Cenni di istologia Ontogenesi Embriogenesi: precursori nel sacco vitellino, strutture vascolari della regione aorta gonade-mesonefro II mese: epatica che prosegue fino al VII assieme alla splenica Al V mese mielopoiesi midollare: inizia nelle ossa piatte e lunghe; nell’invecchiamento residua nelle vertebre, sterno, coste, ali iliache

CELLULE STAMINALI Il potenziale multidifferenziativo della SC caratterizza due principali tipi di SC: le SC ottenute da embrioni e le SC ottenute da soggetto adulto. Le SC embrionali si ottengono mediante la procedura del trasferimento nucleare: il nucleo di una cellula somatica viene inserito all’interno di un ovulo denucleato. Si sviluppa una blastocisti dalla quale possono essere isolate SC, che possono essere espanse in coltura e, indotte a differenziare verso un determinato tipo di tessuto. Si tratta verosimilmente di SC totipotenti. Obiezioni etiche e problemi tecnici rendono assai problematica la loro applicazione. Le SC adulte non sollevano problemi di natura etica. Sono facilmente ottenibili, posseggono una minor capacità espansiva “in vitro” rispetto alle SC embrionali, sono multipotenti (ma non totipotenti), hanno capacità differenziativa limitata a specifici tessuti, sono facilmente applicabili dal punto di vista clinico.

Caratteristiche Capacità di bilanciare autorinnovamento vs differenziazione Sono multipotenti fino a 10 distinte linee cellulari Robusto potenziale proliferativo Rare 1:100.000 Sono quiescenti o in ciclo lento

Dogma dell’embriologia Presenti solo in tessuti capaci di rinnovamento e riparazione Dipendenza dal tipo di tessuto determinato durante lo sviluppo fetale In ogni caso è rispettata l’origine dal foglietto germinativo embrionale

Cellule staminali che rispettano il dogma Staminali epatiche Staminali corneali Ematopoietiche Mieloidi Eritroidi Megacariocitiche Linfatiche

Differenziazione delle cellule emopoietiche

Cellule Staminali Ematopoietiche Mantenimento dell’emopoiesi per tutta la vita Allotrapianto (familiare, MUD, aploidentico, singenico) Autotrapianto Mobilizzazione Purging Tests in vitro Tests in vivo (topi nudi, capre fetali)

CFU-GEMM Mielopoiesi:CS multipotente formante colonie miste (granulo-eritro-macrofagico-megacariocitarie)

CFU-GM Mielopoiesi : Cellula formante colonie granulo-monocitiche

CFU-E Eritropoiesi: cellula che forma piccoli aggregati eritroidi, la BFU-E grandi colonie eritroidi

PLASTICITA’ delle cellule STAMINALI Studi in vivo ed vitro negli ultimi anni hanno evidenziato che in individui adulti il potenziale delle cellule staminali NON sia ristretto irreversibilmente dalla permanenza in un determinato organo. In modelli animali cellule staminali del SNC o del muscolo possono generare cellule emopoietiche, mentre c. midollari possono generare c.muscolari, nervose endoteliali, epatiche. Meccanismo di azione : de-differenziazione? Trans-differenziazione? Fusione cellulare ? Meccanismi di regolazione: fattori solubili? Contatto diretto cellula-cellula? Le cellule staminali nei tessuti adulti hanno capacità proliferativa e differenziativa enorme simili alle c.staminali embrionali che sono all’interno della blastocisti nella fase di pre-impianto nell’endometrio.

Muscle regeneration by bone marrow derived myogenic progenitors Ferrari G et Al Science 1998

Regeneration of ischemic cardiac muscle and vascular endothelium by adult stem cells Kathyjo A. Jackson Incorporation of SP cells into cardiomyocytes. (a) Negative control: C57Bl/6 cardiac tissue stained for lacZ expression. (b) Positive control: C57Bl/6-Rosa26 cardiac tissue stained for lacZ expression. This typical section demonstrates both patterns of punctate and whole-fiber staining. (c) Cross-section of a heart from an SP cell–transplant recipient, which received an infarct. (d) Longitudinal section of an SP cell–transplant recipient, which received an infarct. (e–h) LacZ and -actinin costaining of lacZ-positive fibers. (i) CD45 costaining of the section in g and h. (j) Anti-CD45 staining of spleen (positive control). Sections were stained with X-gal, and LacZ-positive sections were subsequently stained for -actinin (f, h) and CD45 (i), and the sections were photographed.

Regeneration of ischemic cardiac muscle and vascular endothelium by adult stem cells Kathyjo A. Jackson LacZ staining occurs primarily at the border of myocardial infarction. (a) Lower-power (x10) photograph of mouse myocardial infarction after 4 weeks. The arrowhead points to the location of lacZ staining shown in b and c. The lighter pink tissue to the left and above the arrowhead is primarily fibrotic and results from the infarction. (b) Higher-power (x20) photograph of the same section dual stained for lacZ and the antimacrophage Ab F480. The open arrowhead indicates a macrophage, the closed arrowhead indicates lacZ-positive cardiomyocytes (the same region shown in Figure 4, g and h). (c) Higher-power photograph of the same section (x40). (d) Macrophage density of a cardiac section after 1 hour of ischemia and 3 hours of reperfusion. The open arrowheads indicate two of the many macrophages present. The counterstain is eosin.

NEO-RIVASCOLARIZZAZIONE DI ZONE ISCHEMICHE. Kawamoto A et al, 2003 a, Representative findings of NOGA electromechanical mapping before (top) and 4 weeks after (bottom) NA/CD31+ MNC transplantation. Brown dots in pretreatment map show sites of cell transplantation. Red area on pretreatment linear local shortening map (top right) indicates area of decreased wall motion in lateral wall of left ventricle, consistent with ischemia in territory of LCx. Four weeks after local CD31+ cell transplantation, this area of ischemia is no longer evident (bottom right). b, Representative findings of NOGA electromechanical mapping before and 4 weeks after NA/CD31- MNCs transplantation. Area of ischemia on pretreatment map (top right) is unchanged or slightly increased 4 weeks after local transplantation of CD31- cells. c, Representative findings of NOGA electromechanical mapping before and 4 weeks after PBS injection reveal findings similar to those in CD31- transplant animals, with no improvement in ischemic area. d, Change in percentage ischemic area during 4 weeks after treatment. NA/CD31+, swine receiving NA/CD31+ MNCs; NA/CD31-, swine receiving NA/CD31- MNCs. *P<0.05; **P<0.01.

Influence of mobilized stem cells on myocardial infarct repair in a nonhuman primate model Franc¸oise Norol, et Al. Blood 102: 4361; 2003

Generalized potential of adult neural stem cell Clarke DL et Al Science 2000

Turning Brain into Blood: A Hematopoietic Fate Adopted by Adult Neural Stem Cells in Vivo Christopher R. R. Bjornson,*†‡ Rodney L. Rietze,*§Brent A. Reynolds, M. Cristina Magli, Angelo L. Vescovi Science 1999, 283:

Turning Brain into Blood: A Hematopoietic Fate Adopted by Adult Neural Stem Cells in Vivo NSCs produce early hematopoieticcells after transplantationinto irradiated Balb/c recipients.

Turning blood into brain Mezey E et al 2000 Y chromosome staining in the CNS. Coronal sections from 4-month-old nontransplanted (A) female and (B) male brains were mounted and processed together. The panels show the overlay of the NeuN (red) immunostaining, Y chromosome nonradioactive ISH [visualized with tyramide-FITC conjugate (green)], and DAPI staining of cell nuclei (blue). The Y chromosome was restricted to the male brain, demonstrating hybridization specificity. (C) Confocal image of coronal sections from a 4-month-old recipient female striatum that was double-immunostained for the neuron-specific antigens NeuN and NSE. All NeuN-expressing cells (red) were also immunoreactive for NSE (green). (D) Sagittal section from a 1-month-old female PU.1 knockout mouse brain transplanted at birth with male bone marrow. The Y chromosome was visualized with BCIP/NBT (dark purple dots) to identify anatomical landmarks. cc, corpus callosum; cx, cerebral cortex; CPu, caudate putamen; fi, fimbria hippocampi; hi, hippocampus; LV, lateral ventricle. (E to G) Identical fields showing NeuN, Y chromosome, and DAPI nuclear triple staining in the hypothalamic dorsomedial nucleus of a 3-month-old female recipient. Colocalization of the Y chromosome [visualized with tyramide-FITC conjugate (green)] to a NeuN immunopositive (red) nucleus is shown in (E). In (F), DAPI staining identifies all cell nuclei (blue). Overlays of the NeuN, Y chromosome, and DAPI fluorescence are shown in (G). The arrow identifies a cell nucleus that contained both the Y chromosome (indicating the bone marrow origin) and NeuN. Scale bar in (G) represents the following sizes: 30 µm, (A) and (B); 10 µm, (C); 250 µm (D); and 12 µm, (E) to (G). Similar results were observed with three different animals for each experimental condition

Cellule mesenchimali umane ALTRE CELLULE STAMINALI MIDOLLARI Nel midollo emopoietico sono presenti cellule staminali mesenchimali (CSM), le quali sono capaci di dare origine ad osteoblasti, condroblasti adipociti, cellule di tessuto muscolare liscio e scheletrico

Differenziazione in osteoblasti

IPOTESI