MOFs-Based Nitric Oxide Therapy for Tendon Regeneration

Tendon regeneration is still a great challenge due to its avascular structure and low self-renewal capability.The nitric oxide(NO)therapy emerges as a promising treatment for inducing the regeneration of injured tendon by angiogenesis.Here,in this study,a system that NO-loaded metal–organic frameworks(MOFs)encapsulated in polycaprolactone(PCL)/gelatin(Gel)aligned coaxial scaffolds(NMPGA)is designed and prepared for tendon repair.In this system,NO is able to be released in vitro at a slow and stable average speed of 1.67 nM h^−1 as long as 15 d without a burst release stage in the initial 48 h.Furthermore,NMPGA can not only improve the tubular formation capability of endothelial cells in vitro but also obviously increase the blood perfusion near the injured tendon in vivo,leading to accelerating the maturity of collagen and recovery of biomechanical strength of the regenerated tendon tissue.As a NO-loaded MOFs therapeutic system,NMPGA can promote tendon regeneration in a shorter healing period with better biomechanical properties in comparison with control group by angiogenesis.Therefore,this study not only provides a promising scaffold for tendon regeneration,but also paves a new way to develop a NO-based therapy for biomedical application in the future.

PMN-MDSCs modulated by CCL20 from cancer cells promoted breast cancer cell stemness through CXCL2-CXCR2 pathway

Our previous studies have showed that C-C motif chemokine ligand 20(CCL20)advanced tumor progression and enhanced the chemoresistance of cancer cells by positively regulating breast cancer stem cell(BCSC)self-renewal.However,it is unclear whether CCL20 affects breast cancer progression by remodeling the tumor microenvironment(TME).Here,we observed that polymorphonuclear myeloid-derived suppressor cells(PMN-MDSCs)were remarkably enriched in TME of CCL20-overexpressing cancer cell orthotopic allograft tumors.Mechanistically,CCL20 activated the differentiation of granulocyte-monocyte progenitors(GMPs)via its receptor C-C motif chemokine receptor 6(CCR6)leading to the PMN-MDSC expansion.PMN-MDSCs from CCL20-overexpressing cell orthotopic allograft tumors(CCL20-modulated PMN-MDSCs)secreted amounts of C-X-C motif chemokine ligand 2(CXCL2)and increased ALDH+BCSCs via activating CXCR2/NOTCH1/HEY1 signaling pathway.Furthermore,C-X-C motif chemokine receptor 2(CXCR2)antagonist SB225002 enhanced the docetaxel(DTX)effects on tumor growth by decreasing BCSCs in CCL20high-expressing tumors.These findings elucidated how CCL20 modulated the TME to promote cancer development,indicating a new therapeutic strategy by interfering with the interaction between PMN-MDSCs and BCSCs in breast cancer,especially in CCL20high-expressing breast cancer.

Development of a novel method for rapid cloning of shRNA vectors, which successfully knocked down CD44 in mesenchymal triple-negative breast cancer cells

Dear Editor,Since the discovery of short hairpin RNA(shRNA)vec-tor-mediated RNA interference(RNAi),this technology has been widely used in cancer research for its specific-ity,potency,and convenience.However,researchers may find it costly to purchase commercial vectors from bio-companies or time-and labor-consuming to construct their own shRNA vectors using traditional method by inserting annealed duplex into digested vectors.Despite intensive efforts to accelerate shRNA vector cloning in laboratories,the development of a reliable,rapid,conven-ient,and cost-effective method is still in great demand.To this end,we developed a novel method named SuperSH(Super rapid cloning of shRNA vector)for the effective and rapid construction of shRNA-expressing vectors based on high-performance DNA polymerase and seamless cloning technique[1](Additional file 1:Fig-ure S1a;the detailed methods can be found in Additional file 1).In our SuperSH method,the shRNA sequences are introduced into the vector via a pair of polymerase chain reaction(PCR)primers rather than via annealed duplex.In detail,the 3′ends of the primers are designed to bind the template to initiate a PCR to amplify the vector back-bone,and the 5′portions are designed to introduce the sequences of interest as well as to form a short homol-ogous arm for subsequent recombination via seamless cloning[1].

NIR-II live imaging study on the degradation pattern of collagen in the mouse model

The degradation of collagen in different body parts is a critical point for designing collagen-based biomedical products.Here,three kinds of collagens labeled by second near-infrared(NIR-II)quantum dots(QDs),including collagen with low crosslinking degree(LC),middle crosslinking degree(MC)and high crosslinking degree(HC),were injected into the subcutaneous tissue,muscle and joints of the mouse model,respectively,in order to investigate the in vivo degradation pattern of collagen by NIR-II live imaging.The results of NIR-II imaging indicated that all tested collagens could be fully degraded after 35 days in the subcutaneous tissue,muscle and joints of the mouse model.However,the average degradation rate of subcutaneous tissue(k=0.13)and muscle(k=0.23)was slower than that of the joints(shoulder:k=0.42,knee:k=0.55).Specifically,the degradation rate of HC(k=0.13)was slower than LC(k=0.30)in muscle,while HC showed the fastest degradation rate in the shoulder and knee joints.In summary,NIR-II imaging could precisely identify the in vivo degradation rate of collagen.Moreover,the degradation rate of collagen was more closely related to the implanted body parts rather than the crosslinking degree of collagen,which was slower in the subcutaneous tissue and muscle compared to the joints in the mouse model.