The combination of induced pluripotent stem cells and bioscaffolds holds promise for spinal cord regeneration

Spinal cord injuries（SCIs） are debilitating conditions for which no effective treatment currently exists. The damage of neural tissue causes disruption of neural tracts and neuron loss in the spinal cord. Stem cell replacement offers a solution for SCI treatment by providing a source of therapeutic cells for neural function restoration. Induced pluripotent stem cells（i PSCs） have been investigated as a potential type of stem cell for such therapies. Transplantation of i PSCs has been shown to be effective in restoring function after SCIs in animal models while they circumvent ethical and immunological concerns produced by other stem cell types. Another approach for the treatment of SCI involves the graft of a bioscaffold at the site of injury to create a microenvironment that enhances cellular viability and guides the growing axons. Studies suggest that a combination of these two treatment methods could have a synergistic effect on functional recovery post-neural injury. While much progress has been made, more research is needed before clinical trials are possible. This review highlights recent advancements using i PSCs and bioscaffolds for treatment of SCI.

Matrix bound vesicles and miRNA cargoes are bioactive factors within extracellular matrix bioscaffolds

Injury to central nervous system （CNS） tissues in adult mam- mals often leads to neuronal loss, scarring, and permanently lost neurologic functions, and this default healing response is increasingly linked to a pro-inflammatory innate immune response. Extracellular matrix （ECM） technology can reduce inflammation, while increasing functional tissue remodeling in various tissues and organs, including the CNS.

Bioscaffolds embedded with regulatory modules for cell growth and tissue formation:A review

The demand for artificial organs has greatly increased because of various aging-associated diseases and the wide need for organ transplants.A recent trend in tissue engineering is the precise reconstruction of tissues by the growth of cells adhering to bioscaffolds,which are three-dimensional(3D)structures that guide tissue and organ formation.Bioscaffolds used to fabricate bionic tissues should be able to not only guide cell growth but also regulate cell behaviors.Common regulation methods include biophysical and biochemical stimulations.Biophysical stimulation cues include matrix hardness,external stress and strain,surface topology,and electromagnetic field and concentration,whereas biochemical stimulation cues include growth factors,proteins,kinases,and magnetic nanoparticles.This review discusses bioink preparation,3D bioprinting(including extrusion-based,inkjet,and ultraviolet-assisted 3D bioprinting),and regulation of cell behaviors.In particular,it provides an overview of state-of-the-art methods and devices for regulating cell growth and tissue formation and the effects of biophysical and biochemical stimulations on cell behaviors.In addition,the fabrication of bioscaffolds embedded with regulatory modules for biomimetic tissue preparation is explained.Finally,challenges in cell growth regulation and future research directions are presented.

Microfluidic bioscaffolds for regenerative engineering

The construction of biological scaffolds in vitro plays an important role in regenerative engineering,which has always been the focus of research.The application of scaffold materials combined with cells/bioactive factors is considered to have great potential for tissue regeneration.Various strategies have been used for constructing biological scaffolds,including electrospinning/spraying,direct laser writing,solvent casting,and microfluidic technology.Among them,considering the advantages of the safety,low cost,and highly controllable process-ing characteristics,microfluidic technology has become a promising method for the construction of biological scaffolds.This review overviews the recent research progress of microfluidic bioscaffolds for regenerative engi-neering.Firstly,we introduce some typical natural polymers which are widely used to construct bioscaffolds.Then,the bioscaffolds with different structures templated by microfluidic droplets and fibers are described.Fur-therly,we talk about the different applications of microfluidic bioscaffolds in wound healing,drug delivery,bone regeneration,and nerve regeneration.Finally,the challenges and future prospects of the development of microfluidic bioscaffolds for regenerative engineering are discussed.

A nanostructured look of collagen apatite porosity into human mineralized collagen fibril

Bone tissue is a hierarchical material characterized at nanoscale by the mineralized collagen fibril,a recurring structure mainly composed of apatite minerals,collagen and water.Bone nanostructure has a fundamental role in determining the mechanical behavior of the tissue and its mass transport properties.Diffusion phenomenon allows to maintain an adequate supply of metabolites in the mechanisms of bone remodeling,adaptation and repair.Several analytical and computational models have been developed to analyze and predict bone tissue behavior.However,the fine replication of the natural tissue still represents a challenge.Insights on the structural organization at nanoscale and on the influence of apatite mineral crystals on the diffusion coefficient lead to outline the functional conditions for the development of biomimetic strategies for bone tissue engineering.Thorough understanding of bone nanostructure is essential to improve longevity of bioscaffolds and to decrease the risk of failure by controlling their mechanical and biological performance.

Extracellular matrices for gastrointestinal surgery:Ex vivo testing and current applications

AIM:To assess the effects of bile and pancreatic juice on structural and mechanical resistance of extracellular matrices(ECMs) in vitro.METHODS:Small-intestinal submucosa(SIS),porcine dermal matrix(PDM),porcine pericardial matrix(PPM) and bovine pericardial matrix(BPM) were incubated in human bile and pancreatic juice in vitro.ECMs were examined by macroscopic observation,scanning electron microscopy(SEM) and testing of mechanical resistance.RESULTS:PDM dissolved within 4 d after exposure to bile or pancreatic juice.SIS,PPM and PDM retained their integrity for > 60 d when incubated in either digestive juice.The effect of bile was found to be far more detrimental to mechanical stability than pancreatic juice in all tested materials.In SIS,the loss of mechanical stability after incubation in either of the digestive secretions was less distinct than in PPM and BPM [mFmax 4.01/14.27 N(SIS) vs 2.08/5.23 N(PPM) vs 1.48/7.89 N(BPM)].In SIS,the extent of structural damage revealed by SEM was more evident in bile than in pancreatic juice.In PPM and BPM,structural damage was comparable in both media.CONCLUSION:PDM is less suitable for support of gastrointestinal healing.Besides SIS,PPM and BPM should also be evaluated experimentally for gastrointestinal indications.

The effect of porosity on the mechanical properties of 3D-printed triplyperiodic minimal surface (TPMS) bioscaffold

Prevailing tissue degeneration caused by musculoskeletal maladies poses a great demand on bioscaffolds,which are artificial,biocompatible structures implanted into human bodies with appropriate mechanical properties.Recent advances in additive manufacturing,i.e.,3D printing,facilitated the fabrication of bioscaffolds with unprecedented geometrical complexity and size flexibility and allowed for the fabrication of topologies that would not have been achieved otherwise.In our work,we explored the effect of porosity on themechanical properties of a periodic cellular structure.The structure was derived from the mathematically created triply periodic minimal surface(TPMS),namely the Sheet-Diamond topology.First,we employed a series of software including MathMod,Meshmixer,Netfabb and Cura to design the model.Then,we utilized additive manufacturing technology to fabricate the cellular structures with designated scale.Finally,we performed compressive testing to deduce the mechanical properties of each cellular structure.Results showed that,in comparison with the highporosity group,the yield strength of the low-porosity group was 3 times higher,and the modulus was 2.5 times larger.Our experiments revealed a specific relationship between porosity and Young’s modulus of PLA-made Sheet-Diamond TPMS structure.Moreover,it was observed that the high-and low-porosity structures failed through distinctive mechanisms,with the former breaking down via buckling and the latter via micro-fracturing.