Scaffolds containing GAG-mimetic cellulose sulfate promote TGF-ß interaction and MSC Chondrogenesis over native GAGs.

Cartilage tissue engineering strategies seek to repair damaged tissue using approaches that include scaffolds containing components of the native extracellular matrix (ECM). Articular cartilage consists of glycosaminoglycans (GAGs) which are known to sequester growth factors. In order to more closely mimic the native ECM, this study evaluated the chondrogenic differentiation of mesenchymal stem cells (MSCs), a promising cell source for cartilage regeneration, on fibrous scaffolds that contained the GAG-mimetic cellulose sulfate. The degree of sulfation was evaluated, examining partially sulfated cellulose (pSC) and fully sulfated cellulose (NaCS). Comparisons were made with scaffolds containing native GAGs (chondroitin sulfate A, chondroitin sulfate C and heparin). Transforming growth factor-beta3 (TGF-ß3) sequestration, as measured by rate of association, was higher for sulfated cellulose-containing scaffolds as compared to native GAGs. In addition, TGF-ß3 sequestration and retention over time was highest for NaCS-containing scaffolds. Sulfated cellulose-containing scaffolds loaded with TGF-ß3 showed enhanced chondrogenesis as indicated by a higher Collagen Type II:I ratio over native GAGs. NaCS-containing scaffolds loaded with TGF-ß3 had the highest expression of chondrogenic markers and a reduction of hypertrophic markers in dynamic loading conditions, which more closely mimic in vivo conditions. Studies also demonstrated that TGF-ß3 mediated its effect through the Smad2/3 signaling pathway where the specificity of TGF-ß receptor (TGF- ßRI)-phosphorylated SMAD2/3 was verified with a receptor inhibitor. Therefore, studies demonstrate that scaffolds containing cellulose sulfate enhance TGF-ß3-induced MSC chondrogenic differentiation and show promise for promoting cartilage tissue regeneration.

Biomaterials and tissue engineering approaches using glycosaminoglycans for tissue repair: Lessons learned from the native extracellular matrix.

Glycosaminoglycans (GAGs) are an important component of the extracellular matrix as they influence cell behavior and have been sought for tissue regeneration, biomaterials, and drug delivery applications. GAGs are known to interact with growth factors and other bioactive molecules and impact tissue mechanics. This review provides an overview of native GAGs, their structure, and properties, specifically their interaction with proteins, their effect on cell behavior, and their mechanical role in the ECM. GAGs' function in the extracellular environment is still being understood however, promising studies have led to the development of medical devices and therapies. Native GAGs, including hyaluronic acid, chondroitin sulfate, and heparin, have been widely explored in tissue engineering and biomaterial approaches for tissue repair or replacement. This review focuses on orthopaedic and wound healing applications. The use of GAGs in these applications have had significant advances leading to clinical use. Promising studies using GAG mimetics and future directions are also discussed. STATEMENT OF SIGNIFICANCE: Glycosaminoglycans (GAGs) are an important component of the native extracellular matrix and have shown promise in medical devices and therapies. This review emphasizes the structure and properties of native GAGs, their role in the ECM providing biochemical and mechanical cues that influence cell behavior, and their use in tissue regeneration and biomaterial approaches for orthopaedic and wound healing applications.

Comparative Study of Electrospun Scaffolds Containing Native GAGs and a GAG Mimetic for Human Mesenchymal Stem Cell Chondrogenesis.

Articular cartilage has limited healing and self-repair capability. Damage to articular cartilage becomes irreversible leading to osteoarthritis, which can impact a person's quality of life. Approximately, 5-10% of cartilage tissue is made up of sulfated glycosaminoglycans (GAGs), which sequester growth factors as well as provide structural integrity to the native cartilage tissue. This study evaluated the chondrogenic differentiation of human mesenchymal stem cells (MSCs) on gelatin-based scaffolds containing partially sulfated cellulose (pSC), a GAG mimetic derived from cellulose, in comparison to native GAGs, chondroitin sulfate-A (CS-A) and chondroitin sulfate-C (CS-C), where pSC has similarity to CS-C in terms of degree and pattern of sulfation. Scaffolds were prepared by electrospinning gelatin with pSC or the native GAGs. All scaffolds consist of fibers having average diameters of approximately 3 µm and inter-fiber spacing of approximately 30 µm and were hydrolytically stable throughout the culture. MSCs cultured on pSC containing scaffolds showed early production of sulfated GAGs and higher collagen type II to type I ratio than native GAGs. Among the native GAGs, chondrogenesis was promoted to a greater extent for CS-C in comparison to CS-A containing scaffolds, which suggests the pattern of sulfation impacts chondrogenesis. Partially sulfated cellulose could be used as a potential GAG mimic for cartilage tissue engineering applications.

Investigation of glycosaminoglycan mimetic scaffolds for neurite growth.

Spinal cord injury can lead to severe dysfunction as a result of limited nerve regeneration that is due to an inhibitory environment created at the site of injury. Neural tissue engineering using materials that closely mimic the extracellular matrix (ECM) during neural development could enhance neural regeneration. Glycosaminoglycans (GAGs), which are sulfated polysaccharides, have been shown to modulate axonal outgrowth in neural tissue depending upon the position and degree of sulfation. Cellulose sulfate (CelS), which is a GAG mimetic, was evaluated for its use in promoting neurite extension. Aligned fibrous scaffolds containing gelatin blended with 0.25% partially sulfated cellulose sulfate (pCelS), having sulfate predominantly at the 6-carbon position of the glucose monomer unit, and fully sulfated cellulose sulfate (fCelS), which is sulfated at the 2-, 3-, and 6-carbon positions of the glucose monomer unit, were fabricated using the electrospinning method. Comparisons were made with scaffolds containing native GAGs, chondroitin sulfate-A (CS-A) and chondroitin sulfate-C (CS-C), which were obtained from commercial sources. CS-A and CS-C are present in neural tissue ECM. The degree of sulfation and position of sulfate groups was determined using elemental analysis, Fourier-transform infrared spectroscopy (FTIR), Raman microspectroscopy, and 13C nuclear magnetic resonance (NMR). In vitro studies examined both nerve growth factor (NGF) binding on scaffolds and neurite extension by dorsal root ganglion (DRG) neurons. NGF binding was highest on scaffolds containing pCelS and fCelS. Neurite extension was greatest for scaffolds containing fCelS followed by pCelS, with the lowest outgrowth on the CS-A containing scaffolds, suggesting that the degree and position of sulfation of CelS was permissible for neurite outgrowth. This study demonstrated that cellulose sulfate, as a GAG mimetic, could be used for future neural tissue regeneration application. STATEMENT OF SIGNFICANCE: Scaffolds that closely mimic the native extracellular matrix (ECM) during development may be a promising approach to enhance neural regeneration. Here, we reported a glycosaminoglycan (GAG) mimetic derived from cellulose that promotes neurite extension over native GAGs, chondroitin sulfate-A (CS-A) and chondroitin sulfate-C (CS-C), which are present in neural ECM. Depending upon the degree and position of sulfation, the GAG mimetic can impact nerve growth factor binding and permissive neurite outgrowth.

* Gelatin Scaffolds Containing Partially Sulfated Cellulose Promote Mesenchymal Stem Cell Chondrogenesis.

Articular cartilage has a limited capacity to heal after damage from injury or degenerative disease. Tissue engineering constructs that more closely mimic the native cartilage microenvironment can be utilized to promote repair. Glycosaminoglycans (GAGs), a major component of the cartilage extracellular matrix, have the ability to sequester growth factors due to their level and spatial distribution of sulfate groups. This study evaluated the use of a GAG mimetic, cellulose sulfate, as a scaffolding material for cartilage tissue engineering. Cellulose sulfate can be synthesized to have a similar level and spatial distribution of sulfates as chondroitin sulfate C (CSC), the naturally occurring GAG. This partially sulfated cellulose (pSC) was incorporated into a fibrous gelatin construct by the electrospinning process. Scaffolds were characterized for fiber morphology and overall stability over time in an aqueous environment, growth factor interaction, and for supporting mesenchymal stem cell (MSC) chondrogenesis in vitro. All scaffold groups had micron-sized fibers and maintained overall stability in aqueous environments. Increasing concentrations of the transforming growth factor-beta 3 (TGF-ß3) were detected on scaffolds with increasing pSC. MSC chondrogenesis was enhanced on the scaffold with the highest pSC concentration as seen with the highest collagen type II production, collagen type II immunostaining, expression of cartilage-specific genes, and ratio of collagen type II to collagen type I production. These studies demonstrated the potential of pSC sulfate as a scaffolding material for cartilage tissue engineering.