cells underwent gamma-radiation (0 to 10 Gy) in the presence or absence of either WR-2721 or WR-1065, its active metabolite (10 to 10 M). The effects of radiation with and without drugs were assessed using endpoints of colony-forming ability, cell viability, alkaline phosphatase activity, and expression of osteoblastic phenotype genes (alkaline phosphatase, collagen type I, osteocalcin, and osteopontin). All experiments were replicated at least in triplicate. RESULTS: Irradiation resulted in a dose-dependent inhibition of clonogenic cell survival. Pretreatment with WR-1065, but not WR-2721, resulted in a significant improvement of osteoblast-like cell survival. Specifically, maximum radioprotection was observed with 10 M WR-1065 at a clinically relevant 2-Gy dose of irradiation. No significant radioprotection was observed at the lower (5 x 10 M) concentration of WR-1065. Furthermore, radiation seemed to suppress the expression of osteoblastic phenotype-related genes in a dose-dependent manner. CONCLUSIONS: This study reveals improved survival after irradiation in osteoblast-like cells treated with WR-1065 in vitro and corroborates previous findings from animal models. Further studies using this agent and similar drugs are important for devising strategies to prevent radiation-induced inhibition of craniofacial bone growth.

Radiation-induced craniofacial bone growth inhibition: in vitro cytoprotection in the rabbit orbitozygomatic complex periosteum-derived cell culture.

BACKGROUND: Radiotherapy for the management of head and neck cancer in pediatric patients results in severe inhibition of craniofacial bone growth. Previously, the infant rabbit orbitozygomatic complex was established as an experimental model. Amifostine, a cytoprotective agent, was found effective in preventing radiation-induced bone growth inhibition. This study was designed to investigate the effects radiation on osteogenic cells from infant rabbit orbitozygomatic complex periostea and to assess the effects of cytoprotection in vitro. METHODS: Infant New Zealand White rabbits (n = 18) were randomized into three groups and received radiation (0, 10, or 15 Gy) to both orbitozygomatic complexes. Cell cultures were developed from orbitozygomatic complex periostea, and cell numbers, proliferation, alkaline phosphatase, and collagen type I expression and mineralization were assessed. Subsequently, rabbits (n = 18) were randomized into three groups to receive either radiation at the effective dose, pretreatment with amifostine (300 mg/kg, intravenously, 20 minutes before irradiation) with the effective radiation dose, or no treatment. Cell cultures were developed and tested for proliferation and alkaline phosphatase expression. RESULTS: Irradiation resulted in a significant inhibition of cell numbers (p < 0.001) and proliferation (p < 0.01) at the 15-Gy dose and no statistically significant changes in alkaline phosphatase activity. Collagen type I expression and mineralization were also significantly reduced at the 15-Gy dose. Pretreatment with amifostine significantly (p < 0.05) enhanced the number of surviving cells. CONCLUSIONS: Amifostine is capable of protecting orbitozygomatic complex periosteum-derived osteogenic cells from the deleterious effects of radiation. This study provides the basis for understanding the cellular mechanisms of radiation-induced craniofacial bone growth inhibition and cytoprotection by amifostine.

Radioprotection of craniofacial bone growth.

In this review, the potential of pharmacologic therapy for prevention of radiation-induced bone growth inhibition is discussed. Significant radioprotection using the radioprotector Amifostine has been achieved in animal models of radiation-induced retardation of long and craniofacial bone growth. Moreover, radioprotection in vitro has been achieved in a number of cell lines, including osteoblast-like, endothelial, and fibroblastic. This evidence may support future clinical investigations of radioprotector Amifostine or similar substances for radioprotection of the growing craniofacial skeleton.

Radiation-induced craniofacial bone growth disturbances.

Multimodality treatment, including radiotherapy, chemotherapy, and surgery, is required for the management of head and neck cancer in pediatric patients. Despite the modern advances in radiation dosing and targeting techniques, the radiation damage to the growing craniofacial skeleton in children remains a significant clinical problem. The first part of this review summarizes the clinical effects of radiotherapy on craniofacial bone growth in children. Experimental evidence on therapeutic radiation effects on bone growth in in vivo and in vitro models is reviewed. The second part of this review focuses on prevention of radiation-induced craniofacial bone growth inhibition using radioprotective agents.

An in vitro model of radiation-induced craniofacial bone growth inhibition.

Radiation-induced craniofacial bone growth inhibition is a consequence of therapeutic radiation in the survivors of pediatric head and neck cancer. Previously, the infant rabbit orbitozygomatic complex (OZC) was established as a reliable animal model. The purpose of this study was to develop a cell culture model from the rabbit OZC to study the effects of radiation in the craniofacial skeleton. Infant (7-week-old) New Zealand white rabbits were used in this study. Periostea from both OZC were harvested in sterile conditions, introduced into cell culture by way of sequential digestion, and subcultured at confluence. Cultures were analyzed for cellular proliferation (methylthiazoletetrazolium assay), alkaline phosphatase activity, collagen type I expression, and mineralization. Electron microscopy was performed to reveal the in vitro ultrastructure. Subsequently, rabbits were irradiated with sham or 15 Gy radiation, and cell cultures were developed and analyzed for cell numbers. Cell cultures, grown from OZC periostea, expressed osteoblast-like phenotype, with high alkaline phosphatase activity, collagen type 1 expression, and mineralization in an osteogenic environment. Electron microscopy confirmed the characteristic ultrastructural features of osteogenesis in vitro. Finally, significantly (P < 0.01) fewer cells were obtained from animals treated with 15 Gy radiation compared with those from control animals.A primary cell culture with osteoblast-like cellular phenotype was developed from infant rabbit OZC periosteum. This cell culture system responded to in vivo administered radiation by a significant decrease in cell numbers. This in vitro model will be subsequently used to study the cellular mechanisms of radiation and radioprotection in craniofacial osteoblast-like cells.