Characterization of traumatized muscle-derived multipotent progenitor cells from low-energy trauma

Preclinical validation of TGFβ inhibitors as a novel therapeutic strategy for post-traumatic heterotopic ossification

Heterotopic ossification (HO) is characterized by the abnormal growth of ectopic bone in non-skeletal soft tissues through a fibrotic pathway and is a frequent complication in a wide variety of musculoskeletal injuries. We have previously demonstrated that TGFβ levels are elevated in the soft tissues following extremity injuries. Since TGFβ mediates the initial inflammatory and wound-healing response in the traumatized muscle bed, we hypothesized that targeted inhibition of the TGFβ pathway may be able to abrogate the unbalanced fibrotic phenotype and bone-forming response observed in post-traumatic HO. Primary mesenchymal progenitor cells (MPCs) harvested from debrided traumatized human muscle tissue were used in this study. After treatment with TGFβ inhibitors (SB431542, Galunisertib/LY2157299, Halofuginone, and SIS3) cell proliferation/survival, fibrotic formation, osteogenic induction, gene expression, and phosphorylation of SMAD2/3 were assessed. In vivo studies were performed with a Sprague-Dawley rat blast model treated with the TGFβ inhibitors. The treatment effects on the rat tissues were investigated by radiographs, histology, and gene expression analyses. Primary MPCs treated with TGFβ had a significant increase in the number of fibrotic nodules compared to the control, while TGFβ inhibitors that directly block the TGFβ extracellular receptor had the greatest effect on reducing the number of fibrotic nodules and significantly reducing the expression of fibrotic genes. In vivo studies demonstrated a trend towards a lower extent of HO formation by radiographic analysis up to 4 months after injury when animals were treated with the TGFβ inhibitors SB431542, Halofuginone and SIS3. Altogether, our results suggest that targeted inhibition of the TGFβ pathway may be a useful therapeutic strategy for post-traumatic HO patients.

Recent advances in the regulatory and non-coding RNA biology of osteogenic differentiation: biological functions and significance for bone healing

Injuries associated with contemporary life, such as automobile crashes and sports injuries, can lead to large numbers of traumatic neuromuscular injuries that are intimately associated with bone fractures. Regulatory and non-coding RNAs play essential roles in multiple cellular processes, including osteogenic differentiation and bone healing. In this review, we discuss the most recent advances in our understanding of the regulatory and non-coding RNA biology of osteogenic differentiation in stem, stromal and progenitor cells. We focused on circular RNAs, small nucleolar RNAs and PIWI-interacting RNAs and comprehensively summarized their biological functions as well as discussed their significance for bone healing and tissue regeneration.

microRNA-21-5p from M2 macrophage-derived extracellular vesicles promotes the differentiation and activity of pancreatic cancer stem cells by mediating KLF3

AIM

Given the fact that tumor-associated macrophage-derived extracellular vesicles (EVs) are attributable to tumor aggressiveness, this research intends to decode the mechanism of M2 macrophage-derived EVs in the differentiation and activities of pancreatic cancer (PaCa) stem cells via delivering microRNA (miR)-21-5p.

METHODS

Polarized M2 macrophages were induced, from which EVs were collected and identified. miR-21-5p expression in M2 macrophage-derived EVs was tested. After cell sorting, CD24+CD44+EpCAM+ stem cells were co-cultured with M2 macrophages, in which miR-21-5p was upregulated or downregulated. The effects of M2 macrophage-derived EVs and miR-21-5p on Nanog/octamer-binding transcription factor 4 (Oct4) expression, sphere formation, colony formation, invasion and migration capacities, apoptosis, and in vivo tumorigenic ability were examined. Krüppel-like factor 3 (KLF3) expression and its interaction with miR-21-5p were determined.

RESULTS

M2 macrophage-derived EVs promoted PaCa stem cell differentiation and activities. miR-21a-5p was upregulated in M2 macrophage-derived EVs. miR-21a-5p downregulation in M2 macrophage-derived EVs inhibited Nanog/Oct4 expression and impaired sphere-forming, colony-forming, invasion, migration, and anti-apoptosis abilities of PaCa stem cells in vitro and tumorigenic ability in vivo. miR-21-5p targeted KLF3 to mediate the differentiation and activities of PaCa stem cells, and KLF3 was downregulated in PaCa stem cells.

CONCLUSION

This work explains that M2 macrophage-derived exosomal miR-21a-5p stimulates differentiation and activity of PaCa stem cells via targeting KLF3, paving a novel way for attenuating PaCa stemness.