Comparative in vitro treatment of mesenchymal stromal cells with GDF-5 and R57A induces chondrogenic differentiation while limiting chondrogenic hypertrophy

PURPOSE

Hypertrophic cartilage is an important characteristic of osteoarthritis and can often be found in patients suffering from osteoarthritis. Although the exact pathomechanism remains poorly understood, hypertrophic de-differentiation of chondrocytes also poses a major challenge in the cell-based repair of hyaline cartilage using mesenchymal stromal cells (MSCs). While different members of the transforming growth factor beta (TGF-β) family have been shown to promote chondrogenesis in MSCs, the transition into a hypertrophic phenotype remains a problem. To further examine this topic we compared the effects of the transcription growth and differentiation factor 5 (GDF-5) and the mutant R57A on in vitro chondrogenesis in MSCs.

METHODS

Bone marrow-derived MSCs (BMSCs) were placed in pellet culture and in-cubated in chondrogenic differentiation medium containing R57A, GDF-5 and TGF-ß1 for 21 days. Chondrogenesis was examined histologically, immunohistochemically, through biochemical assays and by RT-qPCR regarding the expression of chondrogenic marker genes.

RESULTS

Treatment of BMSCs with R57A led to a dose dependent induction of chondrogenesis in BMSCs. Biochemical assays also showed an elevated glycosaminoglycan (GAG) content and expression of chondrogenic marker genes in corresponding pellets. While treatment with R57A led to superior chondrogenic differentiation compared to treatment with the GDF-5 wild type and similar levels compared to incubation with TGF-ß1, levels of chondrogenic hypertrophy were lower after induction with R57A and the GDF-5 wild type.

CONCLUSIONS

R57A is a stronger inducer of chondrogenesis in BMSCs than the GDF-5 wild type while leading to lower levels of chondrogenic hypertrophy in comparison with TGF-ß1.

[pH and buffer capacity of cerebrospinal fluid after spinal anesthesia]

In 20 patients, undergoing total hip or knee replacement, we studied pH and metabolic changes in the C.S.F. following spinal anaesthesia with two different mixtures of bupivacaine 0.5% and mepivacaine 4% hyperbaric. Our study was made with special regard to the early changes; therefore C.S.F. specimens were obtained at 1, 3, 5, 10, 20, 30, 60 and 90 min intervals and analyses of pH, pCO2, HCO3 and BE estimations were carried out immediately after each obtained sample. Our results showed a marked tendency towards acidosis and therefore do not comply with previous studies. The advantage of this fact is an improved stability of bupivacaine in C.S.F.