Proteolytic Rafts for Improving Intraparenchymal Migration of Minimally Invasively Administered Hydrogel-Embedded Stem Cells

Abstract

The physiological spaces (lateral ventricles, intrathecal space) or pathological cavities (stroke lesion, syringomyelia) may serve as an attractive gateway for minimally invasive deployment of stem cells. Embedding stem cells in injectable scaffolds is essential when transplanting into the body cavities as they secure favorable microenvironment and keep cells localized, thereby preventing sedimentation. However, the limited migration of transplanted cells from scaffold to the host tissue is still a major obstacle, which prevents this approach from wider implementation for the rapidly growing field of regenerative medicine. Hyaluronan, a naturally occurring polymer, is frequently used as a basis of injectable scaffolds. We hypothesized that supplementation of hyaluronan with activated proteolytic enzymes could be a viable approach for dissolving the connective tissue barrier on the interface between the scaffold and the host, such as pia mater or scar tissue, thus demarcating lesion cavity. In a proof-of-concept study, we have found that collagenase and trypsin immobilized in hyaluronan-based hydrogel retain 60% and 28% of their proteolytic activity compared to their non-immobilized forms, respectively. We have also shown that immobilized enzymes do not have a negative effect on the viability of stem cells (glial progenitors and mesenchymal stem cells) in vitro. In conclusion, proteolytic rafts composed of hyaluronan-based hydrogels and immobilized enzymes may be an attractive strategy to facilitate migration of stem cells from injectable scaffolds into the parenchyma of surrounding tissue.

Hyaluronic Acid Allows Enzyme Immobilization for Applications in Biomedicine

“…One developing approach to reduce such limitations is through enzyme immobilization. In particular, enzyme immobilization is seen as a viable means to provide greater user controllability through specific localization strategies and control of enzymes’ catalytic activity using physical [ 66 ] or chemical [ 67 ] bounding to or within synthetic platforms including but not limited to hydrogels [ 17 , 18 , 19 , 20 ], particles [ 15 , 16 , 22 ], nanotubes [ 23 ], or frameworks [ 66 ]. Meanwhile, the recyclability of enzymes can also increase through such immobilization approaches, thus resulting in their repeatable use and reduction in application costs [ 66 ].…”

“…A biocompatible scaffold hydrogel was developed using HA to successfully immobilize active trypsin and collagenase enzymes in a matrix of stem cells to help assist with migration of healing-promoting cells. Glial progenitors (GPs) and mesenchymal stem cells (MSCs) served as examples, with transgenic mice being used as model systems [ 19 ]. Analysis showed that the activity and viability of the HA-enzyme hydrogels were 60 and 28% of that of free enzyme activity, respectively, and that stem cells embedded in the HA-enzyme matrices also retained their survivability.…”

“…Subsequently, particular attention is directed towards enzyme immobilization using hyaluronic acid (HA) scaffolds, a polysaccharide consisting of alternating β-1,4-D-glucuronic acid and β-1,3-N-acetyl-D-glucosamine rings known for its high biocompatibility, biodegradability, viscoelasticity, and hydrophilicity [ 12 , 13 , 14 ], to thus help emphasize enzymes’ implementation in biomedical applications. Discussions are in support of specific applications in drug delivery [ 15 , 16 , 17 ], tissue engineering including wound healing [ 18 , 19 , 20 ] and biosensors [ 21 , 22 , 23 , 24 ], respectively. Challenges associated with enzymes exploitations in synthetic environment are analyzed.…”

Combination of Stem Cells and Rehabilitation Therapies for Ischemic Stroke

“…Physiological and pathological cavities, such as lateral ventricles and stroke lesions, may act as a viable gateway for developing stem cells. Hyaluron, a naturally occurring polymer, can function along with enzymes as an approach to dissolve the connective tissue that acts as a barrier between the scaffold and the host, thus resolving the limited migration of transplanted cells [ 187 ]. Additionally, hyaluronic acid and methylcellulose hydrogels demonstrated improved survival and integration of stem cells [ 188 , 189 ].…”

Epicortical Brevetoxin Treatment Promotes Neural Repair and Functional Recovery after Ischemic Stroke

“…To examine impairment and recovery, we utilized a catwalk test to examine gross motor gait, a pasta matrix reach task to assess fine-motor skills (feeding and coordination) and a foot fault task to examine coordination and gait. An emerging strategy in stroke therapy is the direct application of treatments to the stroke lesion [24][25][26]. Accordingly, we mixed PbTx-2 in a hydrogel composed of thiol-modified hyaluronan and polyethylene glycol diacrylate and this composite was deposited epicortically directly above the stroke cavity.…”