Osteoarthritis (OA) is a common degenerative disease. Its most significant pathological change is destruction of articular cartilage and the main clinical symptoms are pain and dysfunction of joints. Recent studies have shown that the expression of non-coding RNA (ncRNA) in chondrocytes can abnormally up-regulate or down-regulate and alter the activities of chondrocytes like their proliferation, migration and apoptosis, thus leading to the occurrence and development of osteoarthritis. Exosomes are extracellular vesicles with a diameter of 40-100 nm, which are secreted in intercellular fluid, act as medium of intercellular communication. They protect ncRNA, protein, lipid and other bioactive materials from enzymatic degradation by encapsulating them and transferring to sibling chondrocytes, due to their good tissue permeability. They can also improve communication between cells and regulate the activities of chondrocytes. Thus, exosomes behave like gene carriers. The ncRNA carried by exosomes can supplement or adsorb the abnormal ncRNA in chondrocytes, so as to regulate the activity of chondrocytes, and is therefore considered as a possible candidate with capabilities to repair cartilages. In this study we reviewed existing literatures related to the roles and effects of exosome miRNA, lncRNA and circRNA on osteoarthritis. We also reviewed the pathogenesis of exosome ncRNA in osteoarthritis.

Osteosarcoma, the most common primary bone tumor in children and adolescents, is characterized by high malignancy, rapid progression and high metastatic potential. However, no significant progress has been made in treating osteosarcoma recently. The prognosis of osteosarcoma is usually unsatisfied. One of the main reasons is that we cannot be able to identify the Achilles heel of osteosarcoma. A growing number of evidence suggests that different types of RNA play various roles in the development of osteosarcoma. The competing endogenous RNA (ceRNA) is a newly emerging theory, which can propose messenger RNA (mRNA), long non-coding RNA (lncRNA), pseudogene and other different transcripts. Therefore, it can play a role in the regulation of microRNA (miRNA) through competition. In the latest researches, it is shown that the interaction of these transcripts play an important role in the occurrence and development of osteosarcoma by mediating biological processes such as proliferation, apoptosis, metastasis and chemotherapy resistance of osteosarcoma cells. In addition, these different types of transcripts may provide new biomarkers and potential therapeutic targets for osteosarcoma. The present studies review the development of ceRNA hypothesis, summarizes existing knowledge system of ceRNA, and develop a systematic review of the role of different types of ceRNA in the pathogenesis and biological function of osteosarcoma. This review could lay the foundation for the basic and clinical study of osteosarcoma and promote the early diagnosis and treatment effects of osteosarcoma.

Some primary bone tumors are prone to hematogenous metastasis and after that, the therapeutic effect is not that good and prognosis is poor. Circulating tumor cells (CTC) shed from the tumor cells of primary or metastatic focus and then enter into blood circulation. CTC may appear in the early stage of the tumor, which can implant in distant organs to form metastatic sites and self-implant in the primary sites leading to the tumor recurrence; CTC are closely related with the prognosis of patients with tumors. In most primary bone tumors, CTC are heterogeneous compared with primary tumor cells. Studying CTC from various aspects can provide a basis for the early diagnosis and treatment of primary bone tumors. This review summarizes the current researches of CTC in common primary bone tumors, and expects the future of research direction and application practice in clinic.

Malignant bone tumors, one of the most common bone tumors includes osteosarcoma, Ewing's sarcoma, multiple myeloma, and metastatic bone tumors etc. These tumors are often accompanied by distant metastatic lesions at time of diagnosis, leading to low 5-year survival rates. At present, the use of biomarkers for early detection in order to facilitate early treatment are very limited. Therefore, most medical researchers are exploring the roles of exosomes in detecting malignant bone tumors. Exosomes are extracellular microvesicles secreted by different types of cells, which exist in a variety of body fluids. They are new intercellular information carriers that play important physiological roles. Current literature have reported that the RNA contained in exosomes (such as mRNA, miRNAs, lncRNAs and circRNAs) play important roles in the incidence as well as development of malignant bone tumors. However, the previous studies mostly focused on the roles of exosomal RNA in malignant bone tumor diseases, in tumor cell proliferation or apoptosis, transfers, evasion of immune surveillance and chemotherapy drug resistance etc. However, exosomal RNAs may function in the whole process of the disease progression via regulation networks. Our review of existing literature revealed that exosomal RNAs affacted the proliferation, metastasis, immune evasion and drug resistance of five common malignant bone tumors; Osteosarcoma, Ewing sarcoma, Chondrosarcoma, multiple myeloma, and metastatic bone tumors. Therefore, by elucidating on the mechanism of exosomal RNAs in the occurrence and development of malignant bone tumors, this study, could provide new ideas for early diagnosis, concomitant diagnosis, efficacy estimation (chemotherapy, radiotherapy and immunotherapy, etc.) as well as assessing the prognosis of malignant bone tumors.