A universal and approved in vitro tendon model that closely resembles the physiological characteristics of tendons currently is needed. Such models can be used to study different pathologies such as tendinopathy. Tendon models usually rely on mechanical stimulation, which requires the determination of stimulation parameters alongside scaffold selection, characterization and optimization, to induce cellular alignment and production of proper ECM. Here, we employed a tension-based MagneTissue bioreactor to investigate the effect of substrate stiffness on cell morphology. Briefly, 3D fibrin rings were seeded with C3H10T1/2 and C2C12 cells. Cells were cultivated in growth medium and static mechanical strain was subsequently applied. Cell viability and cell alignment were analyzed on day 7 using CalceinAM/PI staining. Cells in both cell lines were viable and had a homogeneous distribution throughout the scaffold. However, the morphology of cells varied. Loaded C2C12 cells were more aligned along strain direction compared to gravity control. In comparison, no differences in cell alignment were observed between loaded and control groups in the C3H10T1/2 cell line. This suggests that scaffold stiffness is not favorable for C3H10T1/2 cells and should be optimized for each cell type to limit cell death and facilitate cell adhesion, alignment, and differentiation