Development of high resilience spiral wound suture-embedded gelatin/PCL/heparin nanofiber membrane scaffolds for tendon tissue engineering.

This study develops a spiral wound scaffold based on gelatin/PCL/heparin (GPH) nanofiber membranes for tendon tissue engineering. By embedding sutures in dual layers of aligned GPH nanofiber membranes, prepared from mixed electrospinning of gelatin and PCL/heparin solutions, we fabricate a high resilience scaffold intended for the high loading environment experienced by tendons. The basic fibroblast growth factor (bFGF) was anchored to GPH scaffold through bioaffinity between heparin and bFGF, aim to provide biological cues for maintenance of tenogenic phenotype. In addition, the aligned nanofiber morphology is expected to provide physical cues toward seeded tenocytes. With sustained release of bFGF, GPH-bFGF can enhance proliferation, up-regulate tenogenic gene expression, and increase synthesis of tendon-specific proteins by tenocytes in vitro. Furthermore, by properly maintaining tendon phenotypes, GPH-bFGF/tenocytes constructs showed improved mechanical properties over GPH-bFGF. From in vivo study using GPH-bFGF/tenocytes constructs to repair rabbit Achilles tendon defects, neotendon tissue formation was confirmed from histological staining and biomechanical analysis. These findings collectively demonstrate that the newly designed GPH-bFGF scaffold could provide a niche for inducing tendon tissue regeneration by effectively restoring the tendon tissue structure and function.

Gelatin/Nanohyroxyapatite Cryogel Embedded Poly(lactic-co-glycolic Acid)/Nanohydroxyapatite Microsphere Hybrid Scaffolds for Simultaneous Bone Regeneration and Load-Bearing.

It is desirable to combine load-bearing and bone regeneration capabilities in a single bone tissue engineering scaffold. For this purpose, we developed a high strength hybrid scaffold using a sintered poly(lactic-co-glycolic acid) (PLGA)/nanohydroxyapatite (nHAP) microsphere cavity fitted with gelatin/nHAP cryogel disks in the center. Osteo-conductive/osteo-inductive nHAP was incorporated in 250⁻500 µm PLGA microspheres at 40% (w/w) as the base matrix for the high strength cavity-shaped microsphere scaffold, while 20% (w/w) nHAP was incorporated into gelatin cryogels as an embedded core for bone regeneration purposes. The physico-chemical properties of the microsphere, cryogel, and hybrid scaffolds were characterized in detail. The ultimate stress and Young's modulus of the hybrid scaffold showed 25- and 21-fold increases from the cryogel scaffold. In vitro studies using rabbit bone marrow-derived stem cells (rBMSCs) in cryogel and hybrid scaffolds through DNA content, alkaline phosphatase activity, and mineral deposition by SEM/EDS, showed the prominence of both scaffolds in cell proliferation and osteogenic differentiation of rBMSCs in a normal medium. Calcium contents analysis, immunofluorescent staining of collagen I (COL I), and osteocalcin (OCN) and relative mRNA expression of COL I, OCN and osteopontin (OPN) confirmed in vitro differentiation of rBMSCs in the hybrid scaffold toward the bone lineage. From compression testing, the cell/hybrid scaffold construct showed a 1.93 times increase of Young's modulus from day 14 to day 28, due to mineral deposition. The relative mRNA expression of osteogenic marker genes COL I, OCN, and OPN showed 5.5, 18.7, and 7.2 folds increase from day 14 to day 28, respectively, confirming bone regeneration. From animal studies, the rBMSCs-seeded hybrid constructs could repair mid-diaphyseal tibia defects in rabbits, as evaluated by micro-computed tomography (µ-CT) and histological analyses. The hybrid scaffold will be useful for bone regeneration in load-bearing areas.