Chondrogenic Priming at Reduced Cell Density Enhances Cartilage Adhesion of Equine Allogeneic MSCs – a Loading Sensitive Phenomenon in an Organ Culture Study with 180 Explants.

This research article investigates the potential of mesenchymal stem cells (MSCs), conditioned under various settings, to adhere to and incorporate into cartilage tissue. The study demonstrates that MSCs, when prepared with chondrogenic induction at a lower density and without loading, demonstrate better incorporation into equine cartilage.

Research Methodology

• The researchers collected peripheral blood (PB) MSCs and subjected them to chondrogenic induction and/or stimulation with pulsed electromagnetic fields (PEMFs) for a brief period. This method is designed to prime the MSCs’ differentiation, a process required for its potential application in cartilage repair.
• An organ culture study was conducted with PKH26 labelled MSCs, added at two different cell densities. The scientists prepared a total of 180 explants of six horses (30 per horse). These were divided into five groups based on different conditions such as no lesion, lesion alone, lesion with naïve MSCs, lesion with chondrogenically-induced MSCs, and lesion with chondrogenically-induced and PEMF-stimulated MSCs.
• To evaluate the impact of mechanical loading, half of the explants were mechanically loaded and compared with unloaded equivalents. For each condition, six explants were histologically assessed at different time points.

Study Findings

• The results of the study revealed that COMP (cartilage oligomeric matrix protein) expression was selectively increased by chondrogenic induction. PEMF stimulation further amplified type II collagen (COL II) expression greater than induced values.
• The study found that the MSC markers remained constant over time after the induction process. This implies that the MSCs had reached a largely predifferentiated state.
• In the absence of mechanical loading, the MSCs adhered to the surface in over 90% of the explants and penetrated into nearly half of the lesions. On the other hand, physiological loading significantly reduced both surface adherence and lesion filling.
• The researchers also noted that MSCs that underwent chondrogenic induction demonstrated a uniform cell distribution whereas uninduced MSCs resulted in clump formation.
• Explant seeded with a moderately low density of MSCs achieved better lesion filling and surface adherence than explants seeded with higher densities of MSCs.
• However, a decrease in the amount of lesion filling was observed from day 5 to 14.

Concluding Remarks

• The significant findings suggest that chondrogenic induction of MSCs at a lower cell density without any mechanical loading results in better MSC adhesion and integration into equine cartilage. This observation is noteworthy and has potential implications for regenerative treatments for conditions like osteoarthritis.