Nongenetic Reprogramming of the Ligand Specificity of Growth Factor Receptors by Bispecific DNA Aptamers.

The reprogramming of receptor-ligand interactions affords an opportunity to direct cells to respond to user-defined external cues. Although this has often been achieved via the genetic engineering of receptors, an alternative, nongenetic approach is highly demanded. In this article, we propose the design of oligonucleotide-based synthetic switches that feature the ability to reprogram the ligand specificity of the growth factor receptor. We demonstrated that our synthetic switches induced growth factor signaling via the formation of the dynamic complex with specific external cues that would otherwise not induce the signaling. This chemical approach may be applied to designing a new class of chemical tools that can control the activities of native cells and represent smart and safer regenerative drugs.

Oligonucleotide-Based Mimetics of Hepatocyte Growth Factor.

Oligonucleotide-based hepatocyte growth factor (HGF) mimetics are described. A DNA aptamer to Met, a cognate receptor for HGF, was shown to induce Met activation when used in dimer form. The most potent aptamer dimer, ss-0, which was composed solely of 100-mer single-stranded DNA, exhibited nanomolar potency. Aptamer ss-0 reproduced HGF-induced cellular behaviors, including migration and proliferation. The present work sheds light on oligonucleotides as a novel chemical entity for the design of growth factor mimetics.

Progressive vitiligo induced by recurrent melanoma.

A woman had undergone excision for primary melanoma of the left heel and dissection of groin lymph nodes. The recurrent tumor on the lateral left lower leg developed six months ago and the depigmented plaques spread extensively on the left lower limb. The depigmented macules were localized to the left lower limb and were not seen in other areas. Although the left groin lymph node had been dissected, the local immune environment of anti-tumor immunity was preserved. The cause of melanoma-associated vitiligo is regarded to be anti-tumor autoimmune mediated, and this phenomenon is recently recognized during the therapy with immune checkpoint inhibitors in the treatment of stage III and IV melanoma.

A DNA Aptamer That Inhibits the Aberrant Signaling of Fibroblast Growth Factor Receptor in Cancer Cells.

Growth factor receptors are activated through dimerization by the binding of their ligands and play pivotal roles in normal cell function. However, the aberrant activity of the receptors has been associated with cancer malignancy. One of the main causes of the aberrant receptor activation is the overexpression of receptors and the resultant formation of unliganded receptor dimers, which can be activated in the absence of external ligand molecules. Thus, the unliganded receptor dimer is a promising target to inhibit aberrant signaling in cancer. Here, we report an aptamer that specifically binds to fibroblast growth factor receptor 2b and inhibits the aberrant receptor activation and signaling. Our investigation suggests that this aptamer inhibits the formation of the receptor dimer occurring in the absence of external ligand molecules. This work presents a new inhibitory function of aptamers and the possibility of oligonucleotide-based therapeutics for cancer.

Successful Treatment of Ulcerative-Type Pyoderma Gangrenosum with a Combination Therapy of Oral Prednisolone, Vacuum-Assisted Closure, and Skin Grafting.

Pyoderma gangrenosum (PG) is a relatively rare inflammatory skin disease that progressively causes necrotic ulceration mainly on the lower extremities and trunk. Systemic corticosteroid is considered a first-line treatment for PG as it facilitates wound healing; however, several cases where tumor necrosis factor-α inhibitors, adalimumab and infliximab, were administered showed good response. For intractable PG with a large ulcer or problematic epithelization, chemical or mechanical debridement of necrotic tissue in combination with skin grafting may be necessary to promote wound healing. Our report presents a case of intractable ulcerative PG requiring oral prednisolone and skin grafting. Although mechanical debridement was performed, granulation was poor; therefore, after the PG activity became quiescent, we utilized a vacuum-assisted closure (VAC) system to promote granulation and adaptation of the grafted skin. Although more cases are required for a definitive conclusion, the VAC system may be a choice for PG with large ulcers.

A chemically unmodified agonistic DNA with growth factor functionality for in vivo therapeutic application.

Although growth factors have great therapeutic potential because of their regenerative functions, they often have intrinsic drawbacks, such as low thermal stability and high production cost. Oligonucleotides have recently emerged as promising chemical entities for designing synthetic alternatives to growth factors. However, their applications in vivo have been recognized as a challenge because of their susceptibility to nucleases and limited distribution to a target tissue. Here, we present the first example of oligonucleotide-based growth factor mimetics that exerts therapeutic effects at a target tissue after systemic injection. The aptamer was designed to dimerize a growth factor receptor for its activation and mitigated the progression of Fas-induced fulminant hepatitis in a mouse model. This unprecedented functionality of the aptamer can be reasonably explained by its high nuclease stability and migration to the liver parenchyma. These mechanistic analyses provided insights for the successful application of aptamer-based receptor agonists.

DNA aptamer assemblies as fibroblast growth factor mimics and their application in stem cell culture.

Replacing expensive and thermally unstable growth factors with synthetic alternatives has been an important issue in stem cell-based regenerative medicines. Here we developed DNA aptamer-assemblies that act as functional mimics of basic fibroblast growth factor (bFGF), one of the essential factors for stem cell culture. The most potent aptamer assembly named TD0, composed solely of 76-mer single-stranded DNA, could support the self-renewal and pluripotency of induced pluripotent stem cells (iPSCs). This work presents the first application of DNA aptamer in the maintenance of iPSCs.

Manipulation of cell mechanotaxis by designing curvature of the elasticity boundary on hydrogel matrix.

Directional cell migration induced by the stiffness gradient of cell culture substrates is known as a subset of the mechanical-cue-induced taxis, so-called mechanotaxis, typically durotaxis toward hard region. To establish the general conditions of biomaterials to manipulate the mechanotaxis, the effect of the shape of the elasticity transition boundary between hard and soft regions of a substrate on mechanotaxis should be systematically determined as well as the conditions of elasticity gradient strength. Here, as a simplified factor of expressing variations in the shape of the elasticity boundary in living tissues, we focus on the curvature of the elasticity boundary. Mask-free photolithographic microelasticity patterning of photocurable gelatin gel was employed to systematically prepare elasticity boundaries with various curvatures, and the efficiency of mechanotaxis of fibroblast cells around each curved boundary was examined. Highly efficient usual durotaxis was induced on a convex boundary with 100 µm in radius and on a concave boundary with 750 µm in radius of curvature. Interestingly, biased migration toward soft regions of the gel, i.e., inverse durotaxis, was first observed for concave boundaries with 50 µm or 100 µm in radius of curvature, which was named as "negative mechanotaxis". The curvature of the elasticity boundary was found to markedly affect the efficiency of induction and the direction of mechanotaxis. The mechanism responsible for this phenomenon and the implication for the curvature effect in in vivo systems are discussed.