Models of ex vivo explant cultures: applications in bone research

Abstract

Ex vivo explant culture models are powerful tools in bone research. They allow investigation of bone and cartilage responses to specific stimuli in a controlled manner that closely mimics the in vivo processes. Because of limitations in obtaining healthy human bone samples the explant growth of animal tissue serves as a platform to study the complex physico-chemical properties of the bone. Moreover, these models enable preserving important cell–cell and cell–matrix interactions in order to better understand the behaviour of cells in their natural three-dimensional environment. Thus, the use of bone ex vivo explant cultures can frequently be of more physiological relevance than the use of two-dimensional primary cells grown in vitro. Here, we describe isolation and ex vivo growth of different animal bone explant models including metatarsals, femoral heads, calvaria, mandibular slices and trabecular cores. We also describe how these explants are utilised to study bone development, cartilage and bone metabolism, cancer-induced bone diseases, stem cell-driven bone repair and mechanoadaptation. These techniques can be directly used to understand mechanisms linked with bone physiology or bone-associated diseases.

Postnatal ex vivo rat model for longitudinal bone growth investigations

“…This study demonstrates that postnatal tibia and metatarsal bone rudiments from rats 7‐15 days old can be experimentally cultured for up to 72 hours and maintain remarkable increases in length. These results contrast with previous reports from investigators such as Marino et a, who assumed that postnatal conventional ex vivo bone growth above 24 hours incubation is slow. The marked ex vivo increase in bone length within the 72 hours culture period suggests there is rapid proliferation and maturation of chondrocytes during early postnatal life, as reported by Crombrugghe et al, Farnum et al, and von Pfeil and DeCamp .…”

“…In those studies, the investigators’ hypothesis was that embryonic bones can be cultured ex vivo for longer than a day without deteriorating, while postnatal bone cannot be cultured for more than 24 hours in conventional ex vivo bone culture medium if optimal bone growth rate is to be sustained. It was also thought that bone growth rates are maximal in embryonic and P7 rats, because, as previously reported, up to P7 bone is considered to be metabolically active and the bones can easily be sectioned for histology without the need for decalcification in order to maintain in situ bone morphology and structures. However, the use of embryonic and P7 bone models has been reported to present challenges in terms of bone handling and manipulation, even when using a dissecting stereo microscope.…”

Scopoletin‐standardized Morinda elliptica leaf extract suppressed inflammation and cartilage degradation to alleviate osteoarthritis: A preclinical study

“…Cartilage degradation are enhanced by inflammation. The ex vivo explant culture was used to test if the extract or scopoletin could directly inhibit cartilage degradation in the presence of the inflammatory IL-1β(Marino, Staines, Brown, Howard-Jones, & Adamczyk, 2016). The articular cartilages were shaved from the joints of freshly slaughtered calves (from the Serdang market) under sterile conditions.…”

Relevance of bioreactors and whole tissue cultures for the translation of new therapies to humans

“…Bone is a mechanically loaded and highly vascularized tissue and these two parameters are key to maintain bone viable. Ex vivo bone explant models (including metatarsals, femoral heads, calvaria, mandibular slices, and trabecular cores) have been used to study cartilage and bone physiology, stem cell driven bone repair and mechano-regulation, as recently reviewed by Marino et al and Abubakar et al 55,56 In these settings, the different cell types were maintained in their native environments and whole bones or bone cores were cultivated with or without external load. Fluid flow and perfusion have been widely used to improve viability and matrix synthesis of both bone explants and bone tissue-engineered constructs (Table 4).…”