Periosteal thickness and cellularity in mid-diaphyseal cross-sections from human femora and tibiae of aged donors

Abstract

Due to lack of access in healthy patients, the structural properties underlying the inherent regenerative power and advanced material properties of the human periosteum are not well understood. Periosteum comprises a cellular cambium layer directly apposing the outer surface of bone and an outer fibrous layer encompassed by the surrounding soft tissues. As a first step to elucidating the structural and cellular characteristics of periosteum in human bone, the current study aims to measure cambium and fibrous layer thickness as well as cambium cellularity in human femora and tibiae of aged donors. The major and minor centroidal axes (CA) serve as automated reference points in cross-sections of cadaveric mid-diaphyseal femora and tibiae. Based on the results of this study, within a given individual, the cambium layer of the major CA of the tibia is significantly thicker and more cellular than the respective layer of the femur. These significant intraindividual differences do not translate to significant interindividual differences. Further, mid-diaphyseal periosteal measures including cambium and fibrous layer thickness and cellularity do not correlate significantly with age or body mass. Finally, qualitative observations of periosteum in amputated and contralateral or proximal long bones of the lower extremity show stark changes in layer organization, thickness, and cellularity. In a translational context, these novel data, though inherently limited by availability and accessibility of human mid-diaphyseal periosteum tissue, provide important reference values for the use of periosteum in the context of facilitated healing and regeneration of tissue.

Keywords: amputee; loading history; mechanobiology; periosteal cells; periosteum.

Figure 1

(A) Tibial cross-section from Donor Number 4 showing major (solid) and minor (dashed) CAs. Scale bar: 5 mm. (B) Region of interest along bone surface and 100-μm divisions (black dashed line) from axis. Scale bar: 100 μm (C) White dashed lines delineate the cambium layer. Cells (blue-staining nuclei, indicated by black arrow heads) are counted within the cambium layer, and thickness of both cambium and fibrous layers are measured in the center of each 100-μm region. Scale bar: 100 μm.

Figure 2

Donor-specific mean measurements major (M) and minor (m) centroidal axes (donors summarized in Table1). Error bars indicate 95% confidence intervals of mean measurement for all samples, where each value is a mean of 20 measurements. (A) Measurements of layer thickness along the major centroidal axes indicated a significantly (*P < 0.05) thicker cambium layer covering the tibia than femur. (B) Significantly more cells (*P < 0.05) are located in the cambium layer along the major axis in the tibia than the femur.

Figure 3

Comparisons of periosteum from amputated and non-amputated bone (b: cortical bone, cam: cambium layer of periosteum, fib: fibrous layer of periosteum). (A,B) Matched comparison of the contralateral, non-amputated tibia (A) compared to the amputated tibia (B), from Donor 10. (C) Normal femur (Donor 7), and (D) periosteum from an amputated femur (Donor 11). Of note, cambium cellularity is lower directly adjacent to amputated bone, and layers are more difficult to distinguish (B,D). Scale bar: 100 μm.