DCs as targets for vaccine design

DEC-205 receptor-mediated long-circling nanoliposome as an antigen and Eucommia ulmoides polysaccharide delivery system enhances the immune response via facilitating dendritic cells maturation

DEC-205 receptor-mediated dendritic cells (DC) targeting nanoliposomes is a promising delivery system in eliciting an immune response against pathogens. When this delivery system carries both antigen and immunomodulator, it can effectively regulate the DC function as well as the initial T cell response. To maximize the desired therapeutic effects of Eucommia ulmoides Oliv. polysaccharides (EUPS), and induce an efficient humoral and cellular immune response against an antigen, we encapsulated the OVA and EUPS in long-circling nanoliposomes and conjugated it with anti-DEC-205 receptor antibody to obtain a DEC-205-targeted nanoliposomes (anti-DEC-205-EUPS-OVA-LPSM). The physicochemical properties and immune-modulating effects were investigated in vitro and in vivo by a series of the experiment to evaluate the targeting efficiency of anti-DEC-205-EUPS-OVA-LPSM. In vitro, anti-DEC-205-EUPS-OVA-LPSM (160 μg mL⁻¹) could enhance DCs proliferation and increase their phagocytic efficiency. In vivo anti-DEC-205-EUPS-OVA-LPSM remarkably promoted the OVA-specific IgG and IgG isotypes levels, enhanced the splenocyte proliferation, and induced the NK cell and CTL cytotoxicity. Besides, the anti-DEC-205-EUPS-OVA-LPSM enhanced the maturation of DCs. These findings suggest that the DEC-205 receptor antibody-conjugated EUPS nanoliposome can act as an efficient antigen delivery system to enhance the cellular and humoral immune response by promoting DC maturation. This indicates that the anti-DEC-205-EUPS-OVA-LPSM has significant potential as an immune-enhancing agent and antigen delivery system.

MUC1 in Cancer Immunotherapy - New Hope or Phantom Menace?

Understanding of the functioning of MUC1 (human mucin) has advanced significantly over 40 years of its investigation. The anti-adhesive properties of the extracellular domain, which were the main focus of early studies initially explaining overexpression of MUC1 in progressing oncological diseases, were gradually put on the back burner. Researchers became more interested in its regulatory and signaling functions in cells rather in its anti-adhesive properties. The found the ability of MUC1 for signal transduction, and its ability to participate in cell metabolism opened new possibilities for improved control over cancer cells in addition to just attracting antigens of the immune system to a target. Nevertheless, there are issues in the functioning of MUC1 that raise doubts about its effectiveness in cancer immunotherapy.

Regeneration and Repair of Skin Wounds: Various Strategies for Treatment

Skin as a mechanical barrier between the inner and outer environment of our body protects us against infection and electrolyte loss. This organ consists of 3 layers: the epidermis, dermis, and hypodermis. Any disruption in the integrity of skin leads to the formation of wounds, which are divided into 2 main categories: acute wounds and chronic wounds. Generally, acute wounds heal relatively faster. In contrast to acute wounds, closure of chronic wounds is delayed by 3 months after the initial insult. Treatment of chronic wounds has been one of the most challenging issues in the field of regenerative medicine, promoting scientists to develop various therapeutic strategies for a fast, qualified, and most cost-effective treatment modality. Here, we reviewed more recent approaches, including the development of stem cell therapy, tissue-engineered skin substitutes, and skin equivalents, for the healing of complex wounds.

Expression of BMP and Actin Membrane Bound Inhibitor Is Increased during Terminal Differentiation of MSCs

Chondrogenic differentiating mesenchymal stem cells (MSCs) are mimicking embryonal endochondral ossification and become hypertrophic. BMP (bone morphogenetic protein) and Activin Membrane Bound Inhibitor (BAMBI) is a pseudoreceptor that regulates the activity of transforming growth factor-β (TGF-β) and BMP signalling during chondrogenesis. Both TGF-β and BMP signalling are regulators of chondrogenic cell differentiation. Human bone marrow derived MSCs were chondrogenically predifferentiated in aggregate culture for 14 days. Thereafter, one group was subjected to hypertrophy enhancing media conditions while controls were kept in chondrogenic medium until day 28. Histological evaluation, gene expression by PCR, and Western blot analysis were carried out at days 1, 3, 7, 14, 17, 21, and 28. A subset of cultures was treated with the BMP inhibitor Noggin to test for BMP dependent expression of BAMBI. Hypertrophic differentiated pellets showed larger cells with increased collagen 10 and alkaline phosphatase staining. There was significantly increased expression of BAMBI on gene expression and protein level in hypertrophic cultures compared to the chondrogenic control and increased BMP4 gene expression. Immunohistochemistry showed intense staining of BAMBI in hypertrophic cells. BAMBI expression was dose-dependently downregulated by Noggin. The pseudoreceptor BAMBI is upregulated upon enhancement of hypertrophy in MSC chondrogenic differentiation by a BMP dependent mechanism.

Rapid and Persistent Delivery of Antigen by Lymph Node Targeting PRINT Nanoparticle Vaccine Carrier To Promote Humoral Immunity

Nanoparticle delivery of subunit vaccines may increase vaccine efficacy, leading to a wide variety of safe and effective vaccines beyond those available through dosing inactivated or live, attenuated whole pathogens. Here we present a versatile vaccine delivery platform based on PRINT hydrogels made of biocompatible hydroxy-poly(ethylene glycol) (PEG) that is able to activate the complement system by the alternative pathway. These lymph node targeting nanoparticles (NPs) promote the immunogenicity of a model antigen, ovalbumin, showing comparable adjuvant effect to alum. We demonstrate that an antigen-specific humoral response is correlated with antigen delivery to the draining lymph nodes, in particular, B cell rich regions of the lymph nodes. 80 × 180 nm cylindrical NPs were able to sustain prolonged antigen presentation to antigen presenting cells (APCs) and elicit a stronger immune response than nondraining 1 × 1 μm NPs or rapidly clearing soluble antigen. The 80 × 180 nm NPs also show high levels of uptake by key APCs and efficiently stimulate CD4(+) helper T cell proliferation in vivo, further promoting antibody production. These features together produce a significant humoral immune response, superior to that produced by free antigen alone. The simplicity of the chemistries used in antigen conjugation to PRINT NPs confers versatility to this antigen delivery platform, allowing for potential application to many infectious diseases.

Freeze-dried rat bone marrow mesenchymal stem cell paracrine factors: a simplified novel material for skin wound therapy

The mesenchymal stem cell (MSC) supernatant is well known as a rich source of autologous cytokines and universally used for tissue regeneration in current clinical medicine. However, the limitation of conditioned medium used in open-wound repair compels the need to find a more sophisticated way to take advantage of the trophic factors of MSCs. We have now fabricated a three-dimensional membrane from freeze-dried bone marrow mesenchymal stem cells-conditioned medium (FBMSC-CM) using a simple freeze-dried protocol. Scanning electron microscopy images showed the microstructure of the FBMSC-CM membrane (FBMSC-CMM) resembling a mesh containing growth factors. ELISA was used to test the paracrine factors retained in the FBMSC-CMM, and the results indicated that FBMSC-CMM withheld over 80% of the paracrine factors. Live/dead assays were adopted to test the toxicity of the FBMSC-CMM on cultured rat dermal fibroblasts, and the results confirmed its biological safety with low toxicity. Moreover, the FBMSC-CMM could significantly accelerate wound healing and enhance the neovascularization as well as epithelialization through strengthening the trophic factors in the wound bed as determined by immunohistochemical staining. Thus, the ability to maintain paracrine factors and enhance the effectiveness of these growth factors in the wound as well as the simple procedure and economical materials required for production qualifies the FBMSC-CMM to be a candidate biomaterial for open-wound regeneration.

A tetracycline expression system in combination with Sox9 for cartilage tissue engineering

Cartilage tissue engineering using controllable transcriptional therapy together with synthetic biopolymer scaffolds shows higher potential for overcoming chondrocyte degradation and constructing artificial cartilages both in vivo and in vitro. Here, the potential regulating tetracycline expression (Tet-on) system was used to express Sox9 both in vivo and in vitro. Chondrocyte degradation was measured in vitro and overcome by Soxf9 expression. Experiments confirmed the feasibility of the combined use of Sox9 and Tet-on system in cartilage tissue engineering. Engineered poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) scaffolds were seeded with recombinant chondrocytes which were transfected with Tet-induced Sox9 expression; the scaffolds were implanted under the skin of 8-week-old rats. The experimental group was injected with Dox in the abdomen, while the control group was injected with normal saline. After 4 or 8 days of implantation in vivo, the newly formed pieces of articular chondrocytes were taken out and measured. Dox injection in vivo showed positive effect on recombinant chondrocytes, in which Sox9 expression was up-regulated by an inducible system with specific matrix proteins. The results demonstrate this controllable transcriptional therapy is a potential approach for tissue engineering.

Thyroid hormone-induced hypertrophy in mesenchymal stem cell chondrogenesis is mediated by bone morphogenetic protein-4

Chondrogenic differentiating mesenchymal stem cells (MSCs) express markers of hypertrophic growth plate chondrocytes. As hypertrophic cartilage undergoes ossification, this is a concern for the application of MSCs in articular cartilage tissue engineering. To identify mechanisms that elicit this phenomenon, we used an in vitro hypertrophy model of chondrifying MSCs for differential gene expression analysis and functional experiments with the focus on bone morphogenetic protein (BMP) signaling. Hypertrophy was induced in chondrogenic MSC pellet cultures by transforming growth factor β (TGFβ) and dexamethasone withdrawal and addition of triiodothyronine. Differential gene expression analysis of BMPs and their receptors was performed. Based on these results, the in vitro hypertrophy model was used to investigate the effect of recombinant BMP4 and the BMP inhibitor Noggin. The enhancement of hypertrophy could be shown clearly by an increased cell size, alkaline phosphatase activity, and collagen type X deposition. Upon induction of hypertrophy, BMP4 and the BMP receptor 1B were upregulated. Addition of BMP4 further enhanced hypertrophy in the absence, but not in the presence of TGFβ and dexamethasone. Thyroid hormone induced hypertrophy by upregulation of BMP4 and this induced enhancement of hypertrophy could be blocked by the BMP antagonist Noggin. BMP signaling is an important modulator of the late differentiation stages in MSC chondrogenesis and the thyroid hormone induces this pathway. As cartilage tissue engineering constructs will be exposed to this factor in vivo, this study provides important insight into the biology of MSC-based cartilage. Furthermore, the possibility to engineer hypertrophic cartilage may be helpful for critical bone defect repair.

Mesenchymal stem cell-based tissue engineering for chondrogenesis

In tissue engineering fields, recent interest has been focused on stem cell therapy to replace or repair damaged or worn-out tissues due to congenital abnormalities, disease, or injury. In particular, the repair of articular cartilage degeneration by stem cell-based tissue engineering could be of enormous therapeutic and economic benefit for an aging population. Bone marrow-derived mesenchymal stem cells (MSCs) that can induce chondrogenic differentiation would provide an appropriate cell source to repair damaged cartilage tissues; however, we must first understand the optimal environmental conditions for chondrogenic differentiation. In this review, we will focus on identifying the best combination of MSCs and functional extracellular matrices that provides the most successful chondrogenesis.

Chondrogenesis of adult stem cells from adipose tissue and bone marrow: induction by growth factors and cartilage-derived matrix

OBJECTIVES

Adipose-derived stem cells (ASCs) and bone marrow-derived mesenchymal stem cells (MSCs) are multipotent adult stem cells with potential for use in cartilage tissue engineering. We hypothesized that these cells show distinct responses to different chondrogenic culture conditions and extracellular matrices, illustrating important differences between cell types.

METHODS

Human ASCs and MSCs were chondrogenically differentiated in alginate beads or a novel scaffold of reconstituted native cartilage-derived matrix with a range of growth factors, including dexamethasone, transforming growth factor beta3, and bone morphogenetic protein 6. Constructs were analyzed for gene expression and matrix synthesis.

RESULTS

Chondrogenic growth factors induced a chondrocytic phenotype in both ASCs and MSCs in alginate beads or cartilage-derived matrix. MSCs demonstrated enhanced type II collagen gene expression and matrix synthesis as well as a greater propensity for the hypertrophic chondrocyte phenotype. ASCs had higher upregulation of aggrecan gene expression in response to bone morphogenetic protein 6 (857-fold), while MSCs responded more favorably to transforming growth factor beta3 (573-fold increase).

CONCLUSIONS

ASCs and MSCs are distinct cell types as illustrated by their unique responses to growth factor-based chondrogenic induction. This chondrogenic induction is affected by the composition of the scaffold and the presence of serum.

Strategies for articular cartilage lesion repair and functional restoration

Injury of articular cartilage due to trauma or pathological conditions is the major cause of disability worldwide, especially in North America. The increasing number of patients suffering from joint-related conditions leads to a concomitant increase in the economic burden. In this review article, we focus on strategies to repair and replace knee joint cartilage, since knee-associated disabilities are more prevalent than any other joint. Because of inadequacies associated with widely used approaches, the orthopedic community has an increasing tendency to develop biological strategies, which include transplantation of autologous (i.e., mosaicplasty) or allogeneic osteochondral grafts, autologous chondrocytes (autologous chondrocyte transplantation), or tissue-engineered cartilage substitutes. Tissue-engineered cartilage constructs represent a highly promising treatment option for knee injury as they mimic the biomechanical environment of the native cartilage and have superior integration capabilities. Currently, a wide range of tissue-engineering-based strategies are established and investigated clinically as an alternative to the routinely used techniques (i.e., knee replacement and autologous chondrocyte transplantation). Tissue-engineering-based strategies include implantation of autologous chondrocytes in combination with collagen I, collagen I/III (matrix-induced autologous chondrocyte implantation), HYAFF 11 (Hyalograft C), and fibrin glue (Tissucol) or implantation of minced cartilage in combination with copolymers of polyglycolic acid along with polycaprolactone (cartilage autograft implantation system), and fibrin glue (DeNovo NT graft). Tissue-engineered cartilage replacements show better clinical outcomes in the short term, and with advances that have been made in orthopedics they can be introduced arthroscopically in a minimally invasive fashion. Thus, the future is bright for this innovative approach to restore function.

Structural requirement for the agonist activity of the TLR2 ligand Pam2Cys

Synthetic lipopeptides have demonstrated great potential as a vaccine strategy for eliciting cellular and humoral immunity. One of the most potent lipid moieties used is S-[2,3-bis(palmitoyloxy)propyl]cysteine (Pam2Cys). Pam2Cys binds to and activates dendritic cells by engagement of Toll like receptor 2 (TLR 2). In this study, we have investigated the structural requirement of the agonist activity of Pam2Cys by varying the three structural elements of the core structure S-(2,3-dihydroxypropyl)-cysteine namely (1) the alpha-amino group of the cysteine residue (2) the sulphur atom of the cysteine residue and (3) the 2,3-dihydroxypropyl moiety. Four novel analogues of Pam2Cys were made and each of these analogues were incorporated into vaccine constructs and examined for immunogenicity. Our results demonstrate that (1) the potency of the peptide vaccine is least affected by removal of the amino group (2) substitution of the sulphur atom with an amide bond leads to significant reduction of biological activity (3) removal of the amino group and at the same time substitution of the sulphur with an amide bond significantly decreases the biological activity (4) in the two analogues in which the sulphur atom is replaced with an amide bond the analogue containing the 1,3-dihydroxypropyl moiety demonstrates higher activity than the one which contains 2,3-dihydroxypropyl. In conclusion, the results demonstrate strict structural requirements for agonist activity of the TLR2 ligand Pam2Cys.

Fibrin: a versatile scaffold for tissue engineering applications

Tissue engineering combines cell and molecular biology with materials and mechanical engineering to replace damaged or diseased organs and tissues. Fibrin is a critical blood component responsible for hemostasis, which has been used extensively as a biopolymer scaffold in tissue engineering. In this review we summarize the latest developments in organ and tissue regeneration using fibrin as the scaffold material. Commercially available fibrinogen and thrombin are combined to form a fibrin hydrogel. The incorporation of bioactive peptides and growth factors via a heparin-binding delivery system improves the functionality of fibrin as a scaffold. New technologies such as inkjet printing and magnetically influenced self-assembly can alter the geometry of the fibrin structure into appropriate and predictable forms. Fibrin can be prepared from autologous plasma, and is available as glue or as engineered microbeads. Fibrin alone or in combination with other materials has been used as a biological scaffold for stem or primary cells to regenerate adipose tissue, bone, cardiac tissue, cartilage, liver, nervous tissue, ocular tissue, skin, tendons, and ligaments. Thus, fibrin is a versatile biopolymer, which shows a great potential in tissue regeneration and wound healing.

Synthetic glycopeptide vaccines combining beta-mannan and peptide epitopes induce protection against candidiasis

The first fully synthetic glycopeptide vaccines against a fungal disease have been used to combat disseminated candidiasis in mice. Six T cell peptides found in Candida albicans cell wall proteins were selected by algorithm peptide epitope searches; each was synthesized and conjugated to the fungal cell wall beta-mannan trisaccharide [beta-(Man)(3)] by novel saccharide-peptide linker chemistry to create glycopeptide conjugates. The six proteins were selected because of expression during human candidiasis and cell wall association and included: fructose-bisphosphate aldolase (Fba); methyltetrahydropteroyltriglutamate (Met6); hyphal wall protein-1 (Hwp1); enolase (Enol); glyceraldehyde-3-phosphate dehydrogenase (Gap1); and phosphoglycerate kinase (Pgk1). By immunization protocols favoring production of protective antibody, the beta-(Man)(3)-Fba, beta-(Man)(3)-Met6 and beta-(Man)(3)-Hwp1 induced protection evidenced by survival and reduced kidney fungal burden, the beta-(Man)(3)-Eno1 and beta-(Man)(3)-Gap1 gave moderate protection, and the beta-(Man)(3)-Pgk1 slightly enhanced disease. For the beta-(Man)(3)-Fba conjugate, protection was uniquely acquired through immunity against the carbohydrate and the Fba peptide. This approach based on fully synthetic chemically defined immunogens should be generally useful in vaccine development.

Xenogenic bone matrix extracts induce osteoblastic differentiation of human bone marrow-derived mesenchymal stem cells

Colloss® and Colloss-E® are sterile acellular lyophilizates extracted from bovine and equine bone matrix, respectively. Animal and clinical studies have shown that these xenogenic bone matrix extracts (BMEs) are effective as bone graft substitutes. In this report, we investigated the effect of Colloss and Colloss-E on human adult in vitro-expanded bone marrow-derived mesenchymal stem cells (BMMSCs). Specifically, we assessed whether these xenogenic BMEs induced osteoblastic differentiation of cultured BMMSC. We show that BMMSCs treated with either Colloss or Colloss-E exhibited characteristic osteoblastic morphological changes accompanied by the expression of osteoblast-specific markers, such as alkaline phosphatase activity, osteopontin secretion and calcium deposits, explicitly demonstrating that these bone matrix extracts induce osteoblastic differentiation of BMMSCs in vitro. Hence, xenogenic BMEs induce bone-specific differentiation of BMMSCs, presumably through providing stem cells with structural and soluble mediators that mimic the in vivo microenvironment. These results may explain the in vivo mode of action of these medical devices, and potentially provide a novel tissue engineering-based treatment of bone defect, using autologous BMMSCs pretreated with BMEs.

A rapid seeding technique for the assembly of large cell/scaffold composite constructs

These studies address critical technical issues involved in creating human mesenchymal stem cell (hMSC)/ scaffold implants for cartilage repair. These issues include obtaining a high cell density and uniform spatial cell distribution within the scaffold, factors that are critical in the initiation and homogeneity of chondrogenic differentiation. For any given scaffold, the initial seeding influences cell density, retention, and spatial distribution within the scaffold, which eventually will affect the function of the construct. Here, we discuss the development of a vacuum-aided seeding technique for HYAFF -11 sponges which we compared to passive infiltration. Our results show that, under the conditions tested, hMSCs were quantitatively and homogeneously loaded into the scaffolds with 90+% retention rates after 24 h in perfusion culture with no negative effect on cell viability or chondrogenic potential. The retention rates of the vacuum-seeded constructs were at least 2 times greater than those of passively seeded constructs at 72 h. Histomorphometric analysis revealed that the core of the vacuum-seeded constructs contained 240% more cells than the core of passively infiltrated scaffolds. The vacuum seeding technique is safe, rapid, reproducible, and results in controlled quantitative cell loading, high retention, and uniform distribution.

Repair of full-thickness articular cartilage defects by cultured mesenchymal stem cells transfected with the transforming growth factor beta1 gene

Articular cartilage repair remains a clinical and scientific challenge with increasing interest focused on the combined techniques of gene transfer and tissue engineering. Transforming growth factor beta 1 (TGF-beta(1)) is a multifunctional molecule that plays a central role in promotion of cartilage repair, and inhibition of inflammatory and alloreactive immune response. Cell mediated gene therapy can allow a sustained expression of TGF-beta(1) that may circumvent difficulties associated with growth factor delivery. The objective of this study was to investigate whether TGF-beta(1) gene modified mesenchymal stem cells (MSCs) could enhance the repair of full-thickness articular cartilage defects in allogeneic rabbits. The pcDNA(3)-TGF-beta(1) gene transfected MSCs were seeded onto biodegradable poly-L-lysine coated polylactide (PLA) biomimetic scaffolds in vitro and allografted into full-thickness articular cartilage defects in 18 New Zealand rabbits. The pcDNA(3) gene transfected MSCs/biomimetic scaffold composites and the cell-free scaffolds were taken as control groups I and II, respectively. The follow-up times were 2, 4, 12 and 24 weeks. Macroscopical, histological and ultrastructural studies were performed. In vitro SEM studies found that abundant cartilaginous matrices were generated and completely covered the interconnected pores of the scaffolds two weeks post-seeding in the experimental groups. In vivo, the quality of regenerated tissue improved over time with hyaline cartilage filling the chondral region and a mixture of trabecular and compact bone filling the subchondral region at 24 weeks post-implantation. Joint repair in the experimental groups was better than that of either control group I or II, with respect to: (1) synthesis of hyaline cartilage specific extracellular matrix at the upper portion of the defect; (2) reconstitution of the subchondral bone at the lower portion of the defect and (3) inhibition of inflammatory and alloreactive immune responses. The transfected MSCs overexpressed their TGF-beta(1) gene products for at least 4 weeks in vivo. The control defects were filled with a mixture of fibrous and fibrocartilaginous tissue. The TGF-beta(1) gene transfected MSCs/poly-L-lysine coated PLA composite allografts used in this study are effective for articular cartilage repair. This novel TGF-beta(1) gene enhanced tissue engineering strategy may be of potential benefit to enhancing the repair of damaged articular cartilage, especially such damage caused by degenerative disease.