Corneal repair by human corneal keratocyte-reprogrammed iPSCs and amphiphatic carboxymethyl-hexanoyl chitosan hydrogel

Potential Role of Induced Pluripotent Stem Cells (IPSCs) for Cell-Based Therapy of the Ocular Surface

The integrity and normal function of the corneal epithelium are crucial for maintaining the cornea’s transparency and vision. The existence of a cell population with progenitor characteristics in the limbus maintains a dynamic of constant epithelial repair and renewal. Currently, cell-based therapies for bio replacement—cultured limbal epithelial transplantation (CLET) and cultured oral mucosal epithelial transplantation (COMET)—present very encouraging clinical results for treating limbal stem cell deficiency (LSCD) and restoring vision. Another emerging therapeutic approach consists of obtaining and implementing human progenitor cells of different origins in association with tissue engineering methods. The development of cell-based therapies using stem cells, such as human adult mesenchymal or induced pluripotent stem cells (IPSCs), represent a significant breakthrough in the treatment of certain eye diseases, offering a more rational, less invasive, and better physiological treatment option in regenerative medicine for the ocular surface. This review will focus on the main concepts of cell-based therapies for the ocular surface and the future use of IPSCs to treat LSCD.

Enhanced antioxidant capacity of dental pulp-derived iPSC-differentiated hepatocytes and liver regeneration by injectable HGF-releasing hydrogel in fulminant hepatic failure

Acute hepatic failure (AHF) is a severe liver injury leading to sustained damage and complications. Induced pluripotent stem cells (iPSCs) may be an alternative option for the treatment of AHF. In this study, we reprogrammed human dental pulp-derived fibroblasts into iPSCs, which exhibited pluripotency and the capacity to differentiate into tridermal lineages, including hepatocyte-like cells (iPSC-Heps). These iPSC-Heps resembled human embryonic stem cell-derived hepatocyte-like cells in gene signature and hepatic markers/functions. To improve iPSC-Heps engraftment, we next developed an injectable carboxymethyl-hexanoyl chitosan hydrogel (CHC) with sustained hepatocyte growth factor (HGF) release (HGF-CHC) and investigated the hepatoprotective activity of HGF-CHC-delivered iPSC-Heps in vitro and in an immunocompromised AHF mouse model induced by thioacetamide (TAA). Intrahepatic delivery of HGF-CHC-iPSC-Heps reduced the TAA-induced hepatic necrotic area and rescued liver function and recipient viability. Compared with PBS-delivered iPSC-Heps, the HGF-CHC-delivered iPSC-Heps exhibited higher antioxidant and antiapoptotic activities that reduced hepatic necrotic area. Importantly, these HGF-CHC-mediated responses could be abolished by administering anti-HGF neutralizing antibodies. In conclusion, our findings demonstrated that HGF mediated the enhancement of iPSC-Hep antioxidant/antiapoptotic capacities and hepatoprotection and that HGF-CHC is as an excellent vehicle for iPSC-Hep engraftment in iPSC-based therapy against AHF.

Synergistic effects of carboxymethyl-hexanoyl chitosan, cationic polyurethane-short branch PEI in miR122 gene delivery: accelerated differentiation of iPSCs into mature hepatocyte-like cells and improved stem cell therapy in a hepatic failure model

MicroRNA122 (miR122), a liver-specific microRNA, plays critical roles in homeostatic regulation and hepatic-specific differentiation. Induced pluripotent stem cells (iPSCs) have promising potential in regenerative medicine, but it remains unknown whether non-viral vector-mediated miR122 delivery can enhance the differentiation of iPSCs into hepatocyte-like cells (iPSC-Heps) and rescue thioacetamide-induced acute hepatic failure (AHF) in vivo. In this study, we demonstrated that embedment of miR122 complexed with polyurethane-graft-short-branch polyethylenimine copolymer (PU-PEI) in nanostructured amphiphatic carboxymethyl-hexanoyl chitosan (CHC) led to dramatically enhanced miR122 delivery into human dental pulp-derived iPSCs (DP-iPSCs) and facilitated these DP-iPSCs to differentiate into iPSC-Heps (miR122-iPSC-Heps) with mature hepatocyte functions. Microarray and bioinformatics analysis further indicated that CHC/PU-PEI-miR122 promoted the gene-signature pattern of DP-iPSCs to shift into a liver-specific pattern. Furthermore, intrahepatic delivery of miR122-iPSC-Heps, but not miR-Scr-iPSC-Heps, improved liver functions and rescued recipient survival, and CHC-mediated delivery showed a better efficacy than that using phosphate buffered saline as a delivery vehicle. In addition, these transplanted miR122-iPSC-Heps remained viable and could produce circulatory albumin for 4 months. Taken together, our findings demonstrate that non-viral delivery of miR122 shortens the time of iPSC differentiation into hepatocytes and the delivery of miR122-iPSC-Heps using CHC as a vehicle exhibited promising hepatoprotective efficacy in vivo. miR122-iPSC-Heps may represent a feasible cell source and provide an efficient and alternative strategy for hepatic regeneration in AHF.

Physical cues of cell culture materials lead the direction of differentiation lineages of pluripotent stem cells

Differentiation methods of hPSCs into specific cell lineages. Differentiation of hPSCsviaEB formation (types AB, A–D) or without EB formation (types E–H).

Role of nanotechnology in epigenetic reprogramming

With the recent advances in regenerative medicine, nanotechnology has created a niche for itself as a promising avenue in this field. Innumerable studies have been carried out by researchers using virus-based methodologies for the purpose of epigenetic reprogramming. Although this method is ostensibly safe, nonetheless, they are tagged with the risk of viral genome integration into the host genome or insertional mutagenesis. Transient transfection by the use of nanocarriers is the best way to overcome these problems. This review focuses on some of the significant works carried out by researchers utilizing nanocarrier systems that have shown promising results and thus created a landmark in the epigenetic reprogramming.

Stem Cell Therapy for Corneal Regeneration Medicine and Contemporary Nanomedicine for Corneal Disorders

The ocular surface is the outermost part of the visual system that faces many extrinsic or intrinsic threats, such as chemical burn, infectious pathogens, thermal injury, Stevens-Johnson syndrome, ocular pemphegoid, and other autoimmune diseases. The cornea plays an important role in conducting light into the eyes and protecting intraocular structures. Several ocular surface diseases will lead to the neovascularization or conjunctivalization of corneal epithelium, leaving opacified optical media. It is believed that some corneal limbal cells may present stem cell-like properties and are capable of regenerating corneal epithelium. Therefore, cultivation of limbal cells and reconstruction of the ocular surface with these limbal cell grafts have attracted tremendous interest in the past few years. Currently, stem cells are found to potentiate regenerative medicine by their capability of differentiation into multiple lineage cells. Among these, the most common cell sources for clinical use are embryonic, adult, and induced stem cells. Different stem cells have varied specific advantages and limitations for in vivo and in vitro expansion. Other than ocular surface diseases, culture and transplantation of corneal endothelial cells is another major issue for corneal decompensation and awaits further studies to find out comprehensive solutions dealing with nonregenerative corneal endothelium. Recently, studies of in vitro endothelium culture and ρ-associated kinase (ROCK) inhibitor have gained encouraging results. Some clinical trials have already been finished and achieved remarkable vision recovery. Finally, nanotechnology has shown great improvement in ocular drug delivery systems during the past two decades. Strategies to reconstruct the ocular surface could combine with nanoparticles to facilitate wound healing, drug delivery, and even neovascularization inhibition. In this review article, we summarized the major advances of corneal limbal stem cells, limbal stem cell deficiency, corneal endothelial cell culture/transplantation, and application of nanotechnology on ocular surface reconstruction. We also illustrated potential applications of current knowledge for the future treatment of ocular surface diseases.

Keratocytes derived from spheroid culture of corneal stromal cells resemble tissue resident keratocytes

Purpose

Corneal stromal cells transform to precursor cells in spheroid culture. We determined whether keratocytes derived from spheroid culture of murine corneal stromal cells resemble tissue resident keratocytes.

Methods

Spheroid culture was performed by seeding dissociated stromal cells onto ultra-low attachment plates containing serum-free mesenchymal stem cell culture medium. Spheroids were characterized with phenotype specific markers and stemness transcription factor genes. Spheroids and adherent cells in culture were induced to differentiate to keratocytes using keratocyte induction medium (KIM) and compared with tissue resident keratocytes.

Results

Stromal cells formed spheroids in ultra-low attachment plates, but not in polystyrene tissue culture dishes. Keratocan expression and abundance was significantly higher in spheroids as compared to adherent cells whereas alpha-smooth muscle actin (α-SMA) was significantly lower. As compared to adherent culture-derived cells, the expressions of keratocan, aldehyde dehydrogenase (ALDH3A1) and α-SMA in spheroid-derived cells approximated much more closely the levels of these genes in tissue resident keratocytes. Of the stemness genes, Nanog and Oct4 were upregulated in the spheroids.

Conclusion

Stemness transcription factor genes are upregulated in spheroids. Keratocytes derived from spheroids resemble tissue resident keratocytes, thus increasing manifolds the quantity of these cells for in-vitro experiments.

Wound healing: an update

Wounds, both chronic and acute, continue to be a tremendous socioeconomic burden. As such, technologies drawn from many disciplines within science and engineering are constantly being incorporated into innovative wound healing therapies. While many of these therapies are experimental, they have resulted in new insights into the pathophysiology of wound healing, and in turn the development of more specialized treatments for both normal and abnormal wound healing states. Herein, we review some of the emerging technologies that are currently being developed to aid and improve wound healing after cutaneous injury.

A novel bubble-forming material for preparing hydrophobic-agent-loaded bubbles with theranostic functionality

In the present study, a new bubble-forming material (carboxymethyl hexanoyl chitosan, CHC), together with superparamagnetic iron oxide (SPIO) nanoparticles, was employed to prepare image-guided bubbles for efficiently encapsulating and delivering hydrophobic agents to kill tumor cells. The results showed that CHC could be used for preparing not only micronized bubbles (CHC/SPIO MBs) to exhibit ultrasound imaging functionality but also nanosized bubbles (CHC/SPIO NBs) to exhibit magnetic resonance T2 image contrast. It was found that the amounts of SPIO nanoparticles and hexane during preparation process were the key factors to obtaining CHC/SPIO NBs. Most importantly, under in vitro cell culture conditions with the same amount of camptothecin (CPT) and therapeutic sonication, CPT-loaded CHC/SPIO NBs demonstrated more significant transcellular delivery and cytotoxicity than free CPT. Subsequently, an intratumoral injection was proposed for the in vivo administration of hydrophobic-agent-loaded CHC/SPIO NBs. After injection, the distribution of a hydrophobic dye (DiR, an agent with near-infrared (NIR) fluorescence used as a model drug) released from the CHC/SPIO NBs was tracked by an NIR imaging technique. A significant tumor-specific accumulation was observed in the mouse that received the DiR-loaded CHC/SPIO NBs; the same was not observed in the mouse that received the free dye (without incorporating with CHC/SPIO NBs). It is expected, in the future, both the dose of the therapeutic agent administered and its side effects can be significantly lowered by using novel CHC/SPIO NBs together with local delivery (intratumoral injection), targeted imaging and enhanced cellular uptake of the drug.

The generation of induced pluripotent stem cells for macular degeneration as a drug screening platform: identification of curcumin as a protective agent for retinal pigment epithelial cells against oxidative stress

Age-related macular degeneration (AMD) is one retinal aging process that may lead to irreversible vision loss in the elderly. Its pathogenesis remains unclear, but oxidative stress inducing retinal pigment epithelial (RPE) cells damage is perhaps responsible for the aging sequence of retina and may play an important role in macular degeneration. In this study, we have reprogrammed T cells from patients with dry type AMD into induced pluripotent stem cells (iPSCs) via integration-free episomal vectors and differentiated them into RPE cells that were used as an expandable platform for investigating pathogenesis of the AMD and in-vitro drug screening. These patient-derived RPEs with the AMD-associated background (AMD-RPEs) exhibited reduced antioxidant ability, compared with normal RPE cells. Among several screened candidate drugs, curcumin caused most significant reduction of ROS in AMD-RPEs. Pre-treatment of curcumin protected these AMD-RPEs from H2O2-induced cell death and also increased the cytoprotective effect against the oxidative stress of H2O2 through the reduction of ROS levels. In addition, curcumin with its versatile activities modulated the expression of many oxidative stress-regulating genes such as PDGF, VEGF, IGFBP-2, HO1, SOD2, and GPX1. Our findings indicated that the RPE cells derived from AMD patients have decreased antioxidative defense, making RPE cells more susceptible to oxidative damage and thereby leading to AMD formation. Curcumin represented an ideal drug that can effectively restore the neuronal functions in AMD patient-derived RPE cells, rendering this drug an effective option for macular degeneration therapy and an agent against aging-associated oxidative stress.

A temperature-induced and shear-reversible assembly of latanoprost-loaded amphiphilic chitosan colloids: characterization and in vivo glaucoma treatment

Hydrogels composed of assembled colloids is a material class that is currently receiving much interest and shows great promise for use in biomedical applications. This emerging material class presents unique properties derived from the combination of nanosized domains in the form of colloidal particles with a continuous gel network and an interspersed liquid phase. Here we developed an amphiphilic chitosan-based, thermogelling, shear-reversible colloidal gel system for improved glaucoma treatment and addressed how preparation procedures and loading with the anti-glaucoma drug latanoprost and commonly used preservative benzalkonium chloride influenced the mechanical properties of and drug release from the colloidal gels. The results highlight that incorporated substances and preparation procedures have effects both on mechanical properties and drug release, but that the release of drug loaded in the colloidal carriers is mainly limited by transport out of the carriers, rather than by diffusion within the gel. The developed colloidal chitosan based gels hold outstanding biomedical potential, as confirmed by the ease of preparation and administration, low cytotoxicity in MTT assay, excellent biocompatibility and lowering of intraocular pressure for 40 days in a rabbit glaucoma model. The findings clearly justify further investigations towards clinical use in the treatment of glaucoma. Furthermore, the use of this shear-reversible colloidal gel could easily be extended to localized treatment of a number of critical conditions, from chronic disorders to cancer, potentially resulting in a number of new therapeutics with improved clinical performance.

Preparation and characterization of a novel tobramycin-containing antibacterial collagen film for corneal tissue engineering

Corneal disease is a major cause of blindness and keratoplasty is an effective treatment method. However, clinical treatment is limited due to a severe shortage of high-quality allogeneic corneal tissues and the bacterial infection after corneal transplantation. In this study, we develop a novel artificial and antibacterial collagen film (called Col-Tob) for corneal repair. In the Col-Tob film, the tobramycin, which is an aminoglycoside antibiotic to treat various types of bacterial infections, was cross-linked by 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide and N-hydroxysuccinimide onto the collagen. Physical properties, antibacterial property and biocompatibility of the films were characterized. The results indicate that the film is basically transparent and has appropriate mechanical properties. Cell experiments show that human corneal epithelial cells could adhere to and proliferate well on the film. Most importantly, the film exhibits excellent antibacterial effect in vitro. Lamellar keratoplasty shows that the Col-Tob film can be sutured in rabbit eyes and are epithelialized completely in 15 ± 5 days, and their transparency is restored quickly in the first month. Corneal rejection reaction, neovascularization and keratoconus are not observed within 3 months. This film, which can be prepared in large quantities and at low cost,should have potential application in corneal repair.

Human fetal keratocytes have multipotent characteristics in the developing avian embryo

The human cornea contains stem cells that can be induced to express markers consistent with multipotency in cell culture; however, there have been no studies demonstrating that human corneal keratocytes are multipotent. The objective of this study is to examine the potential of human fetal keratocytes (HFKs) to differentiate into neural crest-derived tissues when challenged in an embryonic environment. HFKs were injected bilaterally into the cranial mesenchyme adjacent to the neural tube and the periocular mesenchyme in chick embryos at embryonic days 1.5 and 3, respectively. The injected keratocytes were detected by immunofluorescence using the human cell-specific marker, HuNu. HuNu-positive keratocytes injected along the neural crest pathway were localized adjacent to HNK-1-positive migratory host neural crest cells and in the cardiac cushion mesenchyme. The HuNu-positive cells transformed into neural crest derivatives such as smooth muscle in cranial blood vessels, stromal keratocytes, and corneal endothelium. However, they failed to form neurons despite their presence in the condensing trigeminal ganglion. These results show that HFKs retain the ability to differentiate into some neural crest-derived tissues. Their ability to respond to embryonic cues and generate corneal endothelium and stromal keratocytes provides a basis for understanding the feasibility of creating specialized cells for possible use in regenerative medicine.