Functional capacity of the thyroid autograft: an experimental study

Cryopreserved Thyroid Tissue Autotransplant in Pediatric Age Patients: A Feasibility Study and Literature Review

BACKGROUND AND AIMS

This paper aims to study an alternative solution to hormonal replacement therapy in specific groups of patients who underwent thyroidectomy during childhood or adulthood. After cryopreservation, thyroid autotransplantation could be an alternative solution which would allow us to use the ability of the thyroid tissue of producing hormones according to the physiological needs of the body.

MATERIALS AND METHODS

A feasibility study about the effects of the most modern cryopreservation techniques on the structural and functional integrity of the follicular cells of the thyroid tissue has been carried out. Patients who could benefit from the treatment have been found for both autotransplant techniques. Additionally, a literature review has been conducted.

RESULTS

The histological analysis has shown that cryopreservation does not alter the original architecture, and the culture examination that cell viability is successfully preserved. Moreover, both thyroid autotransplantation studies on animals and those on humans that were found in the literature have shown good results regarding the viability and functionality of the transplant.

CONCLUSIONS

The viability of cryopreserved thyroid tissue found in this study is encouraging. Further studies to evaluate the levels of FT3, FT4 and thyroglobulin in thyroid tissue after cryopreservation are needed to verify that the secretory properties of the thyrocytes have been maintained intact. Furthermore, autotransplanted cases found in the literature do not have a long-term follow-up.

Regeneration of Thyroid Glands in the Spleen Restores Homeostasis in Thyroidectomy Mice

Surgical removal of the thyroid gland (TG) for treating thyroid disorders leaves the patients on lifelong hormone replacement that partially compensates the physiological needs, but regenerating TG is challenging. Here, an approach is reported to regenerate TG within the spleen for fully restoring the thyroid's functions in mice, by transplanting thyroid tissue blocks to the spleen. Within 48 h, the transplanted tissue efficiently revascularizes, forming thyroid follicles similar to the native gland after 4 weeks. Structurally, the ectopically generated thyroid integrates with the surrounding splenic tissue while maintaining its integrity, separate from the lymphatic tissue. Functionally, it fully restores the native functions of the TG in hormone regulation in response to physiological stimuli, outperforming the established method of oral levothyroxine therapy in maintaining systemic homeostasis. The study demonstrates the full restoration of thyroid functions post-thyroidectomy by intrasplenic TG regeneration, providing fresh insights for designing novel therapies for thyroid-related disorders.

Cryopreserved Rat Thyroid Autotransplantation in the Treatment of Postoperative Hypothyroidism

To verify the viability and functionality of cryopreserved thyroid autotransplantation in rats who underwent total thyroidectomy in the treatment of postoperative hypothyroidism. Thirty-two Wistar rats were randomly assigned into groups (G) with eight animals each: control (CG); simulation (SG); hypothyroidism (HTG) and transplanted (TG). At the beginning and in the 13th week of the experiment, serum levels of total T3, free T4, TSH and calcium were determined. In both the first and 14th weeks, scintigraphic examinations, 99m-Tc pertechnetate radioisotope biodistribution and histopathology were performed. In the 14th week, the expression of proliferating cell nuclear antigen (PCNA) and cellular apoptosis (caspase-3) were also evaluated. In the 13th week, the transplanted animals had normal serum levels of total T3 and free T4. TSH levels showed a tendency towards normality. In the 14th week, scintigraphic exams displayed graft isotopic uptake in all animals in the TG group. Histological examinations 13 weeks after transplantation showed the viability and functionality of thyroid follicles. PCNA revealed significant immunoreactivity of the graft (p < 0.001) when the TG was compared to the CG. There was no difference between CG and TG considering the expression of activated caspase-3. The experimental study confirmed the viability and functionality of thyroid autotransplantation implanted in skeletal muscle with evidence of cell proliferation without cellular apoptosis. This surgical strategy was effective in the treatment of postoperative hypothyroidism.

Heterotopic thyroid autotransplantation: A preliminary clinical study

BACKGROUND

Thyroid autotransplantation offers an attractive alternative to subtotal thyroidectomy and replacement therapy. However, it has not been sufficiently clinically investigated.

METHODS

Total thyroidectomy was performed for 20 patients with benign thyroid disorders, and at least 10 g of thyroid tissue were implanted intramuscularly. Graft monitoring was achieved through ^99m Tc scan at 2 months, free triiodothyronine (FT3), FT4, and thyroid-stimulating hormone (TSH) measurements at 1, 2, 4, 6, 8, 10, and 12 months postoperatively, and clinical examination.

RESULTS

Grafts survived and gradually functioned in all patients to a variable extent after a latent period (mean ^99m Tc uptake = 1.28 ± 0.37%). Mean values for FT3, FT4, TSH at 12 months were 1.75 ± 0.48 pg/mL, 1.06 ± 0.26 ng/dL, and 28.08 ± 34.01 μIU/mL respectively.

CONCLUSION

Thyroid autotransplantation restored euthyroid status in 33.3% of patients after 12 months. A role of age, operative time, and ^99m Tc-uptake in determining the final graft outcome is possible.

Review of Heterotopic Thyroid Autotransplantation

Total thyroidectomy is increasingly accepted for the management of bilateral benign thyroid disorders. Postoperatively, patients require lifelong levothyroxine replacement therapy to avoid postoperative hypothyroidism, which besides the burden of compliance, has been proven to be associated with several long-term side effects. Heterotopic thyroid autotransplantation was proposed several decades ago to avoid the need for life-long postoperative replacement therapy with maintaining the autoregulatory mechanism of thyroxin production inside the body according to its needs. Available data regarding this topic in literature is relatively poor. Before applying thyroid autotransplantation on humans, several studies have been done on animals, where the autologous transplantations were found to be successful in almost all the cases, proved by follow up postoperative 8-week measurements of thyroid hormones and histopathological examination of the removed autografts. Regarding the clinical application, few trials have been done using cryopreserved in vivo, in vitro or immediately autotransplanted thyroid autografts. Satisfactory results were obtained, however, the number of these studies and the number of patients per each study was very low. Besides the study methodologies were not so consistent.

Technique and outcome of autotransplanting thyroid tissue after total thyroidectomy for simple multinodular goiters

BACKGROUND/OBJECTIVE

Limited animal and human studies have shown function, albeit inadequate, of implanted thyroid tissue in muscles. This work aimed to ascertain results in a larger number of patients, finding practical method for implantation, studying the effect of changing weight of implant and effect of passage of time on its function.

METHODS

Forty patients had total thyroidectomy for simple multinodular goiters. A piece of the excised gland was finely minced, mixed with saline as emulsion, and injected in thigh muscles. Twelve patients had 5-g implants, while 28 patients had 10-g implants. Four parameters were studied at 2 months, 6 months, and 12 months: technetium isotope uptake by the implant; thyroid stimulating hormone (TSH); free T3 (FT3); and free T4 (FT4).

RESULTS

All autotransplanted thyroid tissue survived and functioned. After 12 months, mean values (± standard deviation) of isotope uptake, TSH, FT3, and FT4 of the 5-g implants were 0.44 ± 0.16%, 27.74 ± 30.4 UI/mL, 3.07 ± 1.10 pg/mL, and 1.01 ± 0.3 ng/dL, repectively. Those for the 10 g implants were 0.71 ± 0.20%, 22.78 ± 19.7 UI/mL, 3.92 ± 1.2 pg/mL, and 1.05 ± 0.3 ng/dL, repectively. Ten-gram implants showed significantly higher isotope uptake than 5-g. TSH, FT3, and FT4 significantly improved over the period of 1 year.

CONCLUSION

Injection of thyroid tissue suspension is a simple method for thyroid autotransplantation. TSH was elevated in the majority to maintain normal or near normal thyroid hormones. Ten-gram implants showed higher isotope uptake than 5-g, although this difference was not reflected by thyroid hormone profile. The implant seemed to function better with the passage of time from 2 months to 12 months.

Experimental autotransplantation and cryopreservation of the thyroid gland

BACKGROUND

The purpose of this study was to investigate the functionality of autotransplanted thyroid tissues immediately or after cryopreservation in rabbits.

METHODS

The study was completed with 12 rabbits randomized in 2 groups. Preoperative scintigraphies were performed for all subjects. The rabbits underwent total thyroidectomy. The first group underwent immediate thyroid autotransplantation. Thyroid tissues of the second group were cryopreserved and autoimplanted at the eighth postoperative week. The free triiodothyronine (fT3) and thyroxine (fT4) levels were monitored for 8 weeks. Postoperative scintigraphies were performed at the eigth week after autoimplantation.

RESULTS

The subjects in the first group reached euthyroid levels at the eighth week while none of the second group reached that level, but all showed continuous increase. Although implanted thyroid tissues of 5 of the 6 rabbits in the first group were demonstrated during the first scintigraphy, the number was only 1 in the second group.

CONCLUSION

Thyroid autografts were found to be functional and thought to have a potential preventing postoperative hypothyroidism.

Functional capacity of the thyroid autograft and heterograft: An experimental study

BACKGROUND

The aim of this study was to investigate the functional capacity of thyroid autografts/heterografts in a guinea pig model.

METHODS

A total of 24 guinea pigs were divided into 4 groups. Group A had only a thyroidectomy incision, and group B had total thyroidectomy. We performed autotransplantation in group C and heterotransplantation in group D. We monitored the guinea pigs for an 8-week period, with weekly measurements of free triiodothyronine (fT3), free thyroxine (fT4), and thyroid-stimulating hormone (TSH). At the final stage, the autografts/heterografts were histologically examined.

RESULTS

In group B, fT3/fT4 showed a gradual decrease; however, an increase of TSH was noted. In groups C and D, fT3/fT4 showed a gradual decrease, followed by a gradual increase until euthyroid levels; an exact opposite was noted for TSH. In histologic examination, there were functional thyroid follicles in all animals of groups C and D.

CONCLUSIONS

The autotransplanted/heterotransplanted guinea pig's thyroid tissue provides adequate thyroid function.