Evaluation of skeletal muscle regeneration in experimental model after malnutrition

Abstract

The aim of this study was to analyze muscle regeneration after cryoinjury in the tibialis anterior muscle of young rats that were malnourished and then recovered. Forty Wistar rats were divided into a nourished group that received a normal protein diet (14% casein) for 90 days and a malnourished and recovered rats group (MR) that was submitted to 45 days of malnutrition with a hypoproteic diet (6% casein) followed by 45 days of a normal protein diet (14% casein). After the recovery period, all of the animals underwent cryoinjury in the right tibialis anterior muscle and euthanasia after 7, 14 and 21 days. The amount of connective tissue and the inflammation area was higher in the malnutrition recovered injury MR group (MRI) at 14 days post-injury (p < 0.05). Additionally, the cross-sectional area (CSA) of the regenerated fibers was decreased in the MRI (p < 0.05). The MyoD and myogenin protein levels were higher in the nourished injury group. Similar levels of TGF-β1 were found between groups. The proposed malnutrition protocol was effective in showing delayed changes in the regeneration process of the tibialis anterior muscle of young rats. Furthermore, we observed a delay in muscle repair even after nutritional recovery.Keywords: skeletal muscle, protein malnutrition, cryolesion, myogenic regulatory factors, muscle healing process. Avaliação da regeneração do músculo esquelético em modelo experimental após desnutriçãoResumo O objetivo do presente estudo foi analisar a regeneração muscular após criolesão no músculo tibial anterior de ratos jovens desnutridos e recuperados. Foram utilizados 40 ratos da linhagem Wistar, divididos em 2 grupos: ratos nutridos receberam dieta normoproteica (14% de caseína) por 90 dias; e ratos desnutridos e recuperado submetidos a duas fases nutricionais pós-desmame, correspondendo a 45 dias de desnutrição com dieta hipoproteica (6% caseína), seguida por 45 dias de dieta normoproteica (14% caseína). Ao completar a fase de recuperação, todos os animais foram submetidos à criolesão no músculo tibial anterior direito e a eutanasia ocorreu 7, 14 e 21 dias após a lesão. A quantidade de tecido conjuntivo e a área de inflamação 14 dias pós-lesão foi maior no grupo desnutrido, recuperado e lesado (MRI -malnourished, recovered and injured group) (p < 0,05). A área de secção transversa (AST) das fibras regeneradas do grupo MRI foi menor (p < 0,05). O conteúdo das proteínas MyoD e Miogenina foi maior no grupo nutridos e lesados. A citocina TGF-β1 não apresentou diferença entre os grupos. O protocolo proposto foi eficaz para demonstrar alterações no processo de regeneração do músculo tibial anterior de ratos jovens, atrasando o reparo muscular mesmo após a recuperação nutricional.Palavras-chave: músculo esquelético, desnutrição proteica, criolesão, fatores de regulação miogênica, processo de recuperação do músculo.

Laser de baixa intensidade favorece a regeneração muscular em modelo experimental desnutrido e recuperado

“…The delay in the regeneration of malnourished and recovered animals after 21 days, suggested by the larger inflammation area in group D21, confirms what was observed by Pertille et al 19 14 days after the cryolesion with the same malnutrition protocol.…”

Influence of protein malnutrition on cutaneous wound healing in rats

“…Thus, the observed transformations in the connective tissue matrix suggest that balanced nutrition represents a determining factor for establishing a good healing pattern. Others studies also have similar results and described worse wound healing in malnourished animals [29,30].…”

Traumatic muscle fibrosis

“…The mTOR/AKT pathway is the downstream mediator of multiple anabolic growth factors including insulin-like growth factor (IGF), and regulates cellular processes including proliferation and protein synthesis. Specifically regarding the activation and proliferation of satellite cells, a recent study in a murine model demonstrated a TGFβ-independent decrement in myogenic differentiation markers, and a compromise of myofiber size (25)…”