Vascularity of a Tissue-Engineered Model of Human Phalanges

Abstract

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.

Characterization of the Cellular Origin of a Tissue-Engineered Human Phalanx Model by in Situ Hybridization

“…Although not proven, maintenance of the initial bovine genotype of the constructs appears to be mediated by vascularity provided by the host mice. Evidence for this conclusion lies in the morphological observation that fine capillaries and vessels are present over midshaft surfaces of constructs on their retrieval after implantation 1,12 and that binding of mouse decorin probe is localized within the soft tissue surfaces of the implants as shown in the present results.…”

Design and assessment of a tissue‐engineered model of human phalanges and a small joint

“…In this regard, many capillaries, small muscular arteries and other vessels appear throughout the midshaft portion of the model phalanges and these hold erythrocytes, macrophages and other cells [ Fig. 6; see (15)]. The vasculature itself is found consisting in part of type I collagen, endothelium, elastic laminae and additional structural elements (Fig.…”

“…Results from that work have been extended as described above and summaries of the compiled data are noted subsequently. The relatively brief details presented in Materials and methods and in some of the Results section here may be found in greatly expanded form in several journal articles and book chapters already published and referenced here (3,10,11,15,16,(19)(20)(21)(22). To conclude, it is clear that the formation of tissueengineered models of human phalanges and a small joint can be accomplished with selective placement of periosteum, chondrocytes and tenocytes onto appropriate biodegradable scaffolds.…”

“…Results from that work have been extended as described above and summaries of the compiled data are noted subsequently. The relatively brief details presented in and in some of the section here may be found in greatly expanded form in several journal articles and book chapters already published and referenced here (3,10,11,15,16,19–22).…”

“…Specimens were fixed in 4% paraformaldehyde, dehydrated in ethanol and embedded in Spurr resin (14,15). Sections 80–100 nm thick were prepared and stained with uranyl acetate and lead citrate to enhance ultrastructure of the engineered tissues examined by transmission microscopy (60–100 kV accelerating voltage).…”