Every year, about 105, 000 people in North America needs a kidney transplant. But, less than 20, 000 (a 1/5 of these people) will actually receive a new kidney. Will we one day be able prevent people from dying from kidney disease by growing transplantable kidneys from stem cells?
In one study, scientists in Australia grew complex groupings of kidney tissue from stem cells derived from human skin. The stem cells were grown in a chemical cocktail which caused the cells to change into kidney cells, and the cells self-organized into groupings of tissue known as organoids. These kidney organoids contained important structural components normally found in kidneys, namely the blood-filtering structures known as nephrons and their associated collecting ducts. Furthermore, the organoids were surrounded by cells which normally form connective tissue and blood vessels in kidneys. The organoids were developmentally similar to human fetal kidneys in the first trimester of gestation.
In another study, published online in Proceedings of the National Academy of Sciences, scientists in Japan overcame a barrier faced by previous attempts at growing functioning kidneys, namely the need for a pathway to drain the urine that is produced. The research group had previously grown kidney structures by using human stem cells transplanted into rat embryos, but these structures lacked a pathway to drain urine, and a build-up of urine limited the development of the kidneys. In the new research, the scientists developed a technique to provide the necessary drainage system, whereby embryonic bladders were transplanted along with developing kidneys into recipient animals. The technique was successfully demonstrated in rats and pigs. The pathways drained urine to the bladders of the host animals, and the kidneys continued to develop.
The kidney is a complex, highly structured organ composed of many distinct cell types performing functions which include removal of metabolic wastes, maintaining acid-base balance and regulating salt and fluid balance. A number of challenges must be overcome to successfully grow a functioning kidney from stem cells. The stem cells must be induced to develop into the various types of kidney cells; the cells must organize into the anatomical structures of the kidney including the waste removal structures and associated drainage paths; and the newly grown kidneys must grow and function in the host patient. The new studies are important advances toward the goal of stem-cell-derived kidneys which may one day alleviate the shortage of transplantable donor kidneys.
Kila mwaka, watu zaidi ya 105,500 katika Amerika ya Kaskazini wanahitaji upandikizaji wa figo. Lakini, chini ya 20,000 (kiasi cha 1 katika 5 ya watu hawa) kwa kweli watapokea figo mpya. Je, siku moja tutaweza kuzuia watu wasife kutokana na ugonjwa wa figo kwa kukuza figo zinazoweza kupandikizwa kutoka kwa chembe za msingi? Katika utafiti mmoja, wanasayansi huko Australia walikua vikundi tata vya tishu za figo kutokana na chembe za msingi zilizotokana na ngozi ya binadamu. Chembe hizo za msingi zilipandwa katika mchanganyiko wa kemikali, na hivyo kugeuka kuwa chembe za figo, na chembe hizo zikajipanga zenyewe kuwa makundi ya tishu inayoitwa organoids. Vipengele hivyo vya figo vilikuwa na sehemu muhimu za muundo zinazopatikana kwa kawaida katika figo, yaani, miundo ya kuchuja damu inayojulikana kama nephrons na mifereji yao ya kukusanya. Isitoshe, organoids zilizungukwa na chembe ambazo kwa kawaida hufanyiza tishu ya kuunganisha na mishipa ya damu katika figo. Viungo hivyo vilikuwa na maendeleo yanayofanana na figo za mtoto wa kiume katika miezi mitatu ya kwanza ya ujauzito. Katika utafiti mwingine uliochapishwa mtandaoni katika jarida la Proceedings of the National Academy of Sciences, wanasayansi nchini Japan walishinda kizuizi kilichokabiliwa na majaribio ya zamani ya kukuza figo zinazofanya kazi, yaani, uhitaji wa njia ya kuondoa mkojo unaotokezwa. Watafiti hao walikuwa wametengeneza figo kwa kutumia seli za asili za binadamu zilizopandikizwa kwenye viini vya panya, lakini figo hizo hazikuwa na njia ya kuondoa mkojo na kuunganisha mkojo kulizuia ukuaji wa figo. Katika utafiti huo, wanasayansi walianzisha mbinu ya kuingiza mifupa ya tumbo la uzazi pamoja na figo katika wanyama waliopokea. Mbinu hiyo ilionyeshwa kwa mafanikio kwenye panya na nguruwe. Njia hizo zilitoa mkojo kwenye kibofu cha mkojo cha wanyama waliowatenga, na figo ziliendelea kukua. Figo ni chombo tata, kimeundwa sana, kilicho na aina nyingi tofauti za seli, na kazi zake ni kuondoa taka za kimetaboliki, kudumisha usawa wa asidi na msingi, na kudhibiti usawa wa chumvi na maji. Ni lazima changamoto kadhaa zishindwe ili kufanikiwa kukuza figo inayofanya kazi kutoka kwa chembe za msingi. Chembe za msingi lazima ziendelezwe kuwa aina mbalimbali za seli za figo; chembe lazima ziendelezwe kuwa miundo ya anatomical ya figo ikiwa ni pamoja na miundo ya kuondoa taka na njia zinazohusiana za mifereji; na figo mpya zinazokua lazima zikue na kufanya kazi katika mgonjwa mwenyeji. Utafiti huo mpya ni hatua muhimu kuelekea lengo la figo zinazotokana na seli za shina ambazo siku moja zinaweza kupunguza upungufu wa figo za wafadhili zinazoweza kupandikizwa.