Porous biodegradable silk scaffolds and human bone marrow derived mesenchymal stem cells (hMSCs) were used to engineer bone-like tissue in vitro. Two different scaffolds with the same microstructure were studied: collagen (to assess the effects of fast degradation) and silk with covalently bound RGD sequences (to assess the effects of enhanced cell attachment and slow degradation). The hMSCs were isolated, expanded in culture, characterized with respect to the expression of surface markers and ability for chondrogenic and osteogenic differentiation, seeded on scaffolds, and cultured for up to 4 weeks. Histological analysis and microcomputer tomography showed the development of up to 1.2-mm-long interconnected and organized bonelike trabeculae with cuboid cells on the silk-RGD scaffolds, features still present but to a lesser extent on silk scaffolds and absent on the collagen scaffolds. The X-ray diffraction pattern of the deposited bone corresponded to hydroxyapatite present in the native bone. Biochemical analysis showed increased mineralization on silk-RGD scaffolds compared with either silk or collagen scaffolds after 4 weeks. Expression of bone sialoprotein, osteopontin, and bone morphogenetic protein 2 was significantly higher for hMSCs cultured in osteogenic than control medium both after 2 and 4 weeks in culture. The results suggest that RGD-silk scaffolds are particularly suitable for autologous bone tissue engineering, presumably because of their stable macroporous structure, tailorable mechanical properties matching those of native bone, and slow degradation.

Until recently, detailed analyses of the architecture of nonhuman primate cancellous bone have not been possible due to a combination of methodological constraints, including poor resolution imaging or destructive protocols. The development of micro-computed tomography (microCT) and morphometric methods associated with this imaging modality offers anthropologists a new means to study the comparative architecture of cancellous bone. Specifically, microCT will allow anthropologists to investigate the relationship between locomotor behavior and trabecular structure. We conducted a preliminary study on the trabecular patterns in the proximal humerus and femur of Hylobates lar, Ateles paniscus, Macaca mulatta, and Papio anubis to investigate the quantitative differences in their trabecular architecture and evaluate the potential of microCT in anthropological inquiry. MicroCT allows the researcher to evaluate variables beyond simple two-dimensional orientations and radiographic densities. For example, this methodology facilitates the study of trabecular thickness and bone volume fraction using three-dimensional data. Results suggest that density-related parameters do not reliably differentiate suspensory-climbing species from quadrupedal species. However, preliminary results indicate that measurements of the degree of anisotropy, a measure of trabecular orientation uniformity, do distinguish suspensory-climbing taxa from more quadrupedal species. The microCT method is an advance over conventional radiography and medical CT because it can accurately resolve micron-sized struts that make up cancellous bone, and from these images a wide array of parameters that have been demonstrated to be related to cancellous bone mechanical properties can be measured. Methodological problems pertinent to any comparative microCT study of primate trabecular architecture are discussed.

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