In Vivo Osteogenic Differentiation of Rat Bone Marrow Stromal Cells in Thermosensitive MPEG–PCL Diblock Copolymer Gels

Abstract

Methoxy poly(ethylene glycol)-poly(epsilon-caprolactone) (MPEG-PCL) diblock copolymers were prepared by ring-opening polymerization and their phase transition behavior characterized as a function of temperature. The MPEG-PCL solutions formed a sol at room temperature, and underwent sol-to-gel followed by gel-to-sol phase transitions as the temperature was increased. The temperature range over which the solutions were in a gel state could be extended simply by increasing the PCL chain length in the diblock copolymer. Scanning electron microscopy (SEM) images of MPEG-PCL solutions in the sol and gel states revealed near-regular and irregular porous structures, respectively. in vitro culture of rat bone marrow stromal cells (rBMSCs) on gel surfaces exhibited mostly round cells after 1 day of incubation. SEM images of the attached cells clearly showed the cell body and anchoring filopodia. Injection of room-temperature diblock copolymer solutions into Sprague-Dawley rats produced a gel at body temperature. In situ gel-forming scaffolds in vivo were successfully fabricated by simple subcutaneous injection of MPEG-PCL diblock copolymer solutions. The gel implants retained their original shape for 4 weeks without in- flammation at the injection site. Gel implants removed after 4 weeks were found to be surrounded by a thin fibrous capsule consisting of fibroblasts and blood vessels cells. Hematoxylin and eosin (H&E) and von Kossa staining revealed bone formation in gel implants containing both rBMSCs and dexamethasone, with the degree of bone formation increasing markedly with increasing dexamethasone concentration. Thus, our results show that in situ gel scaffolds fabricated from MPEG-PCL diblock copolymer solutions containing dexamethasone enable multipotent rBMSCs to produce viable bone when injected into rats.

Injectable Biodegradable Hydrogels

“…[104] Histological analysis demonstrated that in situ formed MPEG-PCL hydrogels containing rBMSC and dexamethasone were biocompatible and enhanced bone formation. The in vitro release of FITClabeled bovine serum albumin (FITC-BSA) from the MPEG-PCL hydrogel showed a sustained release profile for more than 20 days.…”

“…PLGA Chondrocyte MPEG-PCL rBMSC, dexamethasone [104] FITC-BSA, BSA [105,106] Cholesterol end-capped star PEG-PLLA L929 cells [46] PEG/PPG/PHB BSA [48] Polyphosphazenes FITC-dextran, HSA [107] Doxorubicin, paclitaxel [108,112] FITC-albumin [109] Pancreatic islets, hepatocytes [110,111] C/GP Camptothecin, insulin [113,114] Bovine chondrocytes [115] pH/temperature-sensitive OSM-PCLA-PEG-PCLA-OSM Paclitaxel [116] hMSCs [117] PAE-PCL-PEG-PCL-PAE Insulin [82,118] (PCL-PEG-PCL-PAU) n Paclitaxel [86] (PEG-PAU) m Chlorambucil [87] PAA-PEG-PAA Flurbiprofen [90] PAE-PEG-PAE Lidocaine [89] matrices or cell growth depots. Table 1 summarizes the biomedical applications of the biodegradable injectable hydrogels.…”

Bioluminescence imaging of calvarial bone repair using bone marrow and adipose tissue-derived mesenchymal stem cells

“…Some of the implants were separated from the bone, washed, fixed and embedded in paraffin. Hematoxylin-eosin and Von Kossa stained sections (5 mM thick) were prepared from samples of bone+implant and implants alone [26]. For immunostaining of eGFP expressing cells, tissue sections were deparaffinized, rehydrated and washed in PBS.…”

Effects of immobilizing sites of RGD peptides in amphiphilic block copolymers on efficacy of cell adhesion

“…The underlying physical gelation happens due to formation of percolated micelle network [51e55]. The resulting hydrogels are promising as drug delivery carriers [44,56] and tissue engineering materials [57,58]. The corresponding gel surface is rich of PEG segments which resists nonspecific protein absorption and cell adhesion, so cells could not adhere on these hydrogels well.…”