Thermotherapy Application Increases The mRNA Expression of Angiogenic Factors in Human Skeletal Muscle

Abstract

Treatment with thermotherapy (TT) reduces the clinical symptoms and improves exercise tolerance in patients with several chronic disease conditions, but the molecular mechanisms by which this therapy exerts its benefits remain poorly defined. We tested the hypothesis that a single session of TT increases systemic and skeletal muscle levels of angiogenic mediators in young individuals. Forty‐one healthy young subjects were recruited to participate in two separate studies (Study 1, n=18 and Study 2, n=23). A water‐circulating garment that covered both legs was used to apply TT or a control intervention on both studies. Water at 48°C was perfused through the garment for 90 min for TT application, while thermoneutral water (33°C) was used in the control intervention. In study 1, participants completed two experimental sessions (TT and control), at least 72 hrs apart, in a randomized, cross‐over design. Blood samples were taken before and 30 and 120 min following the completion of the trials for the determination of the percentage of circulating pro‐angiogenic cells (multiparametric flow‐cytometry) and the levels of inflammatory and angiogenic factors (multiplex immunoassays). In study 2, participants were randomly allocated to either a TT‐treated group (n=11) or to a control group (n=12). The treatments (TT or control) were applied for 90 min as described above. Biopsies were taken from the vastus lateralis muscle prior to and 30 and 120 min following the interventions. The mRNA expression of inflammatory and angiogenic factors and members of the heat shock protein family was determined using real‐time polymerase chain reaction. Application of TT for 90 min in study 1 had no effect on circulating levels of angiogenic cytokines and the percentage of bone marrow‐derived pro‐angiogenic cells (CD34+CD133+), but the levels of vasoconstrictor endothelin‐1 were lower 30 min after TT when compared to the control intervention (p<0.05). Conversely, in skeletal muscle (Study 2), TT evoked a transient increase in the mRNA expression of several important angiogenic factors and heat shock proteins. When compared to the control group, the change in mRNA expression from baseline of vascular endothelial growth factor, angiopoietin‐2, chemokines CCL2 and CX3CL1, the ratio of angiopoietin‐2/angiopoietin‐1 and the angiostatic factor platelet factor‐4 was higher (p<0.05) 30 min after the intervention in the TT‐treated group. Likewise, the expression of members of the heat shock protein family was up‐regulated 30 min after TT compared to control (p<0.05). The expression of the angiostatic transcription factor FoxO1 was lower in the TT group at 120 min following the end of intervention period (p=0.03). These novel findings indicate that TT is a simple, non‐invasive strategy to activate local angiogenic signaling and possibly promote vascular growth in skeletal muscle.