RESUMO
Abstract Mucopolysaccharidosis II (MPS II—Hunter syndrome) is an X-linked lysosomal storage disorder caused by a deficiency in iduronate-2 sulfatase. Enzyme replacement therapy does not cross the blood-brain barrier (BBB), limiting the results in neurological forms of the disease. Another treatment option for MPS, hematopoietic stem cell transplantation (HSCT) has become the treatment of choice for the severe form of MPS I since it can preserve neurocognition when performed early in the course of the disease. Even though the intravenous therapy does not cross the BBB, it has become the recommended treatment for MPS II, and HSCT was not often indicated. In an attempt to understand why this treatment modality is rejected by most specialists as a treatment option for patients with Hunter syndrome, we sought to raise all HSCT cases already reported in the scientific literature. Databases used were Medline/PubMed, Lilacs/BVS Cochrane Library, DARE, SciELO, and SCOPUS. Different combinations of the terms "mucopolysaccharidosis II," "Hunter syndrome," "hematopoietic stem cell transplantation," "bone marrow transplantation," and "umbilical cord blood stem cell transplantation" were used. A total of 780 articles were found. After excluding redundant references and articles not related to the theme, 26 articles were included. A descriptive summary of each article is presented, and the main features are summed up. The clinical experience with HSCT in MPS II is small, and most of the available literature is outdated. The available data reveal poor patient selection criteria, varied conditioning regimens, distinct follow-up parameters, and post-HSCT outcomes of interest, making impossible to compare and generalize the results obtained. Recently, after the development of new conditioning protocols and techniques and the creation of bone marrow donor registries and umbilical cord banks, HSCT has become more secure and accessible. It seems now appropriate to reconsider HSCT as a treatment option for the neuronopathic form of MPS II.
RESUMO
As células-tronco hematopoéticas (CTH) são células que possuem a capacidade de se autorrenovar e se diferenciar em células especializadas do tecido sanguíneo e do sistema imune. Na medicina, sua importância pode ser evidenciada por seu uso rotineiro do tratamento de doenças onco-hematológicas e imunológicas. A dificuldade de se encontrarem doadores compatíveis de medula óssea tem estimulado a busca por fontes alternativas de CTH, notadamente o sangue de cordão umbilical e placentário (SCUP) e o sangue periférico. O número de unidades de SCUP armazenadas no mundo tem sido crescente desde a década de 1990. Em 2004 foi criada a rede BrasilCord, estabelecendo uma rede nacional de bancos de SCUP com o objetivo de aumentar as chances de localização de doadores e ampliar o número de bancos de SCUP no país. A despeito do baixo volume coletado e do maior tempo necessário para regenerar o tecido hematopoético, as CTH de SCUP vêm em alta concentração sanguínea, sua utilização como fonte de CTH para transplante apresenta menor risco de causar doença enxerto versus hospedeiro e possuem maior facilidade de obtenção do que as CTH provenientes de medula óssea.
Hematopoietic stem cells (HSC) are cells capable of self-renewal and differentiation into specialized blood tissue and immune system cells. In medicine, their importance is evidenced by their routine use in the treatment of onco-hematological and immunologic diseases. The difficulty of finding compatible bone marrow donors has motivated the search for alternative sources of HSC, notably placental/umbilical cord blood (PUCB). The number of PUCB units stored worldwide has been increasing since 1990. In 2004, the BrasilCord network was created, establishing a national network of PUCB banks with the aim of increasing the chances of finding donors and expanding the number of PUCB banks in the country. Despite the small volume collected and the greater amount of time required for the regeneration of the hematopoietic tissue, the blood concentration of HSC in PUCB is higher, their use as a source for HSC for transplantation presents a lower risk of causing graft versus host disease and they are more easily obtained compared to HSC originating from the bone marrow.