Design and Characterization of an Injectable Tendon Hydrogel: A Novel Scaffold for Guided Tissue Regeneration in the Musculoskeletal System

Abstract

A biocompatible hydrogel consisting of extracellular matrix (ECM) from human tendons is described as a potential scaffold for guided tissue regeneration and tissue engineering purposes. Lyophilized decellularized tendons were milled and enzymatically digested to form an ECM solution. The ECM solution properties are assessed by proteome analysis with mass spectrometry, and the material's rheological properties are determined as a function of frequency, temperature, and time. In vivo application of the gel in a rat model is assessed for remodeling and host cell repopulation. Histology for macrophage invasion, fibroblast repopulation, and nanoscale properties of the gel is assessed. Gel interaction with multipotent adipoderived stem cells (ASCs) is also addressed in vitro to assess possible cytotoxicity and its ability to act as a delivery vehicle for cells. Proteome analysis of the ECM-solution and gel mass spectroscopy identified the most abundant 150 proteins, of which two isoforms of collagen I represented more than 55% of the sample. Rheology showed that storage (G') and loss (G″) of the ECM solution were stable at room temperature but displayed sigmoidal increases after ∼15 min at 37°C, matching macroscopic observations of its thermo responsiveness. G' and G″ of the gel at 1 rad/s were 213.1±19.9 and 27.1±2.4 Pa, respectively. Electron microscopy revealed fiber alignment and good structural porosity in the gel, as well as invasion of cells in vivo. Histology also showed early CD68(+) macrophage invasion throughout the gel, followed by increasing numbers of fibroblast cells. ASCs mixed with the gel in vitro proliferated, indicating good biocompatibility. This ECM solution can be delivered percutaneously into a zone of tendon injury. After injection, the thermoresponsive behavior of the ECM solution allows it to polymerize and form a porous gel at body temperature. A supportive nanostructure of collagen fibers is established that conforms to the three-dimensional space of the defect. This hydrogel holds the distinctive composition specific for tendon ECM, where tissue-specific cues facilitate host cell infiltration and remodeling. The results presented indicate that injectable ECM materials from tendon may offer a promising alternative in the treatment of tendinopathies and acute tendon injuries.

Biohybrid cardiac ECM-based hydrogels improve long term cardiac function post myocardial infarction

“…Taken together, the data demonstrates that although our pcECM-based gel formulations originate from a porcine source and are combined with chitosan and genipin, the gels are non-immunogenic and are thus good candidates for safe implantation as cardiac scaffolds. These results support our previous work that demonstrated the biocompatibility of a porcine cardiac ECM scaffold [6] as well as the findings of previous studies testing the biocompatibility of decellularized ECM gel, [15,54] genipin [55] and chitosan-based gels. [55][56][57] The biological efficacy of our ECM based hybrid gel formulation was studied in acute and chronic MI rat models.…”

Creation of an injectable in situ gelling native extracellular matrix for nucleus pulposus tissue engineering

“…Injectable in situ gelling matrices are the most viable therapeutic option to prevent damage to the anulus fibrosus and future disc degeneration. Substantial work has been performed in other tissue types to create injectable in situ gelling decellularized matrices [37,51,54], but no work exists in the IVD. To date, the only injectable decellularized nucleus pulposus was developed by IllienJünger et al [47].…”

“…Kwon et al used pepsin in acetic acid to solubilize cartilage [52]. Others have used modifications of these protocols to solubilize a variety of tissues, including brain [41], liver [53], and tendon [54]. However, these protocols have not yet been adapted to create injectable in situ gelling hydrogels from decellularized nucleus pulposus or IVD tissue.…”

Enhanced Mechanical Properties in Cellulose Nanocrystal–Poly(oligoethylene glycol methacrylate) Injectable Nanocomposite Hydrogels through Control of Physical and Chemical Cross-Linking

“…Moreover, these injectable materials can be engineered to display tunable biodegradation under different environmental conditions depending on the chemistry used to form the cross-links. 9,11,12 However, injectable hydrogels are often limited by a relatively low elastic modulus, [13][14][15][16] limiting their utility in applications demanding at least a degree of mechanical strength (e.g. engineering of stiffer tissues such as cartilage, 17 implantation in high-shear environments, 18 or spinal applications 19 ).…”