Fibromodulin reduces scar formation in adult cutaneous wounds by eliciting a fetal-like phenotype.

Blocking transforming growth factor (TGF)ß1 signal transduction has been a central strategy for scar reduction; however, this approach appears to be minimally effective. Here, we show that fibromodulin (FMOD), a 59-kD small leucine-rich proteoglycan critical for normal collagen fibrillogenesis, significantly reduces scar formation while simultaneously increasing scar strength in both adult rodent models and porcine wounds, which simulate human cutaneous scar repair. Mechanistically, FMOD uncouples pro-migration/contraction cellular signals from pro-fibrotic signaling by selectively enhancing SMAD3-mediated signal transduction, while reducing AP-1-mediated TGFß1 auto-induction and fibrotic extracellular matrix accumulation. Consequently, FMOD accelerates TGFß1-responsive adult fibroblast migration, myofibroblast conversion, and function. Furthermore, our findings strongly indicate that, by delicately orchestrating TGFß1 activities rather than indiscriminately blocking TGFß1, FMOD elicits fetal-like cellular and molecular phenotypes in adult dermal fibroblasts in vitro and adult cutaneous wounds in vivo, which is a unique response of living system undescribed previously. Taken together, this study illuminates the signal modulating activities of FMOD beyond its structural support functions, and highlights the potential for FMOD-based therapies to be used in cutaneous wound repair.

Fibromodulin-deficiency alters temporospatial expression patterns of transforming growth factor-ß ligands and receptors during adult mouse skin wound healing.

Fibromodulin (FMOD) is a small leucine-rich proteoglycan required for scarless fetal cutaneous wound repair. Interestingly, increased FMOD levels have been correlated with decreased transforming growth factor (TGF)-ß1 expression in multiple fetal and adult rodent models. Our previous studies demonstrated that FMOD-deficiency in adult animals results in delayed wound closure and increased scar size accompanied by loose package collagen fiber networks with increased fibril diameter. In addition, we found that FMOD modulates in vitro expression and activities of TGF-ß ligands in an isoform-specific manner. In this study, temporospatial expression profiles of TGF-ß ligands and receptors in FMOD-null and wild-type (WT) mice were compared by immunohistochemical staining and quantitative reverse transcriptase-polymerase chain reaction using a full-thickness, primary intention wound closure model. During the inflammatory stage, elevated inflammatory infiltration accompanied by increased type I TGF-ß receptor levels in individual inflammatory cells was observed in FMOD-null wounds. This increased inflammation was correlated with accelerated epithelial migration during the proliferative stage. On the other hand, significantly more robust expression of TGF-ß3 and TGF-ß receptors in FMOD-null wounds during the proliferative stage was associated with delayed dermal cell migration and proliferation, which led to postponed granulation tissue formation and wound closure and increased scar size. Compared with WT controls, expression of TGF-ß ligands and receptors by FMOD-null dermal cells was markedly reduced during the remodeling stage, which may have contributed to the declined collagen synthesis capability and unordinary collagen architecture. Taken together, this study demonstrates that a single missing gene, FMOD, leads to conspicuous alternations in TGF-ß ligand and receptor expression at all stages of wound repair in various cell types. Therefore, FMOD critically coordinates temporospatial distribution of TGF-ß ligands and receptors in vivo, suggesting that FMOD modulates TGF-ß bioactivity in a complex way beyond simple physical binding to promote proper wound healing.

Delayed wound closure in fibromodulin-deficient mice is associated with increased TGF-ß3 signaling.

Fibromodulin (FMOD), a small leucine-rich proteoglycan, mediates scarless fetal skin wound repair through, in part, transforming growth factor-ß (TGF-ß) modulation. Using an adult fmod-null (fmod(-/-)) mouse model, this study further elucidates the interplay between FMOD and TGF-ß expression during cutaneous repair and scar formation. Full-thickness skin wounds on fmod(-/-) and wild-type (WT) mice were closed primarily and analyzed. Histomorphometry revealed delayed dermal cell migration leading to delayed wound closure and significantly increased scar size in fmod(-/-) mice relative to WT, which was partially rescued by exogenous FMOD administration. In addition, fmod(-/-) wounds exhibited early elevation (within 24 hours post-wounding) of type I and type II TGF-ß receptors as well as unexpectedly high fibroblast expression of TGF-ß3, a molecule with reported antifibrotic and antimigratory effects. Consistent with elevated fibroblastic TGF-ß3, fmod(-/-) fibroblasts were significantly less motile than WT fibroblasts. fmod(-/-) fibroblasts were also more susceptible to migration inhibition by TGF-ß3, leading to profound delays in dermal cell migration. Increased scarring in fmod(-/-) mice indicates that TGF-ß3's antimotility effects predominate over its antifibrotic effects when high TGF-ß3 levels disrupt early fibroblastic wound ingress. These studies demonstrate that FMOD presence is critical for proper temporospatial coordination of wound healing events and normal TGF-ß bioactivity.

Synergistic effects of Nell-1 and BMP-2 on the osteogenic differentiation of myoblasts.

UNLABELLED: Osteogenesis is synergistically enhanced by the combined effect of complimentary factors. This study showed that Nell-1 and BMP-2 synergistically enhanced osteogenic differentiation of myoblasts and phosphorylated the JNK MAPK pathway. The findings are important because of the osteochondral specificity of Nell-1 signaling and the potential therapeutic effects of coordinated BMP-2 and Nell-1 delivery. INTRODUCTION: BMPs play an important role in the migration and proliferation of mesenchymal cells and have a unique ability to alter the differentiation of mesenchymal cells toward chondrogenic and osteogenic lineages. Signaling upstream of Cbfa1/Runx2, BMPs effects are not limited to cells of the osteoblast lineage. Thus, additional osteoblast-specific factors that could synergize with BMP-2 would be advantageous for bone regeneration procedures. NELL-1 (NEL-like molecule-1; NEL [a protein strongly expressed in neural tissue encoding epidermal growth factor like domain]) is a novel growth factor believed to preferentially target cells committed to the osteochondral lineage. MATERIALS AND METHODS: C2C12 myoblasts were transduced with AdLacZ, AdNell-1, AdBMP-2, or AdNell-1+AdBMP-2 overexpression viruses. Effects were studied by cell morphology, alkaline phosphatase activity, osteopontin production, and MAPK signaling. Additionally, in a nude mouse model, viruses were injected into leg muscles, and new bone formation was examined after 2 and 8 wk. RESULTS: C2C12 myoblasts co-transduced with AdNell-1+AdBMP-2 showed a synergistic effect on osteogenic differentiation as detected by alkaline phosphatase activity and osteopontin production. Nell-1 stimulation on AdNell-1 + AdBMP-2 preconditioned C2C12 cells revealed significant activation of the non-BMP-2 associated c-Jun N-terminal kinase (JNK) MAPK signaling pathway, but not the p38 or extracellular signal-regulated kinase (ERK1/2) MAPK pathways. Importantly Nell-1 alone did not induce osteogenic differentiation of myoblasts. In a nude mouse model, injection of AdNell-1 alone stimulated no bone formation within muscle; however, injection of AdNell-1+AdBMP-2 stimulated a synergistic increase in bone formation compared with AdBMP-2 alone. CONCLUSIONS: These findings are important because of the confirmed osteochondral specificity of Nell-1 signaling and the potential therapeutic effects of enhanced BMP-2 action with coordinated Nell-1 delivery.