Material-Dependent Formation and Degradation of Bone Matrix—Comparison of Two Cryogels

Abstract

Cryogels represent ideal carriers for bone tissue engineering. We recently described the osteogenic potential of cryogels with different protein additives, e.g., platelet-rich plasma (PRP). However, these scaffolds raised concerns as different toxic substances are required for their preparation. Therefore, we developed another gelatin (GEL)-based cryogel. This study aimed to compare the two scaffolds regarding their physical characteristics and their influence on osteogenic and osteoclastic cells. Compared to the PRP scaffolds, GEL scaffolds had both larger pores and thicker walls, resulting in a lower connective density. PRP scaffolds, with crystalized calcium phosphates on the surface, were significantly stiffer but less mineralized than GEL scaffolds with hydroxyapatite incorporated within the matrix. The GEL scaffolds favored adherence and proliferation of the osteogenic SCP-1 and SaOS-2 cells. Macrophage colony-stimulating factor (M-CSF) and osteoprotegerin (OPG) levels seemed to be induced by GEL scaffolds. Levels of other osteoblast and osteoclast markers were comparable between the two scaffolds. After 14 days, mineral content and stiffness of the cryogels were increased by SCP-1 and SaOS-2 cells, especially of PRP scaffolds. THP-1 cell-derived osteoclastic cells only reduced mineral content and stiffness of PRP cryogels. In summary, both scaffolds present powerful advantages; however, the possibility to altered mineral content and stiffness may be decisive when it comes to using PRP or GEL scaffolds for bone tissue engineering.

3D Environment Is Required In Vitro to Demonstrate Altered Bone Metabolism Characteristic for Type 2 Diabetics

“…Therefore, this scaffold represented an ideal carrier for osteogenic progenitor cells, osteoblastic cells and osteoclastic cells. In respective monocultures, the PRP scaffold proved to be advantageous compared to a more simple gelatin based cryogel, which could not show osteoclast-induced degradation of the bone matrix, despite a higher basal mineral content [ 17 ]. SaOS-2 cells cultured on the PRP scaffold showed both increased ALP activity and collagen production (PINP levels) [ 17 ], this might be partly due to the rough surface of the cryogels reported to induce ALP activity [ 33 ].…”

“…Regarding the carrier, a large variety of materials have been proven to be compatible for bone tissue engineering. Poly-2-hydroxyethyl methacrylate (pHEMA)-based cryogels with different protein additives have been described to be suitable for culturing bone cells in 3D [ 17 , 18 ]. With a mean pore diameter of approx.…”

“…100 µm, a porosity over 50% in a hydrated state, and a stiffness of approx. 65 kPa, the pHEMA-based cryogels are within a range recommended for bone tissue engineering [ 17 ]. Although, the mineral density of the pHEMA-based cryogels (50 mg/cm 3 ) is relatively low when compared to bone, the external crystallization method provides a rough surface that favors osteogenic differentiation as well as an easily accessible calcium deposit for bone resorbing cells.…”

Maqui berry extract prevents cigarette smoke induced oxidative stress in human osteoblasts in vitro

“…The next day membranes were incubated with the secondary antibodies for 2 h at ambient temperature after washing with TBS-T. ECL substrate solution was used for chemiluminescent signal development of membranes. Signals of proteins were detected by a ChemCam imager (INTAS, Göttingen, Germany), and the intensity of signals was quantified by using the ImageJ software (Weng et al, 2020[ 52 ]).…”

Use of in vitro bone models to screen for altered bone metabolism, osteopathies, and fracture healing: challenges of complex models

“…However, 3D cultures also raise new challenges, i.e., proper adjustment of the physical characteristics of the 3D matrix to the human physiology, uniform cell seeding on scaffolds, and adequate supply with nutrients (Henkel et al 2013 ), factors associated with each other. Pore size, porosity, water uptake rate, and stiffness are essential physical characteristics of scaffolds (Haussling et al 2019 ; Weng et al 2020 ; Zhu et al 2018 ). Pore size and porosity affect both cell attachment and cell infiltration into the scaffold (Murphy and O’Brien 2010 ).…”