Living cells can sense and react to the shape of their surroundings. A recent study led by Biomaterials and Tissue Biomechanics professor, Amir Zadpoor, has found that biomaterials with varying degrees of curvature can either inhibit or stimulate new tissue growth in bone cells. In particular, 3D-printed curvatures are a safe and cost-effective way of promoting tissue growth compared to drug-based methods.
During the study, bone cells were grown in Petri dishes surrounded by biomaterial moulds with different curvatures. The results showed that the cells reacted differently to the curvature of the moulds, with some encouraging cell growth and tissue formation while others inhibiting it.
Although there are endless variations of curved shapes, they can generally be categorized as a convex ball, a concave saddle, or a flat plate. The researchers found that bone cells prefer the saddle shape, with the presence of this shape stimulating their growth. The study also revealed that cells preferred valleys over hills, suggesting that the form of the biomaterials used in bone tissue engineering can play a critical role in the success of the process.
Sebastien Callens, the study's lead author, conducted experiments and analyses that revealed an important aspect of cell behaviour. Cells have a skeleton consisting of fibres under varying degrees of tension, and how these fibres are tensed has a significant impact on the behaviour of the cells. The study found that cells align their stress fibres with the curvatures of their environment to reduce the need for bending. Callens explained that cells prefer alignment over turning, indicating the importance of understanding the relationship between cell behaviour and the surrounding environment.
Cells can't exist in an environment with only saddle curves. Just like the angles of a triangle always add up to 180 degrees, the sum of all curvatures must equal specific values. According to Zadpoor, a finite number of saddle shapes are available, and a balance of positive and negative curvatures must be used to keep the sum constant. This emphasizes the importance of effectively using the general budget of shapes to promote optimal tissue regeneration.
The study offers insights into the ideal geometry of biomaterials and implants for promoting tissue regeneration. The complex shapes required can be created using high-precision 3D printing techniques, producing small forms that cells can sense. Callens added that the study has uncovered new rules for stimulating tissue growth using biomaterials, and the next step is to apply these rules optimally in future research.