Progenitor cells from the periosteal niche are of great clinical interest due to their remarkable regenerative capacity. Here we report on progenitor cells from arthritic patients whose femoral neck periosteum was resected over the course of hip replacement. This study aims to determine whether periosteum derived cells (PDCs) can be isolated from tissue resected in the normal course of hip arthroplasty. Further, it aims to determine how different isolation protocols affect PDC behavior (surface marker expression, proliferation, and differentiation). In addition, the study aims to characterise the populations of PDCs, isolated through either enzymatic digestion or migration, and their relative capacity to differentiate down multiple capacities; direct comparison with commercially available human marrow-derived stromal cells cultured under identical conditions will enable the placement of the PDC data in context of the current state of the field.Summary Statement
Introduction
The purpose of this experimental imaging study is to determine the Poisson's ratio of ovine periosteum, using strain mapping data from an imaging study designed to elucidate the mechanical environment of periosteal progenitor cells Periosteum is a composite, so-called “smart” or stimuli responsive material that provides a niche for pluripotent cells that exhibit mechanosensitivity in their proliferative and differentiation behavior. The overarching aim of this research program is to explore, understand, and exploit the mechanical signals that promote cell lineage commitment and Summary Statement
Introduction
Used in conjunction with the words “endoprosthesis” and “bone-implant interface”, fluid flow is usually referred to as a potential mechanism for loosening and implant failure. Paradoxically, recent studies have shown the importance of fluid flow in augmenting molecular transport through the osteocytic syncytium. This transport is essential for maintenance of cellular nutrition as well as communication between osteocytes, osteoblasts and osteoclasts, which are interconnected biochemically by interstitial fluid in bone. In the absence of loading, larger sized molecules are not transported efficiently through bone tissue in vivo [1]. The efficacy of load-induced fluid flow, resulting from normal physiological loading of bone, has been proven for the transport of small (300-400 Da, on the order of smaller amino acids) and larger (1800 Da, on the order of small proteins) molecular weight tracers through bone [2]. Nonetheless, using a similar model to study perfusion and fluid flow in the vicinity of endoprosthetic Recent studies have shown that the distinct porosities within bone tissue act as molecular sieves in situ [4] and that molecules on the order of cytokines and serum derived proteins can not be transported through the lacunocanalicular system without interstitial fluid flow resulting from physiological mechanical loads. These data as a whole suggest that fluid flow regimes in a physiological range are essential for osteocyte viability and function. In order to insure implant stability, health of the tissue at the interface must be insured. Hence, fluid flow in a physiological range could be considered essential for implant stability. These issues will be discussed in light of recent developments in endoprosthetic technology and the design of future generations of implants.
The purpose of this study was to examine the effects of cement-free implant fixation on microperfusion in the vicinity of the bone-implant interface and to elucidate the effects of mechanical loading on interstitial fluid flow. Experiments were conducted on both forelimbs of sheep (n=8, age: 4–7 years) using an ex vivo model. Immediately after euthanasia, forelimbs were amputated and a system of perfusion with Procion red (0,08 %) as flow indicator was established. In one group (4 animals), an prosthesis was inserted into the reamed intramedullary cavity of the metacarpus. In a second group (4 animals) no implant was inserted. For each pair, one limb (chosen randomly) was subjected to cyclic loading. Loading was applied at a rate of 1 Hz for 5 minutes. Infusion lasted 5 minutes in all limbs. After the experiment histological cross sections were taken and analysed for the amount of tracer present. Twelve regions were marked on the slide prior to examination and acquired under fluorescence mode. The average pixel intensity of each field of view, was measured using ‘Scion Image’ software. The mean (± standard deviation) of the 12 readings (pixel intensities) for each group were as follows: Non-implanted group, loaded: 83.31 (± 13.56); Non-implanted group, unloaded 80.80 (± 9.22); Implanted group, loaded: 71.86 (± 19.28); Implanted group, unloaded 66.79 (± 15.52). Anova analysis showed the effect of loading not to be significant statistically (p = 0.082) but the effect of implant to be highly significant (p0.0001). Implant fixation and mechanical loading affect both microperfusion and interstitial fluid flow modulated mass transport in bony tissue surrounding implants. It appears that the presence of an implant per se reduces perfusion as well as fluid flow in the vicinity of the bone-implant interface. Within subchondral bone loading does not have a significant effect on transport of small molecular weight tracers.
