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Vascularity of a Tissue-Engineered Model of Human Phalanges

Methods for tissue engineering have led to many advances in the growth and development of a variety of cell types on biodegradable scaffolds. Resulting cell-polymer constructs hold great promise ultimately as vehicles for generating new tissue in the human body. As an example in this context, models of human phalanges have been fabricated by suturing three different cell-polymer constructs to produce a distal phalanx, a middle phalanx, and a distal interphalangeal joint [1]. Bovine periosteum, cartilage, and tendon were obtained as a source of osteoblasts, chondrocytes, and tenocytes, respectively. Periosteal sheets were wrapped about a biodegradable co-polymer of polyglycolic acid (PGA) and poly-L-lactic acid (PLLA), and isolated chondrocytes and tenocytes were separately seeded on PGA scaffolds [1]. The three phalanx constructs were cultured for one week and then implanted in athymic (nude) mice for up to 60 weeks. On retrieval of constructs after 20 and 40 weeks of implantation, histology [1] or in situ hybridization [2] showed that bone, cartilage and tendon had developed with intact interfaces between the cell types; models maintained original shapes of human phalanges; a putative cartilaginous growth plate appeared in phalanx models; the initial bovine phenotype of models persisted over time; and the bone of models was vascularized in rudimentary fashion by the host nude mice. The latter observation was investigated more completely by transmission electron microscopy to gain insight into possible means by which phalanx models were supported in their nutrition and growth.