We based our studies on the hypothesis that microenvironment components released by young bone forming cells can stimulate the regenerative potential of elderly dysfunctional cells and that such components can be engineered into bone tissue substitutes which could be transplanted to improve the healing.
In Objective 1, we isolated and cultured bone cells from adult/elderly trauma patients and evaluated their functional potential. We also cultured reprogrammed young cells and expanded them to a larger cell stock, which was used to prepare soluble components and matrix components. We found that soluble components contain a number of different factors acting on immune response, stem cell maintenance and blood vessel growth. Extracellular matrix included major components of basal lamina and bone tissue matrix. These microenvironment components were then tested with primary bone cells from the patients. Notably, some of the cell lines from the eldest patients, that exhibited a severe loss of function, increased their growth and bone forming activity when cultured with young cell components. The extent of these responses was patient-specific, requiring further studies of underlying mechanisms.
In Objective 2, we conducted scale-up and tissue engineering studies. We scaled-up the reprogrammed young cell cultivation and the preparation of young cell components. We then developed three-dimensional bone substitutes containing young cell components within silk scaffolds. Remaining cells were removed from soluble fractions by processing and from matrix fractions by a combination of detergent and enzyme treatments for potential allogeneic use.
In Objective 3, the developed bone substitutes were tested in a preclinical model. We found that bone substitutes containing soluble young cell components did not elicit adverse reactions (inflammation, infection) two weeks after transplantation. Compared to controls, tissue substitutes containing young cell components exhibited increased tissue development. Future studies will involve the testing of bone regenerative ability of these developed bone tissue substitutes.
Taken together, our studies showed that young bone cell components have the ability to modulate the activity of aged bone cells from trauma patients and that they can be engineered into bone substitutes and transplanted to modulate tissue regeneration responses. Future studies will involve the testing of developed bone substitutes to enhance bone regeneration during aging.
The results of our project were/will be presented at international meetings of societies from the regenerative medicine field (TERMIS, ESAO, ISCT, EORS) and provide the basis for further investigations and development of these off-the-shelf bone substitutes toward clinical translation to enhance bone regeneration during aging.
