Enhanced homing of mesenchymal stem cells for in situ niche remodeling and bone regeneration

Mesenchymal stem cells(MSCs)transplantation is a promising strategy for osteoporosis treatment.However,limited sources and poor tissue-homing efficiency limit their clinical capabilities.In this study,we isolated a kind of MSCs from women’s menstrual blood(MenSCs)noninvasively and established a novel MSCs bone marrow-targeted delivery system by utilizing waterin-oil-in-water droplet microfluidics.MenSCs were encapsulated withinβ-cyclodextrin-functionalized alginate microcapsules loaded with zoledronates,which has a high affinity for bone.With this delivery system,MenSCs could be preferentially delivered to the bone marrow tissues via intravenous infusion,and restored bone mass by remodeling the bone marrow niche in situ in ovariectomized mouse models.Moreover,scRNA-seq analysis demonstrated that those MenSCs homed to the bone marrow recruited CD4^(+)FOXP3^(+)natural regulatory T(nT_(reg))cells by secreting CCL28.The recruited nTreg promoted CD8^(+)T cells to secret Wnt family member 10B(WNT10B),activating the Wnt signaling in osteoblasts and thus promoting bone formation in situ in the bone marrow.This study reveals a promising application of MenSCs in postmenopausal osteoporosis treatment and highlights the clinical value of MenSCs by encouraging women to reserve autologous MenSCs before menopause to prevent and alleviate postmenopausal osteoporosis.

Exon-centric regulation of pyruvate kinase M alternative splicing via mutually exclusive exons

Alternative splicing of the pyruvate kinase M gene(PK-M)can generate the M2 isoform and promote aerobic glycolysis and tumor growth.However,the cancer-specific alternative splicing regulation of PK-M is not completely understood.Here,we demonstrate that PK-M is regulated by reciprocal effects on the mutually exclusive exons 9 and 10,such that exon 9 is repressed and exon 10 is activated in cancer cells.Strikingly,exonic,rather than intronic,cis-elements are key determinants of PK-M splicing isoform ratios.Using a systematic sub-exonic duplication approach,we identify a potent exonic splicing enhancer in exon 10,which differs from its homologous counterpart in exon 9 by only two nucleotides.We identify SRSF3 as one of the cognate factors,and show that this serine/arginine-rich protein activates exon 10 and mediates changes in glucose metabolism.These findings provide mechanistic insights into the complex regulation of alternative splicing of a key regulator of the Warburg effect,and also have implications for other genes with a similar pattern of alternative splicing.