Coaxial electrohydrodynamic printing of core–shell microfibrous scaffolds with layer-specific growth factors release for enthesis regeneration

The rotator cuff tear has emerged as a significant global health concern.However,existing therapies fail to fully restore the intricate bone-to-tendon gradients,resulting in compromised biomechanical functionalities of the reconstructed enthesis tissues.Herein,a tri-layered core–shell microfibrous scaffold with layer-specific growth factors(GFs)release is developed using coaxial electrohydrodynamic(EHD)printing for in situ cell recruitment and differentiation to facilitate gradient enthesis tissue repair.Stromal cell-derived factor-1(SDF-1)is loaded in the shell,while basic fibroblast GF,transforming GF-beta,and bone morphogenetic protein-2 are loaded in the core of the EHD-printed microfibrous scaffolds in a layer-specific manner.Correspondingly,the tri-layered microfibrous scaffolds have a core–shell fiber size of(25.7±5.1)μm,with a pore size sequentially increasing from(81.5±4.6)μm to(173.3±6.9)μm,and to(388.9±6.9μm)for the tenogenic,chondrogenic,and osteogenic instructive layers.A rapid release of embedded GFs is observed within the first 2 d,followed by a faster release of SDF-1 and a slightly slower release of differentiation GFs for approximately four weeks.The coaxial EHD-printed microfibrous scaffolds significantly promote stem cell recruitment and direct their differentiation toward tenocyte,chondrocyte,and osteocyte phenotypes in vitro.When implanted in vivo,the tri-layered core–shell microfibrous scaffolds rapidly restored the biomechanical functions and promoted enthesis tissue regeneration with native-like bone-to-tendon gradients.Our findings suggest that the microfibrous scaffolds with layer-specific GFs release may offer a promising clinical solution for enthesis regeneration.

Biological approaches to the repair and regeneration of the rotator cuff tendon-bone enthesis:a literature review

Entheses are highly specialised organs connecting ligaments and tendons to bones,facilitating force transmission,and providing mechanical strengths to absorb forces encountered.Two types of entheses,fibrocartilaginous and fibrous,exist in interfaces.The gradual fibrocartilaginous type is in rotator cuff tendons and is more frequently injured due to the poor healing capacity that leads to loss of the original structural and biomechanical properties and is attributed to the high prevalence of retears.Fluctuating methodologies and outcomes of biological approaches are challenges to overcome for them to be routinely used in clinics.Therefore,stratifying the existing literature according to different categories(chronicity,extent of tear,and studied population)would effectively guide repair approaches.This literature review supports tissue engineering approaches to promote rotator cuff enthesis healing employing cells,growth factors,and scaffolds period.Outcomes suggest its promising role in animal studies as well as some clinical trials and that combination therapies are more beneficial than individualized ones.It then highlights the importance of tailoring interventions according to the tear extent,chronicity,and the population being treated.Contributing factors such as loading,deficiencies,and lifestyle habits should also be taken into consideration.Optimum results can be achieved if biological,mechanical,and environmental factors are approached.It is challenging to determine whether variations are due to the interventions themselves,the animal models,loading regimen,materials,or tear mechanisms.Future research should focus on tailoring interventions for different categories to formulate protocols,which would best guide regenerative medicine decision making.

Engineering an enthesis-like graft for rotator cuff repair:An approach to fabricate highly biomimetic scaffold capable of zone-specifically releasing stem cell differentiation inducers

Rotator cuff(RC)attaches to humerus across a triphasic yet continuous tissue zones(bone-fibrocartilage-tendon),termed“enthesis”.Regrettably,rapid and functional enthesis regeneration is challenging after RC tear.The existing grafts bioengineered for RC repair are insufficient,as they were engineered by a scaffold that did not mimic normal enthesis in morphology,composition,and tensile property,meanwhile cannot simultaneously stimulate the formation of bone-fibrocartilage-tendon tissues.Herein,an optimized decellularization approach based on a vacuum aspiration device(VAD)was developed to fabricate a book-shaped decellularized enthesis matrix(O-BDEM).Then,three recombinant growth factors(CBP-GFs)capable of binding collagen were synthesized by fusing a collagen-binding peptide(CBP)into the N-terminal of BMP-2,TGF-β3,or GDF-7,and zone-specifically tethered to the collagen of O-BDEM to fabricate a novel scaffold(CBP-GFs/O-BDEM)satisfying the above-mentioned requirements.After ensuring the low immunogenicity of CBP-GFs/O-BDEM by a novel single-cell mass cytometry in a mouse model,we interleaved urine-derived stem cell-sheets into this CBP-GFs/O-BDEM to bioengineer an enthesis-like graft.Its high-performance on regenerating enthesis was determined in a canine model.These findings indicate this CBP-GFs/O-BDEM may be an excellent scaffold for constructing enthesis-like graft to patch large/massive RC tears,and provide breakthroughs in fabricating graded interfacial tissue.

Stem cell therapy in the management of shoulder rotator cuff disorders

Rotator cuff tears are frequent shoulder problems that are usually dealt with surgical repair. Despite improved surgical techniques, the tendon-to-bone healing rate is unsatisfactory due to difficulties in restoring the delicate transitional tissue between bone and tendon. It is essential to understand the molecular mechanisms that determine this failure. The study of the molecular environment during embryogenesis and during normal healing after injury is key in devising strategies to get a successful repair. Mesenchymal stem cells(MSC) can differentiate into different mesodermal tissues and have a strong paracrine, anti-inflammatory, immunoregulatory and angiogenic potential. Stem cell therapy is thus a potentially effective therapy to enhance rotator cuff healing. Promising results have been reported with the use of autologous MSC of different origins in animal studies: they have shown to have better healing properties, increasing the amount of fibrocartilage formation and improving the orientation of fibrocartilage fibers with less immunologic response and reduced lymphocyte infiltration. All these changes lead to an increase in biomechanical strength. However, animal research is still inconclusive and more experimental studies are needed before human application. Future directions include expanded stem cell therapy in combination with growth factors or different scaffolds as well as new stem cell types and gene therapy.

Scaffold-based tissue engineering strategies for soft-hard interface regeneration

Repairing injured tendon or ligament attachments to bones(enthesis)remains costly and challenging.Despite superb surgical management,the disorganized enthesis newly formed after surgery accounts for high recurrence rates after operations.Tissue engineering offers efficient alternatives to promote healing and regeneration of the specialized enthesis tissue.Load-transmitting functions thus can be restored with appropriate biomaterials and engineering strategies.Interestingly,recent studies have focused more on microstructure especially the arrangement of fibers since Rossetti successfully demonstrated the variability of fiber underspecific external force.In this review,we provide an important update on the current strategies for scaffold-based tissue engineering of enthesis when natural structure and properties are equally emphasized.We firstly described compositions,structures and features of natural enthesis with their special mechanical properties highlighted.Stimuli for growth,development and healing of enthesis widely used in popular strategies are systematically summarized.We discuss the fabrication of engineering scaffolds from the aspects of biomaterials,techniques and design strategies and comprehensively evaluate the advantages and disadvantages of each strategy.At last,this review pinpoints the remaining challenges and research directions to make breakthroughs in further studies.