Osteochondroma Pathogenesis: Mouse Models and Mechanistic Insights into Interactions with Retinoid Signaling

Cartilage Forming Tumors of the Skeleton

Cartilage-forming tumors are a broad and diverse group of neoplasms frequently affecting the skeleton. Distinguishing between the members of this group is important because of significant differences in treatment and prognosis. Accurate diagnosis can be challenging because of similarities in their clinical, radiographic, and pathologic features. Immunohistochemistry and molecular tools are helpful in select instances. Therefore, careful evaluation and correlation of these features are essential in arriving at the correct diagnosis and appropriate patient management. This review provides an overview of the current literature, emphasizing helpful features in diagnosis.

Bone and Joint-on-Chip Platforms: Construction Strategies and Applications

Organ-on-a-chip, also known as "tissue chip," is an advanced platform based on microfluidic systems for constructing miniature organ models in vitro. They can replicate the complex physiological and pathological responses of human organs. In recent years, the development of bone and joint-on-chip platforms aims to simulate the complex physiological and pathological processes occurring in human bones and joints, including cell-cell interactions, the interplay of various biochemical factors, the effects of mechanical stimuli, and the intricate connections between multiple organs. In the future, bone and joint-on-chip platforms will integrate the advantages of multiple disciplines, bringing more possibilities for exploring disease mechanisms, drug screening, and personalized medicine. This review explores the construction and application of Organ-on-a-chip technology in bone and joint disease research, proposes a modular construction concept, and discusses the new opportunities and future challenges in the construction and application of bone and joint-on-chip platforms.

Pediatric Bone Tumors: Location and Age Distribution of 420 Cases

BACKGROUND/OBJECTIVES

One of the most important diagnostic tools in bone tumors is X-rays. Preliminary and, in the case of some benign lesions, definitive diagnoses are formed using this basic tool. Part of the decision making in this stage is based on statistical probability using the patient's age, as well as the incidence and predilection sites of different entities. The information used today is based on older and fragmented data. To verify the underlying principles, we retrospectively evaluated all bone tumors in children and adolescents treated by our tertiary center in the last 20 years.

METHODS

For this retrospective study, patients under the age of 18 years suffering from histopathologically verified bone tumors were evaluated. Data were retrieved from our local musculoskeletal tumor database.

RESULTS

We were able to include 420 children treated for bone tumors in our tertiary center. The cohort consisted of 335 benign and 85 malignant lesions. The most common lesions were 137 osteochondromas; the malignant tumors consisted mainly of osteosarcomas (53) and Ewing's sarcomas (28). The primary predilection sites were the metaphyses of long bones.

CONCLUSIONS

We were able to confirm and supplement the fragmentary data of these rare diseases using our own cohort.

Dorsal Scapular Osteochondroma in a Young Male: A Case Report and Literature Review

Introduction

Osteochondromas are a unique group of benign bone tumors that are characterized by bony outgrowth covered by Cartilage. It has a peculiar micro-architecture as its cortices are extensions of those of parent bone and there is a continuity of medullary cavity; this is akin to branching in plants, rightly earning the name "Exostosis."

Case Report

We report a case of a 21-year-old male who presented with complaints of swelling on the upper back associated with mild discomfort. Examination confirmed a bony mass on the dorsal aspect of the scapula without any restricted range of motion of the shoulder joint. On the confirmation of diagnosis, en bloc excision was performed.

Conclusion

In conclusion, dorsal scapular osteochondromas are a rarity, and excision of the lesion is an effective management for symptomatic lesions.

Analysis of the Actions of RARγ Agonists on Growing Osteochondromas in a Mouse Model

The actions of the retinoic acid nuclear receptor gamma (RARγ) agonist, palovarotene, on pre-existing osteochondromas were investigated using a mouse multiple osteochondroma model. This approach was based on the knowledge that patients often present to the clinic after realizing the existence of osteochondroma masses, and the findings from preclinical investigations are the effects of drugs on the initial formation of osteochondromas. Systemic administration of palovarotene, with increased doses (from 1.76 to 4.0 mg/kg) over time, fully inhibited tumor growth, keeping the tumor size (0.31 ± 0.049 mm3) similar to the initial size (0.27 ± 0.031 mm3, p = 0.66) while the control group tumor grew (1.03 ± 0.23 mm3, p = 0.023 to the drug-treated group). Nanoparticle (NP)-based local delivery of the RARγ agonist also inhibited the growth of osteochondromas at an early stage (Control: 0.52 ± 0.11 mm3; NP: 0.26 ± 0.10, p = 0.008). Transcriptome analysis revealed that the osteoarthritis pathway was activated in cultured chondrocytes treated with palovarotene (Z-score = 2.29), with the upregulation of matrix catabolic genes and the downregulation of matrix anabolic genes, consistent with the histology of palovarotene-treated osteochondromas. A reporter assay performed in cultured chondrocytes demonstrated that the Stat3 pathway, but not the Stat1/2 pathway, was stimulated by RARγ agonists. The activation of Stat3 by palovarotene was confirmed using immunoblotting and immunohistochemistry. These findings suggest that palovarotene treatment is effective against pre-existing osteochondromas and that the Stat3 pathway is involved in the antitumor actions of palovarotene.

Exostosis of Ulna With Developmental Deformity of the Left Forearm: A Rare Case

This case report presents a rare occurrence of exostosis of the ulna associated with a developmental deformity of the left forearm in a 15-year-old female. The patient reported a history of trauma resulting in a supracondylar humerus fracture managed conservatively eight years prior. The patient presented with a two-year history of pain and swelling over the left forearm. Clinical examination revealed a firm, non-tender, immobile swelling closely associated with the ulna, accompanied by a 20-degree cubitus varus deformity and forearm shortening. Radiographs and computed tomography scans confirmed the presence of a solitary external bony protuberance over the ulna shaft, communicating with the medullary cavity. A preliminary diagnosis of osteochondroma was established based on clinical and imaging findings. The patient underwent extraperiosteal en bloc resection of the lesion under supraclavicular nerve block anesthesia. A histopathological examination confirmed the diagnosis. Postoperative physiotherapy was initiated, and at the one-month follow-up, the patient reported being pain-free. This case highlights the rarity of exostosis of the ulna with associated developmental deformity, emphasizing the importance of a comprehensive diagnostic approach. Early surgical intervention resulted in a successful outcome, underscoring the significance of timely management in improving patient outcomes and quality of life.

Rib spur causing a hemothorax, pneumothorax, and diaphragmatic injury in a pediatric patient

Pleural effusion is a relatively common condition encountered in the pediatric emergency department. Evaluation of pleural effusion in the emergency department typically includes advanced imaging such as computer tomography or ultrasound, as well as diagnostic thoracocentesis. We report a case of a 10-year-old female with a rib spur at the anterolateral left sixth rib that caused a hemothorax, pneumothorax, and diaphragmatic injury. The patient underwent video-assisted thoracoscopic surgery and resection of the rib spur. The procedure was well-tolerated without any complications.