ABSTRACT
Stimulation of endogenous neural stem/progenitor cells (NSPCs) with therapeutic factors holds potential for the treatment of stroke. Cyclosporin A (CsA) is a particularly promising candidate molecule because it has been shown to act as a survival factor for these cells over a period of weeks both in vitro and in vivo; however, systemically-delivered CsA compromises the entire immune system, necessitating sustained localized delivery. Herein we describe a local delivery strategy for CsA using an epi-cortical hydrogel of hyaluronan-methylcellulose (HAMC) as the drug reservoir. Three methods of incorporating the drug into the hydrogel (solubilized, particulate, and poly(lactic-co-glycolic) acid (PLGA) microsphere-encapsulated) resulted in tunable release, spanning a period of hours to weeks. Importantly, PLGA-encapsulated CsA released from the hydrogel had equivalent bioactivity to fresh drug as measured by the neurosphere assay. Moreover, when CsA was released from the PLGA/HAMC composite that was injected on the cortex of adult mice, CsA was detected in the NSPC niche at a constant concentration for at least 24days post-implant. Thus this hydrogel composite system may be promising for the treatment of stroke.
Subject(s)
Brain/metabolism , Cyclosporine/administration & dosage , Drug Delivery Systems/methods , Neural Stem Cells/drug effects , Stroke/therapy , Animals , Brain/cytology , Brain/pathology , Chromatography, Liquid , Cyclosporine/cerebrospinal fluid , Cyclosporine/pharmacokinetics , Cyclosporine/therapeutic use , Delayed-Action Preparations , Hyaluronic Acid/chemistry , Hydrogels/chemistry , Lactic Acid/chemistry , Methylcellulose/chemistry , Mice , Mice, Inbred C57BL , Microscopy, Electron, Scanning , Microspheres , Models, Biological , Neural Stem Cells/cytology , Particle Size , Polyglycolic Acid/chemistry , Polylactic Acid-Polyglycolic Acid Copolymer , Solubility , Stroke/cerebrospinal fluid , Stroke/drug therapy , Stroke/pathology , Surface Properties , Tandem Mass Spectrometry , Time FactorsABSTRACT
No effective clinical treatment currently exists for traumatic spinal cord injury. Cell replacement therapy holds promise for attaining functional repair. Cells may be delivered directly or near the injury site; however, this strategy requires a delivery vehicle to maintain cell viability. We have identified an injectable, biocompatible, and biodegradable hydrogel scaffold composed of hyaluronan (HA) and methylcellulose (MC) that may be an effective scaffold for therapeutic cell delivery. The purpose of the present study was to determine the effects of polymer concentration on HAMC mechanical strength, gelation time, and cell viability. The yield stress of HAMC, a measure of mechanical stiffness, was tunable via manipulation of MC and HA content. Measurement of the elastic and storage moduli as functions of time revealed that HAMC gels in less than 5 min at physiological temperatures. Human umbilical tissue-derived cells encapsulated in HAMC were homogenously and stably distributed over 3 days in culture and extended processes into the scaffold. Cell viability was stable over this period in all but the most concentrated HAMC formulation. Because of its strength-tunability, rapid gelation, and ability to maintain cell viability, HAMC is a promising vehicle for cell delivery and is being tested in ongoing in vivo studies.
