[en] Defects in homeostatic mechanisms, such as autophagy, contribute to joint aging and precede joint damage in osteoarthritis (OA). Furthermore, these defects could be pathological mechanisms in comorbidities associated with OA, such as type 2 diabetes (T2D). Therefore, the objective of this Doctoral Thesis focused on identifying autophagy markers involved in joint damage associated with osteoarthritis and osteoarthritis associated with T2D (OA-T2D). To address this objective, we analyzed an autophagy gene expression array using blood from subjects without osteoarthritis and subjects with knee OA from the Prospective Cohort of OA of A Coruña (PROCOAC). A total of 16 autophagy-related genes were found to be decreased in patients with knee OA. Through validation studies, we observed that the expression of HSP90AA1, a relevant marker in chaperone-mediated autophagy (CMA) and involved in protein folding and in the response to stress, was decreased in blood and joint tissues of subjects with knee OA. Functional studies in chondrocytes from subjects with OA indicated that HSP90AA1 plays an important role in chondrocyte homeostasis by regulating the connection between the CMA and the macroautophagy. In fact, the HSP90AA1 defect in OA chondrocytes was related to a decrease in CMA and macroautophagy and, as a consequence, to an increase in inflammation, oxidative stress and senescence that ultimately lead to the death of the chondrocyte by apoptosis, while HSP90AA1 overexpression protected against joint damage. On the other hand, we confirm that HSP90AA1 is more decreased in kee OA-T2D subjects compared to knee OA subjects. In conclusion, we propose that HSP90A is key to maintain chondrocyte homeostasis by regulating CMA and macroautophagy, whereas a CMA defect contributes to joint damage. These results suggest that CMA is a key homeostasis mechanism for joint health and its activation could have therapeutic effect against joint damage and the progression of OA and their comorbidities.

[gl] O defecto nos mecanismos de homeostase, como a macroautofaxia, contribúe ao envellecemento articular e precede ao dano articular na artrose. Ademais, istos defectos poderían ser mecanismos patolóxicos nas comorbilidades asociadas a artrose, como é o caso da diabetes tipo 2 (T2D). Polo tanto, o obxectivo desta Tese Doutoral foi identificar marcadores de autofaxia implicados no dano articular asociado a artrose de xeonllo e a artrose de xeonllo asociada a T2D. Para abordar este obxectivo, analizamos un array de expresión de xenes de autofaxia empregando sangue de suxeitos sen artrose e suxeitos con artrose de xeonllo procedentes da Cohorte Prospectiva de Artrose de A Coruña (PROCOAC). Atopáronse un total de 16 xenes relacionados coa autofaxia diminuídos en doentes con artrose. Mediante estudos de validación observamos que a expresión de HSP90AA1, un marcador relevante da autofaxia mediada por chaperonas (CMA) e implicado na resposta ao estrés e o pregamento de proteínas, estaba diminuída en sangue e tecidos da articulación de suxeitos con artrose de xeonllo. Os estudos funcionais levados a cabo en condrocitos de suxeitos con artrose de xeonllo suxeriron que HSP90AA1 ten un papel relevante na homeostase do condrocito regulando a conexión entre o CMA e a macroautofaxia. De feito, o defecto de HSP90AA1 relacionouse cunha diminución de CMA e de macroautofaxia e como consecuencia, cun incremento de mediadores de inflamación, de estrés oxidativo, e de senescencia, resultando na morte do condrocito por apoptose, mentres que a sobreexpresión de HSP90AA1 protexiu contra o dano articular. Por outro lado, confirmamos que HSP90AA1 está máis diminuído en doentes con artrose de xeonllo e T2D que en doentes con artrose de xeonllo. En vista de estos resultados, propoñemos que HSP90A é clave para o mantenemento da homeostase do condrocito regulando o CMA e a macroautofaxia, mentras que un defecto no CMA contribue o dano articular. Estos resultados suxiren que o CMA é un mecanismo de homoestase relevante e a súa activación poderia presentar potencial terapéutico contra o dano articular así coma na progresión da artrose de xeonllo e das suas comorbilidades.