RESUMO
Allotransplantation of microencapsulated parathyroid tissue is a promising approach to the treatment of permanent hypoparathyroidism. Preoperative assessment of the quality of microencapsulated parathyroid tissue could facilitate selection of the optimal bioartifical graft for human parathyroid allotransplantation. Parathyroid tissue from patients with secondary hyperparathyroidism (n = 15) was processed mechanically or enzymatically (collagenase type II). Tissue particles and single cells/cell clusters were routinely microencapsulated with amitogenic Ba(2+) alginate. Parathyroid secretion dynamics in response to stimulation of nonencapsulated and microencapsulated parathyroid tissue with Ca(2+) were evaluated in a perifusion system. The stability of the different types of microcapsule was assessed using an osmotic pressure test. Mechanical cutting of parathyroid tissue led to peripheral necrosis of tissue particles and impaired their vitality. Collagenase digestion, in contrast, resulted in single cells and cell clusters without peripheral necrosis. The quality of microencapsulation of single cells/cell clusters was significantly better than that of tissue particles (deformed and imperfect capsules). Microencapsulation itself did not decrease cell vitality. Nonencapsulated and microencapsulated tissue particles and single cells/cell clusters from different donors maintained their own levels of response to stimulation with low Ca(2+). Microcapsules containing tissue particles showed poor stability compared with those containing single cells/cell clusters. Preoperative evaluation of microencapsulated parathyroid tissue can disclose differences in vitality and function and thus facilitate selection of the optimal bioartifical graft for human parathyroid allotransplantation.
