Gremlin-1, a highly conserved glycosylated and phosphorylated secretory protein, plays important roles in diverse biological processes including early embryonic development, fibrosis, tumorigenesis, and renal pathophysiology. Aptamers, which are RNA or DNA single-stranded oligonucleotides capable of binding specifically to different targets ranging from small organics to whole cells, have potential applications in targeted imaging, diagnosis and therapy. In this study, we obtained a DNA aptamer against Gremlin-1 (G-ap49) using in vitro Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Binding assay and dot-blot showed that G-ap49 had high affinity for Gremlin-1. Further experiments indicated that G-ap49 was quite stable in a cell culture system and could be used in South-Western blot analysis, enzyme-linked aptamer sorbent assay (ELASA), and aptamer-based cytochemistry and histochemistry staining to detect Gremlin-1. Moreover, our study demonstrated that G-ap49 is capable of revealing the subcellular localization of Gremlin-1. These data indicate that G-ap49 can be used as an alternative to antibodies in detecting Gremlin-1.

Background: High mobility group box 1 (HMGB1) plays an essential role in various pathological conditions, including inflammation, fibrosis, autoimmune diseases, and carcinogenesis. The quantification of HMGB1 in body fluids holds promise for clinical applications. Objectives: This study aimed to isolate high-affinity single-stranded DNA (ssDNA) aptamers that target HMGB1. Methods: In this study, ssDNA aptamers were selected using Systematic Evolution of Ligands by Exponential Enrichment (SELEX). The affinity and specificity of the aptamers were evaluated through South-Western blot analysis, enzyme-linked aptamer sorbent assay (ELASA), and aptamer-based histochemistry staining. The impact of the aptamers on the biological activity of HMGB1 was tested in the human acute monocytic leukemia cell line, THP-1. Results: An aptamer (H-ap25, dissociation constant = 8.20 ± 0.53 nmol/L) with high affinity for the HMGB1 B box was generated. Further experiments verified that H-ap25 can be used to detect HMGB1 in South-Western blot analysis, ELASA, and aptamer-based histochemistry staining. Moreover, H-ap25 significantly augmented HMGB1-induced expression of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, Toll-like receptor 9 (TLR9), and activation of NF-κB in THP-1 cells. Conclusions: Our results demonstrated that H-ap25 can be used both as an enhancer of HMGB1 and as a probe in research.