Microchannel networks within engineered 3D scaffold can allow nutrient exchange and rapid blood vessels formation. However, fabrication of a bone microenvironment‐mimicking scaffold with hierarchical micro/nanofibrous and microchannel structures is still a challenge. Herein, inspired by structural and functional cues of bone remodeling, a microchannel networks‐enriched nanofibrous scaffold by using 3D printing and thermally induced phase separation techniques, which can facilitate cells migration and nutrients transportation, is developed. The customizable vascular‐like structure of polycaprolactone within the nanofibrous gelatin‐silica scaffold is fabricated using 3D‐printed sacrificial templates, while dimethyloxalylglycine (DMOG)‐loaded mesoporous silica nanoparticles (MSNs) located on the scaffold surface and bone forming peptide‐1 (BFP)‐loaded MSNs embedded in the scaffold are implemented for sequential release of DMOG and BFP. The cell experiments show that dual‐drug delivery scaffold (DBM/GP) promotes angiogenesis by stimulating migration, tube formation, and angiogenesis‐related genes/protein expression of endothelial cells, and osteogenesis by promoting osteo‐related genes expression and mineral deposition of osteoblasts. Additionally, DBM/GP scaffold facilitates the angiogenic activity of osteoblasts by activating phosphatidylinositol 3‐kinase/protein kinase B/hypoxia inducible factor‐1α pathway. Furthermore, enhanced vascularization and bone regeneration of DBM/GP scaffold are demonstrated via subcutaneous and skull defect models. Overall, this study reveals that the bone microenvironment‐mimetic dual‐drug delivery scaffold provides a promising strategy for bone defects treatment.
BackgroundFlowering time is an important trait in Brassica rapa crops. FLOWERING LOCUS C (FLC) is a MADS-box transcription factor that acts as a potent repressor of flowering. Expression of FLC is silenced when plants are exposed to low temperature, which activates flowering. There are four copies of FLC in B. rapa. Analyses of different segregating populations have suggested that BraA.FLC.a (BrFLC1) and BraA.FLC.b (BrFLC2) play major roles in controlling flowering time in B. rapa.ResultsWe analyzed the BrFLC2 sequence in nine B. rapa accessions, and identified a 57-bp insertion/deletion (InDel) across exon 4 and intron 4 resulting in a non-functional allele. In total, three types of transcripts were identified for this mutated BrFLC2 allele. The InDel was used to develop a PCR-based marker, which was used to screen a collection of 159 B. rapa accessions. The deletion genotype was present only in oil-type B. rapa, including ssp. oleifera and ssp. tricolaris, and not in other subspecies. The deletion genotype was significantly correlated with variation in flowering time. In contrast, the reported splicing site variation in BrFLC1, which also leads to a non-functional locus, was detected but not correlated with variation in flowering time in oil-type B. rapa, although it was correlated with variation in flowering time in vegetable-type B. rapa.ConclusionsOur results suggest that the naturally occurring deletion mutation across exon 4 and intron 4 in BrFLC2 gene contributes greatly to variation in flowering time in oil-type B. rapa. The observed different relationship between BrFLC1 or BrFLC2 and flowering time variation indicates that the control of flowering time has evolved separately between oil-type and vegetable-type B. rapa groups.
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