Similar cellular migration patterns from niches in intervertebral disc and in knee-joint regions detected by in situ labeling: an experimental study in the New Zealand white rabbit

Abstract

IntroductionPotential stem cell niches (SNs) were recently reported in intervertebral discs (IVDs) and knee joints (KJs) in different mammals (located adjacent to the epiphyseal plate; EP). The aim here was to examine further possible cellular migration and migration directions of cells originating from niches possibly involved in regeneration of cartilaginous tissues in the IVD and in the KJ regions in adult mammals.MethodsIn total, 33 rabbits were used in studies A through C.A. IVD cells were sorted; fluorescence-activated cell sorting (FACS) by size (forward scatter; ≤10 μm or >10 μm or GDF5+ cells (anti-GDF5 antibody). Sorted cells, labeled with cell tracer (carboxyfluorescein-diacetate-succinimidyl ester; CDFA-SE) were applied on IVD explants in vitro. Migrating cells/distance was evaluated by fluorescence- and confocal-microscopy (FC).B. DNA labeling was performed with BrdU (oral administration). Animals were killed (14 to 56 days), KJs collected, and BrdU+ cells visualized with immunohistochemistry (IHC)/anti-BrdU antibody in SN and articular cartilage (AC).C. Cell tracer: (Fe-nanoparticles: Endorem) were injected into SNs of IVDs (LI-LV) and KJs (tibia). Animals were killed after 2 to 6 weeks. Fe-labeled cells were traced by ferric-iron staining (Prussian blue reaction; Mallory method).ResultsA. GDF5+ cells and ≤10-μm cells displayed the best migration capability in IVD explants. GDF5+ cells were detected at a tissue depth of 1,300 μm (16 days). B. BrdU+ cells were observed in early time points in niches of KJs, and at later time points in AC, indicating a gradual migration of cells. C. Fe+ cells were detected in IVDs; in annulus fibrosus (AF) in 11 of 12 animals and in nucleus pulposus (NP) in two of 12 animals. In AC (tibia), Fe+ cells were detected in six of 12 animals. In the potential migration route (PMR), from niches toward the IVD, Fe+ cells (three of 12 animals) and in PMR toward AC (KJs) (six of 12 animals) were detected.ConclusionsResults indicate similar cellular migration patterns in cartilage regions (IVD and KJs) with migration from stem cell niche areas into the mature cartilaginous tissues of both the KJs and the IVD. These findings of a cellular migration pattern in mature cartilage are of interest from tissue-repair and engineering perspectives.

The presence of stem cells in potential stem cell niches of the intervertebral disc region: an in vitro study on rats

“…This result was confirmed by a series of in vivo studies where the stem cell migration route was defined from the niches to the AF and inner part of the IVD (Fig. 1) [22][23][24]. As a consequence, ISN-derived stem cells (ISN-SCs) are likely to be involved in self-regenerative attempts in the IVD.…”

Localization of bone morphogenetic protein 13 in human intervertebral disc and its molecular and functional effects in vitro in 3D culture

“…24,25 In addition, new findings suggest that cells derived from potential stem cell niches can also migrate into the rabbit disc. 26 The signals that instigate these migratory processes are still elusive but the role of BMPs in the promotion of cellular migration has been known 27 and its role in IVD or IVD stem cell migration maybe possible. 8,26 In support, we demonstrate that nucleus pulposus cells derived from human degenerate IVD showed a pronounced chemotactic ability towards BMP-13 (Fig.…”

“…26 The signals that instigate these migratory processes are still elusive but the role of BMPs in the promotion of cellular migration has been known 27 and its role in IVD or IVD stem cell migration maybe possible. 8,26 In support, we demonstrate that nucleus pulposus cells derived from human degenerate IVD showed a pronounced chemotactic ability towards BMP-13 (Fig. 6A); this was comparable to that of a potent chemoattractant such as fetal calf serum, which contains a multitude of factors (Fig.…”

From gristle to chondrocyte transplantation: treatment of cartilage injuries

“…With specific labelling of cells in the niche we were also able to demonstrate that cells from the niche migrate and support joint structures, e.g. meniscus, ligament and cartilage [57]. The niche cells could thus potentially be involved in human cartilage regeneration-a finding that would mean a paradigm shift for the concept of cellular treatment for cartilage defects and the OA disease mechanism.…”