Integration of osteoclastogenesis through addition of PBMCs in human osteochondral explants cultured ex vivo

The preservation of tissue specific cells in their native 3D extracellular matrix in bone explants provides a unique platform to study remodeling. Thus far, studies involving bone explant cultures showed a clear focus on achieving bone formation and neglected osteoclast activity and resorption. To s...

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Bibliographic Details
Published in:Bone (New York, N.Y.) N.Y.), 2024-01, Vol.178, p.116935-116935, Article 116935
Main Authors: Cramer, Esther E.A., de Wildt, Bregje W.M., Hendriks, Johannes G.E., Ito, Keita, Hofmann, Sandra
Format: Article
Language:English
Subjects:
Bone explant
Ex vivo
Osteoclasts
Remodeling
Resorption
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Summary:The preservation of tissue specific cells in their native 3D extracellular matrix in bone explants provides a unique platform to study remodeling. Thus far, studies involving bone explant cultures showed a clear focus on achieving bone formation and neglected osteoclast activity and resorption. To simulate the homeostatic bone environment ex vivo, both key elements of bone remodeling need to be represented. This study aimed to assess and include osteoclastogenesis in human osteochondral explants through medium supplementation with RANKL and M-CSF and addition of peripheral blood mononuclear cells (PBMCs), providing osteoclast precursors. Osteochondral explants were freshly harvested from human femoral heads obtained from hip surgeries and cultured for 20 days in a two-compartment culture system. Osteochondral explants preserved viability and cellular abundance over the culture period, but histology demonstrated that resident osteoclasts were no longer present after 4 days of culture. Quantitative extracellular tartrate resistant acid phosphatase (TRAP) analysis confirmed depletion of osteoclast activity on day 4 even when stimulated with RANKL and M-CSF. Upon addition of PBMCs, a significant upregulation of TRAP activity was measured from day 10 onwards. Evaluation of bone loss trough μCT registration and measurement of extracellular cathepsin K activity revealed indications of enhanced resorption upon addition of PBMCs. Based on the results we suggest that an external source of osteoclast precursors, such as PBMCs, needs to be added in long-term bone explant cultures to maintain osteoclastic activity, and bone remodeling. [Display omitted] •Resident osteoclasts were not preserved in an ex vivo culture of human bone cores.•Medium supplantation with RANKL and M-CSF could not induce osteoclastogenesis from resident cells within the explants.•Upon addition of PBMCs, containing osteoclast precursors, osteoclast activity was maintained in human bone explant cultures.•The culture system facilitated longitudinal μCT imaging to monitor bone resorption ex vivo.
ISSN:8756-3282
1873-2763
DOI:10.1016/j.bone.2023.116935