The development of TEMPs is complex since it poses challenge

The development of TEMPs is complex since it poses challenges in both basic biology and engineering. Before devoting time and resources to a new product, it often useful to quickly estimate parameters involved with the problem to more fully understand the problem and the issued that need to be addressed to make a clinically effective product.

1. For tissue graft application, consider two different types of tissue, cartilage and skin. For a defect of 5cm3, estimate:
a. The number or cells needed to repair a defect

b. The number of cells needed prior to ex vivo expansion to achieve this therapeutic number of cells

c. The time it would take to start with the minimum number of cells and to end with final. therapeutic cell number assuming a doubling time of 36 hours for chondrocytes and 15 hours for fibroblasts. Assume normal cell density for cartilage is 1 million cells/cm3 and fibroblasts is 200 million cells/cm3.

2. What are some potential issues that need to be considered for the development of these two tissue types for use in a clinical setting?

Solution

1.

a.We can assume that the normal cell densities in case of cartilage is 1x10⁶ cells/cm³

So, for a defect of 5cm^3, number of cells needed will be 5 *10⁶

Similarly ,we can assume that the normal cell densities in case of skin= 200x10⁶ cells /cm³

So, for a defect of 5cm^3, number of cells needed will be 5 *200* 10^{6 =} 1 * 10⁹.

b. Chondrocytes undergo 10 fold expansion while fibroblasts undergo 10⁶ fold expansion.

So. assume number of cells required prior to expansion be x and y for chondrocytes and fibroblasts.

chondrocytes: x * 10 = 5* 10⁶ = x = 5* 10⁵ cells

fibroblasts : y * 10⁶ = 1* 10⁹ , y = 10³ cells

c.

Nt = N*2 ^{t/d..................equation 1}

where Nt = final number of cells

N = initial number of cells

t= time

d = doubling time

from equation 1 , we can get

t= d* 3.3 log (Nt/N)

For cartilage :t = 36 *3.3 log( 5*10⁶ / 1* 10⁶) = 83 hrs ( ans )

For fibrolasts :t = 15 *3.3 log(1*10⁹ / 200*10⁶ ) = 34.6 hrs. ( ans )

2.Some potential issues that need to be considered for the development of these two tissue types for use in a clinical setting is that a cell seeding density should be maintained properly, in vivo conditions required for growth such as required temperature, oxygen content(for example: chondrocytes should be given hypoxia conditions) hormones etc should be maintained appropriately in the the culture medium.These conditions will help for the proper development as well as functioning of the cells.