Comparative assessment of the effects of gender-specific heparan sulfates on mesenchymal stem cells

Vascular Heparan Sulfate and Amyloid-β in Alzheimer's Disease Patients

Alzheimer's disease (AD) is a debilitating neurodegenerative disease characterized by the accumulation of extracellular amyloid-β peptides (Aβ) within the cerebral parenchyma and vasculature, which is known as cerebral amyloid angiopathy (CAA). This study utilized confocal imaging to investigate heparan sulfate (HS) expression within the cerebrovasculature and its associations with Aβ, gender, and ApoE4 genotype in AD. Our investigation revealed elevated levels of HS in the cerebrovasculature of AD patients with severe CAA. Additionally, these patients exhibited higher HS colocalization with Aβ in the cerebrovasculature, including both endothelial and vascular smooth muscle cell compartments. Intriguingly, a reversal in the polarized expression of HS within the cerebrovasculature was detected in AD patients with severe CAA. Furthermore, male patients exhibited lower levels of both parenchymal and cerebrovascular HS. Additionally, ApoE4 carriers displayed heightened cerebrovascular Aβ expression and a tendency of elevated cerebrovascular HS levels in AD patients with severe CAA. Overall, these findings reveal potential intricate interplay between HS, Aβ, ApoE, and vascular pathology in AD, thereby underscoring the potential roles of cerebrovascular HS in CAA development and AD pathology. Further study of the underlying mechanisms may present novel therapeutic avenues for AD treatment.

Affinity Selection of FGF2-Binding Heparan Sulfates for Ex Vivo Expansion of Human Mesenchymal Stem Cells

The future of human mesenchymal stem cells (hMSCs) as a successful cell therapy relies on bioprocessing strategies to improve the scalability of these cells without compromising their therapeutic ability. The culture-expansion of hMSCs can be enhanced by supplementation with growth factors, particularly fibroblast growth factor 2 (FGF2). The biological activity of FGF2 is controlled through interactions with heparan sulfate (HS) that facilitates ligand-receptor complex formation. We previously reported on an FGF2-interacting HS variant (termed HS2) isolated from embryonic tissue by anionic exchange chromatography that increased the proliferation and potency of hMSCs. Here, we detail the isolation of an FGF2 affinity-purified HS variant (HS8) using a scalable platform technology previously employed to generate HS variants with increased affinity for BMP-2 or VEGF₁₆₅ . This process used a peptide sequence derived from the heparin-binding domain of FGF2 as a substrate to affinity-isolate HS8 from a commercially available source of porcine mucosal HS. Our data show that HS8 binds to FGF2 with higher affinity than to FGF1, FGF7, BMP2, PDGF-BB, or VEGF₁₆₅ . Also, HS8 protects FGF2 from thermal destabilization and increases FGF signaling and hMSC proliferation through FGF receptor 1. Long-term supplementation of cultures with HS8 increased both hMSC numbers and their colony-forming efficiency without adversely affecting the expression of hMSC-related cell surface antigens. This strategy further exemplifies the utility of affinity-purifying HS variants against particular ligands important to the stem cell microenvironment and advocates for their addition as adjuvants for the culture-expansion of hMSCs destined for cellular therapy. J. Cell. Physiol. 232: 566-575, 2017. © 2016 Wiley Periodicals, Inc.

Advancing biomaterials of human origin for tissue engineering

Biomaterials have played an increasingly prominent role in the success of biomedical devices and in the development of tissue engineering, which seeks to unlock the regenerative potential innate to human tissues/organs in a state of deterioration and to restore or reestablish normal bodily function. Advances in our understanding of regenerative biomaterials and their roles in new tissue formation can potentially open a new frontier in the fast-growing field of regenerative medicine. Taking inspiration from the role and multi-component construction of native extracellular matrices (ECMs) for cell accommodation, the synthetic biomaterials produced today routinely incorporate biologically active components to define an artificial in vivo milieu with complex and dynamic interactions that foster and regulate stem cells, similar to the events occurring in a natural cellular microenvironment. The range and degree of biomaterial sophistication have also dramatically increased as more knowledge has accumulated through materials science, matrix biology and tissue engineering. However, achieving clinical translation and commercial success requires regenerative biomaterials to be not only efficacious and safe but also cost-effective and convenient for use and production. Utilizing biomaterials of human origin as building blocks for therapeutic purposes has provided a facilitated approach that closely mimics the critical aspects of natural tissue with regard to its physical and chemical properties for the orchestration of wound healing and tissue regeneration. In addition to directly using tissue transfers and transplants for repair, new applications of human-derived biomaterials are now focusing on the use of naturally occurring biomacromolecules, decellularized ECM scaffolds and autologous preparations rich in growth factors/non-expanded stem cells to either target acceleration/magnification of the body's own repair capacity or use nature's paradigms to create new tissues for restoration. In particular, there is increasing interest in separating ECMs into simplified functional domains and/or biopolymeric assemblies so that these components/constituents can be discretely exploited and manipulated for the production of bioscaffolds and new biomimetic biomaterials. Here, following an overview of tissue auto-/allo-transplantation, we discuss the recent trends and advances as well as the challenges and future directions in the evolution and application of human-derived biomaterials for reconstructive surgery and tissue engineering. In particular, we focus on an exploration of the structural, mechanical, biochemical and biological information present in native human tissue for bioengineering applications and to provide inspiration for the design of future biomaterials.

Effect of heparin on the biological properties and molecular signature of human mesenchymal stem cells

Chronic use of heparin as an anti-coagulant for the treatment of thrombosis or embolism invokes many adverse systemic events including thrombocytopenia, vascular reactions and osteoporosis. Here, we addressed whether adverse effects might also be directed to mesenchymal stem cells that reside in the bone marrow compartment. Harvested human bone marrow-derived mesenchymal stem cells (hMSCs) were exposed to varying doses of heparin and their responses profiled. At low doses (<200 ng/ml), serial passaging with heparin exerted a variable effect on hMSC proliferation and multipotentiality across multiple donors, while at higher doses (≥ 100 μg/ml), heparin supplementation inhibited cell growth and increased both senescence and cell size. Gene expression profiling using cDNA arrays and RNA-seq analysis revealed pleiotropic effects of low-dose heparin on signaling pathways essential to hMSC growth and differentiation (including the TGFβ/BMP superfamily, FGFs, and Wnts). Cells serially passaged in low-dose heparin possess a donor-dependent gene signature that reflects their altered phenotype. Our data indicate that heparin supplementation during the culturing of hMSCs can alter their biological properties, even at low doses. This warrants caution in the application of heparin as a culture supplement for the ex vivo expansion of hMSCs. It also highlights the need for careful evaluation of the bone marrow compartment in patients receiving chronic heparin treatment.

Structural determinants of heparin-transforming growth factor-β1 interactions and their effects on signaling

Transforming growth factor-β1 (TGF-β1, Uniprot: P01137) is a heparin-binding protein that has been implicated in a number of physiological processes, including the initiation of chondrogenesis by human mesenchymal stem cells (hMSCs). Here, we identify the molecular features in the protein and in heparin required for binding and their effects on the potentiation of TGF-β1's activity on hMSCs. Using a proteomics "Protect and Label" approach, lysines K291, K304, K309, K315, K338, K373, K375 and K388 were identified as being directly involved in binding heparin (Data are available via ProteomeXchange with identifier PXD002772). Competition assays in an optical biosensor demonstrated that TGF-β1 does require N- and 6-O-sulfate groups for binding but that 2-O-sulfate groups are unlikely to underpin the interaction. Heparin-derived oligosaccharides as short as degree of polymerization (dp) 4 have a weak ability to compete for TGF-β1 binding to heparin, which increases with the length of the oligosaccharide to reach a maximum between dp18 and dp24. In cell-based assays, heparin, 2-O-, 6-O- and N-desulfated re-N-acetylated heparin and oligosaccharides 14-24 saccharides (dp14-24) in length all increased the phosphorylation of mothers against decapentaplegic homolog 2 (SMAD2) after 6 h of stimulation with TGF-β1. The results provide the structural basis for a model of heparin/heparan sulfate binding to TGF-β1 and demonstrate that the features in the polysaccharide required for binding are not identical to those required for sustaining the signaling by TGF-β1 in hMSCs.

Engineering a vascular endothelial growth factor 165-binding heparan sulfate for vascular therapy

The therapeutic use of VEGF165 to stimulate blood vessel formation for the treatment of peripheral arterial disease or cardiovascular-related disease has met with limited success. Here we describe an affinity-isolated heparan sulfate glycotherapeutic (HS7(+ve)) that binds to, and enhances the bioactivity of, VEGF165. Application of HS7(+ve) complexed with VEGF165 results in enhanced VEGF165-VEGFR2 interaction, prolonged downstream pErk1/2 signalling, and increased cell proliferation and tube formation in HUVECs, compared with VEGF165 alone. The pro-angiogenic potential of HS7(+ve) was further assessed in vivo using the chick embryo chorioallantoic membrane (CAM) assay. Exogenous dosing with HS7(+ve) alone significantly enhanced the formation of new blood vessels with potencies comparable to VEGF165. These results demonstrate the potential for vascular therapy of glycotherapeutic agents targeted at augmenting the bioactivity of VEGF165.

Heparan sulfate containing unsubstituted glucosamine residues: biosynthesis and heparanase-inhibitory activity

Degradation of heparan sulfate (HS) in the extracellular matrix by heparanase is linked to the processes of tumor invasion and metastasis. Thus, a heparanase inhibitor can be a potential anticancer drug. Because HS with unsubstituted glucosamine residues accumulates in heparanase-expressing breast cancer cells, we assumed that these HS structures are resistant to heparanase and can therefore be utilized as a heparanase inhibitor. As expected, chemically synthetic HS-tetrasaccharides containing unsubstituted glucosamine residues, GlcAβ1-4GlcNH3 (+)(6-O-sulfate)α1-4GlcAβ1-4GlcNH3 (+)(6-O-sulfate), inhibited heparanase activity and suppressed invasion of breast cancer cells in vitro. Bifunctional NDST-1 (N-deacetylase/N-sulfotransferase-1) catalyzes the modification of N-acetylglucosamine residues within HS chains, and the balance of N-deacetylase and N-sulfotransferase activities of NDST-1 is thought to be a determinant of the generation of unsubstituted glucosamine. We also report here that EXTL3 (exostosin-like 3) controls N-sulfotransferase activity of NDST-1 by forming a complex with NDST-1 and contributes to generation of unsubstituted glucosamine residues.

Affinity-selected heparan sulfate for bone repair

Bone morphogenetic protein (BMP)-2 is a potent bone healing compound produced at sites of bone trauma. Here we present a therapeutic strategy to harness the activity of endogenously produced BMP-2 by delivery of an affinity-matched heparan sulfate (HS) glycos aminoglycan biomaterial that increases the bioavailability, bioactivity and half-life of this growth factor. We have developed a robust, cost effective, peptide-based affinity platform to isolate a unique BMP-2 binding HS variant from commercially available preparations of HS, so removing the manufacturing bottleneck for their translation into the clinic. This affinity-matched HS enhanced BMP-2-induced osteogenesis through improved BMP-2 kinetics and receptor modulation, prolonged pSMAD signaling and reduced interactions with its antagonist noggin. When co-delivered with a collagen implant, the HS was as potent as exogenous BMP-2 for the healing of critical-sized bone defects in rabbits. This affinity platform can be readily tuned to isolate HS variants targeted ata range of clinically-relevant growth and adhesive factors.

Sulfated hyaluronan/collagen I matrices enhance the osteogenic differentiation of human mesenchymal stromal cells in vitro even in the absence of dexamethasone

Glycosaminoglycans (GAG) are multifunctional components of the extracellular matrix (ECM) involved in different steps of the regulation of cellular differentiation. In this study artificial extracellular matrices (aECM) consisting of collagen (Col) I and different GAG derivatives were used as a substrate for human mesenchymal stromal cells (hMSC) to study osteogenic differentiation in vitro. hMSC were cultured on aECM containing col and hyaluronan sulfates (HyaS) with increasing degrees of sulfation (DS(S)) and were compared with aECM containing col and the natural GAG hyaluronan or chondroitin 4-sulfate. hMSC were analyzed for osteogenic differentiation markers such as calcium phosphate deposition, tissue non-specific alkaline phosphatase (TNAP) and expression of runt-related transcription factor 2 (runx2), osteocalcin (ocn) and bone sialoprotein II (bspII). Compared with aECM containing Col and natural GAG all Col/HyaS-containing aECM induced an increase in calcium phosphate deposition, TNAP activity and tnap expression. These effects were also seen in the absence of dexamethasone (an established osteogenic supplement). The expression of runx2 and ocn was not altered and the expression of bspII was diminished on the col/HyaS-containing aECM. The impact of the Col/HyaS-containing aECM on hMSC differentiation was independent of the DS(S) of the HyaS derivatives, indicating the importance of the primary (C-6) hydroxyl group of N-acetylglucosamine. These results suggest that Col/HyaS-containing aECM are able to stimulate hMSC to undergo osteogenic differentiation even in the absence of dexamethasone, which makes these matrices an interesting tool for hMSC-based tissue engineering applications and biomaterial functionalizations to enhance bone formation.

Bone marrow-derived heparan sulfate potentiates the osteogenic activity of bone morphogenetic protein-2 (BMP-2)

Lowering the efficacious dose of bone morphogenetic protein-2 (BMP-2) for the repair of critical-sized bone defects is highly desirable, as supra-physiological amounts of BMP-2 have an increased risk of side effects and a greater economic burden for the healthcare system. To address this need, we explored the use of heparan sulfate (HS), a structural analog of heparin, to enhance BMP-2 activity. We demonstrate that HS isolated from a bone marrow stromal cell line (HS-5) and heparin each enhances BMP-2-induced osteogenesis in C2C12 myoblasts through increased ALP activity and osteocalcin mRNA expression. Commercially available HS variants from porcine kidney and bovine lung do not generate effects as great as HS5. Heparin and HS5 influence BMP-2 activity by (i) prolonging BMP-2 half-life, (ii) reducing interactions between BMP-2 with its antagonist noggin, and (iii) modulating BMP2 distribution on the cell surface. Importantly, long-term supplementation of HS5 but not heparin greatly enhances BMP-2-induced bone formation in vitro and in vivo. These results show that bone marrow-derived HS effectively supports bone formation, and suggest its applicability in bone repair by selectively facilitating the delivery and bioavailability of BMP-2.