Organogenesis最新文献

Diabetes can be treated with β cell replacement therapy, where a patient is transplanted with cadaveric human islets to restore glycemic control. Despite this being an effective treatment, the process of isolating islets from the pancreas requires collagenase digestion which disrupts the islet extracellular matrix (ECM) and activates anoikis-mediated apoptosis. To improve islet survival in culture and after transplantation, the islet microenvironment may be enhanced with the addition of ECM components which are lost during isolation. Furthermore, novel β cell replacement strategies, such as stem cell-derived beta cell (SCβC) treatments or alternative transplant sites and devices, could benefit from a better understanding of how β cells interact with ECM. In this mini-review, we discuss the current understanding of the pancreas and islet ECM composition and review decellularization approaches to generate a native pancreatic ECM scaffold for use in both islet and SCβC culture and transplantation.

Maintaining hepatic functional characteristics in-vitro is considered one of the main challenges in engineering liver tissue. As hepatocytes cultured ex-vivo are deprived of their native extracellular matrix (ECM) milieu, developing scaffolds that mimic the biomechanical and physicochemical properties of the native ECM is thought to be a promising approach for successful tissue engineering and regenerative medicine applications. On the basis that the decellularized liver matrix represents the ideal design template for engineering bioinspired hepatic scaffolds, to derive quantitative descriptors of liver ECM architecture, we characterised decellularised liver matrices in terms of their biochemical, viscoelastic and structural features along with porosity, permeability and wettability. Together, these data provide a unique set of quantitative design criteria which can be used to generate guidelines for fabricating biomaterial scaffolds for liver tissue engineering. As proof-of-concept, we investigated hepatic cell response to substrate viscoelasticity. On collagen hydrogels mimicking decellularised liver mechanics, cells showed superior morphology, higher viability and albumin secretion than on stiffer and less viscous substrates. Although scaffold properties are generally inspired by those of native tissues, our results indicate significant differences between the mechano-structural characteristics of untreated and decellularised hepatic tissue. Therefore, we suggest that design rules - such as mechanical properties and swelling behaviour - for engineering biomimetic scaffolds be re-examined through further studies on substrates matching the features of decellularized liver matrices.

We report a high-sensitivity cell secretome detection method using competitive immuno-aggregation and a micro-Coulter counter. A target cell secretome protein competes with anti-biotin-coated microparticles (MPs) to bind with a biotinylated antibody (Ab), causing decreased aggregation of the functionalized MPs and formation of a mixture of MPs and aggregates. In comparison, without the target cell secretome protein, more microparticles are functionalized, and more aggregates are formed. Thus, a decrease in the average volume of functionalized microparticles/aggregates indicates an increase in cell secretome concentration. This volume change is measured by the micro-Coulter counter, which is used to quantitatively estimate the cell secretome concentration. Vascular endothelial growth factor (VEGF), one of the key cell secretome proteins that regulate angiogenesis and vascular permeabilization, was used as the target protein to demonstrate the sensing principle. A standard calibration curve was generated by testing samples with various VEGF concentrations. A detection range from 0.01 ng/mL to 100.00 ng/mL was achieved. We further demonstrated the quantification of VEGF concentration in exogenous samples collected from the secretome of human mesenchymal stem cells (hMSCs) at different incubation times. The results from the assay agree well with the results of a parallel enzyme-linked immunoabsorbent assay (ELISA) test, indicating the specificity and reliability of the competitive immuno-aggregation assay. With its simple structure and easy sample preparation, this assay not only enables high sensitivity detection of VEGF but also can be readily extended to other types of cell secretome analysis as long as the specific Ab is known.

Cryopreservation is the only long-term storage option for the storage of vessels and vascular constructs. However, endothelial barrier function is almost completely lost after cryopreservation in most established cryopreservation solutions. We here aimed to improve endothelial function after cryopreservation using the 2D-model of porcine aortic endothelial cell monolayers. The monolayers were cryopreserved in cell culture medium or cold storage solutions based on the 4°C vascular preservation solution TiProtec^®, all supplemented with 10% DMSO, using different temperature gradients. After short-term storage at -80°C, monolayers were rapidly thawed and re-cultured in cell culture medium. Thawing after cryopreservation in cell culture medium caused both immediate and delayed cell death, resulting in 11 ± 5% living cells after 24 h of re-culture. After cryopreservation in TiProtec and chloride-poor modifications thereof, the proportion of adherent viable cells was markedly increased compared to cryopreservation in cell culture medium (TiProtec: 38 ± 11%, modified TiProtec solutions ≥ 50%). Using these solutions, cells cryopreserved in a sub-confluent state were able to proliferate during re-culture. Mitochondrial fragmentation was observed in all solutions, but was partially reversible after cryopreservation in TiProtec and almost completely reversible in modified solutions within 3 h of re-culture. The superior protection of TiProtec and its modifications was apparent at all temperature gradients; however, best results were achieved with a cooling rate of -1°C/min. In conclusion, the use of TiProtec or modifications thereof as base solution for cryopreservation greatly improved cryopreservation results for endothelial monolayers in terms of survival and of monolayer and mitochondrial integrity.

Extracellular matrix (ECM) materials have had remarkable success as scaffolds in tissue engineering (TE) and as therapies for tissue injury whereby the ECM microenvironment promotes constructive remodeling and tissue regeneration. ECM powder and solubilized derivatives thereof have novel applications in TE and RM afforded by the capacity of these constructs to be dynamically modulated. The powder form allows for effective incorporation and penetration of reagents; hence, ECM powder is an efficacious platform for 3D cell culture and vehicle for small molecule delivery. ECM powder offers minimally invasive therapy for tissue injury and successfully treatment for wounds refractory to first-line therapies. Comminution of ECM and fabrication of powder-derived constructs, however, may compromise the biological integrity of the ECM. The current lack of optimized fabrication protocols prevents a more extensive and effective clinical application of ECM powders. Further study on methods of ECM powder fabrication and modification is needed.

To investigate the molecular mechanism underlying taurine-stimulated proliferation and differentiation of cochlear neural stem cells (NSCs) and potential involvement of Sonic Hedgehog (Shh) pathway. The NSCs were characterized with immunofluorescence stained with nestin antibody. Cell viability was determined by MTT assay. The relative proliferation was measured by BrdU incorporation assay. The morphologic index was measured under light microscope. The relative protein level was determined by immunoblotting. Here we presented our findings that taurine stimulated proliferation and neurite outgrowth of NSCs, which was completely abolished by Shh inhibitor cyclopamine. In addition, cyclopamine antagonized taurine's effect on glutamatergic and GABAergic neuron population via suppressing expressions of Ptc-1, Smo and Gli-1. Our data supported the critical role of Shh pathway underlying the protective effect of taurine on auditory neural system.

We aimed to investigate the beneficial effect of Celastrol on inner ear stem cells and potential therapeutic value for hearing loss. The inner ear stem cells were isolated and characterized from utricular sensory epithelium of adult mice. The stemness was evaluated by sphere formation assay. The relative expressions of Atoh1, MAP-2 and Myosin VI were measured by RT-PCR and immunoblotting. The up-regulation of MAP-2 was also analysed with immunofluorescence. The in vitro neuronal excitability was interrogated by calcium oscillation. The electrophysiological property was determined by inward current recorded on patch clamp. Our results demonstrated that Celastrol treatment significantly improved the viability and proliferation of mouse inner ear stem cells, and facilitated sphere formation. Moreover, Celastrol stimulated differentiation of mouse inner ear stem cells to neuronal-like cells and enhanced neural excitability. Celastrol also enhanced neuronal-like cell identity in the inner ear stem cell derived neurons, as well as their electrophysiological function. Most notably, these effects were apparently associated with the upregulation of Atoh1 in response to Celastrol treatment. Celastrol showed beneficial effect on inner ear stem cells and held therapeutic promise against hearing loss.

Nervous system injury represent the most common injury and was unique clinical challenge. Using of growth factors (GFs) for the treatment of nervous system injury showed effectiveness in halting its process. However, simple application of GFs could not achieve high efficacy because of its rapid diffusion into body fluids and lost from the lesion site. The drug delivery systems (DDSs) construction used to deliver GFs were investigated so that they could surmount its rapid diffusion and retain at the injury site. This study summarizes commonly used DDSs for sustained release of GFs that provide neuroprotection or restoration effects for nervous system injury.

Understanding the mechanisms of controlled expansion and differentiation of basal progenitor cell populations during organogenesis is essential for developing targeted regenerative therapies. Since the cytokeratin 5-positive (K5⁺) basal epithelial cell population in the salivary gland is regulated by retinoic acid signaling, we interrogated how isoform-specific retinoic acid receptor (RAR) signaling impacts the K5⁺ cell population during salivary gland organogenesis to identify RAR isoform-specific mechanisms that could be exploited in future regenerative therapies. In this study, we utilized RAR isoform-specific inhibitors and agonists with murine submandibular salivary gland organ explants. We determined that RARα and RARγ have opposing effects on K5⁺ cell cycle progression and cell distribution. RARα negatively regulates K5⁺ cells in both whole organ explants and in isolated epithelial rudiments. In contrast, RARγ is necessary but not sufficient to positively maintain K5⁺ cells, as agonism of RARγ alone failed to significantly expand the population. Although retinoids are known to stimulate differentiation, K5 levels were not inversely correlated with differentiated ductal cytokeratins. Instead, RARα agonism and RARγ inhibition, corresponding with reduced K5, resulted in premature lumenization, as marked by prominin-1. With lineage tracing, we demonstrated that K5⁺ cells have the capacity to become prominin-1⁺ cells. We conclude that RARα and RARγ reciprocally control K5⁺ progenitor cells endogenously in the developing submandibular salivary epithelium, in a cell cycle-dependent manner, controlling lumenization independently of keratinizing differentiation. Based on these data, isoform-specific targeting RARα may be more effective than pan-RAR inhibitors for regenerative therapies that seek to expand the K5⁺ progenitor cell pool.

Summary statement: RARα and RARγ reciprocally control K5⁺ progenitor cell proliferation and distribution in the developing submandibular salivary epithelium in a cell cycle-dependent manner while regulating lumenization independently of keratinizing differentiation.

Before the secretion of hard dental tissues, tooth germs undergo several distinctive stages of development (dental lamina, bud, cap and bell). Every stage is characterized by specific proliferation patterns, which is regulated by various morphogens, growth factors and homeodomain proteins. The role of MSX homeodomain proteins in odontogenesis is rather complex. Expression domains of genes encoding for murine Msx1/2 during development are observed in tissues containing highly proliferative progenitor cells. Arrest of tooth development in Msx knockout mice can be attributed to impaired proliferation of progenitor cells. In Msx1 knockout mice, these progenitor cells start to differentiate prematurely as they strongly express cyclin-dependent kinase inhibitor p19^INK4d. p19^INK4d induces terminal differentiation of cells by blocking the cell cycle in mitogen-responsive G1 phase. Direct suppression of p19^INK4d by Msx1 protein is, therefore, important for maintaining proliferation of progenitor cells at levels required for the normal progression of tooth development. In this study, we examined the expression patterns of MSX1, MSX2 and p19^INK4d in human incisor tooth germs during the bud, cap and early bell stages of development. The distribution of expression domains of p19^INK4d throughout the investigated period indicates that p19^INK4d plays active role during human tooth development. Furthermore, comparison of expression domains of p19^INK4d with those of MSX1, MSX2 and proliferation markers Ki67, Cyclin A2 and pRb, indicates that MSX-mediated regulation of proliferation in human tooth germs might not be executed by the mechanism similar to one described in developing tooth germs of wild-type mouse.