Collagen fiber alignment and biaxial mechanical behavior of porcine urinary bladder derived extracellular matrix

The collagen fiber alignment and biomechanical behavior of naturally occurring extracellular matrix (ECM) scaffolds are important considerations for the design of medical devices from these materials. Both should be considered in order to produce a device to meet tissue specific mechanical requirements (e.g., tendon vs. urinary bladder), and could ultimately affect the remodeling response in vivo. The present study evaluated the collagen fiber alignment and biaxial mechanical behavior of ECM scaffold material harvested from porcine urinary bladder tunica mucosa and basement membrane (together referred to as urinary bladder matrix (UBM)) and ECM harvested from urinary bladder submucosa (UBS). Since the preparation of UBM allows for control of the direction of delamination, the effect of the delamination method on the mechanical behavior of UBM was determined by delaminating the submucosa and other abluminal layers by scraping along the longitudinal axis of the bladder (apex to neck) (UBML) or along the circumferential direction (UBMC). The processing of UBS does not allow for similar directional control. UBML and UBS had similar collagen fiber distributions, with a preferred collagen fiber alignment along the longitudinal direction. UBMC showed a more homogenous collagen fiber orientation. All samples showed a stiffer mechanical behavior in the longitudinal direction. Despite similar collagen fiber distributions, UBML and UBS showed quite different mechanical behavior for the applied loading patterns with UBS showing a much more pronounced toe region. The mechanical behavior for UBMC in both directions was similar to the mechanical behavior of UBML. There are distinct differences in the mechanical behavior of different layers of ECM from the porcine urinary bladder, and the processing methods can substantially alter the mechanical behavior observed.