Researchers working in the field of tissue engineering ideally combine autologous cells and biocompatible scaffolds to replace defect tissues/organs. Due to their differentiation capacity, mesenchym-derived stem cells, such as human mesenchymal stem cells (hMSC), are a promising autologous cell source for the treatment of human diseases. As natural precursors for mesenchymal tissues, hMSC are particularly suitable for bone, cartilage, and adipose tissue replacement. In this study a detailed histological and ultrastructural analysis of long-term cultured and terminally differentiated hMSC on 3D collagen scaffolds was performed. Standardized 2D differentiation protocols for hMSC into adipocytes and osteoblasts were adapted for longterm 3D in vitro cultures in porous collagen matrices. After a 50-day culture period, large numbers of mature adipocytes and osteoblasts were clearly identifiable within the scaffolds. The adipocytes exhibited membrane free lipid vacuoles. The osteoblasts were arranged in close association with hydroxyapatite crystals, which were deposited on the surrounding fibers. The collagen matrix was remodeled and adopted a contracted and curved form. Human MSC survive long-term culture within these scaffolds and could be terminally differentiated into adipocytes and osteoblasts. Thus, the combination of hMSC and this particular collagen scaffold is a possible candidate for bone and adipose tissue replacement strategies.
INTRODUCTIONideal cell source for tissue substitutes, because they can be differentiated into several cell types and can be isolated and retransplanted autologously (17). In the past Tissue engineering in modern medicine aims to reconstruct damaged tissues or organs by transplanting decade extensive effort has been made to explore the differentiation capacity of various somatic stem cells. cells, seeded on a biomaterial scaffold. Ideally, such biological hybrids would then be capable of fulfilling the Human mesenchymal stem cells (hMSC) are adult stem cells that can be readily isolated from bone marrow (2). original function of the damaged tissue or organ (8). However, suboptimal fulfillment of such demands reThey can be expanded ex vivo and differentiated into several cell types, such as osteoblasts, adipocytes, chonsults in continued research in this field. Novel findings in embryonic and adult stem cell research and the underdrocytes, and smooth muscle cells (14 shown to be relevant in the simulation of a three-dimensional (3D) stem cell niche. Therefore, such biopolymers are preferred for the production of complex scaffolds. Collagen, as a degradable biopolymer and a component of the extracellular matrix, is often used as a scaffold and is available in several 3D structures, such as gels, sponges, or foams. It can be easily colonized and remodeled by surrounding cells, which results in its integration into the natural microenvironment (10).Whether seeded on a 3D scaffold or as monolayer culture on TCPS (tissue culture plastic), hMSC differentiation into adipocytes and osteobla...