Effects of suppressing Smads expression on wound healing in Hyriopsis cumingii

The role of Smad1/5 in mantle immunity of the pearl oyster Pinctada fucata martensii

The Smad protein family is an important medium for transducing BMP-Smads signals, and which have been proved that their important role in regulating shell biomineralization in Pinctada fucata martensii in our previous study. The members of TGF-β superfamily were involved in innate immunity in vertebrates and invertebrates, and Smad regulatory networks construct a balanced immune system. However, little is known about the role of Smad1/5 in immunity in P. f. martensii. The present study shows that the tissue distribution and the expression profiles of Smad1/5 at developmental stages suggested its wide distribution and crucial role in development at embryonic stages other than larval stage; the increased expression of bone morphogenetic proteins 2 (BMP2), Smad4, Smad1/5 and MSX mRNAs at mantle tissue after LPS and Poly (I:C) challenged implied the potential immune role of Smad1/5 and BMP2-Smad signals to defense against bacterial and virus infections; the reduced expression of immune gene nuclear factor kappa-B (NF-κB), matrix metalloproteinase (MMP), interleukin 17 (IL-17), CuZn-superoxide dismutase (CuZn-SOD), tissue inhibitors of metalloproteinase (TIMP) and lipopolysaccharide-induced TNF-α factor (LITAF) mRNA following knockdown of Smad1/5 indicated that Smad1/5 can regulate their expression via BMP2-Smads pathway in the immunity process; the up-regulated expression of Smad1/5 and BMP2-Smad signals genes, and immune genes during wound healing indicated that Smad1/5 and BMP2-Smad signals genes may be involved in wound healing collaborated with immune genes via a different and complex Smads signaling pathway. These results indicated Smad1/5 could regulate innate immunity via BMP2-Smads signal pathway, and which provided new insights into the relationship between BMP2-Smads signal pathway and mantle immunity.

The role of Smad7 in cutaneous wound healing

Chronic refractory wounds are generally caused by local tissue defects and necrosis, and they are characterized by delayed wound healing as well as high recurrence, which seriously affects life quality. However, effective therapeutics to treat wounds are currently unavailable. Therapy primarily aims to accelerate generation of granulation tissue and decrease recurrence. The pathogenesis of chronic refractory wounds is closely related to multiple complex signaling pathways and a series of cytokines. Among these signaling pathways, TGF-β/Smad7 axis plays a critical role. Specifically, Smad7 is an antagonist of TGF-β that inhibits activation of TGF-β. Moreover, Smad7 promotes wound healing by regulating cytokines and controlling growth, differentiation and apoptosis of cells, which may be exploited to cure the disease. This review aims to reveal the exact functions and mechanisms of Smad7 in regulation of wound healing.