Exosomes derived from differentiated human ADMSC with the Schwann cell phenotype modulate peripheral nerve-related cellular functions

Peripheral nerve regeneration remains a significant clinical challenge due to the unsatisfactory functional recovery and public health burden.Exosomes,especially those derived from mesenchymal stem cells(MSCs),are promising as potential cell-free therapeutics and gene therapy vehicles for promoting neural regeneration.In this study,we reported the differentiation of human adipose derived MSCs(hADMSCs)towards the Schwann cell(SC)phenotype(hADMSC-SCs)and then isolated exosomes from hADMSCs with and without differentiation(i.e.,dExo vs uExo).We assessed and compared the effects of uExo and dExo on antioxidative,angiogenic,anti-inflammatory,and axon growth promoting properties by using various peripheral nerve-related cells.Our results demonstrated that hADMSC-SCs secreted more neurotrophic factors and other growth factors,compared to hADMSCs without differentiation.The dExo isolated from hADMSC-SCs protected rat SCs from oxidative stress and enhanced HUVEC migration and angiogenesis.Compared to uExo,dExo also had improved performances in downregulating pro-inflammatory gene expressions and cytokine secretions and promoting axonal growth of sensory neurons differentiated from human induced pluripotent stem cells.Furthermore,microRNA(miRNA)sequencing analysis revealed that exosomes and their parent cells shared some similarities in their miRNA profiles and exosomes displayed a distinct miRNA signature.Many more miRNAs were identified in dExo than in uExo.Several upregulated miRNAs,like miRNA-132-3p and miRNA-199b-5p,were highly related to neuroprotection,anti-inflammation,and angiogenesis.The dExo can effectively modulate various peripheral nerve-related cellular functions and is promising for cell-free biological therapeutics to enhance neural regeneration.

3D printing of multilayered scaffolds for rotator cuff tendon regeneration

Repairing massive rotator cuff tendon defects remains a challenge due to the high retear rate after surgical intervention.3D printing has emerged as a promising technique that enables the fabrication of engineered tissues with heterogeneous structures and mechanical properties,as well as controllable microenvironments for tendon regeneration.In this study,we developed a new strategy for rotator cuff tendon repair by combining a 3D printed scaffold of polylactic-co-glycolic acid(PLGA)with cell-laden collagen-fibrin hydrogels.We designed and fabricated two types of scaffolds:one featuring a separate layer-by-layer structure and another with a tri-layered structure as a whole.Uniaxial tensile tests showed that both types of scaffolds had improved mechanical properties compared to single-layered PLGA scaffolds.The printed scaffold with collagen-fibrin hydrogels effectively supported the growth,proliferation,and tenogenic differentiation of human adipose-derived mesenchymal stem cells.Subcutaneous implantation of the multilayered scaffolds demonstrated their excellent in vivo biocompatibility.This study demonstrates the feasibility of 3D printing multilayered scaffolds for application in rotator cuff tendon regeneration.

Anisotropic scaffolds for peripheral nerve and spinal cord regeneration

The treatment of long-gap(>10 mm)peripheral nerve injury(PNI)and spinal cord injury(SCI)remains a continuous challenge due to limited native tissue regeneration capabilities.The current clinical strategy of using autografts for PNI suffers from a source shortage,while the pharmacological treatment for SCI presents dissatisfactory results.Tissue engineering,as an alternative,is a promising approach for regenerating peripheral nerves and spinal cords.Through providing a beneficial environment,a scaffold is the primary element in tissue engineering.In particular,scaffolds with anisotropic structures resembling the native extracellular matrix(ECM)can effectively guide neural outgrowth and reconnection.In this review,the anatomy of peripheral nerves and spinal cords,as well as current clinical treatments for PNI and SCI,is first summarized.An overview of the critical components in peripheral nerve and spinal cord tissue engineering and the current status of regeneration approaches are also discussed.Recent advances in the fabrication of anisotropic surface patterns,aligned fibrous substrates,and 3D hydrogel scaffolds,as well as their in vitro and in vivo effects are highlighted.Finally,we summarize potential mechanisms underlying the anisotropic architectures in orienting axonal and glial cell growth,along with their challenges and prospects.