Effective strategies to guide cell alignment and the deposition of an oriented extracellular matrix are critical for the development of anisotropic engineered tissues suitable for the repair of ligament defects. Electrospinning is a promising means to create meshes that can align adherent cells, but the effect of fiber mesh architecture on differentiation has not been examined closely. Therefore, the goal of this study was to determine the effect of fiber diameter and the degree of fiber alignment on mesenchymal progenitor cell morphology, proliferation, and ligament gene expression. Specifically, a poly(ester urethane)urea elastomer was electrospun onto rigid supports under conditions designed to independently vary the mean fiber diameter (from 0.28 to 2.3 microm) and the degree of fiber alignment. Bone marrow stromal cells--seeded onto supported meshes--adhered to and proliferated on all surfaces. Cells assumed a more spindle-shaped morphology with increasing fiber diameter and degree of fiber alignment, and oriented parallel to fibers on aligned meshes. Expression of the ligament markers collagen 1alpha1, decorin, and tenomodulin appeared to be sensitive to fiber diameter and greatest on the smallest fibers. Concurrently, expression of the transcription factor scleraxis appeared to decrease with increasing fiber alignment. These results suggest that the formation of a ligament-like tissue on electrospun scaffolds is enhanced when the scaffolds consist of aligned submicron fibers.

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ObjectiveThis experiment was set to determine if human amniotic fluid‐derived stem (hAFS) cells could be differentiated into cardiac lineage, engraft into infarcted myocardium and affect heart function.MethodsAFS cells were treated with 5‐aza‐2‐deoxycytidine and analyzed for expression of cardiac markers by PCR and immunostaining. For in vivo study, 5 million cells were injected into hearts immediately after infarction. Heart function was monitered by echocardiography and invasive hemodynamic study. All hearts were analyzed 3 months after injection.ResultsDifferentiated cells expressed cardiac Troponin I, Troponin T, Myosin light chain 2v, MEF2C, MEF2D and Nkx2.5. Undifferentiated and differentiated hAFS cells engraft into infarcted hearts. When compared to control, injection of undifferentiated cells reduced left ventricular end systolic diameter (p=0.098) and improving fractional shortening (p=0.074) while differentiated cells had opposite effect (p = 0.017 and 0.01).ConclusionsThe result indicates that hAFS cells can be differentiated into cardiac phenotype, engraft into infarcted myocardium and affecting cardiac function. Undifferentiated hAFS cells tend to improve cardiac function while differentiated cells worsen function. The reason for this difference remains unclear.