To evaluate the in vitro potential of umbilical cord(UC)-derived cells as an allogeneic cell source that could be used ‘off-the-shelf’ in orthopaedics for bone and cartilage regeneration. The study also assesses the in-vivo efficacy of cell therapy in orthopaedics for the formation of de novo bone, cartilage and integration of both.
- In vitro potential of cells isolated from the four structural layers of the umbilical cord were characterised according to the criteria of the International Society for Cellular Therapy (ISCT). The differentiation potentials of these cell preparations, particularly for bone and cartilage formation, were also evaluated to ascertain their efficacy as potential cell sources for orthopaedic regenerative medicine.
- Efficacy of autologous bone marrow-derived mesenchymal stromal cells (BMSC) for new bone formation in vivo for patients with lower limb long bone nonunions were assessed with a self-controlled randomised trial.
- Efficacy and structural outcome of simultaneous autologous bone plug graft to restore subchondral bone with Autologous Chondrocyte Implantation (ACI) were evaluated to identify the quality and integration of the repair cartilage with the subchondral bone, described as the ‘Osplug’ technique.
- Efficacy of concurrent realignment with ACI in patients with underlying chondral defects and idiopathic varus or valgus malalignments of the knee joint were studied to ascertain the outcome of simultaneous correction of the mechanical axis in patients receiving biological repair of the cartilage.
- Potential of UC-derived cells in bone and cartilage formation: Cell preparations from four structural regions of umbilical cord were isolated via an in vitro explant culture technique. Osteogenic differentiation in these cell preparations correlated with a significant rise in alkaline phosphatase activity in the culture medium of the differentiated cells, in comparison to their respective controls. Following chondrogenic differentiation, a considerable variation in metachromasia was noted with toluidine blue staining, although type II collagen immunostaining was predominantly absent except in one sample of cells from Wharton’s Jelly. Cells from all the four layers of UC also expressed surface markers according to the ISCT criteria for Mesenchymal Stem Cells (MSC). However, it did not conform to the recommended standards quantitatively on fluorometric analysis.
- New bone formation in nonunion: There was absence of significant increase in new bone formation on the side of BMSC insertion in cases with nonunion of fracture. Four predictors of successful fracture union in this study were shorter in-vitro cell doubling times of patient’s BMSC, the absence of diabetes, younger age and fewer operative procedures to treat the nonunion before the trial intervention.
- Bone and cartilage healing in osteochondral defects: Significant improvement in clinical and functional outcome was found at mid-term follow-up after concurrent bone graft and ACI to restore subchondral bone and cartilage. Integration of the grafted bone had a direct correlation with the clinical outcome in these patients.
- Cartilage repair with realignment: Simultaneous ACI with correction of malalignment led to significant improvement in clinical outcome, particularly in patients with varus deformity. Patients with valgus deformity were noted to fail relatively early with poor outcome.
The current thesis extends from exploring the in vitro potential of UC to the clinical application of autologous chondrocytes and BMSC for cartilage and bone regeneration. UCderived cells were noted to have properties akin to MSC with trilineage differentiation capacity. However, regeneration of new bone with BMSC in nonunions remains challenging. Nonetheless, significant clinical improvement was noted in patients receiving ACI with underlying malalignment and subchondral bone defect when treated with concurrent realignment and bone graft respectively. Further work on the immunomodulatory effect of UC-derived cells in addition to longer-term follow-up of the patients receiving cell-based therapy is required to consolidate our understanding of future cell therapy in orthopaedics.