The role of cell seeding density and nutrient supply for articular cartilage tissue engineering with deformational loading

Abstract

Taken together, these results point to the utility of dynamic deformational loading in the mechanical preconditioning of engineered articular cartilage constructs and the necessity for increasing feed media volume and serum supplementation with increasing cell seeding densities.

The Local Matrix Distribution and the Functional Development of Tissue Engineered Cartilage, a Finite Element Study

“…5,[36][37][38][39][40]59 Based on the distinct matrix distributions in Fig. 2(a) and (b) and the similar resulting mechanical properties in Fig.…”

“…The matrix production rate per cell q cell was set to 3 × 10 −12 g cell −1 h −1 . This value for q cell was derived based on the case of an initial cell seeding density of 10 million cells cm −3 , free swelling culture in 2% agarose with medium containing 10% serum, where matrix accumulation showed a linear increase in time over 42 days, 40 the percentage wet weight GAG and collagen were pooled and a construct density of 1 g cm −3 was assumed (natural cartilage: 1.15 g cm −3 ). 16 Note that the value for q cell is an underestimate, since it was based on matrix accumulation data in the construct and did not account for matrix molecules lost to the medium.…”

“…Values for A Ha ranging from 2.2 MPa cm 3 g −1 to 10 MPa cm 3 g −1 can be derived based on global correlation relations 38,49,59,61 and the GAG to collagen synthesis ratio from the case considered for q, see above. 40 The lower value of A Ha = 2.2 MPa cm 3 g −1 was used, which was derived for agarose culture, 38 reflecting a lower degree of molecular ECM organization than mature tissue. Since the global effective stiffness can underestimate the local stiffness, depending on the local distribution, also A Ha = 5 MPa cm 3 g −1 was considered.…”

“…8 The construct's mechanical properties can be modulated by adjusting the parameters that define the culture environment, such as scaffold material, 25 hydrodynamic conditions, 36,59 mechanical loading, 5,37,39 addition of growthfactors, 37,44 cell seeding density and nutrition. 40 Although it has been shown that mechanical properties which approach those of natural cartilage can be obtained after long term culture, 17 there is still a lack of control over the functional development of tissue engineered constructs.…”

“…5,37,47 It has been hypothesized that mechanical functionality arises when contact occurs between zones of matrix associated with individual cells. 5,37,40,47 In addition it has been speculated that one of the mechanisms by which dynamic loading could contribute to improved mechanical functionality is the dispersion of matrix constituents by compression induced fluid flow, leading to a local matrix redistribution. 37,46 The main question is whether assessment of tissue functionality from the main ECM constituents requires in the first place additional information about the local matrix distribution from histology, or complementary global measurements of molecular organization.…”